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Takeshi Tsuji Last modified date:2021.10.27

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Multiscale Science and Engineering for Energy and the Environment Thrust, International Institute for Carbon-Neutral Energy Research (I2CNER) .
Exploration Geophysics Lab .
Academic Degree
PhD (Science) University of Tokyo
Country of degree conferring institution (Overseas)
Field of Specialization
Earth and Planetary Science; Resource engineering; Space exploration
ORCID(Open Researcher and Contributor ID)
Total Priod of education and research career in the foreign country
Outline Activities
My activities are described in the following URL;
Research Interests
  • We have focused on the underlying science associated with the roadblocks for implementation of CO2 storage, including risk of CO2 leakage and risk of injection induced seismicity, that are intimately related to the highly uncertain local geological characteristics of potential CO2 storage sites. Especially, tectonically active area including Japanese Island has heterogeneous geological formation. With respect to reservoir characterization, efforts are directed at understanding rock heterogeneity in constructing geologic models and in designing monitoring surveys. Furthermore, since it is difficult to find structural closure (i.e., anticline) for CO2 injection in the Japanese islands and around their continental margins, substantial research effort is focused on uncovering the physical mechanisms responsible residual, dissolution, and mineralogical trapping of CO2 in porous formations. The current efforts involve two-phase lattice Boltzmann simulation to predict CO2 migration fate in the heterogeneous rock structure and develop effective CO2 injection (and trapping) method. With regard to monitoring of injected CO2, efforts are directed to the development and deployment of effective monitoring methods that can address the long time scales associated with permanent trapping of CO2 in geological formations. Furthermore, pore pressure and stress variation due to CO2 injection should be monitored and controlled in order to prevent induced earthquake. We are therefore developing an effective geophysical monitoring technique (e.g., using the noise signal of ground tremors).
    keyword : Carbon Capture and Storage; Geophysical exploration; Geophysics; Space exploration; Geothermics
Academic Activities
1. Takeshi Tsuji, Carbon Capture Journal "I2CNER - efforts to achieve effective, safe CO2 storage", Future Energy Publishing, Nov/Dec 2016, Issue 54, 4-6, 2016.11.
2. Toshifumi Matsuoka, Wawan Gunawan Kadir, Rachmat Sule, Yasuhiro Yamada, Takeshi Tsuji, Susanti Alawiyah, Setianingsih (eds), The Contribution of Geosciences to Human Security
, Logos Verlag Berlin, 248 pp, 2012.06, Environmental problems, the development of sustainable and environment-friendly energy resources, and also the prevention and management of disasters have become major human security issues in Asian urban areas. This book, ``The Contribution of Geosciences to Human Security'', explains how geosciences can contribute to solving problems related to human security, and it also describes the recent achievements. The authors not only originated from ITB and Kyoto University but were also researchers and engineers from the oil and gas exploration industry, geothermal energy industry, and consultants from Indonesia and Japan who also participated in giving contributions to this book. .
3. Andrew Fisher, Takeshi Tsuji, Katerina Petronotis, the Expedition 327 Scientists, Proceedings of the Integrated Ocean Drilling Program, Volume 327, Integrated Ocean Drilling Program Management International, Inc., doi:10.2204/iodp.proc.327.101.2011, 2011.09, [URL], Integrated Ocean Drilling Program (IODP) Expedition 327 and related experiments focus on understanding fluid-rock interactions in young upper ocean crust on the eastern flank of the Juan de Fuca Ridge, delineating the magnitude and distribution of hydrologic properties; the extent to which crustal compartments are connected or isolated (laterally and with depth); the rates and spatial extent of ridge-flank fluid circulation; and links between ridge-flank circulation, crustal alteration, and geomicrobial processes. Expedition 327 built on the achievements of Ocean Drilling Program (ODP) Leg 168, IODP Expedition 301, and subsequent submersible and remotely operated vehicle (ROV) expeditions. During earlier drilling expeditions, subseafloor borehole observatories (“CORKs”) were installed in basement holes to allow borehole conditions to recover to a more natural state after the dissipation of disturbances caused by drilling, casing, and other operations; to provide a long-term monitoring and sampling presence for determining fluid pressure, temperature, composition, and microbiology; and to facilitate the completion of active experiments to resolve crustal hydrogeologic conditions and processes.

During Expedition 327, two basement holes were cored and drilled at Site U1362. Hole U1362A was cored and drilled to 528 meters below seafloor (mbsf) (292 meters subbasement [msb]), geophysically logged and hydrologically tested, and instrumented with a multilevel CORK observatory. Hole U1362B was drilled to 359 mbsf (117 msb), tested with a 24 h pumping and tracer injection experiment, and instrumented with a single-level CORK observatory. Both CORK observatories include pressure and temperature monitoring and downhole fluid and microbiology sampling and experiments. Wellhead samplers will be added and a long-term cross-hole test will be initiated during a postdrilling ROV expedition scheduled for summer 2011. In addition, part of an instrument string deployed in Hole U1301B during Expedition 301 was recovered during Expedition 327, and a replacement string of thermal sensors was installed. Finally, a program of shallow sediment coring was completed adjacent to Grizzly Bare outcrop, a location where regional hydrothermal recharge occurs. Thermal measurements and analyses of pore fluid and microbiological samples from a series of holes aligned radially from the outcrop edge will elucidate rates of fluid transport and evolution during the initial stages of ridge-flank hydrothermal circulation..
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1. Andrew Fisher, Takeshi Tsuji, Kusali Gamage, Katerina Petronotis, Integrated Ocean Drilling Program Expedition 327 Scientific Prospectus, Juan de Fuca Ridge-Flank Hydrogeology: The hydrogeologic architecture of basaltic oceanic crust: compartmentalization, anisotropy, microbiology, and crustal-scale properties on the eastern flank of Juan de Fuca Ridge, eastern Pacific Ocean, Integrated Ocean Drilling Program Management International, Inc., doi:10.2204/iodp.sp.327.2010, 2010.03, [URL], Integrated Ocean Drilling Program (IODP) Expedition 327 is a critical part of a long-term multidisciplinary experiment that builds from technical and scientific achievements and lessons learned during Ocean Drilling Program (ODP) Leg 168 and IODP Expedition 301. The main goal of this experiment is to evaluate formation-scale hydrogeologic properties (transmission and storage) within oceanic crust; determine how fluid pathways are distributed within an active hydrothermal system; establish links between fluid circulation, alteration, and geomicrobial processes; and determine relations between seismic and hydrologic anisotropy. During Expedition 327 we will install subseafloor observatories in two new holes in oceanic crust (at proposed Site SR-2); replace an observatory in an existing hole (ODP Site 1027) to facilitate long-term monitoring; recover and replace an instrument string deployed in one of the Expedition 301 subseafloor borehole observatories (CORKs); and complete remedial cementing of another Expedition 301 CORK that is not sealed at the seafloor. Following Expedition 327, submersible expeditions will allow us to conduct single- and cross-hole hydrologic experiments using a complete network of six observatory systems that use CORKs as perturbation and monitoring points. This expedition will be dominated by subseafloor observatory installation operations, and hence science activities will consist of ~200 m of basement coring at proposed Site SR-2 and ODP Site 1027, downhole logging, and drill string hydrologic testing. Expedition 327 will also include an international education and outreach program intended to develop tools and techniques that facilitate the communication of exciting scientific drilling results to a broad audience, build educational curricula, and create media products that will help achieve critical outreach goals. .
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1. A.B. Ahmad,T. Tsuji, Machine learning for automatic slump identification from 3D seismic data at convergent plate margins, Marine and Petroleum Geology,, 133, 105290, 2021.08, Plate subduction zones cause earthquakes and build mountain ranges due to plate collisions, which generate complex structures and induce the down-slope transport of large masses (i.e., slumps). Extensive 3D seismic data have been collected in plate subduction zones and can be used to investigate the slumps associated with earthquakes and hydrocarbon accumulations (i.e., hydrate and gas reservoirs). The development of artificial intelligence has provided new techniques (i.e., association rule learning, decision tree learning, and neural networks) for big-data analysis, such as interpreting large seismic data volumes. Here, we use a convolutional neural network (CNN) to automatically detect complex geological structures, such as slump units. We tested our method on the 3D seismic data acquired in the Nankai subduction zone. After manually defining slump units in several seismic profiles within the 3D data volume, we fed the information to the CNN, which accurately identified the spatial distribution of slump units. The CNN model was trained using real 3D seismic data until it achieved 90 % classification accuracy for slump units in the same region as the model was trained. We further applied our CNN model trained by the Nankai data to the 3D seismic data at another plate convergent margin (Sanriku-Oki in northeast Japan) and succeeded in identifying slump units in the Sanriku-Oki seismic volume. In addition to slump identification, our CNN predicted faults better than well-known methods based on seismic attributes. The slump units identified via CNN are distributed at fewer normal fault zone in the Nankai data. The high accuracy of these automatic interpretations shows that this approach can be applied to other forearc basins to investigate geological structures (e.g., slump and faults) at high spatial resolution..
2. T. Hirose, Y. Hamada, W. Tanikawa, N. Kamiya, Y. Yamamoto, T. Tsuji, M. Kinoshita, V. B. Heuer, F. Inagaki, Y. Morono, Y. Kubo, High Fluid-Pressure Patches beneath the Decollement: A Potential Source of Slow Earthquakes in the Nankai Trough off Cape Muroto, Journal of Geophysical Research,, 2021.06.
3. T. Tsuji, M. Sorai, M. Shiga, S. Fujikawa, T. Kunitake, Geological storage of CO2-N2-O2 mixtures produced by membrane-based direct air capture (DAC), Greenhouse Gases: Science and Technology, doi: 10.1002/ghg.2099, 2021.05.
4. C. Chhun, T. Tsuji, Pore pressure and gas saturation distribution in the forearc basin of the Nankai subduction zone inferred from high-resolution Vp and Vs, Journal of Petroleum Science and Engineering, 2021.05.
5. A.B. Ahmad, T. Tsuji, Traffic monitoring system based on deep learning and seismometer data, Applied Sciences, 11, 10, 4590, 2021.04.
6. T. Ikeda, T. Tsuji, C. Konishi, H. Saito, Spatial autocorrelation method for reliable measurements of two-station dispersion curves in heterogeneous ambient noise wavefields, Geophysical Journal International,, 226, 2, 1130-1147, 2021.04.
7. K. Sawayama, T. Ishibashi, F. Jiang, T. Tsuji, O. Nishizawa, Y. Fujimitsu, Scale-independent relationship between permeability and resistivity in mated fractures with natural rough surfaces, Geothermics, 10.1016 /j.geothermics.2021.102065, 2020.12.
8. #K. Sawayama, T. Ishibashi, #F. Jiang, @T. Tsuji, Y. Fujimitsu,, Relating hydraulic-electrical-elastic properties of natural rock fractures at elevated stress and associated transient changes of fracture flow, Rock Mechanics and Rock Engineering, 10.1007/s00603-021-02391-5, 2021.02, Monitoring the hydraulic properties within subsurface fractures is vitally important in the contexts of geoengineering developments and seismicity. Geophysical observations are promising tools for remote determination of subsurface hydraulic properties; however, quantitative interpretations are hampered by the paucity of relevant geophysical data for fractured rock masses. This study explores simultaneous changes in hydraulic and geophysical properties of natural rock fractures with increasing normal stress and correlates these property changes through coupling experiments and digital fracture simulations. Our lattice Boltzmann simulation reveals transitions in three-dimensional flow paths, and finite-element modeling enables us to investigate the corresponding evolution of geophysical properties. We show that electrical resistivity is linked with permeability and flow area regardless of fracture roughness, whereas elastic wave velocity is roughness-dependent. This discrepancy arises from the different sensitivities of these quantities to microstructure: velocity is sensitive to the spatial distribution of asperity contacts, whereas permeability and resistivity are insensitive to contact distribution, but instead are controlled by fluid connectivity. We also are able to categorize fracture flow patterns as aperture-dependent, aperture-independent, or disconnected flows, with transitions at specific stress levels. Elastic wave velocity offers potential for detecting the transition between aperture-dependent flow and aperture-independent flow, and resistivity is sensitive to the state of connection of the fracture flow. The hydraulic-electrical-elastic relationships reported here may be beneficial for improving geophysical interpretations and may find applications in studies of seismogenic zones and geothermal reservoirs..
9. A. Hendriyana, and @T. Tsuji,, Influence of structure and pore pressure of plate interface on tectonic tremor in the Nankai subduction zone, Earth and Planetary Science Letters,, Volume 558, 116742, 2021.03, Episodes of tectonic tremor are observed in the Nankai accretionary prism close to the trough axis; however, their non-impulsive signals and the distortion of seismic signals in the accretionary prism make it challenging to accurately estimate their locations. Reliable tremor locations would help to characterize geological conditions favourable for tremor generation and could offer insights into the up-dip limit of coseismic ruptures. Here we report a new approach to pinpoint tremor locations based on seismic phase polarization. The estimated epicentres of tremor distribution mostly coincide with low-velocity shear zone or thick underthrust sediments where high pore pressures are inferred, and the distribution of tremor appears to be controlled by characteristics of the shear zone. A tremor episode occurred a couple days after the off-Mie earthquake clearly shows migration at a velocity similar to that of very low frequency earthquakes. Migration of tremor initiated around the outer ridge where the estimated pore pressure is greatest. The spatio-temporal tremor distribution indicates that pore pressure relaxation could trigger the tremor migration. The occurrence of tremor thus may indicate a weak shallow plate interface that is prone to slip following large earthquakes. Based on the information of tremor migration, the permeability along the fault can be estimated as m2..
10. #Rezkia Dewi Andajani, @T. Tsuji, R. Snieder, @T. Ikeda, Spatial and temporal influence of rainfall on crustal pore pressure based on seismic velocity monitoring, Earth,Planets and Space, doi:10.1186/s40623-020-01311-1, 72, Article number: 177 (2020), 2020.11, Crustal pore pressure, which controls the activities of earthquakes and volcanoes, varies in response to rainfall. The status of pore pressure can be inferred from observed changes in seismic velocity. In this study, we investigate the response of crustal pore pressure to rainfall in southwestern Japan based on time series of seismic velocity derived from ambient noise seismic interferometry. To consider the heterogeneity of the area, rainfall and seismic velocity obtained at each location were directly compared. We used a band-pass filter to distinguish the rainfall variability from sea level and atmospheric pressure, and then calculated the cross-correlation between rainfall and variations in S-wave velocity (Vs). A mostly negative correlation between rainfall and Vs changes indicates groundwater recharge by rainfall, which increases pore pressure. The correlations differ between locations, where most of the observation stations with clear negative cross-correlations were located in areas of granite. On the other hand, we could not observe clear correlations in steep mountain areas, possibly because water flows through river without percolation. This finding suggests that geographical features contribute to the imprint of rainfall on deep formation pore pressure. We further modelled pore pressure change due to rainfall based on diffusion mechanism. A strong negative correlation between pore pressure estimated from rainfall and Vs indicates that the Vs variations are triggered by pore pressure diffusion in the deep formation. Our modelling results show a spatial variation of diffusion parameter which controls the pore pressure in deep formation. By linking the variations in seismic velocity and crustal pore pressure spatially, this study shows that seismic monitoring may be useful in evaluating earthquake triggering processes or volcanic activity..
11. F. Jinag and @T. Tsuji, Investigation of viscous coupling effects in three-phase flow by lattice Boltzmann direct simulation and machine learning technique, Advances in Water Resources, doi:10.1016/j.advwatres.2020.103797, Vol. 14,103797, 2021, 2021.01, The momentum transfer across fluid interfaces in multi-phase flow leads to a non-negligible viscous coupling effect. In this study, we use the lattice Boltzmann method (LBM) as a direct simulator to solve the three-phase flow at pore scale. The viscous coupling effects are investigated for various fluid configurations in simple pore geometries with different conditions in terms of saturation, wettability and viscosity ratio. It is found that the viscous coupling effect can be significant for certain configurations. A parametric modification factor for conventional three-phase conductance model is then proposed to estimate the viscous coupling effect. The modification factor as a function of viscosity ratios can be easily incorporated into existing pore network model (PNM) to eliminate errors from viscous coupling effect. Moreover, an elegant approach using machine learning technique is proposed to predict the multi-phase permeability by a trained Artificial Neural Network (ANN) from the direct simulation database. Such data-driven approach can be extended to develop a more sophisticated PNM for a better prediction of transport properties taking account of the viscous coupling effects..
12. @C. Chhun and @T. Tsuji, Pore pressure analysis for distinguishing earthquakes induced by CO2 injection from natural earthquakes, Sustainability,, 12(22), 9723, 2020.11, [URL], It is important to distinguish between natural earthquakes and those induced by CO2 injection at carbon capture and storage sites. For example, the 2004 Mw 6.8 Chuetsu earthquake occurred close to the Nagaoka CO2 storage site during gas injection, but we could not quantify whether the earthquake was due to CO2 injection or not. Here, changes in pore pressure during CO2 injection at the Nagaoka site were simulated and compared with estimated natural seasonal fluctuations in pore pressure due to rainfall and snowmelt, as well as estimated pore pressure increases related to remote earthquakes. Changes in pore pressure due to CO2 injection were clearly distinguished from those due to rainfall and snowmelt. The simulated local increase in pore pressure at the seismogenic fault area was much less than the seasonal fluctuations related to precipitation and increases caused by remote earthquakes, and the lateral extent of pore pressure increase was insufficient to influence seismogenic faults. We also demonstrated that pore pressure changes due to distant earthquakes are capable of triggering slip on seismogenic faults. The approach we developed could be used to distinguish natural from injection-induced earthquakes and will be useful for that purpose at other CO2 sequestration sites..
13. A. Chapman and T. Tsuji, Impacts of COVID-19 on a transitioning energy system, society, and international cooperation, Sustainability, doi:10.3390/su12198232, 2020.10, Short term outcomes of the COVID-19 pandemic have included improved air quality and reduced carbon dioxide (CO2) and other greenhouse gas emissions, while long term repercussions may include a disruption to joint international research efforts, the creation of silos, and the potential for internalizing efforts toward national rather than global goals. In this study, we identified the impacts of reduced mobility on pollutants and emissions, the emergence of nationalist approaches and effects on international cooperation, and how these issues will affect the achievement of global carbon targets and the Sustainable Development Goals (SDGs). COVID-19 presents a global short-term crisis and there is a demonstrated global desire and effort to develop a vaccine and effective treatments. Similarly, climate change is also a near future issue, and as a result we need to reduce CO2 emissions rapidly. This review highlights potential policy interventions, which capitalize on learnings from COVID-19, while identifying SDGs 10, 13 and 17 as critical to engendering a successful, cooperative transition toward sustainability. The recognition of the earth as a closed system, demonstrated by the shared impacts of the COVID-19 crisis, may encourage positive future effects on cooperative approaches toward mitigating climate change, another looming crisis for humanity..
14. K. Ishitsuka, T. Tsuji, W. Lin, M. Kagabu, J. Shimada, Seasonal and transient surface displacements in the Kumamoto area, Japan, associated with the 2016 Kumamoto earthquake: Implications for seismic-induced groundwater level change, Earth, Planets and Space,, 2020.10, The 2016 Kumamoto earthquake sequence on April 14 (Mw 6.2) and April 16 (Mw 7.0) altered the regional groundwater level. To better understand the relationship between groundwater level change and surface displacement, we estimated surface displacement in the Kumamoto area (Japan) using persistent scatterer interferometry from 19 ALOS/PALSAR images acquired between January 7, 2007 and March 5, 2011, 28 ALOS-2/PALSAR-2 images acquired between April 17, 2016 and December 10, 2018, and 113 Sentinel-1 images acquired between May 26, 2016 and December 30, 2018. Our estimation shows that transient surface displacement occurred following the 2016 Kumamoto earthquake sequence, together with seasonal surface displacement that was not detected from the 2007–2011 images. We suggest that a portion of the transient displacement occurred via groundwater drawdown through new ruptures that formed owing to the 2016 Kumamoto earthquake sequence and sediment compaction. Seasonal surface displacements detected after the 2016 Kumamoto earthquake sequence are linked to groundwater level variations..
15. F. L. Hutapea,T. Tsuji, M. Katou, and E. Asakawa, Data processing and interpretation schemes for a deep-towed high-frequency seismic system for gas and hydrate exploration, Journal of Natural Gas Science and Engineering, doi:10.1016/j.jngse.2020.103573., 103573, 2020.09, The deep-towed Autonomous Cable Seismic (ACS) system is a high-resolution acoustic survey system designed for use in deep-water environments. This system uses a high-frequency acoustic source and a multichannel receiver cable. A common problem in the analysis of deep-towed ACS data is the unstable positioning of the source and receivers due to ocean currents and seafloor bathymetry. Since the data acquisition using high-frequency source with unstable source–receiver positions causes destructive interference on the final stack profile, correction of the unstable source-receiver is a crucial issue. In this study, we propose a method to solve the unstable source–receiver position problem and thus to construct an accurate final stack profile. We used deep-towed ACS data acquired in the Joetsu Basin in Niigata, Japan, where hydrocarbon features in the form of gas chimneys, gas hydrate, and free gas have been observed. Because sidelobes in the ACS source signature defocus the source wavelet and decrease the bandwidth frequency content, we designed a filter to focus the source signature. Our proposed approach considerably improved the quality of the final stack profile. Even though depth information was not available for all receivers, the velocity spectra in the velocity analysis were well focused. Furthermore, shaping the source wavelet considerably increased the bandwidth frequency of the source signature. We applied seismic attribute analysis to the post-stack profile to identify the distributions of free gas and hydrate. Our seismic attribute analyses for the high-frequency ACS data demonstrated that free gas accumulations are characterized by low reflection amplitude and an unstable frequency component, and that hydrate close to the seafloor can be identified by its high reflection amplitude..
16. T. Akuhara, T. Tsuji, and T. Tonegawa, Overpressured underthrust sediment in the Nankai Trough forearc inferred from transdimensional inversion of high-frequency teleseismic waveforms, Geophysical Research Letters, 10.1029/2020GL088280, 47, 15, e2020GL088280, 2020.08, Active‐source seismic surveys have resolved the fine‐scale P‐wave velocity (Vp) of the subsurface structure in subduction forearcs. In contrast, the S‐wave velocity (Vs) structure is poorly resolved despite its usefulness in understanding rock properties. This study estimates Vp and Vs structures of the Nankai Trough forearc, by applying transdimensional inversion to high‐frequency teleseismic waveforms. As a result, a thin (∼1 km) low‐velocity zone (LVZ) is evident at ∼6 km depth beneath the sea level, which is located ~3 km seaward from the outer ridge. Based on its high Vp/Vs ratio (∼2.5) and comparison to an existing seismic reflection profile, we conclude that this LVZ reflects a high pore pressure zone at the upper portion of the underthrust sediment. We infer that this overpressured underthrust sediment hosts slow earthquake activities and that accompanied strain release helps impede coseismic rupture propagation further updip..
17. B. Nthabaa, E. Shemanga, A. Hengaria, B. Kgosidintsia, and T. Tsuji, Characterizing coal seams hosted in Mmamabula Coalfield, Central Botswana using pseudo-3D electrical resistivity imaging technique, Journal of African Earth Sciences, 10.1016/j.jafrearsci.2020.103866, 167, 103866, 2020.07, We used 2D and 3D electrical resistivity imaging (ERI) data inversion to locate and characterize the coal seams in Mmamabula Coalfield. The 2D ERI data inversion usually assumes that subsurface geological units (e.g. coal seams) are infinitely continuous in the direction perpendicular to the profiles. However, this assumption might be violated due to the heterogeneous nature of fluvial/deltaic environments. The lateral variation of the subsurface material can be effectively determined in 3D ERI inversion models. In this study, 2D ERI data were acquired along ten parallel profiles trending north-south, then inverted to produce 2D and 3D models. From the 2D ERI inversion results, we observed that the shallower coal seam occurs around a consistent depth of 13.6 m whereas the second observable coal seam occurs at variable depths including at 50 m and 60 m along the two profiles. Discontinuities in coal seams were also identified. However, the information provided by 2D data inversion in such an environment is insufficient to determine the geometry of coal seams as well as to produce accurate and precise resource estimates for future exploitation. As an alternative, 3D data inversion gives better insight on the subsurface geology complexity and significantly resolves the geometry of coal within the study area. The presented 3D inversion results indicate that coal seams are intermittent and alternate well with other coexisting sedimentary units. We also deduced that they trend east-west and are split and adjoined in some areas along the north-south direction. Overall, 3D data inversion result resolves the elongated coal seams in Mmamabula Coalfield and reveals additional information that cannot be determined on 2D ERI inversion results..
18. A. Suzuki, M. Miyazawa, A. Okamoto, H. Shimizu, I. Obayashi, Y. Hiraoka, T. Tsuji, P. K. Kang, T. Ito., Inferring fracture forming processes by characterizing fracture network patterns with persistent homology., Computers and Geosciences, 2020.07.
19. Kakda Kret, Takeshi Tsuji, Chanmaly Chhun, Osamu Takano, Distributions of gas hydrate and free gas accumulations associated with upward fluid flow in the Sanriku-Oki forearc basin, northeast Japan, Marine and Petroleum Geology, 10.1016/j.marpetgeo.2020.104305, 116, 2020.06, We applied automated velocity analysis to a 3D seismic data volume to obtain a high-resolution seismic velocity model that we used to investigate the influence of fluid behavior on the subsurface distribution of gas in the Sanriku-Oki forearc basin, northeast Japan. We identified free gas accumulations as zones of low P-wave velocity separated from overlying high-velocity gas hydrates by the clear seismic boundary of the bottom-simulating reflection (BSR) between them. We then used conductive modeling to map upward heat flow in our study area from the depth of the BSR derived from the velocity model. The estimated heat flow demonstrates that upward fluid flux has considerable influences on the distributions of both gas hydrate and free gas. The areas of high heat flow (representing high fluid flux) correspond to underlying permeable geological features such as gas chimneys, faults, and the edges of porous slumps, suggesting that these features provide fluid migration pathways from Eocene to Oligocene source rocks to free gas and hydrate accumulations in overlying sedimentary rocks. The techniques we have employed can contribute to the high-resolution mapping of gas hydrate and free gas accumulations in similar deep-water reservoirs off the eastern continental margin of Japan and at tectonically similar plate subduction margins in other regions..
20. Y. Suemoto, T. Ikeda, T. Tsuji, Temporal variation and frequency dependence of seismic ambient noise on Mars from polarization analysis, Geophysical Research Letters, 10.1029/2020GL087123, 47, e2020GL0871 23, 2020.06, We applied a polarization analysis of InSight seismic data to estimate the temporal variation and frequency dependence of the Martian ambient noise field. Low‐frequency (<1 Hz) P waves show a diurnal variation in their dominant back azimuths that are apparently related to wind and the direction of sunlight in a distant area. Low‐frequency Rayleigh waves (0.25–1 Hz) show diurnal variations and a dominant back azimuth related to the wind direction in a nearby area. Low‐frequency signals that are derived mainly from wind may be sensitive to subsurface structure deeper than the lithological boundary derived from an autocorrelation analysis. On the other hand, dominant back azimuths of high‐frequency (>1 Hz) waves point toward the InSight lander, especially in daytime, indicating that wind‐induced lander noise is dominant at high frequencies. These results point to the presence of several ambient noise sources as well as geologic structure at the landing site..
21. H. Nimiya, T. Ikeda, and T. Tsuji, , Three‐dimensional S‐wave Velocity Structure of Central Japan Estimated by Surface‐wave Tomography Using Ambient Noise, JGR Solid Earth, doi:10.1029/2019JB019043, 2020.03, [URL].
22. Hiroki Matsui, Jihui Jia, Takeshi Tsuji, Yunfeng Liang, Yoshihiro Masuda, Microsecond simulation study on the replacement of methane in methane hydrate by carbon dioxide, nitrogen, and carbon dioxide–nitrogen mixtures, Fuel, 10.1016/j.fuel.2019.116640, 263, 2020.03, Replacement of methane (CH4) in CH4 hydrate by carbon dioxide (CO2) can enable recovery of CH4, which is a potential future energy resource, while sequestering CO2 to mitigate the effects of global warming. However, little work has been done to address the effects of impurities on CO2 replacement, and the detailed mechanisms. Here, microsecond molecular dynamics simulations were performed to understand the influence of nitrogen (N2) gas on the process of replacing CH4 in CH4 hydrate with CO2 at 280 K and 6 MPa. The results show that CO2 molecules can penetrate more deeply into CH4 hydrate phase when it is mixed with N2. This is mainly because N2 can favor the decomposition of CH4 hydrate and expand the replacement area of CH4 by guest molecules. We confirm that the replacement of CH4 by CO2 and N2 preferably occurs in large and small cages, respectively. In most cases, a mixture hydrate reforms at the outmost layer of the hydrate surface. The CO2/N2 mixture shows an overall higher replacement efficiency than pure CO2 case. Our work demonstrates that CH4 recovery by CO2 injection in CH4 hydrate can be facilitated by N2. The penetration depth of replacement is sensitive to the ratio of N2 to CO2. The knowledge obtained in this study will be helpful for the effective utilization of CO2/N2 mixtures to maximize the recovery percentage of CH4 from hydrate..
23. F. L. Hutapea, T. Tsuji, and T. Ikeda, Real-time crustal monitoring system of Japanese Islands based on spatio-temporal seismic velocity variation, Earth, Planets and Space, doi:10.1186/s40623-020-1147-y, 72, 19, 72:19, 2020.02, [URL], To continuously monitor crustal behavior associated with earthquakes, magmatic activities and other environmental effects (e.g., tides and rain precipitation), we have developed a continuous monitoring system of seismic velocity of the Japanese Islands. The system includes four main processing procedures to obtain spatio-temporal velocity changes: (1) preparing ambient-noise data; (2) creating virtual seismograms between pairs of seismometer stations by applying seismic interferometry; (3) estimating temporal velocity variations from virtual seismograms by stretching interpolation approach, and (4) mapping spatio-temporal velocity variations. We developed a data-processing scheme that removes unstable stretching interpolation results by using the median absolute deviation technique and a median filter. To map velocity changes with high stability and high temporal resolution during long-term (i.e., longer-term monitoring), we proposed the “sliding reference method”. We also developed evaluation method to select the optimum parameters related to stability and temporal resolution. To reduce computation time for continuous monitoring, we applied parallel computation methods, such as shared memory and hybrid distributed memory parallelization. Using our efficient and stable monitoring system, we succeeded to continuously monitor the spatio-temporal velocity variation of the whole Japanese Islands using ambient-noise data from 767 seismometers. Finally, we developed a web application that displays spatio-temporal velocity changes. In the monitoring results that we open through the website, we identified velocity variation (e.g., pore pressure variation) that could be related to earthquake, aftershock, magmatic activities and environmental effects in a stable manner..
24. Yudai Suemoto, Tatsunori Ikeda, Takeshi Tsuji, Yoshihisa Iio, Identification of a nascent tectonic boundary in the San-in area, southwest Japan, using a 3D S-wave velocity structure obtained by ambient noise surface wave tomography, earth, planets and space, 10.1186/s40623-020-1139-y, 72, 1, 2020.02, We derived a three-dimensional S-wave velocity model for the San-in area of southwest Japan to examine heterogeneous structures such as tectonic faults. Many earthquakes occur in this area, but much of the activity has been relatively recent, so the fault distribution has yet to be fully clarified. Here, we used continuous ambient noise data from a dense seismic network, deployed from November 2009 to extract Rayleigh and Love wave dispersion data between station pairs, and then applied a direct surface wave inversion to the phase velocities of each station pair to determine a three-dimensional S-wave velocity model. In the resulting model, faults and a previously unrecognized tectonic boundary appeared as low-velocity anomalies or velocity boundaries, and the velocity anomalies were also associated with many past earthquake hypocenters. These results contribute to our understanding of heterogeneous structures caused by recent tectonic motion and of possible future tectonic activity, such as intraplate earthquakes. Surface wave tomography using ambient noise recorded in dense seismic networks could also be applied in other parts of the world to reveal new heterogeneous geological structures (i.e., unrevealed tectonic faults) and could contribute to disaster mitigation.[Figure not available: see fulltext.].
25. Mokhamad Yusup Nur Khakim, Akhmad Aminuddin Bama, Indra Yustian, Pradanto Poerwono, Takeshi Tsuji, Toshifumi Matsuoka, Peatland subsidence and vegetation cover degradation as impacts of the 2015 El niño event revealed by Sentinel-1A SAR data, International Journal of Applied Earth Observation and Geoinformation, 10.1016/j.jag.2019.101953, 84, 2020.02, Indonesia has the world's largest tropical peatland, mostly located in the southern province of Sumatra, the south of Kalimantan, and Papua. The catastrophic fires between June and October 2015 induced by the El Niño event burnt most of these peatland areas. We analyzed spatio-temporal peat subsidence during pre- and post-fires in the peat hydrological unit of Sungai Sugihan – Sungai Saleh (KHGSS), South Sumatra using Sentinel-1 images by applying DInSAR-SBAS algorithm. Based on our analysis, the linear subsidence rate after the 2015 peat fires increased by a factor 6.4 compared to that of pre-fires. Generally, the estimated subsidence is temporally well-correlated with the precipitation variation. In addition, the subsidence patterns are spatially correlated with the hotspot distribution, peat thickness, and drainage networks. Furthermore, we mapped vegetation cover over the KHGSS by using the Sentinel-1 images as well. The results show that the vegetation degradation is correlated with the hotspot distribution and the highly-degraded vegetation associated with the 2015 peat fires. It demonstrated that the 2015 El Niño event has significant impacts on increasing the amount of the subsidence and the vegetation degradation in KHGSS area..
26. Chanmaly Chhun, Takeshi Tsuji, Sound speed of thermohaline fine structure in the Kuroshio Current inferred from automatic sound speed analysis, Exploration Geophysics, 10.1080/08123985.2020.1736548, 2020.01, Fine-scale thermohaline structure within ocean column can be mapped seismically in the Kuroshio Current, off the Muroto Peninsula of Shikoku Island, Japan. In this paper, we present the application of automatic sound speed picking analysis to the multi-channel seismic reflection data acquired in a different period to estimate time-lapse sound speed distribution across the Kuroshio Current. This method is based on an optimal velocity trajectory solving by the eikonal equation with a finite-difference algorithm. In contrast to the seismic inversion technique, this automatic analysis enables us to obtain contrast sound speed profiles without heavy dependency on sound speed or temperature data directly measured at discrete locations. As a result, this method can visualise sound speed profiles of fine-scale thermohaline structure developed at interleaving or diapycnal mixing processes of different water masses in the Kuroshio Current. The images of all profiles mapped from automatic sound speed analysis distinguish water masses and their fine-scale internal structure such as cold and warm water eddies, thermohaline staircases and internal waves revealing acoustic contrasts at interfaces across where sound speed and temperature change. Applying our approach for individual seismic line acquired in different time-steps for 3D seismic data can provide time–space variant images of fine-scale thermohaline structure for studies of oceanographic processes as well as large-scale ocean current and climate systems..
27. Tatsunori Ikeda, Takeshi Tsuji, Two-station continuous wavelet transform cross-coherence analysis for surface-wave tomography using active-source seismic data, GEOPHYSICS, 10.1190/geo2019-0054.1, 85, 1, EN17-EN28, 2020.01, ABSTRACT Surface-wave tomography has great potential to improve the lateral resolution of near-surface characterization compared to 2D surface-wave analysis with multichannel analysis of surface waves (MASW). Surface-wave tomography has been widely applied to obtain high-resolution maps of phase or group velocity from dispersion curves between pairs of stations in seismological studies. However, very few studies have done surface-wave tomography with active-source (exploration) seismic data, probably because extracting surface-wave dispersion curves between two stations is difficult due to the complex wave propagation in heterogeneous near-surface structures. Here, we describe a method to estimate reliable phase-velocity dispersion curves between two stations from exploration seismic data. In our approach, we compute cross coherences between pairs of stations to extract phase information, stacking the cross coherences from different shot gathers to improve the signal-to-noise ratio. To further distinguish surface-wave signals from noise in the time domain, we perform a time-frequency analysis using the continuous wavelet transform (CWT) on the stacked cross coherences. We used modeling of the wavelet transform between station pairs to extract phase-velocity dispersion curves from the stacked cross coherences. We apply this two-station CWT cross-coherence method to synthetic and field data sets. Both applications demonstrate that our method can extract stable phase-velocity dispersion curves between two stations better than two-station or multistation analysis without time-domain filtering. In phase-velocity distributions constructed by surface-wave tomography from the dispersion curves between two stations, the horizontal resolution is improved over MASW-based analyses. Improvement of the horizontal resolution is also achieved in S-wave velocity structures derived by inversion of the phase-velocity distributions. Our method is effective in estimating reliable phase-velocity dispersion curves and may contribute to constructing high-resolution S-wave velocity models located with a laterally heterogeneous structure, by subsequent surface-wave tomography and S-wave velocity inversion..
28. Kosuke Takahashi, Takeshi Tsuji, Tatsunori Ikeda, Hiro Nimiya, Yuichiro Nagata, Yudai Suemoto, Underground structures associated with horizontal sliding at Uchinomaki hot springs, Kyushu, Japan, during the 2016 Kumamoto earthquake, earth, planets and space, 10.1186/s40623-019-1066-y, 71, 1, 2019.12, The 2016 Kumamoto earthquake (Mw 7.0) caused hot springs in the Uchinomaki area of Aso caldera to become dormant. Geodetic and borehole observations have previously demonstrated that the area around the hot springs slid horizontally ~ 2 m to the northwest during the earthquake. However, the subsurface structure in the area has not been investigated and the mechanism of sliding is unclear. To reveal geological structures in and around the hot spring area, we conducted a seismic microtremor survey at 60 sites and used the Extended Spatial Auto Correlation (ESPAC) method to determine surface-wave dispersion curves from the microtremor data. We then derived S-wave velocity profiles by inversion of the dispersion curves and constructed from them a 3D S-wave velocity model to ~ 100 m depth over the hot springs and surrounding areas. New surface fissures (indicative of extension) that opened during the 2016 earthquake correspond to a boundary in the southeast of the study area between modeled lower velocities (to the northwest) and higher velocities (to the southeast). In the central area of the hot springs, where the largest displacement occurred, the 3D model shows a plume-like high-velocity anomaly, indicative of more-competent sediments there. The lowest S-wave velocities (less-competent rocks) are in paddy fields north of the hot spring area. We interpret the above aspects of the 3D velocity model to indicate that during the 2016 earthquake the relatively competent (higher S-wave velocity) sediments in the central area of the hot springs slid northwestward, causing compressional deformation of the less-competent (lower S-wave velocity) sediments in the northern paddy fields and extensional deformation (fissures) southeast of the sliding block. A distinct increase in S-wave velocity at ~ 50 m depth coincides with the depth of a pumice layer in drillcore from the central hot spring area. Shaking during the 2016 earthquake could have caused a sudden increase in pore pressure in this widely distributed porous layer, thus providing a slip plane for the observed horizontal sliding to the northwest.[Figure not available: see fulltext.]..
29. K. Ishizu, T. Goto, Y. Ohta, T. Kasaya, H. Iwamoto, C. Vachiratienchai, W. Siripunvaraporn, T. Tsuji, H. Kumagai, K. Koike, Internal Structure of a Seafloor Massive Sulfide Deposit by Electrical Resistivity Tomography, Okinawa Trough, Geophysical Research Letters, 10.1029/2019GL083749, 46, 20, 11025-11034, 2019.10, Although seafloor massive sulfide (SMS) deposits are crucially important metal resources that contain high-grade metals such as copper, lead, and zinc, their internal structures and generation mechanisms remain unclear. This study obtained detailed near-seafloor images of electrical resistivity in a hydrothermal field off Okinawa, southwestern Japan, using deep-towed marine electrical resistivity tomography. The image clarified a semi-layered resistivity structure, interpreted as SMS deposits exposed on the seafloor, and another deep-seated SMS layer at about 40-m depth below the seafloor. The images reinforce our inference of a new mechanism of SMS evolution: Upwelling hydrothermal fluid is trapped under less-permeable cap rock. The deeper embedded SMS accumulates there. Then hydrothermal fluids expelled on the seafloor form exposed SMS deposits..
30. Kota Mukumoto, Takeshi Tsuji, Andri Hendriyana, Large Gas Reservoir Along the Rift Axis of a Continental Back-Arc Basin Revealed by Automated Seismic Velocity Analysis in the Okinawa Trough, Geophysical Research Letters, 10.1029/2019GL083065, 46, 16, 9583-9590, 2019.08, In the Okinawa Trough off southwestern Japan, hydrothermal circulation due to back-arc rifting is active. Biogenic CH4 in discharging hydrothermal fluids at the Iheya North Knoll is derived from outside the knoll; however, the location of the gas reservoir has not been identified. Here, we applied automated velocity analysis to seismic reflection data to obtain a P wave velocity structure in high spatial resolution. The resulting profiles reveal large gas reservoirs as low-velocity zones along the rifting axis (>5 km for axis direction) around the Iheya North Knoll. The main gaseous components in the reservoir could be CO2 and CH4. The heat flow inferred from seismic profiles (i.e., depth of reflector) indicates that CH4; hydrate could be trapping the gas. Furthermore, the heat flow is higher at the rifting axis and close to the knoll, reflecting the large gas reservoir feeding the hydrothermal fluids in the discharging area at the knoll..
31. Kazuya Ishitsuka, Takeshi Tsuji, Mapping Surface Displacements and Aquifer Characteristics Around the Kumamoto Plain, Japan, Using Persistent Scatterer Interferometry, 39th IEEE International Geoscience and Remote Sensing Symposium, IGARSS 2019 2019 IEEE International Geoscience and Remote Sensing Symposium, IGARSS 2019 - Proceedings, 10.1109/IGARSS.2019.8897893, 9654-9657, 2019.07, In this study, we used persisitent scatterer interferometry to monitor surface displacements related to groundwater level changes around the Kumamoto plain. Groundwater has been used for daily purposes in the area, and the 2016 Kumamoto earthquake with a maximum magnitude of Mw 7.0 occurred at the area. The use of ALOS/PALSAR data showed seasonal displacements that correspond to seasonal groundwater flow from January 2007 to January 2011. On the other hand, the analysis of ALOS-2/PALSAR-2 data revealed local surface displacements after the 2016 Kumamoto earthquake, which were validated by Sentinel-1A and GNSS data. Especially, we found that the local ground uplifts that correspond to groundwater level increase after the earthquake. From changes in skeletal storage coefficient, we interpreted that aquifer properties such as porosity and aquifer matrix compressibility altered by the earthquake. Our results demonstrate the effectiveness of aquifer monitoring using persistent scatterer interferometry..
32. Andri Hendriyana, Takeshi Tsuji, Migration of Very Long Period Seismicity at Aso Volcano, Japan, Associated With the 2016 Kumamoto Earthquake, Geophysical Research Letters, 10.1029/2019GL082645, 46, 15, 8763-8771, 2019.07, Earthquakes are known to precede volcanic activity, including long-period or very long period (VLP) volcanic seismicity. However, the relationships among earthquakes, VLP seismicity, and volcanic eruptions are not well understood. Here we present the locations of VLP seismicity at Aso volcano, Japan, between January 2015 and December 2016, a period that includes the Mw 7.0 Kumamoto earthquake and phreatomagmatic eruptions. By using a differential-time backprojection method developed in this study to accurately locate VLP events, we clearly identified two distinct VLP clusters. Whereas the eastern cluster was active during eruptions, the western cluster displayed intense VLP seismicity only for a few months after the earthquake. The western cluster may be associated with opening of new fractures during the earthquake. This study explores the mechanisms that can relate earthquake to volcanic activities and provides a new approach to analyze the dynamic behaviors inside volcanoes that may yield useful information for hazard evaluation..
33. Takeshi Tsuji, Tatsunori Ikeda, Fei Jiang, Evolution of hydraulic and elastic properties of reservoir rocks due to mineral precipitation in CO 2 geological storage, Computers and Geosciences, 10.1016/j.cageo.2019.02.005, 126, 84-95, 2019.05, To investigate the evolution of the hydraulic and elastic properties of reservoir rocks associated with CO 2 mineralization in carbon capture and storage projects, we simulated the mineral precipitation process in a 3D model of natural sandstone, created from micro-CT scanned images, and a 3D model consisting of close-packed beads. Two different mineralization schemes were used: the first calculated pore filling by calcite by applying an advection-reaction equation to the fluid flow velocity field within the pore spaces of the rock models using a lattice Boltzmann simulation, and the second simulated pore filling by increasing the grain radius. We estimated the P-wave and S-wave velocities in the rock models using a dynamic wave propagation simulation and estimated the permeabilities using a lattice Boltzmann simulation. The simulation results showed that the elastic properties of the digital rocks were strongly influenced by mineralization around the grains, whereas their hydraulic properties were influenced by mineralization within the pore body. The elastic and hydraulic properties calculated from our rock models agree with those calculated using conventional rock physics theories, such as effective medium theory and the Kozeny-Carman equation, in terms of crack aspect ratio and tortuosity. Direct simulation using digital rocks enables us to explore the complex relations among the hydraulic and elastic parameters of rocks during CO 2 mineralization. The relationships between permeability and seismic velocity are strongly influenced by mineralization types as well as rock types; nevertheless, permeabilities have a definite relationship with the P-wave to S-wave velocity ratio (Vp/Vs). By applying the rock modeling approach of this study to target reservoirs, permeability evolution due to CO 2 mineralization could be evaluated on the basis of seismic velocities from geophysical monitoring data..
34. Rezkia Dewi Andajani, Tatsunori Ikeda, Takeshi Tsuji, Surface wave analysis for heterogeneous geological formations in geothermal fields
Effect of wave propagation direction, Exploration Geophysics, 10.1080/08123985.2019.1597497, 50, 3, 255-268, 2019.05, We applied advanced surface wave analysis for multichannel and multishot seismic data to estimate S-wave velocity structure with high lateral resolution. Although a horizontally layered structure is typically assumed in surface wave analysis, this assumption might be violated in environments such as geothermal fields because of their heterogeneous geological formation. The lateral variation of phase velocity can be effectively estimated with common midpoint (CMP) cross-correlation (CMPCC) analysis. In this study, we introduced two additional approaches into the CMPCC analysis workflow, to further improve lateral resolution of phase velocity estimates. One approach is window-controlled CMPCC analysis, which applies a spatial window for the CMP gathers while maintaining the accuracy of the phase velocity estimates. In this analysis, we found that it is difficult to improve phase velocity estimates at lower frequencies, as a wider spatial window must be kept to maintain the accuracy of the dispersion curve. Therefore, we introduced another approach in which we consider the direction of surface wave propagation from sources to receivers. Selection of cross-correlations based on source-CMP direction provides a significant improvement in dispersion curve resolution in the presence of lateral velocity variations, for a wide frequency range. We applied direction-controlled CMPCC analysis to seismic data acquired in the Yamagawa geothermal field, Kyushu Island, southwest Japan, and obtained dispersion curves in the heterogeneous geological setting. We then obtained S-wave velocity profiles by applying genetic algorithm inversion to the dispersion curves. The S-wave velocity profiles in the geothermal field resolve shallow and local heterogeneous structures (e.g. volcanic ash, pumice and igneous intrusions) that cannot be identified on reflection seismic profiles..
35. Y. Ozaki, Y. Mugita, M. Aramaki, O. Furukimi, S. Oue, F. Jiang, T. Tsuji, A. Takeuchi, M. Uesugi, K. Ashizuka, Four-dimensional observation of ductile fracture in sintered iron using synchrotron X-ray laminography, Powder Metallurgy, 10.1080/00325899.2019.1585032, 62, 2, 146-154, 2019.03, Synchrotron X-ray laminography was used to examine the time-dependent evolution of the three-dimensional (3D) morphology of micropores in sintered iron during the tensile test. 3D snapshots showed that the networked open pores grow wider than 20 µm along the tensile direction, resulting in the internal necking of the specimen. Subsequently, these pores initiated the cracks perpendicular to the tensile direction by coalescing with the surrounding pre-existing microvoids or with the secondary-generated voids immediately before fracture. Topological analysis of the barycentric positions of these microvoids showed that they form the two-dimensional networks within the ∼20 µm of radius area. These observations strongly indicate that the microvoid coalescence could occur on shear planes formed close to the enlarged open pores or between closed pores by strain accumulation and play an important role in the crack initiation..
36. A. Kioka, T. Tsuji, H. Otsuka, J. Ashi, Methane Concentration in Mud Conduits of Submarine Mud Volcanoes
A Coupled Geochemical and Geophysical Approach, Geochemistry, Geophysics, Geosystems, 10.1029/2018GC007890, 20, 2, 792-813, 2019.02, Mud volcanoes are among the largest geological sources releasing methane gas. Numerous studies have revealed their origins and compositions released from submarine mud volcanoes. However, quantification of the amount of gas inside submarine mud volcanoes has been challenging due to the difficulty of in situ measurements, which has hampered better evaluation for their contribution to the global methane budget. Here we provide a coupled geochemical and geophysical model that bridges bulk methane concentrations and seismic wave velocities in the mud conduit of submarine mud volcano. This model is applicable to most submarine mud volcanoes and is able to estimate methane concentration at the upper several hundreds of meters in the mud conduits using downhole logging data or seismic data. Our calculation for submarine mud volcanoes in the Eastern Mediterranean and the Nankai plate subduction zones shows that the weight fractions of gaseous and dissolved methane in total weight of sediment are 1,000–3,500 ppm within their mud conduits, which are much higher than previously expected from pore-water evidence from conventional shallow subsurface sampling. Although more definitive calculations cannot be made until the model parameters are better constrained, our approach provides an opportunity for re-estimating the global methane budget in submarine mud volcanoes, shedding new light upon the impact of submarine mud volcanism on carbon cycle..
37. Jihui Jia, Yunfeng Liang, Takeshi Tsuji, Caetano R. Miranda, Yoshihiro Masuda, Toshifumi Matsuoka, Ab Initio Molecular Dynamics Study of Carbonation and Hydrolysis Reactions on Cleaved Quartz (001) Surface, Journal of Physical Chemistry C, 10.1021/acs.jpcc.8b12089, 123, 8, 4938-4948, 2019.01, Geochemical trapping (i.e., mineralization) is considered to be the most efficient way for long-term CO 2 storage in order to mitigate "global warming effect" induced by anthropogenic CO 2 emission. The common view is that the reaction process takes hundreds of years; however, recent field pilots have demonstrated that it only took 2 years to convert injected CO 2 to carbonates in reactive basaltic reservoirs. In this work, ab initio molecular dynamics simulations were employed to investigate chemical reactions among CO 2 , H 2 O, and newly cleaved quartz (001) surfaces in order to understand the mechanisms of carbonation and hydrolysis reactions, which are essential parts of CO 2 mineralization. It is shown that CO 2 can react with undercoordinated Si and nonbridging O atoms on the newly cleaved quartz surface, leading to formation of CO 3 configuration that is fixed on the surface by Si-O bonds. Furthermore, these Si-O bonds can break under hydrolysis reaction, and HCO 3 occurs simultaneously. Electron localization function and Bader charge analysis were used to describe the bonding mechanism and charge transfer during the two reaction processes. The result highlights the importance of the intermediate configuration of CO 2 γ- in the carbonation reaction process. Furthermore, it confirms the formation of CO 3 2- and HCO 3 - . We conclude that CO 3 2- and HCO 3 - in the formation water do not necessarily originate from dissociation of H 2 CO 3 , and these anions may accelerate the CO 2 mineralization process in the presence of required cations, such as Ca 2+ , Mg 2+ , or Fe 2+ ..
38. Kakda Kret, Tatsunori Ikeda, Takeshi Tsuji, Grid-search inversion based on rock physics model for estimation of pore geometry and grain elastic moduli
Application to hydrothermal ore deposits and basalt, Exploration Geophysics, 10.1080/08123985.2018.1548605, 50, 1, 1-11, 2019.01, The seismic velocity of rock material is sensitively affected by the pore geometry, and pore geometry is a key parameter related to the hydraulic properties of the rock. In this study, we propose a grid-search inversion method to estimate pore geometry and grain elastic moduli from observed velocity-porosity relationships. In our inversion, we compare laboratory-derived velocity-porosity relationships with the theoretical relationship calculated via the differential effective medium (DEM) model, assuming rock samples of the same lithology have the same crack aspect ratio. Compared with existing approaches to estimate elastic moduli and pore geometry, our approach is easy to apply because it can be applied to physical properties measured at atmospheric pressure without changing pressure. We tested our proposed inversion method using synthetic data, and successfully estimated the grain elastic moduli and crack aspect ratio. We also applied our inversion method to P-wave velocity and porosity measured in the laboratory on various rock samples acquired at the hydrothermal field and plate spreading centre, and found that the velocity-porosity relationship derived from DEM theory for the inverted model parameters agreed with the laboratory data. Using our proposed method, we estimate the average pore aspect ratio and grain bulk moduli for basaltic and hydrothermal ore deposit samples. Furthermore, the root mean square error (RMSE) distribution obtained in the grid-search inversion enables us to evaluate the uncertainty of the estimated values..
39. Chandoeun Eng, Takeshi Tsuji, Influence of faults and slumping on hydrocarbon migration inferred from 3D seismic attributes
Sanriku-Oki forearc basin, northeast Japan, Marine and Petroleum Geology, 10.1016/j.marpetgeo.2018.10.013, 99, 175-189, 2019.01, Seismic imaging of the Sanriku-Oki forearc basin in the Japan Trench plate convergent margin provides insights into the geological controls on hydrocarbon systems in sediment deposited on the continental slope. We perform a series of seismic attribute analyses on 3D seismic reflection data to better define the influence of geological structures (e.g., faults, slumps and gas chimneys) on hydrocarbon sources, migration pathways and reservoirs. In order to identify coal-bearing strata from the 3D seismic volume, we calculate acoustic impedance distribution by integrating seismic and logging data via waveform inversion. Two Late Oligocene to Early Miocene major coal-bearing strata are characterized as low acoustic impedance strata. Gas-bearing strata characterized by anomalously high reflection strength are widely distributed beneath a bottom simulating reflector (BSR). A greater accumulation of gas occurs in the northeast of the study area, where successive slump deposits and gas chimneys are observed. We propose that a BSR with an underlying gas accumulation in the Sanriku-Oki forearc basin developed as a consequence of the expulsion of gas from Cretaceous to Oligocene coal beds and their subsequent upward migration through gas chimneys and faults. Furthermore, the migration and accumulation of gas and gas hydrate were strongly controlled by a series of porous slump deposits. As chimneys and gas pockets occur above the edges of the slumps, gas migration processes controlled by the slumps could be important in the forearc basin. Our study based on seismic attribute analyses demonstrates that features produced by tectonic movements at plate subduction margins (e.g., faults) and associated instability processes (e.g., slumps) represent important controls on the migration and accumulation of hydrocarbons in forearc basins..
40. G. Kimura, H. Koge, T. Tsuji,, Punctuated Growth of an Accretionary Prism and the Onset of a Seismogenic Megathrust in the Nankai Trough, Progress in Earth and Planetary Science, doi:10.1186/s40645-018-0234-1, 5:78, 2018.11, [URL].
41. T. Ikeda, T. Tsuji, M. Nakatsukasa, H. Ban, A. Kato, K. Worth, D. White, and B. Roberts, Imaging and monitoring of the shallow subsurface using spatially windowed surface-wave analysis with a single permanent seismic source, Geophysics, doi:10.1190/geo2018-0084.1, 83, 6, EN23-EN38, 2018.10, [URL].
42. T. Ikeda, T. Tsuji, Temporal change in seismic velocity associated with an offshore MW 5.9 Off-Mie earthquake in the Nankai subduction zone from ambient noise cross-correlation, Progress in Earth and Planetary Science, doi:10.1186/s40645-018-0211-8, 5:62, 2018.10, [URL].
43. T. Sasaoka, H. Shimada, K. Watanabe, T. Tsuji, R. Imai, H. Miki, Y. Fujimitsu, Y. Sugai, K. Yonezu, and N. Hiroyoshi, Cooperative Program for Resources Engineering Between Kyushu University and Hokkaido University, International Journal of Georesources and Environment, doi:10.15273/ijge.2018.03.028, 2018., 4, 3, 174-179, 2018.09.
44. K. Kawabata, A. Sakaguchi, Y. Hamada, T. Tsuji, Y. Kitamura, and S. Saito, Thermal fluid migration in the Kumano forearc basin, Nankai Trough, estimated via vitrinite reflectance measurement, Geological Society of America (GSA) Books, doi:10.1130/2018.2534(09), 2018.08, [URL].
45. A. Ijiri, F. Inagaki, Y. Kubo, R. R. Adhikari, S. Hattori, T. Hoshino, H. Imachi, S. Kawagucci, Y. Morono, Y. Ohtomo, S. Ono, S. Sakai, K. Takai, T. Toki, D. T. Wang, M. Y. Yoshinaga, G. L. Arnold, J. Ashi, D. H. Case, T. Feseker, K. Hinrichs, Y. Ikegawa, M. Ikehara, J. Kallmeyer, H. Kumagai, M. A. Lever, S. Morita, K. Nakamura, Y. Nakamura, M. Nishizawa, V. J. Orphan, H. Roy, F. Schmidt, A. Tani, W. Tanikawa, T. Terada, H. Tomaru, T. Tsuji, U. Tsunogai, Y. T. Yamaguchi, and N. Yoshida, Deep-biosphere methane production stimulated by geofluids in the Nankai accretionary complex, Science Advances, doi:10.1126/sciadv.aao4631, 4, 6, eaao4631, 2018.06, [URL].
46. F. Jiang, T. Tsuji, and T. Shirai, Pore Geometry Characterization by Persistent Homology Theory, Water Resources Research (AGU), doi:10.1029/2017WR021864, Vol. 54, Issue 6, 4150-4163, 2018.05, [URL].
47. T. Tsuji, F. Jiang, A. Suzuki, T. Shirai, Mathematical Modeling of Rock Pore Geometry and Mineralization: Applications of Persistent Homology and Random Walk, Agriculture as a Metaphor for Creativity in All Human Endeavors, doi:10.1007/978-981-10-7811-8_11, 2018.03, [URL].
48. A.R.K. Asikin, A. Priyono, T. Ariadji, B. Sapiie, M. R. Sule, T. Tsuji, W. G. A. Kadir, T. Matsuoka, and S. Rahardjo, Forward Modeling Time-Lapse Seismic based on Reservoir Simulation Result on The CCS Project at Gundih Field, Indonesia, Modern Applied Science, doi:10.5539/mas.v12n1p75, 12, 1, 2018.01, [URL].
49. C. Chhun, A. Kioka, J. Jia, T. Tsuji, Characterization of hydrate and gas reservoirs in plate convergent margin by applying rock physics to high-resolution seismic velocity model, Marine and Petroleum Geology, doi:10.1016/j.marpetgeo.2017.12.002, Vol.92, 719-732, 2017.12, [URL].
50. H. Nimiya, T. Ikeda, T. Tsuji, Spatial and temporal seismic velocity changes on Kyushu Island during the 2016 Kumamoto earthquake, Science Advances, doi:10.1126/sciadv.1700813, Vol. 3, no. 11, e1700813, 2017.11, [URL].
51. Takeshi Tsuji, Shohei Minato, Rie Kamei, Tetsuro Tsuru, Gaku Kimura, 3D geometry of a plate boundary fault related to the 2016 Off-Mie earthquake in the Nankai subduction zone, Japan, Earth and Planetary Science Letters, 10.1016/j.epsl.2017.08.041, 478, 234-244, 2017.11, We used recent seismic data and advanced techniques to investigate 3D fault geometry over the transition from the partially coupled to the fully coupled plate interface inboard of the Nankai Trough off the Kii Peninsula, Japan. We found that a gently dipping plate boundary décollement with a thick underthrust layer extends beneath the entire Kumano forearc basin. The 1 April 2016 Off-Mie earthquake (Mw6.0) and its aftershocks occurred, where the plate boundary décollement steps down close to the oceanic crust surface. This location also lies beneath the trenchward edge of an older accretionary prism (∼14 Ma) developed along the coast of the Kii peninsula. The strike of the 2016 rupture plane was similar to that of a formerly active splay fault system in the accretionary prism. Thus, the fault planes of the 2016 earthquake and its aftershocks were influenced by the geometry of the plate interface as well as splay faulting. The 2016 earthquake occurred within the rupture area of large interplate earthquakes such as the 1944 Tonankai earthquake (Mw8.1), although the 2016 rupture area was much smaller than that of the 1944 event. Whereas the hypocenter of the 2016 earthquake was around the underplating sequence beneath the younger accretionary prism (∼6 Ma), the 1944 great earthquake hypocenter was close to oceanic crust surface beneath the older accretionary prism. The variation of fault geometry and lithology may influence the degree of coupling along the plate interface, and such coupling variation could hinder slip propagation toward the deeper plate interface in the 2016 event..
52. C. Eng, T. Ikeda, T. Tsuji, Study of the Nankai seismogenic fault using dynamic wave propagation modelling of digital rock from the Nobeoka fault, Exploration Geophysics, accepted, 2017.10.
53. S. Minato, R. Ghose, T. Tsuji, M. Ikeda, K. Onishi, Hydraulic properties of closely-spaced dipping open fractures intersecting a fluid-filled borehole derived from tube-wave generation and scattering, Journal of Geophysical Research, doi:10.1002/2017JB014681, 2017.09, [URL].
54. S. Singh, F. Jiang, T. Tsuji, Impact of the kinetic boundary condition on porous media flow in lattice Boltzmann formulation, Physical Review E, doi:10.1103/PhysRevE.96.013303, 96, 013303, 2017.07, [URL].
55. T. Ikeda, T. Tsuji, Robust Subsurface Monitoring Using a Continuous and Controlled Seismic Source, Energy Procedia, doi:10.1016/j.egypro.2017.03.1527, Vol.114, 3956-3960, 2017.07, [URL].
56. S. Singh, F. Jiang, T. Tsuji, Influence of Slip Flow at Fluid-solid Interface upon Permeability of Natural Rock , Energy Procedia, doi:10.1016/j.egypro.2017.03.1487, Vol.114, 3572-3577, 2017.07, [URL].
57. T. Tsuji, T. Ikeda, F. Jiang, Hydrologic and Elastic Properties of CO2 Injected Rock at Various Reservoir Conditions: Insights into Quantitative Monitoring of Injected CO2 , Energy Procedia, doi:10.1016/j.egypro.2017.03.1487, Vol.114, 4047-4055, 2017.07, [URL].
58. K. Ishitsuka, T. Matsuoka, T. Nishimura, T. Tsuji, T. ElGharbawi, Ground uplift related to permeability enhancement following the 2011 Tohoku earthquake in the Kanto Plain, Japan, Earth, Planets and Space, doi:10.1186/s40623-017-0666-7, 69:81, 2017.06, [URL].
59. Y. Liang, S. Tsuji, J. Jia, T. Tsuji, T. Matsuoka, Modeling CO2-Water-Mineral Wettability and Mineralization for Carbon Geosequestration, Acc. Chem. Res., doi: 10.1021/acs.accounts.7b00049, 50, 7, 1530-1540, 2017.06, [URL].
60. J. Jia, Y. Liang, T. Tsuji, S. Murata, T. Matsuoka, Elasticity and Stability of Clathrate Hydrate: Role of Guest Molecule Motions, Scientific Reports , doi:10.1038/s41598-017-01369-0, 7, Article number: 1290 , 2017.05, [URL].
61. T. Ikeda, T. Tsuji, M. Takanashi, I. Kurosawa, M. Nakatsukasa, A. Kato, K. Worth, D. White, B. Roberts, Temporal variation of the shallow subsurface at the Aquistore CO2 storage site associated with environmental influences using a continuous and controlled seismic source, Journal of Geophysical Research - Solid Earth, DOI: 10.1002/2016JB013691, Volume 122, Issue 4, 2859-2872, in press, 2017.04, [URL].
62. T. Tsuji, J. Ishibashi, K. Ishitsuka, R. Kamata, Horizontal sliding of kilometre-scale hot spring area during the 2016 Kumamoto earthquake, Scientific Reports, doi:10.1038/srep42947, 7, 42947, 2017.02, [URL].
63. W. Lin, T.B. Byrne, M. Kinoshita, L.C. McNeill, C. Chang, J.C. Lewis, Y. Yamamoto, D.M. Saffer, J.C. Moore, H-Y. Wu, T. Tsuji, Y. Yamada, M.Conin, S. Saito, T. Ito, H.J. Tobin, G. Kimura, K. Kanagawa, J. Ashi, M.B. Underwood, T. Kanamatsu, Distribution of stress state in the Nankai subduction zone, southwest Japan and a comparison with Japan Trench, Tectonophysics, doi:10.1016/j.tecto.2015.05.008, 692, 120-130, 2016.12, [URL].
64. F. Jiang, T. Tsuji, Estimation of three-phase relative permeability by simulating fluid dynamics directly on rock-microstructure images, Water Resources Research, DOI: 10.1002/2016WR019098, 53, 1, 11-32, 2016.11, [URL].
65. T. Tsuji, T. Ikeda, T.A. Johansen, B.O. Ruud, Using seismic noise derived from fluid injection well for continuous reservoir monitoring, Interpretation (SEG-AAPG journal), doi: 10.1190/INT-2016-0019.1, 4, 4, SQ1-SQ11, 2016.08, [URL].
66. T. Ikeda, T. Tsuji, Surface wave attenuation in the shallow subsurface from multichannel-multishot seismic data: a new approach for detecting fractures and lithological discontinuities, Earth, Planets and Space, DOI: 10.1186/s40623-016-0487-0, 68:111, 2016.07, [URL].
67. F. Jiang, T. Tsuji, Numerical investigations on the effect of initial state CO2 topology on capillary trapping efficiency, International Journal of Greenhouse Gas Control, doi:10.1016/j.ijggc.2016.03.006, 49, 179-191, 2016.06, [URL].
68. K. Ishitsuka, T. Tsuji, T. Matsuoka, Pixel-based interferometric pair selection in InSAR time series analysis with baseline criteria, Remote Sensing Letters, doi:10.1080/2150704X.2016.1182660, 7, 7, 711-720, 2016.05, [URL].
69. T. Yamabe, T. Tsuji, Y. Liang, T. Matsuoka, Influence of fluid displacement patterns on seismic velocity during supercritical CO2 injection: Simulation study for evaluation of the relationship between seismic velocity and CO2 saturation, International Journal of Greenhouse Gas Control, doi:10.1016/j.ijggc.2016.01.011, 46, 197-204, 2016.03, [URL].
70. T. Tsuji, F. Jiang, K. Christensen, Characterization of immiscible fluid displacement processes with various capillary numbers and viscosity ratios in 3D natural sandstone, Advances in Water Resources, doi:10.1016/j.advwatres.2016.03.005, 95, 3-15, 2016.03, [URL].
71. J. Jia, Y. Liang, T. Tsuji, S. Murata, T. Matsuoka, Microscopic Origin of Strain Hardening in Methane Hydrate, Scientific Reports, doi:10.1038/srep23548, 6, Article 23548, 2016.03, [URL].
72. 辻 健, 蒋 飛, Two-phase Porous Flow Simulation for Natural Sandstone on GPU Supercomputer, TSUBAME e-Science Journal, 14, 18-23, 2016.03.
73. , [URL].
74. K. Ishitsuka, T. Tsuji, T. Matsuoka, J. Nishijima, Y. Fujimitsu, Heterogeneous Surface Displacement Pattern at the Hatchobaru Geothermal Field Inferred from SAR Interferometry Time-Series, International Journal of Applied Earth Observation and Geoinformation, doi:10.1016/j.jag.2015.07.006, 44, 95-103, 2016.02, [URL].
75. T. Ikeda, T. Tsuji, T. Watanabe, K. Yamaoka, Development of surface-wave monitoring system for leaked CO2 using a continuous and controlled seismic source, International Journal of Greenhouse Gas Control, doi:10.1016/j.ijggc.2015.11.030, 45, 94-105, 2016.02, [URL].
76. J. Jia, T. Tsuji, T. Matsuoka, Gas hydrate saturation and distribution in the Kumano Forearc Basin of the Nankai Trough, Exploration Geophysics, doi:10.1071/EG15127, 2016.02, [URL].
77. Takeshi Tsuji, Juichiro Ashi, Michael Strasser, Gaku Kimura, Identification of the static backstop and its influence on the evolution of the accretionary prism in the Nankai Trough, Earth and Planetary Science Letters, 10.1016/j.epsl.2015.09.011, 431, 15-25, 2015.12, To reveal the origin of a backstop and its influence on the evolution of the accretionary prism, we analyzed reflection seismic data acquired in the Nankai Trough off the Kii Peninsula. The deformation features of the forearc basin sequence show that the landward accretionary prism close to the coast was not deformed after the development of the forearc basin about 2-4 Ma. The surface of the landward prism can be identified as strong amplitude reflector, indicating that the landward prism has higher seismic velocity. Therefore, the landward accretionary prism inferred to be of higher strength constitutes a static backstop. Based on seismic and geologic observations, we interpret that the backstop was generated due to the large age differences of accreted material resulting from an inferred hiatus in subduction between ~13 and 6 Ma. The time-dependent processes such as the igneous activity in middle Miocene further contribute to the development of the backstop. A ridge structure beneath the forearc basin located trenchward of this backstop and running roughly parallel to it appears to reflect activity on an ancient splay fault. The strike of the ancient splay fault runs parallel to the backstop identified in this study and oblique to the current trench. This geometry suggests that location and mechanical behavior of this splay fault system is influenced by the backstop, and its distribution could be related to the coseismic rupture area..
78. T. Ikeda, T. Tsuji, Advanced surface-wave analysis for 3D ocean bottom cable data to detect localized heterogeneity in shallow geological formation of a CO2 storage site, International Journal of Greenhouse Gas Control, doi: 10.1016/j.ijggc.2015.04.020, 39, 107-118, 2015.08, [URL].
79. Fei Jiang, T. Tsuji, Impact of Interfacial Tension on Residual CO2 Clusters in Porous Sandstone, Water Resources Research, doi:10.1002/2014WR016070, 51, 2015.03, [URL].
80. R. Hino, T. Tsuji, N.L. Bangs, Y. Sanada, J-O. Park, R. vonHuene, G.Moore, E. Araki, M Kinoshita, Qp structure of the accretionary wedge in the Kumano Basin, Nankai Trough, Japan, revealed by long-offset walk-away VSP, Earth, Planets and Space, doi:10.1186/s40623-014-0175-x, 67, 7, 2015.01, [URL].
81. Tatsunori Ikeda, Toshifumi Matsuoka, Takeshi Tsuji, Toru Nakayama, Characteristics of the horizontal component of Rayleigh waves in multimode analysis of surface waves, Geophysics, doi: 10.1190/geo2014-0018.1 , 80, 1, EN1-EN11, 2014.12, [URL].
82. F. Jiang, T. Tsuji, Interfacial Tension Effect on Cluster Size Distributions for Residual Trapping of CO2 in Sandstones, Energy Procedia, doi:10.1016/j.egypro.2014.11.580, 63, 5483-5489, 2014.12, [URL].
83. S. Kimura, K. Honda, K. Kitamura, I. Taniguchi, K. Shitashima, T. Tsuji, S. Fujikawa, Preliminary feasibility study for on-site hydrogen station with distributed CO2 capture and storage system, Energy Procedia, doi:10.1016/j.egypro.2014.11.490, 63, 4575-4584, 2014.12, [URL].
84. K. Kitamura, Y. Yamada, K. Onishi, T. Tsuji, S. Chiyonobu, B. Sapiie, A. Bahar, H. Danio, A. Muhammad, A. Erdi, V.M. Sari, T. Matsuoka, W.G.A. Kadir, Gundih CCS project team, Potential evaluation of CO2 reservoir using the measured petrophysical parameter of rock samples in the Gundih CCS Project, Indonesia, Energy Procedia, doi:10.1016/j.egypro.2014.11.525, 63, 4965-4970, 2014.12.
85. T. Tsuji, K. Kitamura, T. Matsuoka, Y. Yamada, W. G. A. Kadir, M. R. Sule, A. Priyonom, T. Ariadji, B. Sapiie, M. Hato, T. Takahashi, K. Onishi, DS Widarto, R.I. Sebayang, A. Prasetyo, Pertamina, Gundih CCS Project Team, Reservoir characterization for site selection in the Gundih CCS Project, Indonesia, Energy Procedia, doi:10.1016/j.egypro.2014.11.666, 63, 6335-6343, 2014.12, [URL], A pilot CCS project in Indonesia will be implemented in Gundih area, Central Java Province in Indonesia. Before the CO2 injection, the reservoirs for CO2 injection must be characterized carefully by conducting geophysical exploration as well as reservoir simulation, in order to make sure that the reservoir is suitable for CO2 storage. Here we report results of reservoir characterization and simulation for the determination of CO2 injection site in the Gundih area. Subsurface structures imaged on seismic reflection profiles indicate that the Ngrayong formation is one of the candidates for CO2 injection. We observed the outcrop of the Ngrayong formation and measured hydrological and geophysical properties (e.g., permeability, seismic velocity) of the rock samples obtained from outcrop and wells. The Ngrayong formation has layered structure and heterogeneous characteristics. Using (1) hydrological properties, (2) subsurface structures (i.e., geometry of the Ngrayong formation) and (3) physical properties predicted by integrating seismic and logging data via acoustic impedance inversion, we applied reservoir simulation and evaluated security of the CO2 injection sites..
86. Tatsunori Ikeda, Takeshi Tsuji, Azimuthal anisotropy of Rayleigh waves in the crust in southern Tohoku area, Japan, Journal of Geophysical Research, DOI: 10.1002/2014JB011567, 119, 12, 8964-8975, 2014.12, [URL], To reveal seismic anisotropy within the crust in the southern Tohoku area, Japan, we analyze the azimuthal anisotropy of Rayleigh waves in the frequency range of 40-65 mHz. Rayleigh wave anisotropy is estimated by array analysis of 102 teleseismic events that occurred between 2007 and 2014. The frequency variation of the estimated azimuthal anisotropy indicates depth variation of the seismic anisotropy within the crust: (1) both north-south fast velocity direction around the upper crust and (2) trench-normal fast velocity direction in the deeper crust. We also conduct a time-lapse analysis of Rayleigh wave anisotropy to demonstrate the stability of the estimated anisotropy in time and to estimate possible changes in seismic anisotropy associated with the 2011 Tohoku-oki earthquake. We demonstrate that the azimuthal location of teleseismic events influences the accuracy of time-lapse analysis. Moreover, a decrease of azimuthal anisotropic ratio in time-lapse results might be related to changes in the velocity structure associated with release of crustal stress during the Tohoku-oki earthquake..
87. Fei Jiang, Takeshi Tsuji, Changes in pore geometry and relative permeability caused by carbonate precipitation in porous media, Physical Review E, DOI:, 90, 053306 , 2014.11, [URL], The CO 2 behavior within the reservoirs of carbon capture and storage projects is usually predicted from large-scale simulations of the reservoir. A key parameter in reservoir simulation is relative permeability. However, mineral precipitation alters the pore structure over time, and leads correspondingly to permeability changing with time. In this study, we numerically investigate the influence of carbonate precipitation on relative permeability during CO 2 storage. The pore spaces in rock samples were extracted by high-resolution microcomputed tomography (CT) scanned images. The fluid velocity field within the three-dimensional pore spaces was calculated by the lattice Boltzmann method, while reactive transport with calcite deposition was modeled by an advection-reaction formulation solved by the finite volume method. To increase the computational efficiency and reduce the processing time, we adopted a graphics processing unit parallel computing technique. The relative permeability of the sample rock was then calculated by a highly optimized two-phase lattice Boltzmann model. We also proposed two pore clogging models. In the first model, the clogging processes are modeled by transforming fluid nodes to solid nodes based on their precipitated mass level. In the second model, the porosity is artificially reduced by adjusting the gray scale threshold of the CT images. The developed method accurately simulates the mineralization process observed in laboratory experiment. Precipitation-induced evolution of pore structure significantly influenced the absolute permeability. The relative permeability, however, was much more influenced by pore reduction in the nonwetting phase than in the wetting phase. The output of the structural changes in pore geometry by this model could be input to CO 2 reservoir simulators to investigate the outcome of sequestered CO 2 ..
88. Y. Yamabe, T. Tsuji, Y. Liang, T. Matsuoka, Lattice Boltzmann simulations of supercritical CO2-water drainage displacement in porous media: CO2 saturation and displacement mechanism, Environmental Science & Technology, doi: 10.1021/es504510y, 49, 1, 537-543, 2014.11, [URL].
89. Fumihiko Ikegami, Takeshi Tsuji, Hidenori Kumagai, Jun-ichiro Ishibashi, Ken Takai, Active Rifting Structures in Iheya Graben and Adjacent Area of the Mid-Okinawa Trough Observed Through Seismic Reflection Surveys, Subseafloor Biosphere Linked to Hydrothermal Systems, 10.1007/978-4-431-54865-2_28, 361-368, 2014.11, [URL], The mid-Okinawa Trough is recognized as an area with extensive volcanism and hydrothermal activity. The Iheya Graben is a depression in the mid-Okinawa Trough, extending approximately 100 km in an ENE-WSW strike. The graben lies 200 m below the surrounding flat-surfaced trough floor (from −1,400 to −1,600 m below sea level). The latest seismic profiles in the western Iheya Graben and adjacent areas reveal numerous normal faults, possibly in association with the rifting activity of the Okinawa Trough. The faulting of the Iheya Graben is non-listric syn-depression faulting, in contrast with dense listric faulting of the adjacent trough floor. The faulting in both areas consists of numerous seafloor-reaching active faults; however, recent activity is concentrated within the Iheya Graben. Non-listric faulting in the Iheya Graben shapes its present structure with large displacements. The displacements and fault propagations indicate the depression of the Iheya Graben was created with an abrupt flexural subsidence followed by extension with normal faulting. The event occurred largely before the formation of the overlying Iheya Ridge, which was reported to be at least 0.2 Ma. Such a significant event may be related to the present extensive volcanism in the region by means of rifting tectonics and magmatism..
90. Jun-ichiro Ishibashi, Fumihiko Ikegami, Takeshi Tsuji, Tetsuro Urabe, Hydrothermal Activity in the Okinawa Trough Back-Arc Basin: Geological Background and Hydrothermal Mineralization, Subseafloor Biosphere Linked to Hydrothermal Systems, 10.1007/978-4-431-54865-2_27, 337-359, 2014.11, [URL], The Okinawa Trough is a back-arc basin behind the Ryukyu trench-arc system and located along the eastern margin of the Eurasian continent. Sulfide and sulfate mineralization associated with hydrothermal activity has been recognized in ten hydrothermal fields in the Okinawa Trough. Hydrothermal mineralization recognized in these fields is commonly represented by coexisting occurrence of zinc- and lead-enriched polymetallic sulfides and abundant sulfate minerals. The mineralogy and geochemical signatures present has led researchers to suggest these areas may be a modern analogue for the formation of ancient Kuroko-type volcanogenic massive sulfide (VMS) deposits. Recent seafloor drilling during IODP (Integrated Ocean Drilling Program) Expedition 331 documented the subseafloor structure of a hydrothermal system at the Iheya North Knoll. Mineral textures and hydrothermal assemblages present in the drilled cores obtained from a hydrothermal mound in the proximal area are consistent with Kuroko-type mineralization. Based on geochemical studies, the intra-field diversity of mineralization commonly recognized in the Okinawa Trough can be explained by subseafloor phase separation of the hydrothermal fluid, which reflects shallow water depth (from 700 to 1,600 m). The subseafloor phase separation may. play an important role to accumulate metal elements beneath the seafloor. Based on geophysical and geological studies, the Okinawa Trough is considered a back-arc basin in the rifting stage. Such a tectonic setting is characterized by development of normal faulting in brittle continental crust and frequent intrusion of a magma, which can be expected to provide favorable environment for development of a hydrothermal system.
91. K. Kitamura, F. Jiang, A. J. Valocchi, S. Chiyonobu, T. Tsuji, K.T. Christensen, The study of heterogeneous two-phase flow around small-scale heterogeneity in porous sandstone by measured elastic wave velocities and lattice Boltzmann method simulation, Journal of Geophysical Research-Solid Earth, doi:10.1002/2014JB011281, 119, 10, 7564-7577, 2014.10, [URL], Two-phase fluid flow is strongly controlled by small-scale (sub-core scale) heterogeneity of porous sandstone. We monitor the heterogeneous/anisotropic two-phase flow (CO2 and water) in porous sandstone and conduct multi-channel Vp and Vp-anisotropy measurements under super critical CO2 conditions during CO2 injection (drainage) and water re-injection (imbibition) processes. In drainage, Vp shows large reduction (~10 %) in all sections of the core sample and changes from the bottom inlet side to upper outlet side. It is considered that Vp reduction reflects the CO2movement in the specimen. The Vp-anisotropy of the upper two planes indicates clear increase. The results of this experiment indicate the heterogeneous CO2-flow around laminae in porous sandstone and characteristic behavior of these laminae as a barrier for CO2. On the other hand, flow of water is not affected by this barrier. This characteristic CO2-water flow around laminae is observed in the numerical simulation results. This simulation study also indicates that the capillary number is not directly affected on two-phase fluid flow around small-scale heterogeneity in porous sandstone. These results suggest that the small-scale heterogeneity behaves as a CO2-gate and strongly controls CO2 behavior in porous sandstone..
92. Takeshi Tsuji, Juichiro Ashi, Yasutaka Ikeda, Strike-slip motion of a mega-splay fault system in the Nankai oblique subduction zone, Earth, Planets and Space, doi:10.1186/1880-5981-66-120, 66, 120, 2014.09, [URL], We evaluated the influence of the trench-parallel component of plate motion on the active fault system within the Nankai accretionary wedge from reflection seismic profiles, high-resolution seafloor bathymetry, and deep-towed sub-bottom profiles. Our study demonstrated that a large portion of the trench-parallel component of oblique plate subduction is released by strike-slip motion along a fault located just landward of and merging down-dip with a mega-splay fault. The shallow portion of the splay fault system, forming a flower structure, seems to accommodate dominant strike-slip motion, while most of the dip-slip motion could propagate to the trenchward décollement. Numerous fractures developed around the strike-slip fault release overpressured pore fluid trapped beneath the mega-splay fault. The well-developed fractures could be related to the change in stress orientation within the accretionary wedge. Therefore, the strike-slip fault located at the boundary between the inner and outer wedges is a key structure controlling the stress state (including pore pressure) within the accretionary prism. In addition, the strike-slip motion contributes to enhancing the continuous mega-splay fault system (outer ridge), which extends for approximately 200 km parallel to the Nankai Trough..
93. Takeshi Tsuji, Rie Kamei, Gerhard Pratt, Pore pressure distribution of a mega-splay fault system in the Nankai Trough subduction zone: Insight into up-dip extent of the seismogenic zone, Earth and Planetary Science Letters, doi:10.1016/j.epsl.2014.04.011, 396, 165-178, 2014.06, [URL].
94. Rie Kamei, R. Gerhard Pratt, Takeshi Tsuji, Misfit functionals in Laplace-Fourier domain waveform inversion, with application to wide-angle ocean bottom seismograph data, Geophysical Prospecting, doi: 10.1111/1365-2478.12127, 62, 5, 1054-1074, 2014.04, In seismic waveform inversion, non-linearity and non-uniqueness require appropriate strategies. We formulate four types of L2 normed misfit functionals for Laplace-Fourier domain waveform inversion: i) subtraction of complex-valued observed data from complex-valued predicted data (the ‘conventional phase-amplitude’ residual), ii) a ‘conventional phase-only’ residual in which amplitude variations are normalized, iii) a ‘logarithmic phase-amplitude’ residual and finally iv) a ‘logarithmic phase-only’ residual in which the only imaginary part of the logarithmic residual is used. We evaluate these misfit functionals by using a wide-angle field Ocean Bottom Seismograph (OBS) data set with a maximum offset of 55 km. The conventional phase-amplitude approach is restricted in illumination and delineates only shallow velocity structures. In contrast, the other three misfit functionals retrieve detailed velocity structures with clear lithological boundaries down to the deeper part of the model. We also test the performance of additional phase-amplitude inversions starting from the logarithmic phase-only inversion result. The resulting velocity updates are prominent only in the high-wavenumber components, sharpening the lithological boundaries. We argue that the discrepancies in the behaviours of the misfit functionals are primarily caused by the sensitivities of the model gradient to strong amplitude variations in the data. As the observed data amplitudes are dominated by the near-offset traces, the conventional phase-amplitude inversion primarily updates the shallow structures as a result. In contrast, the other three misfit functionals eliminate the strong dependence on amplitude variation naturally and enhance the depth of illumination. We further suggest that the phase-only inversions are sufficient to obtain robust and reliable velocity structures and the amplitude information is of secondary importance in constraining subsurface velocity models..
95. Ayumu Miyakawa, Saneatsu Saito, Yasuhiro Yamada, Hitoshi Tomaru, Masataka Kisnoshita, Takeshi Tsuji, Gas hydrate saturation at Site C0002, IODP Expeditions 314 and 315,in the Kumano Basin, Nankai Trough, Island Arc, doi:10.1111/iar.12064, 23, 2, 142-156, 2014.04, The degree of gas hydrate saturation at Integrated Ocean Drilling Program (IODP) Site C0002 in the Kumano Basin, Nankai Trough, was estimated from logging-while-drilling logs and core samples obtained during IODP Expeditions 314 and 315. Sediment porosity data necessary for the calculation of saturation were obtained from both core samples and density logs. Two forms of the Archie equation (‘quick-look’ and ‘standard’) were used to calculate gas hydrate saturation from two types of electrical resistivity log data (ring resistivity and bit resistivity), and a three-phase Biot-type equation was used to calculate gas hydrate saturation from P-wave velocity log data. The gas hydrate saturation baseline calculated from both resistivity logs ranges from 0% to 35%, and that calculated from the P-wave velocity log ranges from 0% to 30%. High levels of gas hydrate saturation (>60%) are present as spikes in the ring resistivity log and correspond to the presence of gas hydrate concentrations within sandy layers. At several depths, saturation values obtained from P-wave velocity data are lower than those obtained from bit resistivity data; this discrepancy is related to the presence of free gas at these depths. Previous research has suggested that gas from deep levels in the Kumano Basin has migrated up-dip towards the southern and seaward edge of the basin near Site C0002. The high saturation values and presence of free gas at site C0002 suggest that a large gas flux is flowing to the southern and seaward edge of the basin from a deeper and/or more landward part of the Kumano Basin, with the southern edge of the Kumano Basin (the location of site C0002) being the main area of fluid accumulation..
96. Mokhamad Yusup Nur Khakim, Takeshi Tsuji, Toshifumi Matsuoka, Lithology-controlled subsidence and seasonal aquifer response in the Bandung basin, Indonesia, observed by synthetic aperture radar interferometry, International Journal of Applied Earth Observation and Geoinformation, doi: 10.1016/j.jag.2014.04.012, 32, 199-207, 2014.04, [URL], Land subsidence in the Bandung basin, West Java, Indonesia, is characterized based on differential interferometric synthetic aperture radar (DInSAR) and interferometric point target analysis (IPTA). We generated interferograms from 21 ascending SAR images over the period 1 January 2007 to 3 March 2011. The estimated subsidence history shows that subsidence continuously increased reaching a cumulative 45 cm during this period, and the linear subsidence rate reached ∼12 cm/yr. This significant subsidence occurred in the industrial and densely populated residential regions of the Bandung basin where large amounts of groundwater are consumed. However, in several areas the subsidence patterns do not correlate with the distribution of groundwater production wells and mapped aquifer degradation. We conclude that groundwater production controls subsidence, but lithology is a counteracting factor for subsidence in the Bandung basin. Moreover, seasonal trends of nonlinear surface deformations are highly related with the variation of rainfall. They indicate that there is elastic expansion (rebound) of aquifer system response to seasonal-natural recharge during rainy season..
97. Kazuya Ishitsuka, Yo Fukushima, Takeshi Tsuji, Yoshihiro Yamada, Toshifumi Matsuoka, Pham Huy Giao, Natural surface rebound of the Bangkok plain and aquifer characterization by persistent scatterer interferometry, Geochemistry, Geophysics, Geosystems, doi: 10.1002/2013GC005154, 15, 4, 965-974, 2014.02, We estimated recent surface displacements around Bangkok by means of persistent scatterer interferometry with ALOS/PALSAR images acquired from November 2007 to December 2010. Land subsidence due to excessive groundwater pumping has been reported in this region. However, we detected ground surface uplift around the mega-city, along with seasonal surface displacement, with high spatial resolution. We then discriminated long-term natural rebound and seasonal displacement by fitting exponential and sinusoidal functions to displacement time-series, and mapped their spatial distributions. This mapping allowed us to infer that the second and third shallowest aquifers are laterally continuous, whereas the shallowest aquifer has lateral discontinuities. The temporal decay rate of the long-term rebound might reflect spatial changes of the Chao Phraya River watershed or the magnitude of the preceding groundwater extraction. We demonstrated that our method of decomposing the displacement time series into different spatial and temporal patterns is useful for understanding aquifer connectivity and the elastic response pattern in an aquifer system..
98. Tatsunori Ikeda, Takeshi Tsuji, Toshifumi Matsuoka, Window-controlled CMP crosscorrelation analysis for surface waves in laterally heterogeneous media, Geophysics, doi: 10.1190/geo2013-0010.1 , 78, 6, EN95-EN105, 2013.11, [URL],
CMP crosscorrelation (CMPCC) analysis of surface waves enhances lateral resolution of surface wave analyses. We found the technique of window-controlled CMPCC analysis, which applies two kinds of spatial windows to further improve the lateral resolution of CMPCC analysis. First, a spatial weighting function given by the number of crosscorrelation pairs is applied to CMPCC gathers. Because the number of crosscorrelation pairs is concentrated near the CMP, the lateral resolution in extracting dispersion curves on CMPs can be improved. Second, crosscorrelation pairs with longer receiver spacing are excluded to further improve lateral resolution. Although removing crosscorrelation pairs generally decreases the accuracy of phase velocity estimations, the required accuracy to estimate phase velocities is maintained by considering the wavenumber resolution defined for given receiver configurations. When applied to a synthetic data set simulating a laterally heterogeneous structure, window-controlled CMPCC analysis improved the retrieval of the lateral variation in local dispersion curves beneath each CMP. We also applied the method to field seismic data across a major fault. The window-controlled CMPCC analysis improved lateral variations of the inverted S-wave velocity structure without degrading the accuracy of S-wave velocity estimations. We discovered that window-controlled CMPCC analysis is effective in improving lateral resolution of dispersion curve estimations with respect to the original CMPCC analysis..
99. Yasuhiro Yamada, Reona Masui, Takeshi Tsuji, Characteristics of a tsunamigenic megasplay fault in the Nankai Trough, Geophysical Research Letters, doi: 10.1002/grl.50888, 40, 17, 4594-4598, 2013.09, [URL], Slip on the shallow part of a megasplay fault that is an out-of-sequence thrust and branch of the main subduction plate boundary can cause devastating tsunamis after earthquakes. We analyzed the three-dimensional geometry, including dip amount and azimuths, roughness distributions, and thickness variations, of the shallow part of a megasplay fault in the Nankai Trough using a three-dimensional seismic data set. The fault is divided into three zones based on its geometry: thick, smooth, and simply convex in the east; complexly curved in the middle; and thin and kinked in the west. Results of scientific drilling indicate that the eastern region of the fault is most active, and local heterogeneities in fault geometry, including roughness and thickness, may control the slip on this part of the fault. The present findings can be used to evaluate the risk of future tsunamis arising from movement on shallow thrust faults at subduction margins..
100. Shun Chiyonobu, Nakajima Takahiro, Yi Zhang, Takeshi Tsuji, Zique Xue, Effect of reservoir heterogeneity of Haizume Formation, Nagaoka Pilot Site, based on high-resolution sedimentological analysis, Energy Procedia, doi:10.1016/j.egypro.2013.06.247, 37, 3546-3553, 2013.08, The Nagaoka pilot site is located in the onshore area of Nagaoka oil field in the Niigata plane of central Honshu on the Japan sea side of central Japan. The selected formation was the early Pleistocene Haizume Formation. This paper presents the realistic modeling strategy that was applied to Nagaoka site. The CO2 reservoir zone in this site was described in terms of three depositional elements and eleven lithofacies. These descriptions were incorporated into the model at a resolution, with a cell size of 10 cm high, which ensured capture of the most significant heterogeneities. The detailed reservoir model matched well log and core performance in this site..
101. Keir Becker, Andrew T. Fisher, Takeshi Tsuji, New Packer Experiments and Borehole Logs in Upper Oceanic Crust: Evidence for Ridge-parallel Continuity in Crustal Hydrogeological Properties, Geochemistory, Geophysics, Geosystems, doi:10.1002/ggge.20201, 14, 8, 2900-2915, 2013.08, [URL], [1] We report new drillstring packer permeability tests conducted during Integrated Ocean Drilling Program (IODP) Expedition 327 in upper oceanic basement in Hole U1362A on the eastern flank of the Juan de Fuca Ridge. Hole U1362A lies within a closely spaced array (40–2460 m separation) of six holes in well-sedimented 3.5–3.6 m.y. old crust that were drilled, tested, and instrumented with borehole observatories during Ocean Drilling Program Leg 168 and IODP Expeditions 301 and 327. The permeability tests in Hole U1362A complement similar experiments previously conducted in nearby Holes 1026B, 1027C, and U1301B. The new results suggest consistency of upper crustal permeability between Holes U1362A and U1301B, which penetrate 290 and 320 m of basement and are separated by ∼825 m. We obtain similar bulk permeability values of 1–3 × 10−12 m2 for the sections deeper than ∼150 m into basement in both holes. These values are significantly higher than results of packer experiments in the shallowest few tens of meters of basement in nearby Holes 1026B and 1027C, suggesting that the highest basement permeabilities in this area are not found in the shallowest basement layers. Downhole logs of density and penetration rate during drilling and coring in Holes U1362A and U1301B show similar trends within the upper crust, reinforcing the inference that there may be considerable lateral continuity in hydrogeologic properties. This continuity may be associated with the fundamental lithostratigraphy of the crust and/or influenced by ridge-parallel faulting and fracturing associated with the formation of abyssal hill topography..
102. Yoshitaka Hashimoto, Noriaki Doi, Takeshi Tsuji, Difference in acoustic properties at seismogenic fault along a subduction interface: Application to estimation of effective pressure and fluid pressure ratio, Tectonophysics,, doi:10.1016/j.tecto.2013.03.016, 600, 17, 134-141, 2013.07, Fluid pressure along subduction plate boundaries plays a role in seismogenesis and tsunami genesis because it is strongly related to the physical properties of faults. In this study, we conducted P-wave velocity (Vp) and S-wave velocity (Vs) measurements for the hanging wall and footwall of a fossil subduction interface with pseudotachylyte located at the northern edge of the Mugi mélange in the Cretaceous Shimanto Belt, Shikoku, southwest Japan. This area corresponds to the depth of the shallow seismogenic zone in the transition zone between the inner and outer wedges. By combining the acoustic properties with parameters obtained from Amplitude Variation with Offset (AVO) analysis on the Nankai seismic profile, we estimated the fluid pressure at the seismogenic fault.

The Mugi mélanges are composed of shale matrices and are juxtaposed with the coherent unit of the Hiwasa formation in the north, which is composed mainly of sandstone. We collected 5 sandstone samples from the hanging wall (Hiwasa formation) and 4 mudstone samples from the footwall (Mugi mélange). We conducted velocity measurements while controlling both the fluid pressure and confining pressure by using two pumps. The effective pressure in each measurement ranged from 5 to 65 MPa with intervals of 5 MPa.

The Vp and Vs of sandstone increase exponentially with effective pressure from ~ 4500 to ~ 5000 m/s and ~ 2500 to ~ 3000 m/s, respectively. The Vp and Vs of the mudstone also increased exponentially from ~ 4100 to ~ 4500 m/s and ~ 1900 to ~ 2200 m/s, respectively.

We used AVO parameters along the décollement based upon a seismic profile of the Nankai trough, which is off Muroto 40–45 km landward from the trench axis, corresponding to approximately 66 MPa of effective pressure under a hydrostatic condition. By combining the velocities obtained from this study and the AVO parameters derived from the Muroto seismic data, we estimate the mean effective pressures for the hanging wall and the footwall as approximately 10–20 MPa and 8–10 MPa, respectively. The normalized fluid pressure ratios for the hanging wall and the footwall correspond to approximately 0.82–0.91 and 0.91–0.93, respectively. This high fluid pressure indicates a very low effective friction coefficient along the décollement in the transition zone, possibly causing a rupture to propagate to the shallower outer wedge and thus generating a large tsunami.
103. Khakim, M.Y.N., Tsuji, T., Matsuoka, T., Detection of Localized Surface Uplift by Differential SAR Interferometry at the Hangingstone Oil Sand Field, Alberta, Canada, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, doi:10.1109/JSTARS.2013.2254471, 6, 6, 2344-2354, 2013.06, We estimated the surface uplift (heave) rate due to steam-assisted gravity drainage (SAGD) at the Hangingstone oil sand field in Alberta, Canada, by stacking differential synthetic aperture radar (SAR) interferograms. To improve accuracy, a Landsat-7 Enhanced Thematic Mapper Plus intensity image was coregistered with the SAR intensity image. We examined three interferogram filtering methods and identified one that provided the desired effect of light filtering in areas of low noise and heavier filtering in high-noise areas. Based on our analysis of interferogram coherences, site-specific decorrelation highly depends on local seasonal changes. Stacking was performed to estimate the surface uplift rate while removing atmospheric and seasonal effects. The amounts of the uplift rate and slope change estimated by means of InSAR analysis reached a maximum of 3.6 cm/yr and 0.003%, respectively, for the period of 2007-2008. Comparison of the magnitude and patterns of the estimated surface uplift demonstrated that the uplift estimated from InSAR analysis agrees well with that obtained by conventional geodetic (GPS) surveys from a network of 54 monuments. Surface slope changes due to SAGD that we detected by using InSAR over one year in this oil sand field were small, so destruction of surface facilities by uplift is unlikely in the short term..
104. Shohei Minato, Toshifumi Matsuoka, Takeshi Tsuji, Singular-value decomposition analysis of source illumination in seismic interferometry by multidimensional deconvolution, Geophysics, doi: 10.1190/geo2012-0245.1, 78, Q25-Q34, 2013.05.
105. Takeshi Tsuji, Shuichi Kodaira, Juichiro Ashi, Jin-Oh Parkc, Widely distributed thrust and strike-slip faults within subducting oceanic crust in the Nankai Trough off the Kii Peninsula, Japan, Tectonophysics, doi:10.1016/j.tecto.2013.03.0142, 600, 17, 52-62, 2013.05, [URL], We identified widely distributed thrust and strike-slip faults within subducting oceanic crust in the Nankai Trough, southeast of the Kii Peninsula, Japan, on the basis of 2D and 3D seismic reflection data. The seafloor seaward of the trough axis is deformed by displacement on these intraoceanic reverse faults, producing topographic highs (part of Kashinosaki Knoll). Because the thrust faults extend to the Moho and offset the Moho reflection, they may be related to serpentinization of the mantle due to seawater invasion. These faults are seismically active, given that their geometries are consistent with the focal mechanisms of intraplate earthquakes and microearthquakes. The thrust faults appear to extend landward to a high-density dome within the accretionary prism off the Kii Peninsula. Because the dome and the associated thick accretionary prism are expected to generate high friction at the plate interface due to their large vertical load, the intraoceanic thrusts are likely to have grown with ongoing subduction. Furthermore, because the geometry of the fault system we identified off the Kii Peninsula has characteristics similar to faults at Zenisu Ridge east of our study area, the thrusts observed in the study area may be considered to be the westward continuation of those at Zenisu Ridge. Since the Euler rotation pole of relative motion between the Philippine Sea plate and Zenisu Ridge is consistent with the high-density dome off the Kii Peninsula, we interpret the high-density dome as well as Kashinosaki Knoll as a westward termination of the Zenisu compression zone..
106. Rie Kamei, R. Gerhard Pratt, Takeshi Tsuji, On acoustic waveform tomography of wide-angle OBS data - Strategies for preconditioning and inversion, Geophysical Journal International,, doi: 10.1093/gji/ggt165 , 194, 2, 1250-1280, 2013.04, We successfully apply the acoustic Laplace–Fourier waveform tomography method to delineate P-wave velocity structures of the mega-splay fault system in the central part of the seismogenic Nankai subduction zone offshore Japan, using densely sampled wide-angle ocean bottom seismograph (OBS) data originally acquired in 2004. Our success is due to new and carefully designed data preconditioning and inversion strategies to mitigate (i) the well-known non-linearity of waveform inversion, (ii) the challenges arising from crustal-scale survey designs (e.g. undersampling of the OBSs), and (iii) modelling errors due to the use of the acoustic assumption.

We identify a sixfold set of key components that together lead to the success of the high-resolution waveform tomography image: (i) Availability of low-frequency components (starting at 2.25 Hz) reducing the non-linearity, and access to large offset data (up to 55 km) increasing the depth of illumination and the recovery of low wavenumber components. (ii) A highly accurate traveltime tomography result (with an rms error of approximately 60 ms) that further mitigates the non-linearity. (iii) A hierarchical inversion approach in which phase spectra are inverted first to reduce artefacts from the acoustic assumption, and amplitude information is only incorporated in the final stages. (iv) A Laplace–Fourier domain approach that facilitates a multiscale approach to mitigate non-linearity by restricting the inversion to the low frequency components and early arrivals first, and sequentially including higher frequencies and later arrivals. (v) A pre-conditioning strategy for eliminating undesirable high wavenumber components from the the gradient. (vi) A strategy for source estimation that reduce the influence of the instrumental design.

In the OBS case study used for illustration purposes, Laplace–Fourier waveform tomography retrieves velocity anomalies as small as 700 m (horizontally) and 350 m (vertically) above the top of the Philippine Sea Plate. The resulting velocity structures include low-velocity zones and thrust structures which have not been previously identified clearly. The velocity models are validated by scrutiny of synthetic and observed waveforms, by evaluating the coherency of source estimates, and by comparison with 3-D pre-stack migrated (PreSDM) images. Chequerboard tests and point-scatter tests demonstrate both the reliability and the limitations of the acoustic implementation.
107. Takeshi Tsuji, Kiichiro Kawamura, Toshiya Kanamatsu, Takafumi Kasaya, Katsunori Fujikura, Yoshihiro Ito, Tetsuro Tsuru, Masataka Kinoshita, Extension of continental crust by anelastic deformation during the 2011 Tohoku-oki earthquake: The role of extensional faulting in the generation of a great tsunami, Earth and Planetary Science Letters, doi:10.1016/j.epsl.2012.12.038, 364, 15, 44-58, 2013.03, [URL], Observations of seafloor morphologies and environments made before and after the 2011 Tohoku-oki earthquake reveal open fissures, generated during the earthquake, where the fault trace is interpreted on seismic profiles to intersect the seafloor. Anomalously high heat flow was observed at a landward-dipping normal fault in August 2011, five months after the earthquake, but by August 2012 heat flow measured at the same station had decreased to close to the background value, which suggests that the normal fault ruptured during the 2011 earthquake. These seafloor observations and measurements demonstrate deformation that was both extensional and anelastic within the overriding continental plate during the 2011 earthquake. Seismic profiles as well as seafloor bathymetry data in the tsunami source area further demonstrate that landward-dipping normal faults (extensional faults) collapse the continental framework and detach the seaward frontal crust from the landward crust at far landward from the trench. The extensional and anelastic deformation (i.e., normal faulting) observed in both seafloor observations and seismic profiles allows the smooth seaward movement of the continental crust. Seaward extension of the continental crust close to the trench axis in response to normal faulting is a characteristic structure of tsunami source areas, as similar landward-dipping normal faults have been observed at other convergent plate margins where tsunamigenic earthquakes have occurred. We propose that the existence of a normal fault that moves the continental crust close to the trench can be considered one indicator of a source area for a huge tsunami..
108. Yoshihiro Ito, Ryota Hino, Motoyuki Kido, Hiromi Fujimoto, Yukihito Osada, Daisuke Inazu, Yusaku Ohta, Takeshi Iinuma, Mako Ohzono, Satoshi Miura, Masaaki Mishina, Kensuke Suzuki, Takeshi Tsuji, Juichiro Ashi, Episodic slow slip events in the Japan subduction zone before the 2011 Tohoku-Oki earthquake, Tectonophysics, doi: 10.1016/j.tecto.2012.08.022, 600, 17, 14-26, 2012.11, [URL], We describe two transient slow slip events that occurred before the 2011 Tohoku-Oki earthquake. The first transient crustal deformation, which occurred over a period of a week in November 2008, was recorded simultaneously using ocean-bottom pressure gauges and an on-shore volumetric strainmeter; this deformation has been interpreted as being an M6.8 episodic slow slip event. The second had a duration exceeding 1 month and was observed in February 2011, just before the 2011 Tohoku-Oki earthquake; the moment magnitude of this event reached 7.0. The two events preceded interplate earthquakes of magnitudes M6.1 (December 2008) and M7.3 (March 9, 2011), respectively; the latter is the largest foreshock of the 2011 Tohoku-Oki earthquake. Our findings indicate that these slow slip events induced increases in shear stress, which in turn triggered the interplate earthquakes. The slow slip event source area on the fault is also located within the downdip portion of the huge-coseismic-slip area of the 2011 earthquake. This demonstrates episodic slow slip and seismic behavior occurring on the same portions of the megathrust fault, suggesting that the faults undergo slip in slow slip events can also rupture seismically..
109. Kazuya Ishitsuka, Takeshi Tsuji, Toshifumi Matsuoka, Detection and mapping of soil liquefaction associated with the 2011 Tohoku earthquake using SAR Interferometry
, Earth, Planets and Space, 64, 1267-1276, 2012.11, [URL], We identified areas of soil liquefaction by analysis of surface changes caused by the 2011 Tohoku earthquake, using synthetic aperture radar (SAR) interferometry in the Kanto region of Japan. Changes in surface scattering properties were evaluated using phase-corrected coherence, computed from the reflective intensity (amplitude) of SAR data. Often, loss of coherence (decorrelation) is simply considered to represent areas damaged from the disaster. However, temporal decorrelation part could be also induced by ordinal surface cover change in addition to disaster damage. Therefore, we use a coherence change threshold to discriminate significant decorrelation caused by soil liquefaction from that produced by ordinal surface cover changes. Moreover, local surface displacements are estimated using phase information from the SAR data. Our results compare favorably with those from surveys of sand boils and aerial photography, showing that surface changes derived from SAR data are associated with soil liquefaction. Our results demonstrate that soil liquefaction occurred mainly near the waterfront along Tokyo Bay and the Tone River, and ground subsidence was widely distributed..
110. M. Yusup Nur Khakim, Takeshi Tsuji, Toshifumi Matsuoka, Geomechanical Modeling for InSAR-derived surface deformation at steam-injection oil sand fields, Journal of Petroleum Science and Engineering, doi:10.1016/j.petrol.2012.08.003, 96-97, 152-161, 2012.10, [URL], To estimate the distribution of reservoir deformation and reservoir volume change in an oil sand reservoir undergoing steam injection, we applied geomechanical inversion to surface uplift data derived from a differential interferometric synthetic-aperture radar (InSAR) stacking technique. We tested a two-step inversion method based on a tensional rectangular dislocation model. The first step of the inversion used genetic algorithms to estimate the depth of the reservoir and roughly model its deformation. The estimated depth of the reservoir was consistent with the depth of the injection point. The second step used a least-squares inversion with a penalty function and smoothing factor to efficiently invert the distribution of reservoir deformation and volume change from the surface uplift data. The distribution of reservoir deformation can be accurately estimated from InSAR-derived ground surface deformations using our proposed inversion techniques..
111. Tatsunori Ikeda, Toshifumi Matsuoka, Takeshi Tsuji, Koichi Hayashi, Multimode inversion with amplitude response of surface waves in the spatial autocorrelation method, Geophysical Journal International, DOI: 10.1111/j.1365-246X.2012.05496.x, 190, 1, 541-552, 2012.06, [URL], Microtremors are usually analysed without any consideration of the higher modes of surface waves. However, recent studies have demonstrated that higher modes contain useful information for improving the inverted S-wave velocity model. In this study, we propose two inversion methods that consider higher modes by using the amplitude response of each mode, which can avoid mode misidentification in the spatial autocorrelation (SPAC) method. One method is to compare the observed phase velocities by the extended spatial autocorrelation (ESPAC) method with the effective phase velocities calculated from theoretical dispersion curves and the amplitude responses of each mode. In the other method, SPAC coefficients are fit directly by comparing theoretical SPAC coefficients determined from dispersion curves and amplitude responses with the observed ones. The latter, direct-fitting approach is much simpler than the method using effective phase velocities. To investigate the effectiveness of these methods, a simulation study was conducted. Simulated microtremors that included higher modes were successfully inverted by the proposed multimode methods. The observed phase velocities and SPAC coefficients determined from field data were also consistent with theoretical ones constructed by the proposed methods except at low frequencies. The inversion using effective phase velocities required prior information about an infinite half-space to obtain a better S-wave velocity model whereas the direct-fitting inversion worked well without prior information, suggesting the direct-fitting method is more robust than the method using effective phase velocities. We conclude that our proposed inversion methods are effective for estimating the S-wave velocity structure even if higher modes of surface waves are predominant in observed microtremors..
112. Shohei Minato, Takeshi Tsuji, Toshifumi Matsuoka, Koichiro Obana, Crosscorrelation of earthquake data using stationary phase evaluation: Insight into reflection structures of oceanic crust surface in the Nankai Trough, International Journal of Geophysics, doi:10.1155/2012/101545, 2012, 8 pages, Article ID 101545, 2012.06, [URL], Seismic interferometry (SI) has been recently employed to retrieve the reflection response from natural earthquakes. We perform experimental study to apply SI to Ocean Bottom Seismogram (OBS) records in the Nankai Trough, southwest Japan in order to reveal the relatively shallow geological boundaries including surface of oceanic crust. Although the local earthquakes with short raypath we use to retrieve reflection response are expected to contain the higher-frequency components to detect fine-scale structures by SI, they cannot be assumed as plane waves and are inhomogeneously distributed. Since the condition of inhomogeneous source distribution violates the assumption of SI, the conventional processing yields to the deteriorated subsurface images. Here we adopt the raypath calculation for stationary phase evaluation of SI in order to overcome this problem. To find stationary phase, we estimate the raypaths of two reflections: (1) sea-surface P-wave reflection and (2) sea-surface multiple P-wave reflection. From the estimated raypath, we choose the crosscorrelation traces which are expected to produce objective reflections considering the stationary phase points. We use the numerical-modeling data and field data with 6 localized earthquakes and show that choosing the crosscorrelation traces by stationary phase evaluation improves the quality of the reflections of the oceanic crust surface..
113. Gaku Kimura, Shoko Hina, Yohei Hamada, Jun Kameda, Takeshi Tsuji, Masataka Kinoshita, Asuka Yamaguchi, Runaway slip to the trench due to rupture of highly pressurized megathrust beneath the middle trench slope: The tsunamigenesis of the 2011 Tohoku earthquake off the east coast of northern Japan, Earth and Planetary Science Letters, DOI: 10.1016/j.epsl.2012.04.002, 339-340, 32-45, 2012.06, [URL], The gigantic 2011, March 11 Mw 9 Tohoku earthquake is examined from the viewpoint of the pre-seismic forearc structure, the seismic reflection properties of a megathrust around the usual up-dip limit of the seismogenic zone, the thermal state of a shallow subduction zone, and the dehydration of underthrust sediments.

At the Japan Trench the Pacific Plate is subducting westward beneath northeast Japan at a dip angle of 4.6°. The middle and lower slopes of the landward side dip eastward at angles of ∼2.5° and ∼8.0°, respectively. The forearc prism beneath the middle and lower slopes is inferred to be in extensionally and compressively critical states, respectively, based on the presence of clear internal deformation features and on the occurrence of aftershock earthquakes. The rapid uplift of the forearc that caused the 2011 Tohoku tsunami may have been associated with this internal deformation of the prism. The critical state of the prism indicates that the effective basal friction (μb′) of the plate boundary megathrust is <0.03 for the middle prism and >0.08 for the lower prism.

The megathrust, especially under the middle slope, is characterized by a prominent reflector with negative polarity. One of multiple possible explanations is that the megathrust hosts highly pressurized fluids. Underthrust sediments in this part of the Japan Trench are dominated by pelagic and siliceous vitric diatomaceous silt with clay. The dehydration kinetics of opal-A to quartz, the clay transformation of smectite–illite, and the thermal structure of the Japan Trench suggest that maximum dehydration of the sediments would take place at 50–60 km horizontally from the deformation front, where the temperature along the megathrust is 100–120 °C. The zone of maximum dehydration coincides with the prominent seismic reflector that has negative polarity. We hypothesize a possible free slip along this portion of the megathrust during the 2011 Tohoku earthquake, caused by anomalously high fluid pressure resulting from fluid accumulation over centuries..
114. Shohei Minato, Takeshi Tsuji, Shiro Ohmi, Toshifumi Matsuoka, Monitoring seismic velocity change caused by the 2011 Tohoku-oki earthquake using ambient noise records, Geophysical Research Letters, doi:10.1029/2012GL051405, 39, L09309, 6, 2012.05, [URL], We estimated the changes in seismic velocity in the southern Tohoku district of Japan during the six-month period centered on the 11 March 2011 Tohoku-oki earthquake, using scattered waves retrieved by autocorrelation of ambient seismic noise. The estimated velocity decrease after the earthquake, and after two large aftershocks in the study area, was as great as 1.5\% in the area nearest to the mainshock. The velocity changes displayed gradual healing. The spatial distribution of the velocity change showed a correlation with both the changes in static strain, derived from GPS records, and the peak particle velocity experienced during the three earthquakes, derived from strong-motion records. Therefore, our results show that velocity changes possibly contain information from deep in the crust bearing on coseismic stress release, in addition to shallower effects due to strong ground motion..
115. Norimitsu Nakata, Roel Snieder, Takeshi Tsuji, Ken Larner, Toshifumi Matsuoka, Shear-wave imaging from traffic noise using seismic interferometry by cross-coherence, GEOPHYSICS, doi:10.1190/GEO2010-0188.1, 76, 6, SA97–SA106, 2012.04, [URL], We apply seismic interferometry to traffic noise to retrieve both body waves and surface waves. Our preferred algorithm in the presence of highly variable and strong additive random noise uses cross‐coherence, which uses normalization by the spectral amplitude of each of the traces, rather than cross‐correlation or deconvolution. This normalization suppresses the influence of additive noise and overcomes problems resulting from amplitude variations among input traces. By using only the phase information and ignoring amplitude information, the method effectively removes the source signature from the extracted response and yields a stable structural reconstruction even in the presence of strong noise. This algorithm is particularly effective where the relative amplitude among the original traces is highly variable from trace to trace. We use the extracted reflected shear waves from the traffic noise data to construct a stacked and migrated image, and use the extracted surface waves (Love waves) to estimate the shear velocity as a function of depth. This shear‐velocity profile agrees well with the interval velocity obtained from normal moveout of reflected shear waves constructed by seismic interferometry. These results are useful for a wide range of situations applicable in both geophysics and civil engineering..
116. Takeshi Tsuji, Tor Arne Johansen, Bent Ole Ruud, Tatsunori Ikeda, Toshifumi Matsuoka, Surface-wave analysis for identifying unfrozen zones in subglacial sediments, GEOPHYSICS, doi:10.1190/GEO2011-0222.1, 77, 3, EN17–EN27, 2012.04, [URL], To reveal the extent of freezing in subglacial sediments, we estimated S-wave velocity along a glacier using surface-wave analysis. Because the S-wave velocity varies significantly with the degree of freezing of the pore fluid in the sediments, this information is useful for identifying unfrozen zones within subglacial sediments, which again is important for glacier dynamics. We used active-source multichannel seismic data originally acquired for reflection analysis along a glacier at Spitsbergen in the Norwegian Arctic and proposed an effective approach of multichannel analysis of surface waves (MASW) in a glacier environment. Common-midpoint crosscorrelation gathers were used for the MASW to improve lateral resolution because the glacier bed has a rough topology. We used multimode analysis with a genetic algorithm inversion to estimate the S-wave velocity due to the potential existence of a low-velocity layer beneath the glacier ice and the observation of higher modes in the dispersion curves. In the inversion, we included information of ice thickness derived from high-resolution ground-penetrating radar data because a simulation study demonstrated that the ice thickness was necessary to estimate accurate S-wave velocity distribution of deep subglacial sediment. The estimated S-wave velocity distribution along the seismic line indicated that low velocities occurred below the glacier, especially beneath thick ice (~1300 m/s for ice thicknesses larger than 50 m). Because this velocity was much lower than the velocity in pure ice (~1800 m/s), the pore fluid was partially melted at the ice–sediment interface. At the shallower subglacial sediments (ice thickness less than 50 m), the S-wave velocity was similar to that of the pure ice, suggesting that shallow subglacial sediments are more frozen than sediments beneath thick ice..
117. Andrew T. Fisher, Takeshi Tsuji, Katerina Petronotis, C. Geoff Wheat, Keir Becker, Jordan F. Clark, James Cowen, Katrina Edwards, Hans Jannasch, the IODP Expedition 327 and Atlantis Expedition AT18-07 Shipboard Parties, IODP Expedition 327 and Atlantis Expedition AT 18-07: Observatories and Experiments on the Eastern Flank of the Juan de Fuca Ridge, Scientific Drilling, doi:10.2204/, 13, 4-11, ISSN: 1816-8957, 2012.04, [URL], Integrated Ocean Drilling Program (IODP) Expedition 327 (summer 2010) was designed to resolve the nature of fluid-rock interactions in young, upper volcanic crust on the eastern flank of the Juan de Fuca Ridge. Expedition 327 drilled, cased and cored two new basement holes, conducted hydrogeologic experiments, and installed subseafloor borehole observatories (Circulation Obviation Retrofit Kits, CORKs). These CORKs were intended to allow borehole conditions to recover to a more natural state after the dissipation of disturbances caused by drilling, casing, and other operations; provide a long-term monitoring and sampling presence for determining fluid pressure, temperature, composition, and microbiology; and facilitate the completion of active experiments to resolve crustal hydrogeologic conditions and processes. Expedition 327 was followed (summer 2011) by R/V Atlantis Expedition AT18-07, with the remotely-operated vehicle (ROV) Jason, to service these CORKs, collect subseafloor pressure data, recover and deploy autonomous fluid and microbial samplers, collect large volumes of borehole fluids, and initiate a cross-hole hydrogeologic experiment using an electromagnetic flow meter. In addition, Atlantis Expedition AT18-07 refurbished an old CORK that could not be replaced during IODP Expedition 327, completing a critical part of the three-dimensional observation network that is currently being used to monitor a large-scale, directional formation response to long-term fluid flow from the crust..
118. Shohei Minato, Takeshi Tsuji, Toshifumi Matsuoka, Naoki Nishizaka, Michiharu Ikeda, Global optimization by simulated annealing for common reflection surface stacking, and its application to low-fold marine data in southwest Japan, Exploration Geophysics,, 43, 2, 59-69, 2012.03, [URL], The common reflection surface (CRS) stack is an alternative method of producing a zero-offset stacked section with a higher signal-to-noise ratio (SNR) than the conventional normal moveout (NMO)/dip moveout (DMO) stack method. Since, however, it is difficult to determine global optimal parameters for the CRS stack method by the conventional three-step search method, especially for complex structures and low-fold data, we investigate the ability of simulated annealing (SA) to optimise our estimation of these parameters. We show a detailed but practical procedure for the application of SA to the CRS stack method. We applied the CRS stack method with SA to numerically modelled seismic reflection data, and to multichannel marine seismic data over complicated geological structures around the Median Tectonic Line (MTL) in Japan. We used the results of the conventional three-step search algorithm as the initial model for the SA search and showed that with this approach SA can estimate CRS parameters accurately within a reasonable number of calculations. The CRS stack method with this approach provided a clearer seismic profile with a higher SNR than either a conventional NMO stack method or a conventional CRS stack method..
119. Takeshi Tsuji, Ken Takai, Hisashi Oiwane, Yasuyuki Nakamura, Yuka Masaki, Hidenori Kumagai, Masataka Kinoshita, Fujio Yamamoto, Tadashi Okano, Shin'ichi Kuramoto, Hydrothermal fluid flow system around the Iheya North Knoll in the mid-Okinawa Trough based on seismic reflection data, Journal of Volcanology and Geothermal Research, doi:10.1016/j.jvolgeores.2011.11.007, 213-214, 41-50, 2012.02, [URL], Seismic reflection data around the Iheya North Knoll hydrothermal field provide insights into geological structures that control subseafloor hydrothermal fluid flow in the sediment-covered continental backarc basin of the mid-Okinawa Trough. We identified the seismic expression of widespread porous volcaniclastic pumiceous deposits and intrusions as a result of silicic arc volcanism. The porous and permeable volcanic deposits are distributed in an area extending updip from the thick succession of the deep trough to the seafloor at the hydrothermal field. Their regional structure focuses the flow of hydrothermal fluids derived from the surrounding trough-fill sediments and directs them to the vents of the hydrothermal field. The high concentrations of CH4 and NH4 in the fluids of the hydrothermal field are likely derived from the interaction of migrating fluids with trough-fill sediments..
120. Rie Kamei, R. Gerhard Pratt, Takeshi Tsuji, Waveform Tomography Imaging of a Megasplay Fault System in the Seismogenic Nankai Subduction Zone, Earth and Planetary Science Letters, doi:10.1016/j.epsl.2011.10.042, 317-318, 1, 343-353, 2012.01, [URL], We apply Frequency-domain Waveform Tomography to form quantitative, high-resolution P-wave velocity images of a megasplay fault system within the central Nankai subduction zone offshore of southwest Japan, using controlled source Ocean Bottom Seismometer (OBS) data originally acquired in 2004. The Waveform Tomography method exploits recorded seismic waveforms beyond their first arrivals, and thus achieves a much higher resolution (of the order of a wavelength) than that of conventional Traveltime Tomography methods. Frequency-domain Waveform Tomography facilitates a multi-scale approach to stabilize the inversion, in which initial Traveltime Tomography results are sequentially improved on by first fitting low frequency components of the seismic records (starting at 2.25 Hz); higher frequency components (up to 8.5 Hz) are then introduced progressively.

Our final Waveform Tomography image allows velocity anomalies as small as 700 m (horizontally) and 350 m (vertically) to be discerned and interpreted, as confirmed by checkerboard modeling tests. The improved explanatory power of the final images is verified by observing that synthetic waveforms calculated from the final results yield much better fit to the observed waveforms than those estimated from the original Traveltime Tomography image. Apparent lithological boundaries from Waveform Tomography agree well with corresponding reflections on seismic migration images, providing further confidence in the validity of the results.

The megasplay fault is evident on the final Waveform Tomography image as a sharp velocity discontinuity, delineating the upper surface of a velocity reduction of nearly 1 km/s with respect to the regional 1D velocity trend. The megasplay fault can be traced continuously throughout the entire image, from a nearly horizontal section at the landward extent, moving seaward through to a steeper angle penetrating the old accretionary prisms, with several additional splays appearing to branch in the shallow subsurface. The location of the low-velocity zones imaged by our waveform tomography method coincides with two-previously-identified low velocity zones. The image reveals a low velocity zone that is continuous from deeper to shallower portions of the subsurface, suggesting that pore-fluids may be transported from the inner wedge, to the transition zone, and to the surface, through fluid conduits associated with the megasplay fault system..
121. Takeshi Tsuji, Ryota Hino, Yoshinori Sanada, Kiyohiko Yamamoto, Jin-Oh Park, Tetsuo No, Eiichiro Araki, Nathan Bangs, Roland von Huene, Gregory Moore, Masataka Kinoshita, In situ stress state from walkaround VSP anisotropy in the Kumano basin southeast of the Kii Peninsula, Japan, GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, doi:10.1029/2011GC003583, 12, Q0AD19, 2011.09, [URL], To reveal the stress state within the Kumano basin, which overlies the Nankai accretionary prism, we estimated seismic anisotropy from walkaround vertical seismic profiling (VSP) data recorded at Site C0009 during Integrated Ocean Drilling Program (IODP) Expedition 319. We obtained the following anisotropic parameters: (1) P wave velocity anisotropy derived from azimuthal normal moveout (NMO) velocity analysis, (2) P wave amplitude variation with azimuth, and (3) axes of symmetry of S wave splitting. Azimuthal variations of P wave velocity by ellipsoidal fitting analysis showed that P wave velocity anisotropy within sediments of the Kumano basin was ∼5%. Both the directions of fast P wave velocity and strong amplitude are aligned with the convergence vector of the Philippine Sea plate. Furthermore, S wave splitting analysis indicated that S wave polarization axes were parallel to and normal to the direction of plate subduction. These results indicate that the maximum horizontal stress at Site C0009 in the Kumano basin is in the direction of plate subduction. The horizontal differential stress estimated from the P wave velocity anisotropy (2.7∼5.5 MPa) indicates that the maximum horizontal stress is similar in magnitude to (or a little higher than) the vertical stress. .
122. Yoshihiro Ito, Takeshi Tsuji, Yukihito Osada, Motoyuki Kido, Daisuke Inazu, Yutaka Hayashi, Hiroaki Tsushima, Ryota Hino, Hiromi Fujimoto, Frontal wedge deformation near the source region of the 2011 Tohoku-Oki earthquake, Geophysical Research Letters, doi:10.1029/2011GL048355, 38, L00G05, 2011.08, [URL], We report an uplift of 5 m with a horizontal displacement of more than 60 m due to the 2011 Tohoku-Oki earthquake. The uplift was measured by an ocean-bottom pressure gauge installed before the earthquake on a frontal wedge, which formed an uplift system near the Japan Trench. Horizontal displacements of the frontal wedge were measured using local benchmark displacements obtained by acoustic ranging before and after the earthquake. The average displacements at the frontal wedge were 58 m east and 74 m east-southeast. These results strongly suggest a huge coseismic slip beneath the frontal wedge on the plate boundary. The estimated magnitude of the slip along the main fault was 80 m near the trench. Our results suggest that the horizontal and vertical deformations of the frontal wedge due to the slip generated the tremendous tsunami that struck the coastal area of northeastern Japan. .
123. Takeshi Tsuji, Jack Dvorkin, Gary Mavko, Norimitsu Nakata, Toshifumi Matsuoka, Ayako Nakanishi, Shuichi Kodaira, Osamu Nishizawa, Vp/Vs ratio and shear-wave splitting in the Nankai Trough seismogenic zone: Insights into effective stress, pore pressure and sediment consolidation, GEOPHYSICS, doi:10.1190/1.3560018, 76, 3, WA71-WA82, 2011.05, [URL], To estimate variation of stress state and sediment consolidation in the Nankai plate subduction zone off southwest Japan, we measured the P-wave to S-wave velocity ratio (VP/VS) and S-wave splitting along the seismic line extending from the trench to the seismogenic zone. For this purpose, we used active-source seismic data recorded by multicomponent ocean bottom seismometers (OBS). Because it is difficult to identify the PS-converted reflection waveforms for each of the geological boundaries in this deep offshore region, we focused on the more easily identified PPS-refracted waveforms that register the conversion of the up-going P-waves to S-waves at the igneous crust surface. We estimated the average VP/VS ratio within the sedimentary section by using the time lag between the P-refracted waves and PPS-converted waves. This VP/VS ratio changes abruptly at the trough axis (i.e., the deformation front of the accretionary prism) arguably because of compaction associated with the accretion process. We observed relatively high VP/VS around the seismogenic megasplay fault, which may partially indicate the abnormal pore pressure and intensive fractures associated with the fault. To estimate the stress-induced fracture orientation and stress magnitude, we computed the fast S-wave polarization direction and estimated S-wave velocity anisotropy by applying the crosscorrelation method to the PPS-converted waves. To improve signal-to-noise ratio of the waveform for S-wave splitting analysis, we stacked PPS-converted waveforms on receiver gather. These anisotropic characteristics change at the seismogenic megasplay fault: the fast polarization direction is nearly parallel to the subduction direction seaward of the megasplay fault and is perpendicular to the subduction direction landward of the megasplay fault. This velocity anisotropy is especially strong around the megasplay fault. These results imply that the preferred fracture orientation, as well as the principal stress orientation, is oblique to the direction of plate subduction near the megasplay fault..
124. Takeshi Tsuji, Yoshihiro Ito, Motoyuki Kido, Yukihito Osada, Hiromi Fujimoto, Juichiro Ashi, Masataka Kinoshita, Toshifumi Matsuoka, Potential tsunamigenic faults of the 2011 off the Pacific coast of Tohoku Earthquake, Earth Planets Space, doi:10.5047/eps.2011.05.028, 63, 7, 831-834, 2011.05, [URL], Faults related to the tsunamigenic 2011 Tohoku-Oki Earthquake (Mw 9.0) were investigated by using multi-channel seismic reflection data acquired in 1999 and submersible seafloor observations from 2008. The location of the fault system interpreted in the seismic reflection profile is distributed around the area with largest slip and tsunami induction of the 2011 event. Cold-seep communities along the trace of the branch reverse fault and a high scarp associated with the trace of a normal fault suggest current activity on these faults. We interpret the fault system in the seismic profile as a shallow extension of the seismogenic fault that may have contributed to the resulting huge tsunami. .
125. Andrew Fisher, Takeshi Tsuji, Katerina Petronotis, Expedition 327 Shipboard Scientists, Juan de Fuca Ridge Flank Hydrogeology: The hydrogeologic architecture of basaltic oceanic crust: compartmentalization, anisotropy, microbiology, and crustal-scale properties on the eastern flank of Juan de Fuca Ridge, eastern Pacific Ocean, Proceedings of the Integrated Ocean Drilling Program, 327, Published by Integrated Ocean Drilling Program Management International, Inc., for the Integrated Ocean Drilling Program; World Wide Web: 1930–1014, 2011.04, [URL].
126. Norimitsu Nakata, Takeshi Tsuji, Toshifumi Matsuoka, Acceleration of computation speed for elastic wave simulation using a Graphic Processing Unit, Exploration Geophysics,, 42, 1, 98-104, 2011.02, [URL], Numerical simulation in exploration geophysics provides important insights into subsurface wave propagation phenomena. Although elastic wave simulations take longer to compute than acoustic simulations, an elastic simulator can construct more realistic wavefields including shear components. Therefore, it is suitable for exploration of the responses of elastic bodies. To overcome the long duration of the calculations, we use a Graphic Processing Unit (GPU) to accelerate the elastic wave simulation. Because a GPU has many processors and a wide memory bandwidth, we can use it in a parallelised computing architecture. The GPU board used in this study is an NVIDIA Tesla C1060, which has 240 processors and a 102 GB/s memory bandwidth. Despite the availability of a parallel computing architecture (CUDA), developed by NVIDIA, we must optimise the usage of the different types of memory on the GPU device, and the sequence of calculations, to obtain a significant speedup of the computation. In this study, we simulate two- (2D) and three-dimensional (3D) elastic wave propagation using the Finite-Difference Time-Domain (FDTD) method on GPUs. In the wave propagation simulation, we adopt the staggered-grid method, which is one of the conventional FD schemes, since this method can achieve sufficient accuracy for use in numerical modelling in geophysics. Our simulator optimises the usage of memory on the GPU device to reduce data access times, and uses faster memory as much as possible. This is a key factor in GPU computing. By using one GPU device and optimising its memory usage, we improved the computation time by more than 14 times in the 2D simulation, and over six times in the 3D simulation, compared with one CPU. Furthermore, by using three GPUs, we succeeded in accelerating the 3D simulation 10 times..
127. Shohei Minato, Toshifumi Matsuoka, Takeshi Tsuji, Deyan Draganov, Jurg Hunziker, Kees Wapenaar, Seismic interferometry using multidimensional deconvolution and crosscorrelation for crosswell seismic reflection data without borehole sources, GEOPHYSICS, doi:10.1190/1.3511357, 76, 1, SA19–SA34, 2011.01, [URL], Crosswell reflection method is a high-resolution seismic imaging method that uses recordings between boreholes. The need for downhole sources is a restrictive factor in its application, for example, to time-lapse surveys. An alternative is to use surface sources in combination with seismic interferometry. Seismic interferometry (SI) could retrieve the reflection response at one of the boreholes as if from a source inside the other borehole. We investigate the applicability of SI for the retrieval of the reflection response between two boreholes using numerically modeled field data. We compare two SI approaches — crosscorrelation (CC) and multidimensional deconvolution (MDD). SI by MDD is less sensitive to underillumination from the source distribution, but requires inversion of the recordings at one of the receiver arrays from all the available sources. We find that the inversion problem is ill-posed, and propose to stabilize it using singular-value decomposition. The results show that the reflections from deep boundaries are retrieved very well using both the CC and MDD methods. Furthermore, the MDD results exhibit more realistic amplitudes than those from the CC method for downgoing reflections from shallow boundaries. We find that the results retrieved from the application of both methods to field data agree well with crosswell seismic-reflection data using borehole sources and with the logged P-wave velocity..
128. Takeshi Tsuji, Katsuya Yamamoto, Toshifumi Matsuoka, Yasuhiro Yamada, Kyosuke Onishi, Alfian Bahar, Irwan Meilano, Hasanuddin Z. Abidin, Earthquake Fault of the 26 May 2006 Yogyakarta Earthquake Observed by SAR Interferometry, Earth Planets Space (e-letter), 61, 7, e29-e32, 2009.08, [URL], We analyzed synthetic aperture radar interferometry (InSAR) to reveal surface deformation associated with the 26 May 2006 Yogyakarta earthquake, for which the fault location and geometry have not been clearly determined. Our results demonstrate that surface deformation occurred ∼10 km east of the Opak River fault thought to be the source of the May 2006 event and that the probable causative fault delineated in this study is consistent with aftershock epicenters determined by a temporary seismic network. The trace of the causative fault bends at its southern termination toward the Opak River fault as if it were a splay. Our data demonstrate that another probable slip plane extends across Yogyakarta and that the heavily damaged areas covered by young volcanic deposits may have undergone subsidence during the earthquake. .
129. Takeshi Tsuji, Haruka Yamaguchi, Teruaki Ishii, Toshifumi Matsuoka, Mineral Classification from Quantitative X-ray Maps using Neural Network: Application to Volcanic Rocks, Island Arc, DOI: 10.1111/j.1440-1738.2009.00682.x, 18, 1, 105-119, 2009.08, [URL], We developed a mineral classification technique of electron probe microanalyzer (EPMA) maps in order to reveal the mineral textures and compositions of volcanic rocks. In the case of lithologies such as basalt that include several kinds of minerals, X-ray intensities of several elements derived from EPMA must be considered simultaneously to determine the mineral map. In this research, we used a Kohonen self-organizing map (SOM) to classify minerals in the thin-sections from several X-ray intensity maps. The SOM is a type of artificial neural network that is trained using unsupervised training to produce a two-dimensional representation of multi-dimensional input data. The classified mineral maps of in situ oceanic basalts of the Juan de Fuca Plate allowed us to quantify mineralogical and textural differences among the marginal and central parts of the pillow basalts and the massive flow basalt. One advantage of mineral classification using a SOM is that relatively many minerals can be estimated from limited input elements. By applying our method to altered basalt which contains multiple minerals, we successfully classify eight minerals in thin-section..
130. Hidenori Kumagai, Satoshi Tsukioka, Hiroyuki Yamamoto, Takeshi Tsuji, Kiminori Shitashima, Miho Asada, Fujio Yamamoto, Masataka Kinoshita, Hydrothermal plumes imaged by high-resolution side-scan sonar on a cruising AUV, Urashima, GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, doi:10.1029/2010GC003337 , 11, Q12013, 2010.12, [URL], An autonomous underwater vehicle (AUV) is an ideal platform that enables a closer approach to the seafloor than other platforms. The AUV provides remarkable advancement not only in imaging small-scale bathymetry with high resolution but also in imaging the spatial distribution of scattering signals within a water column. Acoustic echoes can be recorded continuously by AUVs, potentially providing information related to hydrothermal plumes within a water column. In May 2007, such an AUV, Urashima, of the Japan Agency for Marine–Earth Science and Technology, captured fantastic acoustic images within the water column above an active hydrothermal field, the Iheya-North field, off Okinawa. Numerous filamentous and hyperbolic echoes were recorded on the side-scan sonar images. According to the temperature and geochemical anomaly, the scattering signals within the water column were hydrothermal plumes upwelling from the vent area. This proof of concept has implications for long-range exploration for vent field with AUVs. .
131. Takeshi Tsuji, Jin-Oh Park, Gregory Moore, Shuichi Kodaira, Yoshio Fukao, Shin'ichi Kuramoto, Nathan Bangs, Intraoceanic Thrusts in the Nankai Trough off the Kii Peninsula: Implications for Intraplate Earthquakes, Geophysical Research Letters, doi:10.1029/2008GL036974, 36, L06303, 2009.03, [URL], We identified intraoceanic thrusts developed as imbricate structures within the subducting Philippine Sea plate off the Kii Peninsula in central Japan manifesting as strong-amplitude reflections observed in an industry-standard three-dimensional (3D) seismic reflection data set. These imbricate intraoceanic thrusts cut through the oceanic crust as a discontinuous thrust plane striking approximately parallel to the trench. In our survey area, large intraplate earthquakes with moment magnitudes (Mw) over 7 occurred on 5 September 2004, causing strong ground motions on the islands of Japan and tsunami waves. The locations of the intraoceanic thrusts recognized in the seismic data are distributed around the estimated hypocenters of the mainshocks and aftershocks of the 2004 earthquakes. Furthermore, their geometry extracted from the 3D seismic data could explain the kind of complex rupture pattern observed during the 2004 events. Therefore we propose that the intraoceanic thrusts are seismogenically active. .
132. Takeshi Tsuji, Hidekazu Tokuyama, Patrizia Costa Pisani, Gregory Moore, Effective stress and pore pressure in the Nankai accretionary prism off the Muroto Peninsula, southwestern Japan, Journal of Geophysical Research - Solid Earth, doi:10.1029/2007JB005002 , 113, B11401, 2008.11, [URL], We developed a theoretical method for predicting effective stress and pore pressure based on rock physics model. We applied the method to reveal the pore pressure distribution within the Nankai accretionary prism off southwestern Japan and to investigate variations in pore pressure associated with evolution of the plate boundary décollement. From the crack aspect ratio spectrum estimated from laboratory and well-log data, we calculated a theoretical relationship between acoustic velocity and mean effective stress by using differential effective medium theory. By iteratively fitting the theoretically calculated velocity to the seismic velocities derived from 3D tomographic inversion, we estimated in situ mean effective stress within the accretionary prism. Pore pressure is then the difference between the effective stress and the confining stress. When we calculated pore pressure, we considered compressive state of stress in the accretionary prism. Our results confirm that pore fluid pressure is high within the subducting sedimentary sequence below the décollement; we determined a normalized pore pressure ratio (λ*) of 0.4–0.7. Abnormal pore pressures develop in the underthrust sequence as a result of the increase in overburden load because of the thickened overlying prism and a low permeability barrier across the décollement. Overpressuring within the accreted sequence is initiated at the deformation front and proceeds landward. The increase in horizontal compaction within the accreted sequence may raise pore pressures within the accreted sequence, and the pore pressure (mean effective stress) contrast at the décollement becomes smaller landward of the deformation front. .
133. Takeshi Tsuji, Gerardo Iturrino, Velocity-porosity relationships of oceanic basalt from eastern flank of the Juan de Fuca ridge: The effect of crack closure on seismic velocity, Exploration Geophysics,, 39, 1, 41-51, 2008.03, [URL], To construct in situ velocity-porosity relationships for oceanic basalt, considering crack features, P- and S-wave velocity measurements on basaltic samples obtained from the eastern flank of the Juan de Fuca Ridge were carried out under confining pressures up to 40 MPa. Assuming that the changes in velocities with confining pressures are originated by micro-crack closure, we estimated micro-crack aspect ratio spectra using the Kuster-Toksöz theory. The result demonstrates that the normalised aspect ratio spectra of the different samples have similar characteristics. From the normalised aspect ratio spectrum, we then constructed theoretical velocity-porosity relationships by calculating an aspect ratio spectrum for each porosity. In addition, by considering micro-crack closure due to confining pressure, a velocity-porosity relationship as a function of confining pressure could be obtained. The theoretical relationships that take into account the aspect ratio spectra are consistent with the observed relationships for over 100 discrete samples measured at atmospheric pressure, and the commonly observed pressure dependent relationships for a wide porosity range. The agreement between the laboratory-derived data and theoretically estimated values demonstrates that the velocity-porosity relationships of the basaltic samples obtained from the eastern flank of the Juan de Fuca Ridge, and their pressure dependence, can be described by the crack features (i.e. normalised aspect ratio spectra) and crack closure..
134. Takeshi Tsuji, Yasuyuki Nakamura, Hidekazu Tokuyama, Millard F. Coffin, Keita Koda, Oceanic crust and Moho of the Pacific Plate in the eastern Ogasawara Plateau region, Island Arc, DOI: 10.1111/j.1440-1738.2007.00589.x, 16, 3, 361-373, 2007.08, [URL], To show the structure of oceanic crust and Moho around the eastern Ogasawara Plateau, we have analyzed industry-standard two-dimensional multichannel seismic reflection data. To obtain improved velocity models, phase information of seismic signals was used for velocity analysis and velocity models for oceanic crust above Moho were determined. We apply this velocity analysis technique to seismic reflection data around the eastern Ogasawara Plateau, with the result of clear images of structures within oceanic crust and Moho. South of the Ogasawara Plateau, Moho deepens proximal to the Plateau. Moho distal to the Plateau is ca 7 km below sea floor (bsf), whereas it is ca 10 km bsf near the Plateau. The characters of oceanic crust and Moho differ significantly north and south of the Plateau. To the north, the structure of oceanic crust is ambiguous, the sea floor is shallower and less smooth, and Moho is discontinuous. To the south, structures within oceanic crust and Moho are imaged clearly, and the sea floor is deeper. A strong Moho reflection south of the Plateau might represent a sharp boundary between layered gabbro and peridotite. However, discontinuous Moho reflections north of the Plateau might represent rough topography because of intensive magmatism or a gradual downward increase in velocity within a thick Moho transition zone. A fracture zone north of the Plateau also appears to separate oceanic crust and Moho of different characters, suggesting vigorous magmatism between the Plateau and the fracture zone, and that the Ogasawara Plateau and the fracture zone influenced the genesis of oceanic crust and upper mantle. Differences in acoustic characteristics to the north and south of the Plateau are apparent in profiles illuminated by seismic attributes..
135. Yasuyuki Nakamura, Takashi Noguchi, Takeshi Tsuji, Sachihiko Ito, Hiroshi Niino, Toshifumi Matsuoka, Simultaneous seismic reflection and physical oceanographic observations of oceanic finestructure in the Kuroshio extension front, Geophysical Research Letters , doi:10.1029/2006GL027437 , 33, L23605, 2006.12, [URL], New simultaneous seismic reflection and physical oceanographic observations east of Japan demonstrate the utility of the seismic reflection method in mapping oceanic fine structure. Synthetic seismograms calculated from temperature and salinity data confirm that seismic reflections correlate with physical oceanographic structures. Seismic reflections at the boundary between the warm Kuroshio and the cold Oyashio water masses correspond to well developed, ∼10 m scale, temperature fine structure. Vertical current profiles suggest that this fine structure is caused by interleaving of these two water masses. We compare our seismic images with acoustic Doppler current profiler (ADCP) intensity maps and discuss similarities and the differences between seismic images and the ADCP maps. Our study demonstrates that even relatively low-energy seismic sources, in this case a 3.4 l (210 in3) generator-injector (GI) airgun, can be used to image upper oceanic fine structure..
136. Takeshi Tsuji, Gaku Kimura, Shinya Okamoto, Fumio Kono, Hisako Mochinaga, Tatsuo Saeki, Hidekazu Tokuyama, Modern and ancient seismogenic out-of-sequence thrusts in the Nankai accretionary prism: Comparison of laboratory-derived physical properties and seismic reflection data, Geophysical Research Letters , doi:10.1029/2006GL027025 , 33, L18309, 2006.09, [URL], To investigate characteristics of a seismogenic out-of-sequence thrust (OOST) imaged as a strong reflection on seismic profiles in the Nankai accretionary prism, we determined acoustic properties of discrete samples from an fossil Nobeoka OOST outcrop under confining pressures, and compared the acoustic properties with those of an active OOST in the Nankai accretionary prism. We observed anisotropy of velocity and attenuation in the hanging wall of Nobeoka OOST attributed to foliation of pelitic-phyllite. In contrast, the footwall is composed of brittlely deformed, chaotic shales and fine sandstones, and velocities in the footwall are lower than those in the hanging wall. Amplitude variation with offset (AVO) modeling utilizing contrasts in P- and S-wave velocities and densities between the hanging wall and footwall of the Nobeoka OOST indicates that fractures filled with overpressured fluid likely account for angle-dependent reflection amplitudes of the active OOST in the Nankai Trough. .
137. Takeshi Tsuji, Toshifumi Matsuoka, Yasuhiro Yamada, Yasuyuki Nakamura, Juichiro Ashi, Hidekazu Tokuyama, Shin’ichi Kuramoto, Nathan Bangs, Initiation of plate boundary slip in the Nankai Trough off the Muroto peninsula, southwest Japan, Geophysical Research Letters, doi:10.1029/2004GL021861, 32, L12306, 2005.06, [URL], To investigate variations in physical properties accompanying the development of the decollement, we used a neural network analysis of seismic attributes derived from 3D seismic reflection data gathered in the Nankai Trough convergent margin off the Muroto peninsula of southwest Japan. This analysis resulted in a detailed map of the geological features along the decollement and revealed a drastic change in physical properties at the sole of the protothrust. Ocean Drilling Program (ODP) data suggest that the decollement physical property change coincides with the initiation of slip. Furthermore, changes in the structure of the accretionary prism and reorganization of the decollement geometry also attend the initiation of plate boundary slip..
138. Takeshi Tsuji, Takashi Noguchi, Hiroshi Niino, Toshifumi Matsuoka, Yasuyuki Nakamura, Hidekazu Tokuyama, Sin’ichi Kuramoto, Nathan.Bangs, Two-dimensional mapping of fine structures in the Kuroshio Current using seismic reflection data, Geophysical Research Letters, doi:10.1029/2005GL023095 , 32, L14609, 2005.07, [URL], Multi-channel seismic reflection data acquired in the Pacific Ocean off the Muroto peninsula of Shikoku Island, Japan reveal the two-dimensional distribution of fine structures in the Kuroshio Current. Eighty-one seismic sections, each extending 80 km perpendicular to the current and separated by 100 m, were acquired from 20 June to 15 August 1999 (57 days). The seismic data clearly show that fine structures extend over 40 km perpendicular to the current in almost all of the profiles. A simulation study using acoustic model from CTD data demonstrates that fine structure of temperature and salinity identified in CTD data acquired from the Kuroshio Current off the Ashizuri peninsula yield a synthetic seismic profile with characteristics similar to the Muroto transect profiles. .
139. Fumihiko Ikegami, Takeshi Tsuji, Hidenori Kumagai, Jun-ichiro Ishibashi, ken Takai, Active rifting structures in Iheya Graben and adjacent area of the mid-Okinawa Trough observed through seismic reflection surveys, Subseafloor Biosphere Linked to Global Hydrothermal Systems; TAIGA Concept, Springer Japan, in press.
140. Jun-ichiro Ishibashi, Fumihiko Ikegami, Takeshi Tsuji, Tetsuro Urabe, Hydrothermal activity in the Okinawa Trough back-arc basin - geological background and hydrothermal mineralization -, Subseafloor Biosphere Linked to Global Hydrothermal Systems; TAIGA Concept, Springer Japan, in press,
Works, Software and Database
1. .
1. T. Tsuji, Geophysical monitoring system for CO2 managements using the earth, 1st international symposium on construction resources for environmentally sustainable technologies, 1st international symposium on construction resources for environmentally sustainable technologies, 2021.03.
2. R.D. Andajani, T. Tsuji, T. Ikeda, F.L Hutapea, Preliminary Investigation on Pore Pressure Changes Induced by Rain Precipitation from Seismic Velocity Monitoring, 1st international symposium on construction resources for environmentally sustainable technologies, 2021.03.
3. K. Sawayama, F. Jiang, T. Ikeda, T. Ishibashi, T. Tsuji, Y. Fujimitsu, H. Asamuma, Estimation of Permeability and Water Saturation from the Resistivity and Elastic Wave Velocity: Insight from Laboratory Experiment and Digital Fracture Simulation, World Geothermal Congress 2020, 2021.04.
4. T. Tsuji, CO2 managements using the earth, Challenges and Opportunities of Geophysical Exploration to Meet Future Energy Demands SEACG2020, 2020.11.
5. T. Tsuji, Induced Seismicity, ITB and IEAGHG will organize an International CCUS Virtual Lecture, 2020.11.
6. T. Tsuji, T. Ikeda, K. Yamaoka, Continuous source system and distributed acoustic sensing for reservoir to crust monitoring, EGU General Assembly 2020, 2020.05.
7. T. Tsuji, J. Kinoshita, T. Ikeda, T. Kawamura, T. Kobayashi, T. Maeda, Y. Ishihara, K. Ogawa, S. Tanaka, A. Araya, H. Miyamoto, Optimization and Miniaturization of Lunar Active Seismic Profiler (LASP), ISAS Planetary Exploration Workshop 2020, 2020.09.
8. A. Kioka, V.S. Isaev, M. Fujii, T. Tsuji, P. I.Kotov, S. A. Ogorodov, O.M. Tsarapov and T. Mironova, Field-based monitoring, assessment and forecast of the permafrost coast retreat along the Kara Sea, The 11th Symposium on Polar Science Symposium, 2020.12.
9. R. D. Andajani, T. Tsuji, R. Sneider, T. Ikeda, A Study of Coastal Sea Variability Influence in Temporal Changes of Seismic Velocity Estimated from Ambient Noise Monitoring, International Symposium on Earth Science and Technology (CINEST) 2020, 2020.11.
10. K. Mukumoto, T. Tsuji, S wave velocity Model Estimation using full waveform tomography in Central Japan Island, nternational Symposium on Earth Science and Technology (CINEST) 2020, 2020.11.
11. T. Tsuji, T. Ikeda, R. Matsuura, K. Yamaoka, T. Kimura, Continuous reservoir monitoring system based on permanent seismic source and distributed acoustic sensing, SEG Annual Meeting 2020, 2020.10.
12. T. Ikeda, T. Tsuji, C. Konishi, H. Saito, Extracting surface wave dispersion curves from two-station microtremor analysis in heterogeneous ambient noise wavefield, SEG Annual Meeting, 2020.10.
13. R. D. Andajani, T. Tsuji and T. Ikeda, Extracting slump units and faults from seismic data using CNNs, SIS Technology Day for Universities 2020, 2020.11.
14. A.B.Ahmad and T. Tsuji, Extracting slump units and faults from seismic data using CNNs, SIS Technology Day for Universities 2020, 2020.11.
15. B. Nthaba, E. Shemang, A. Hengari, B. Kgosidintsi, T. Tsuji, The Utilization of Pseudo-3D Electrical Resistivity Imaging Method to Characterize Coal Seams Hosted in Mmamabula Coalfield, Central Botswana, International Symposium on Earth Science and Technology (CINEST) 2020, 2020.11.
16. Y. Zhang, F. Jiang, T. Tsuji, Dynamic evolution of hydraulic and electrical properties of porous rock induced by mineral dissolution in porescale, International Symposium on Earth Science and Technology (CINEST) 2020, 2020.11.
17. K. Sawayama, F. Jiang, T. Tsuji, Y. Fujimitsu, Development of two-phase fracture flow simulation method using Shan-Chen type lattice Boltzmann model, International Symposium on Earth Science and Technology (CINEST) 2020, 2020.11.
18. M. Mourad, T. Tsuji, T. Ikeda, S. Senna, K. Ishitsuka, Spatial prediction of shear-wave velocity structure for detecting fractured zones using microtremor data analysis
, International Symposium on Earth Science and Technology (CINEST) 2020, 2020.11.
19. T.Hirose,Y.Hamada,W.Tanigawa,N.Kamiya,Y.Yamamoto,T.Tsuji,M.Kinoshita, High Fluid Pressure Patch beneath the Décollement as a Potential Source of Slow Earthquakes at the Nankai Trough, JpGU-AGU Joint Meeting 2020, 2020.07.
20. Rezkia Dewi Andajani,@T. Tsuji,, Investigation of the pore pressure sensitivity toward ocean loading influence from seismic ambient noise monitoring, JpGU-AGU Joint Meeting 2020, 2020.07.
21. M.Ikeda,#K.Kret,#@T.Tsuji,@T,Ikeda,T.Tsuji,K.Onishi,N.Nishizaka, Pore geometry and elastic moduli of fault rocks accompanied by the Median Tectonic Line in Shikoku, southwestern Japan, JpGU-AGU Joint Meeting 2020, 2020.07.
22. A.Suzuki,M.Miyazawa,J. Minto@T,Tsuji,T.Ito, Characterization of permeability based on topological data of fracture network, JpGU-AGU Joint Meeting 2020, 2020.07.
23. R.Matsuura,T.Ikeda,T.Tsuji,K.Yamaoka, Analysis of Seismic Waves from Continuous and Controlled Seismic Signal System in Kyushu Area, JpGU-AGU Joint Meeting 2020, 2020.07.
24. F. L. Hutapea,T. Tsuji,E. Asakawa,M.Kato, Processing the Deep-towed Autonomous Continous System (ACS) Data in Joetsu Basin, Niigata Prefecture, Japan, JpGU-AGU Joint Meeting 2020, 2020.07.
25. K.Nimiya,T.Ikeda,T.Tsuji, Estimation of shallow 3D S-wave velocity structure by applying surface-wave tomography using MeSO-net, JpGU-AGU Joint Meeting 2020, 2020.07.
26. M.Kimura,T.Tsuji,A.Yamaguchi, Two steps of onset of the modern geodynamic framework; ~6Ma and ~2.5Ma in east Asia and western Pacific margin, JpGU-AGU Joint Meeting 2020, 2020.07.
27. G.Akuhara,@T.Tsuji,T.Tonegawa, Overpressured underthrust sediment in the Nankai Trough forearc revealed by high-frequency receiver function inversion,, JpGU-AGU Joint Meeting 2020, 2020.07.
28. Takeshi Tsuji, Tatsunori Ikeda, Koshun Yamaoka, Continuous source system and distributed acoustic sensing for reservoir to crust monitoring, European Geophysical Union, 2020.04, We have developed a permanent seismic monitoring system using a continuous seismic source and distributed acoustic sensing (DAS). The active seismic source system continuously generates waveforms with wide frequency range. By stacking the continuous waveforms, our monitoring system improves signal-to-noise ratio of the seismic signal. Thus, less-energy vibration using small-size source could be utilized for the exploration of deeper geological targets. Presently, we have deployed the small-size monitoring source system in the Kuju geothermal field in the northeast Kyushu Island, Japan. Although our monitoring source system is small and generates high frequency vibrations (10-20Hz), the signal propagated >80 km distance using two-month continuous source data. Our field experiments demonstrate that variation of seismic velocity of the crust could be identified with high accuracy (~0.01 %). To record the monitoring signal from continuous source system, we need to deploy seismometers. Deployment of many seismometers increase spatial resolution of the monitoring results. Recently, we have deployed the DAS system close to the continuous seismic source system. Using DAS, dense and long seismometer network can be realized, and we succeeded to identify the temporal variation of seismic velocity. By using both continuous source and DAS, we are able to monitor wide area with lower cost. Our monitoring system could accurately monitor the larger-scale crust and smaller-scale reservoir in high temporal resolution..
29. T. Akuhara, T. Tsuji, and T. Tonegawa, Sediment compaction and fluid processes in the Nankai Trough forearc inferred from teleseismic body waves, AGU Fall Meeting 2019, 2019.12, [URL].
30. M. L. Doan, Y. Hamada, T. Jeppson, G. Guerin, T. Tsuji, S. Yabe, M. Conin, G. F. Moore, Y. Sanada, Y. Nakasa Kido, S. Saito, E. L. Ber, A. Yamaguchi, M. Ikari, H. J. Tobin, D. M. Saffer, H. Kitajima, M. Kinoshita, G. Kimura, T. Hirose, L. Maeda, S. Toczko, N. Eguchi, Y. Kubo and the IODP Expedition 358 Shipboard Scientific Party, Insight on the physical properties of sediments within the Nankai inner accretionary prism, from repeated borehole geophysics of NanTroSEIZE IODP expeditions 348 and 358, AGU Fall Meeting 2019, 2019.12, [URL].
31. H. Uchida, M. Ikeda, T. Tsuji, K. Onishi and N. Nishizaka, Paleostress analysis and fault property of the Median Tectonic Line in the central Shikoku, southwest Japan, AGU Fall Meeting 2019, 2019.12, [URL].
32. M. Ikeda, T. Tsuji, T. Tsuji, K. Onishi and N. Nishizaka, Characterization of a fault gouge region of the Median Tectonic Line in Shikoku, southwestern Japan, AGU Fall Meeting 2019, 2019.12, [URL].
33. G. Kimura, T. Tsuji, A. Yamaguchi and Y. Yamamoto, Revisit of a tectonics linkage in the western Pacific margin since ~6Ma, AGU Fall Meeting 2019, 2019.12, [URL].
34. R. D. Andajani, T. Tsuji, T. Ikeda and F. L. Hutapea, Impact of seasonal rainfall on crustal pore pressure: Insight from monitoring of seismic velocity changes, International Symposium on Earth Science and Technology (CINEST) 2019, 2019.12.
35. R. Matsuura, T. Tsuji and T. Ikeda, Analysis of seismic waves from continuous and controlled seismic signal system in Kyushu area, International Symposium on Earth Science and Technology (CINEST) 2019, 2019.12.
36. F. L. Hutapea, T. Tsuji and T. Ikeda, Development of quasi-real time monitoring system of spatial seismic velocity variation on Kyushu Island using ambient noise, International Symposium on Earth Science and Technology (CINEST) 2019, 2019.12.
37. L. Yuhan and T. Tsuji, Fault detection using pre-trained convolutional neural networks by synthetic seismic data, International Symposium on Earth Science and Technology (CINEST) 2019, 2019.12.
38. H. Matsui and T. Tsuji, Potential assessment of gas hydrate and free gas reservoir in Kumano basin, Japan, International Symposium on Earth Science and Technology (CINEST) 2019, 2019.12.
39. Y. Zhang, T. Tsuji and F. Jiang, The influence of polymorphs of CaCO3 on CO2 mineralization, International Symposium on Earth Science and Technology (CINEST) 2019, 2019.12.
40. K. Takahashi and T. Tsuji, Tectonic history in Hidaka-oki basin and Sanriku-oki basin estimated by sedimentation rates using 3D seismic reflection data, International Symposium on Earth Science and Technology (CINEST) 2019, 2019.12.
41. A. B. Ahmad and T. Tsuji, Automatic Interpretation of Nankai Trough seismic data using Convolutional Neural Networks (CNNs), International Symposium on Earth Science and Technology (CINEST) 2019, 2019.12.
42. C. Fujita, H. Yamamoto, J. Ishibashi and T. Tsuji, Numerical simulation of submarine hydrothermal ore-deposits, ISRM2019 Specialized Conference, The 5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future (YSRM2019 and REIF2019), 2019.12, [URL].
43. K. Sawayama, T. Ishibashi, F. Jiang, T. Tsuji and Y. Fujimitsu, Changes in hydraulic, electric and mechanical properties with aperture closure: Insight from experimental and numerical approaches, The 5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future (YSRM2019 and REIF2019), 2019.12, [URL].
44. R.D. Andajani, T. Tsuji and F. Hutapea, The impact of seasonal rainfall toward crustal pore pressure: Insight from seismic velocity change monitoring, 5th International Exchange and Innovation Conference on Engineering and Sciences (IEICES), 2019.10, [URL].
45. T. Tsuji, Characterization of Gas-Hydrate and Free-Gas around Japanese Island, International Conference on Asia Pacific Mining and Metallurgy (APMM 2019), 2019.11, [URL].
46. , [URL].
47. T. Tsuji, Permanent monitoring system using continuous and controlled seismic source: Monitoring of dynamic behaviors from smaller reservoir to larger crust, Fifth International Conference on Engineering Geophysics (ICEG), 2019.10, [URL].
48. T. Tsuji, Imaging, Monitoring and Modeling of the Earth: Our Past Works and Future Visions, 27th IUGG General Assembly, 2019.07, [URL].
49. , [URL].
50. K. Ishitsuka, and T. Tsuji, Mapping surface displacements and aquifer characteristics around the Kumamoto plain, Japan, using persistent scatterer interferometry, IGARSS 2019(2019 IEEE International Geoscience and Remote Sensing Symposium), 2019.08, [URL].
51. T. Tsuji, Geophysics for Tsunami and Earthquake, Climatology, and Geophysics of the Republic of Indonesia (BMKG), 2019.04.
52. K. Ishitsuka and T. Tsuji,, Surface displacements and groundwater level changes around the Kumamoto plain, Japan, associated with the 2016 Kumamoto earthquake sequence, AGU Fall Meeting 2018, 2018.12, [URL].
53. H. Nimiya, T. Ikeda and T. Tsuji,, High Resolution Shallow S-wave Velocity Structure of the Central Japan Using Surface Wave Tomography, AGU Fall Meeting 2018, 2018.12, [URL].
54. T. Tsuji, Monitoring and modeling of injected CO2 for effective and safe CO2 storage, Princeton University, 2018.12.
55. K. Sawayama, T. Ikeda, T. Tsuji and Y. Fujimitsu, Numerical experiments of elastic wave propagation through digitalized fractures under various aperture and saturation conditions, International Symposium on Earth Science and Technology(CINEST) 2018, 2018.11.
56. K. Kret, T. Tsuji and O. Takano, Hydrate and gas reservoirs off Sanriku area: Insights from automatic seismic velocity picking, International Symposium on Earth Science and Technology(CINEST) 2018, 2018.11.
57. Y. Suemoto, H. Nimiya, T. Ikeda and T. Tsuji, High resolution shallow S-wave velocity structure in the San-in area using ambient noise and two-station phase velocity measurements, International Symposium on Earth Science and Technology(CINEST) 2018, 2018.11.
58. Y. Nagata, T. Tsuji, T. Kawamura, A. Araya, Y. Ishihara, K. Ogawa, T. Kobayashi, Y. Karouji and S. Tanaka,, Exploration of ice deposits on the Moon using continuous seismic source system, International Symposium on Earth Science and Technology(CINEST) 2018, 2018.11.
59. Fernando Lawrens Hutapea, T. Tsuji and T. Ikeda, Building Passive Seismic Monitoring System by using Ambient Noise Cross-correlation and Python, International Symposium on Earth Science and Technology(CINEST) 2018, 2018.11.
60. K. Mukumoto and T. Tsuji, Geologic structure related to hydrothermal fluid flow in Iheya North Knoll based on automatic velocity analysis for multi-channel seismic data, International Symposium on Earth Science and Technology(CINEST) 2018, 2018.11.
61. C. Chhun and T. Tsuji, Reflection mapping of oceanic thermohaline fine structure in the Kuroshio Current: Insights from automatic seismic velocity analysis, International Symposium on Earth Science and Technology(CINEST) 2018, 2018.11.
62. A. Hendriyana and T. Tsuji, Imaging of Long-Period Seismicity Beneath the Nakadake-Aso Volcano by Using Cross-correlation Back Projection Technique, International Symposium on Earth Science and Technology(CINEST) 2018, 2018.11.
63. Fernando Hutapea-Lawrens, H. Nimiya, T. Ikeda, and T. Tsuji, Evaluation of Optimal Processing Parameters for Automatic Continuous, The 13th SEGJ International Symposium, 2018.11, [URL].
64. T. Ikeda, and T. Tsuji, Surface-wave phase velocity tomography using active-source seismic data, The 13th SEGJ International Symposium, 2018.11, [URL].
65. Y. Morifuji, T. Tsuji, T. Ikeda, M. Ikeda, N. Nishizaka, and K. Oonishi, Surface wave analysis using active-source multi-channel seismic data in the Median Tectonic Line (MTL): Comparison of S-wave velocity along the MTL, The 13th SEGJ International Symposium, 2018.11, [URL].
66. C. Chhun, and T. Tsuji, Reflection mapping of oceanic thermohaline fine structures in the Kuroshio, Current: Insights from automatic seismic velocity analysis, The 13th SEGJ International Symposium, 2018.11, [URL].
67. K. Kakda, T. Tsuji, and O. Takano, Characterization of hydrate and gas reservoirs off Sanriku area from highresolution seismic velocity model, The 13th SEGJ International Symposium, 2018.11, [URL].
68. T. Tsuji, T. Kawamura, A. Araya, Y. Nagata, Y. Ishihara, K. Ogawa, T. Kobayashi, S. Tanaka, and T. Aizawa, Lunar Active Seismic Profiler (LASP): Investigation of shallow regolith layer for resource exploration and base camp construction, The 13th SEGJ International Symposium, 2018.11, [URL].
69. Rezkia Dewi Andajani, T.Ikeda, T. Tsuji , Development of Surface Wave Analysis Method: Surface Wave Dispersion Behavior depending Wave Propagation Direction, 4th International Exchange and Innovation Conference on Engineering & Sciences (IEICES), 2018.10.
70. T. Ikeda, T. Tsuji, Surface-wave tomography for near-surface characterization with continuous-wavelet transform for two-station crosscorrelation, The Society of Exploration Geophysicists(SEG) 2018 International Exposition and 88th Annual Meeting, 2018.10, [URL].
71. , [URL].
72. , [URL].
73. , [URL].
74. T. Tsuji and T. Ikeda, Continuous geophysical monitoring of Nankai subduction zone and Japanese Island: Insight from ambient noise interferometry for DONET and Hi-net, International Joint Workshop on Slow Earthquakes 2018, 2018.09, [URL].
75. T.Tsuji, Continuous geophysical monitoring system for injected CO2: Utilize ambient noise and continuous controlled source system, CCUS forum, 2018.09.
76. T. Tsuji, C. Chhun, Gas reservoirs around Japanese Island identified by automatic velocity analysis, 日本地球惑星科学連合2018年大会( JpGU 2018 ), 2018.05, [URL].
77. 池田 達紀, 二宮 啓, 辻 健, 雑微動の相互相関解析による2016年熊本地震に伴う地震波速度の時空間変化, 日本地球惑星科学連合2018年大会( JpGU 2018 ), 2018.05, [URL].
78. 浅田 美穂, 土岐 知弘, 井尻 暁, 辻 健, 泥火山研究に関する議論の時間, 日本地球惑星科学連合2018年大会( JpGU 2018 ), 2018.05, [URL].
79. H. Matsui, J. Jia, T. Tsuji, Y. Liang, Molecular Dynamics Study of Replacement of CH4 by CO2 in Clathrate Hydrate with H2S, 日本地球惑星科学連合2018年大会( JpGU 2018 ), 2018.05, [URL].
80. Y. Suemoto, H. Nimiya, T. Ikeda, T. Tsuji, Y. Iio, Three dimensional S-wave velocity structure near the fault zones of the 2000 western Tottori earthquake using surface wave tomography, 日本地球惑星科学連合2018年大会( JpGU 2018 ), 2018.05, [URL].
81. J. Ashi, H. Koge, A. Yamaguchi, T. Tsuji, K. Ikehara, Active tectonics of Muroto-off Ashizuri uplifted ridges, southwest Japan, 日本地球惑星科学連合2018年大会( JpGU 2018 ), 2018.05, [URL].
82. , [URL].
83. , [URL].
84. T. Tsuji, T. Kawamura, A. Araya, Y. Nagata, Y. Ishihara, K. Ogawa, T. Kobayashi, S. Tanaka, T. Aizawa, Active seismic exploration on the Moon: Investigation of water ice deposit near the Moon’s polar region, 日本地球惑星科学連合2018年大会( JpGU 2018 ), 2018.05, [URL].
85. , [URL].
86. , [URL].
87. , [URL].
88. , [URL].
89. Takeshi Tsuji, Multi-phase fluid behaviors with various capillary numbers, viscosity and wettability: Insight into effective and safe CO2 storage , InterPore 2018, 2018.05, The behavior of CO2 inside a reservoir (i.e., two-phase flow in CCS, or three-phase flow in CCUS) is influenced by interfacial tension, pore structure, wettability and other reservoir parameters (e.g., pressure gradient), which vary significantly from one reservoir to the next. Therefore, understanding multi-phase flow under various reservoir conditions is crucial to estimating CO2 storage capacity, leakage risk, and storage efficiency. In this study, we calculated two-phase or three-phase fluid displacements in natural digital rocks using lattice Boltzmann (LB) simulation, and characterized the influence of reservoir conditions (e.g., interfacial tension, pressure gradient, and wettability) upon CO2 behavior. By mapping the CO2 saturation on the diagram of capillary number and viscosity ratio of the two fluids, we could identify the suitable environments for effective CO2 storage. We further calculated two-phase and three-phase relative permeability of digital rocks under various conditions. Porous flow simulation also contributes to geophysical monitoring of CO2 behavior in reservoirs. For example, we calculated geophysical properties (e.g., seismic velocity) of the digital rocks with injected CO2 under various reservoir conditions. Using the relationship between seismic velocity and CO2 saturation parameterized by reservoir conditions, we could quantify in situ CO2 saturation in reservoir from geophysical monitoring data (seismic velocity). In this presentation, we would like to show how porous flow simulations practically contribute to the safe and effective CO2 storage..
90. T. Tsuji, T. Kawamura, A. Araya, Y. Nagata, Y. Ishihara, K. Ogawa, T. Kobayashi, S. Tanaka, T. Aizawa, Active seismic exploration package on the moon, The New Views of the Moon 2 - Asia, 2018.04.
91. T. Tsuji, Continuous monitoring of geothermal reservoirs and crustal-scale faults and volcanoes, 15th International Workshop on WATER DYNAMICS, Deeper and Hotter in Frontier Earth, 2018.03.
92. K. Sawayama, T. Ishikawa, T. Tsuji, Y. Fujimitsu, Effect of aperture closure on fracture permeability:experimental and numerical approaches, 15th International Workshop on WATER DYNAMICS, Deeper and Hotter in Frontier Earth, 2018.03, [URL].
93. T. Tsuji, CO2 behavior characterization from digital rock physics and innovative monitoring system, International CCS/CCUS Seminar, 2018.02.
94. Rezkia Dewi Andajani, T. Ikeda, T. Tsuji, Development of Surface Wave Analysis Method for Heterogeneous Geological Condition in Geothermal Field, CINEST International Symposium on Earth Science and Technology 2017, 2017.12.
95. K. Ikuo, F. Jiang, T. Tsuji, Hydraulic Property Evolution of Sheared Fracture: Insight from Digital Rock Approach, CINEST International Symposium on Earth Science and Technology 2017, 2017.12.
96. K. Sawayama, T. Tsuji, K. Kitamura, Y. Fujimitsu, Numerical Simulation and Laboratory Measurement of Hydraulic and Electric Properties of Digitalized Fractures, CINEST International Symposium on Earth Science and Technology 2017, 2017.12.
97. H. Matsui, J. Jia, T. Tsuji, Y. Liang, Influence of H2S on Replacement of CH4 by CO2 in Gas Hydrate, CINEST International Symposium on Earth Science and Technology 2017, 2017.12.
98. M. Miyazawa, A. Suzuki, H. Shimizu, A. Okamoto, Y. Hiraoka, I. Obayashi, T. Tsuji, T. Ito,, Topological patterns of mesh textures in serpentinites, AGU Fall Meeting 2017, 2017.12, [URL].
99. K. Sawayama, K. Kitamura, T. Tsuji, Y. Fujimitsu, Fracture Flow Characterization from Seismic and Electric Properties: Insight from Experimental and Numerical Approaches, AGU Fall Meeting 2017, 2017.12, [URL].
100. T. Tsuji, T. Ikeda, H.Nimiya, Spatial and temporal variation of seismic velocity during earthquakes and volcanic eruptions in western Japan: Insight into mechanism for seismic velocity variation, AGU Fall Meeting 2017, 2017.12, [URL].
101. S.Saito, Y.Yamada, Y.Sanada, Y.N.Kido, Y.Hamada, K.Shiraishi, K.-H. Hsiung, T.Tsuji, C.Eng, L.Maeda, H.Kumagai,T.Nozaki, J.Ishibashi, Spatial and temporal variation of seismic velocity during earthquakes and volcanic eruptions in western Japan: Insight into mechanism for seismic velocity variation, AGU Fall Meeting 2017, 2017.12, [URL].
102. , [URL].
103. T. Tsuji, Multiphase Flow in Sandstone Controlled by Capillary Number, Viscosity and Wettability, The 4th International Symposium on "Application of Nano-Geosciences in Petroleum Engineering", 2017.11.
104. C. Cao, T. Tsuji, Self-organizing map method for spatial mineral identification and mapping”, Esri Canada User Conference, 2017.11, [URL].
105. C. Eng, J. Jia, T. Tsuji, Acoustic Impedance Inversion and Porosity Characterization of Coalbed-bearing Sediments Offshore Shimokita Peninsula, Northeast Japan, CINEST International Symposium on Earth Science and Technology 2017, 2017.11.
106. K. Kret, T. Ikeda, T. Tsuji, Monte Carlo Inversion for Pore Geometry and Elastic Moduli Estimation of Oceanic Basalt of the Juan De Fuca Ridge, CINEST International Symposium on Earth Science and Technology 2017, 2017.11.
107. C. Chhun, A. Kioka, J. Jia, T. Tsuji, Gas Hydrate and Free Gas Accumulations in the Kumano Forearc Basin in the Nankai Trough: Insights from Seismic velocity analysis via Automatic Velocity Picking Algorithm, CINEST International Symposium on Earth Science and Technology 2017, 2017.11.
108. K. Takahashi, H. Nimiya, Y. Nagata, Y. Suemoto, T. Ikeda, T. Tsuji, K. Hayashi, 3D Geological Model in the Uchinomaki Hot Spring Area using Surface Wave Analysis, CINEST International Symposium on Earth Science and Technology 2017, 2017.11.
109. H. Nimiya, T. Ikeda, T. Tsuji, Monitoring Temporal Changes of Seismic Velocity Caused by the 2016 Kumamoto Earthquake using Cross-correlations of Ambient Seismic Noise, CINEST International Symposium on Earth Science and Technology 2017, 2017.11.
112. T. Tsuji, Fault and lithology from trench to coast on seismic profiles off Kii peninsula, French-Japanese week on Disasster Risk Reduction "Mega-earthquakes in subduction zones: insights from fossil examples, 2017.10.
113. International Field Examination in Czech Republic, [URL].
114. Continuous and accurate monitoring system for injected CO2, [URL].
115. ~6 Ma is the start-age of the modern tectonics of the Japanese Islands, [URL].
116. High-resolution subbottom structure of a large submarine landslide in the eastern Nankai Trough, [URL].
117. Geological structures and recent tectonic movement of Muroto-off Ashizuri uplifted ridges, SW Japan, [URL].
118. Study on geological structure around the MTL active fault zone in the Iyo-nada Sea area by using seismic profiles, [URL].
119. C. Chhun, T. Tsuji, A. Kioka, Hydrocarbon accumulation controlled by tectonic activity in the subduction zone: Insight from advanced seismic velocity analysis, IAG-IASPEI, 2017.08, [URL].
120. H.Nimiya, T. Ikeda, T. Tsuji, A temporal and spatial change in seismic velocity caused by the 2016 Kumamoto earthquake using crosscorrelations of ambient seismic noise, IAG-IASPEI, 2017.08, [URL].
121. C.Eng, T. Ikeda, T. Tsuji, Evaluation of rock evolution process in seismogenic fault: Dynamic wave propagation modeling to the digitalized fault rocks, IAG-IASPEI, 2017.08, [URL].
122. K. Ogawa, T. Kawamura, Y. Ishihara, T. Tsuji, T. Kobayashi, R. Yamada, A. Araya, S. Tanaka, N.Takeuchi, Conceptual Study of Small Active Seismic Exploration Package on Moons and Small Bodies, IAG-IASPEI, 2017.08, [URL].
123. S.Shiwani, S. Ansumali, T. Tsuji, Lattice Boltzmann Approach For A Coupled Two-Fluid Kinetic Theory Of Polymer Solutions, 26th International Conference on Discrete Simulation of Fluid Dynamics (DSFD 2017), 2017.07, [URL].
124. , [URL].
125. , [URL].
126. , [URL].
127. , [URL].
128. , [URL].
129. , [URL].
130. , [URL].
131. , [URL].
132. T. Kawamura, Y. Ishihara, K. Ogawa, T. Tsuji, T. Kobayashi, R. Yamada, A. Araya, S. Tanaka, N. Takeuchi, Conceptual Study of Small Active Seismic Exploration Package on Moons and Small Bodies, JpGU-AGU Joint Meeting 2017, 2017.05, [URL].
133. , [URL].
134. C. Chhun, A. Kioka, T. Tsuji, Hydrocarbon gas accumulation and mud volcanoes in the Nankai subduction margin: Insight from 3D seismic velocity analysis using automatic picking algorithm, JpGU-AGU Joint Meeting 2017, 2017.05, [URL].
135. J. Haruyama, I. Kawano, T. Nishibori, T. Iwata, Y. Yamamoto, K. Shimada, K. Yamamoto, S. T. Crites, T. Kaku, T. Hasenaka, T. Morota, M. N. Nishino, K. Hashizume, M. Shirao, G. Komatsu, N. Hasebe, H. Shimizu, K. Kobayashi, S. Yokobori, Y. Miyake, Y. Michikawa,, T. Tsuji, R. Shinoda,, Unprecedented Zipangu Underworld of the Moon/Mars Exploration (UZUME) project from SELENE (Kaguya), 5th European Lunar Symposium, 2017.05, [URL].
136. K. Ishitsuka, T. Matsuoka, T. Tsuji, Post- seismic displacement around the Kanto plain, Japan after the 2011 Tohoku earthquake and the implication to subsurface structure, European Geosciences Union (EGU) General Assembly 2017, 2017.04, [URL].
137. A. Kioka, T. Tsuji, H. Otsuka, J. Ashi, Methane concentration inside a submarine mud volcano examined through seismic velocity profiles, European Geosciences Union (EGU) General Assembly 2017, 2017.04, [URL].
138. T. Kawamura, Y. Ishihara, K. Ogawa, T. Tsuji, T. Kobayashi, R. Yamada, A. Araya, S. Tanaka, N. Takeuchi, Conceptual study of small active scismic exploration package on moons and small bodies, Lunar and Planetary Science Conference 48th(LPSC), 2017.03, [URL].
139. T. Tsuji, Modeling of Rock Evolution Process: Insight from Digital Rock Physics, 4th International Geoscience Symposium “Precambrian World 2017”, 2017.03, [URL].
140. T. Tsuji, CO2 behavior and reaction in geological formations, 2nd UNSW-I2CNER workshop, 2017.02.
141. Digital rock physics to quantify geophysical data.
142. M. Kido, J. Ashi, T. Tsuji, F. Tomita, Measuring Relative Motions Across a Fault Using Seafloor Transponders Installed at Close Range to each Other Based on Differential GPS/Acoustic Technique, AGU Fall Meeting, 2016.12, [URL].
143. G. Kimura, H. Koge, T. Tsuji, G.F. Moore, Latest-Miocene onset of Nankai Trough Subduction due to regional Change in Plate tectonic Framework, AGU Fall Meeting, 2016.12, [URL].
144. M. Hamahashi, T. Tsuji, S. Saito, W. Tanikawa, Y. Hamada, Y. Hashimoto, G. Kimura, Core-Log-Seismic Integrative Study of a Subduction Zone Megasplay Fault –An Example from the Nobeoka Thrust, Shimanto Belt, Southwest Japan, AGU Fall Meeting, 2016.12, [URL].
145. C. Eng, T. Ikeda, T. Tsuji, Effect of Crack-Filling Materials on Seismic Velocity Using Digital Rock Physics, International Symposium on Earth Science and Technology (CINEST) 2016, 2016.12.
146. C. Cao, T. Tsuji, The application of neural network for mineral classification, International Symposium on Earth Science and Technology (CINEST) 2016, 2016.12.
147. T. Tsuji, Fault displacement and fluid in the earth, Hungary-Japan (HAS-JSPS) Workshop on Physics of Rheology and Fracture, 2016.12.
148. T. Tsuji, Mathematical descriptions of rock pore geometry and its evolution, Forum "Math-for-Industry" 2016, 2016.11, [URL].
149. S. Singh, F. Jiang, T. Tsuji, Influence of slip flow at fluid-solid interface upon permeability of natural rock, GHGT-13, 2016.11, [URL].
150. T. Ikeda, T. Tsuji, Robust subsurface monitoring using a continuous and controlled seismic source, GHGT-13, 2016.11, [URL].
151. T. Tsuji, T. Ikeda, F. Jiang, Hydrologic and elastic properties of CO2 injected rock at various reservoir conditions: Insights into quantitative monitoring of injected CO2, GHGT-13, 2016.11, [URL].
152. S.Minato, R. Ghose, T. Tsuji, M.Ikeda, K.Onishi, Modeling and imaging multiply generated and scattered tube waves due to multiple hydraulic fractures, Society of Exploration Geophysicists Annual Meeting, 2016.10, [URL].
153. 池田 達紀, T. Tsuji, M. Takanashi, I. Kurosawa, M. Nakatsukasa, K. Worth, D.J. White, Time-lapse monitoring of shallow subsurface in the Aquistore CO2 storage site from surface-wave analysis using a continuous and controlled seismic source, Society of Exploration Geophysicists Annual Meeting, 2016.10, [URL].
154. Develop a method for continuous monitoring of reservoir.
156. G. Kimura, H. Koge, T. Tsuji, G.F. Moore, Latest-Miocene onset of Nankai Trough Subduction due to regional Change in Plate tectonic Framework, 日本地質学会第123年学術大会, 2016.09, [URL].
157. K. Ishitsuka, T. Tsuji, T. Matsuoka, A pixel-based baseline criteria selection for InSAR time-series analysis based on the estimation accuracy of surface displacement, CEOS(The Committee on Earth Observation Satellites) Calibration and Validation Workshop 2016, 2016.09, [URL].
158. A. Miyakawa, K. Onishi, T. Tsuji, T. Takahashi, T. Matsuoka, A. Priyono, B. Sapiie, R. Sule, W.G.A. Kadir, Case study of fault stability analysis in Indonesia "Gundih CCS project" on the basis of the fault orientation and stress state, Southeast Asian Conference on Geophysics (SEACG), 2016.09, [URL].
159. F. Jiang, T. Tsuji, A Three Phase Numerical Simulation Method for CCS-EOR, AOGS 2016 13th Annual Meeting, 2016.08, [URL].
160. T. Ikeda, F. Jiang, T. Tsuji, Digital Rock Physics for Evaluating Effects of CO2 Saturation on Seismic Velocity in Natural Sandstone, AOGS 2016 13th Annual Meeting, 2016.08, [URL].
161. Y. Sanada, S. Saito, Y. Hamada, T. Tsuji, K. Shiraishi, K. Hsiung, C. Eng, K. Yoshimoto, Y. Kido, H. Kumagai, T. Nozaki, J. Ishibashi, L. Maeda, CK16-01 Shipboard Party, New application with logging while drilling to deep water hydrothermal deposits with at Okinawa Trough, SPWLA ASIA & AUSTRALIA -REGIONAL CONFERENCE 2016, 2016.08.
162. , [URL].
163. T. Tsuji, Description of heterogeneous rock pore structures using mathematical methods, Study Group Workshop 2016, 2016.07, [URL].
164. T. Tsuji, T. Ikeda, Hydrologic and elastic modeling for time-evolved digital rock models : Insight into rock and fault evolution process, Crustal Dynamics 2016: Unified Understanding of Geodynamic Processes at Different Time and Length Scales, 2016.07, [URL].
165. T. Ikeda, T. Tsuji, Spatial and temporal variation of stress state in east Japan during the 2011 Tohoku-oki Earthquake from S-wave splitting analysis for ambient noise records, Crustal Dynamics 2016: Unified Understanding of Geodynamic Processes at Different Time and Length Scales, 2016.07, [URL].
166. T. Tsuji, Digitization of Natural Rocks for Estimation of The Hydrologic and Elastic Properties, SEG-AGU Workshop: Upper Crust Physics of Rocks, 2016.07, [URL].
167. F. Jiang, X. Li, T. Tsuji, A parallel implementation of three-phase LB model for CO2-EOR, 25th International Conference on Discrete Simulation of Fluid Dynamics (DSFD) 2016, 2016.07, [URL].
168. J. Jihui, Y. Liang, S. Murata, T. Tsuji, T. Matsuoka, Diagram of Elastic Moduli of CH4 and CO2 Hydrate, Goldschmidt 2016, 2016.07, [URL].
169. , [URL].
170. , [URL].
171. , [URL].
172. C. Eng, T. Ikeda, T. Tsuji, Characterization of Nankai Seismogenic Fault by Applying Dynamic Wave Propagation Simulation to Digital Rock Models, 日本地球惑星連合大会2016, 2016.05, [URL].
173. T. Ikeda, T. Tsuji, Spatial and temporal variation of stress state in east Japan during the 2011 Tohoku-oki earthquake: Insights from S-wave splitting analysis from ambient noise records, 日本地球惑星連合大会2016, 2016.05, [URL].
174. , [URL].
175. K.Ogawa, S.Tanaka, N.Sakatani, M.Ueno, T.Hoshino, K.Sakamoto, T.Kawamura, Y.Ishihara, N. Takeuchi, P. Lognonné, A.Araya, R.Yamada, T. Tsuji, T.Kobayashi, K.Shirai, M.Grott, J.Grygorczuk, A.Hagermann, J.Knollenberg, Geophysical experiments on Phobos proposed for JAXA Mars Moon Exploration mission, Japan Geoscience Union Meeting 2016, 2016.05, [URL].
176. S. Minato, R. Ghose, T. Tsuji, M. Ikeda, K. Onishi, Imaging hydraulic fractures at Median Tectonic Line, Japan using multiply generated and scattered tube waves in a shallow VSP experiment, EGU General Assembly 2016, 2016.05, [URL].
177. , [URL].
178. , [URL].
179. T. Tsuji, F. Jiang, Immiscible fluid displacement patterns under various reservoir conditions and their influence on geophysical properties, 8th International Conference on Porous Media & Annual Meeting, 2016.05, [URL].
180. F. Jiang, T. Tsuji, Numerical Simulations of Three-Phase Relative Permeability in Berea Sandstone using Lattice Boltzmann Method, 8th International Conference on Porous Media & Annual Meeting, 2016.05, [URL].
181. Cong Cao, Fei Jiang, T. Tsuji, Effects of segmentation methods on physical and hydrologic properties for 3-D digital rock model, 資源・素材学会 2016年 春季大会, 2016.03, [URL].
182. T. Tsuji, Digital rock physics: Influence of mineral precipitation on interrelations among hydrological and elastic properties, 13th International Workshop on WATER DYNAMICS, Hydrogen in the Earth and Fluid Behaviors, 2016.03, [URL].
183. Y. Ishihara, T. Kawamura, R. Yamada, K. Ogawa, N. Takeuchi, A. Araya, Philippe Lognonné, K. Shirai, T. Tsuji, T. Kobayashi, S. Tanaka, N. Kobayashi, Seismic observation package for Mars Moon Exploration Mission, Phobos, Deimos, and Mars Workshop, 2016.02, [URL].
184. K. Ogawa, S. Tanaka, N. Sakatani, M. Ueno, T. Hoshino, K. Sakamoto, T. Kawamura, Y. Ishihara, N. Takeuchi, P. Lognonné, A. Araya, R. Yamada, T. Tsuji, T. Kobayashi, et al., Geophysical Experiments on Phobos Proposed in MMX, Phobos, Deimos, and Mars Workshop, 2016.02, [URL].
185. T. Ikeda, T. Tsuji, Spatial and temporal variation of stress state in east Japan during the 2011 Tohoku-oki earthquake: Insights from S-wave splitting analysis from ambient noise records, Symposium on Subduction zone earthquakes in Nankai Trough & Japan Trench, 2016.02.
186. T. Tsuji, Pore pressure and stress state in the Nankai seismogenic fault: Insight from digital rock physics approach, Symposium on Subduction zone earthquakes in Nankai Trough & Japan Trench, 2016.02.
187. T. Tsuji, Fluid flow from the pore-scale to the field-scale, I2CNER Annual Symposium 2016, 2016.02, [URL].
188. T. Tsuji, F. Jiang, K. Christensen, Influence of reservoir conditions on multiphase flow in natural sandstone using lattice Boltzmann simulation: Investigation of suitable conditions in CCS and EOR, AGU Fall Meeting 2015, 2015.12, [URL].
189. B. Sapiie, H. Danio, A. Priyono, A. R. Asikin, D. S. Widarto, E. Widianto, T. Tsuji, Geological characteristic and fault stability of the Gundih CCS pilot project at Central Java, Indonesia, The 12th SEGJ International Symposium, 2015.11, [URL].
190. K. Onishi, D. T. Nguyen, H. Fujii, T. Tsuji, M. Hato, T. Takahashi, T. Takahashi, M. R. Sule, W. G. A. Kadir, Fluid flow simulations for the safety injection of carbon dioxide in Gundih CCS site, Indonesia, The 12th SEGJ International Symposium, 2015.11, [URL].
191. R. Sule, A. Asikin, A. Priyono, T. Tsuji, S. Raharjo, Simulation of time lapse seismic for CO2- injection monitoring: preliminary result, The 12th SEGJ International Symposium, 2015.11, [URL].
192. T. Ikeda, T. Tsuji, Characterization of near-surface heterogeneity by integrating surface-wave phase velocity and attenuation, The 12th SEGJ International Symposium, 2015.11, [URL].
193. S-wave splitting analysis using ambient noise records, [URL].
194. , [URL].
195. T. Tsuji, T. Ikeda, T. A. Johansen, B. O. Ruud, Time-lapse seismic profiles derived from passive seismic interferometry in fluid-injection experiments, SEG 85th Annual Meeting, 2015.10, [URL].
196. , [URL].
197. T. Tsuji, Digital rock physics for identification of suitable reservoir conditions in CO2 storage, The Third International Symposium on “Application of Nano-geosciences in Petroleum Engineering (NanoGeoscience 2015), 2015.09, [URL].
198. F. Jiang, T. Tsuji, Residual Non-Wetting Phase Saturation in Porous Media Controlled by Its Initial Distribution, AOGS 2015, 2015.08, [URL].
199. T. Ikeda, T. Tsuji, Characterization of Localized Heterogeneity in Shallow Formation by the Advanced Surface-Wave Analysis, AOGS 2015, 2015.08, [URL].
200. T. Tsuji, F. Jiang, K. Christensen, Elucidating the Influence of Reservoir Conditions on CO2-Brine Behavior in Natural Sandstone via Lattice Boltzmann Simulation, AOGS 2015, 2015.08, [URL].
201. T. Tsuji, Continuous monitoring of injected CO2 using ambient noise and controlled seismic source, IEA Greenhouse Gas R&D 10th Monitoring Network Meeting, 2015.06, [URL].
202. “Pore pressure in the subduction zone: Insight into tsunami earthquake", Workshop in Earthquake Research Institute“Subduction zone", The University of Tokyo..
203. Hydrocarbon gas efflux from an active deep-water mud volcano constrained by seismic velocity profiles, [URL].
204. Two-phase flow simulation in the large digital rock by using high performance cluster, [URL].
205. F. Jiang, T. Tsuji, Investigations on Relationship between Initial and Residual Saturation by Lattice Boltzmann Simulations, 7th International Conference on Porous Media & Annual Meeting, 2015.05, [URL].
206. Takeshi. Tsuji, F. Jiang, K. Christensen, Influence of reservoir conditions upon multiphase fluid displacement patterns within natural sandstone, 7th International Conference on Porous Media & Annual Meeting, 2015.05, [URL].
207. Digital rock physics for seismic monitoring of injected CO2.
208. Digital rock physics for energy and environmental geosciences.
209. New interpretation for shallow plate boundary fault and mega-splay fault in the Nankai Trough.
210. CO2 Dissolution Enhancement due to Velocity Circulation during Injection.
211. Development of geophysical monitoring method of injected CO2 using ambient noise, and its quantitative estimation using digital rock physics.
212. T. Ikeda, T. Tsuji, Detecting localized fracture and lithological boundary by the analysis of spatial variation of surface wave attenuation estimated from multichannel-multishot data, Annual Meeting/Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP) 2015, 2015.03.
213. New science using digital rock.
214. The potential and challenges on CO2 storage sites in Japan – approaches by I²CNER.
215. F. Jiang, Takeshi Tsuji, Investigations on Capillary Trapping Mechanism by a Digital Rock Approach, International Symposium on Earth Science and Technology 2014, 2014.12.
216. Hiroki Fukagawa, Takeshi Tsuji, A Formulation for Dissolution in Inhomogeneous Temperature Field, International Symposium on Earth Science and Technology 2014, 2014.12.
217. T. Ikeda, Takeshi Tsuji, Detecting localized fracture and lithological boundary in shallow formation from surface wave attenuation, International Symposium on Earth Science and Technology 2014, 2014.12.
218. Weiren Lin, Timothy B. Byrne, Masataka Kinoshita, Lisa C. McNeill, Chandong Chang, Jonathan C. Lewis, Yuzuru Yamamoto, Demian M. Saffer, J. Casey Moore, Hung-Yu Wu, Takeshi Tsuji, Yasuhiro Yamada, Marianne Conin, Saneatsu Saito, Takatoshi Ito, Harold J. Tobin, Gaku Kimura, Kyuichi Kanagawa, Juichiro Ashi, Michael B. Underwood, Toshiya Kanamatsu, Distribution of stress state in the Nankai subduction zone, southwest Japan and a comparison with Japan Trench, The GEEA 2014 conference, 2014.11.
219. A variational analysis of the absorption of supercritical CO2 in water in porous rock.
220. Takeshi. Tsuji, Geophysical exploration and monitoring, and Rock physics for subsurface property estimation from geophysical data, Institute of Technology of Cambodia, JICA invited lecture, 2014.10.
221. Two-dimensional analysis of surface wave attenuation coefficients by using multichannel seismic data.
222. Takeshi Tsuji, Keigo Kitamura, Toshifumi Matsuoka, Yasuhiro Yamada, Wawan Gunawan A Kadir, Mohammad Rachmat Sule, Awali Priyonom, Tusuka Ariadji, Benyamin Sapiie, Masami Hato, Toru Takahashi, Kyosuke Onishi, Djedi S Widarto, Rio I Sebayang, Agung Prasetyo, Pertamina, Gundih CCS Project Team, Reservoir characterization for site selection in the Gundih CCS Project, Indonesia, GHGT-12, 2014.10.
223. S. Kimura, K. Honda, K. Kitamura, I. Taniguchi, K. Shitashima, T. Tsuji, S. Fujikawa, Preliminary feasibility study for on-site hydrogen station with distributed CO2 capture and storage system, GHGT-12, 2014.10.
224. Keigo Kitamura, Takeshi Tsuji, Yasuhiro Yamada, Toshifumi Matsuoka, Kyosuke Onishi, Benyamin Sapiie, Alfian Bahar, Harya, Algifari Muhammad, Agung Prasetyo, Aurio Erdi, Vani Mutia Sari, Wawan Gunawan A Kadir, Gundih CCS Project Team, Potential evaluation of CO2 reservoir using the measured petrophysical parameter of rock samples in the Gundih CCS Project, Indonesia, GHGT-12, 2014.10.
225. F. Jiang, T. Tsuji, Interfacial tension effect on cluster size distributions for residual trapping of CO2 in sandstones, GHGT-12, 2014.10.
226. Takeshi Tsuji, Digital rock physics for CO2 dynamic modeling and monitoring, The 7th Symposium on CCS in Gundih Area, Central Java, Indonesia, 2014.09.
227. Kyosuke Onishi, Takeshi Tsuji, Current research status of Geology and Geophysics - from Japanese team –, The 7th Symposium on CCS in Gundih Area, Central Java, Indonesia, 2014.09.
228. The interfacial tension effect on capillary trapping of CO2 in porous media.
229. Pore pressure distribution of a mega-splay fault system in the Nankai Trough subduction zone.
230. Takeshi Tsuji, Pore pressure distribution of a mega-splay fault and seaward plate boundary decollement in the Nankai Trough subduction zone: Up-dip extent of the seismogenic zone? , Joint Workshop on Slow earthquakes, 2014, 2014.09.
231. 辻 健, Digital rock physics: Insight into fluid flow and elastic deformation of porous media, GeoMod2014, 2014.09.
232. W. Lin, T. Byrne, M. Kinoshita, L. McNeill, C. Chang, Y. Yamamoto, H. Wu, Y. Yamada, T. Tsuji, S. Saito, Distribution of Stress State in Nankai Subduction Zone, Southwest Japan Determined During NanTroSEIZE Stage 1 and 2, Asia Oceania Geosciences Society 2014, 2014.08, [URL].
233. 辻 健, Rie Kamei, Gerhard Pratt, Pore Pressure Distribution in the Nankai Accretionary Prism Off Kumano, Asia Oceania Geosciences Society 2014, 2014.08.
234. 辻 健, 蒋 飛, Evolution of Hydrological and Elastic Properties Due to Carbonate Precipitation within Digital Rock Sample, Asia Oceania Geosciences Society 2014, 2014.07.
235. F. Jiang, T. Tsuji, Lattice Boltzmann Simulation of Cluster Size Distributions for Residual Trapping of CO2 in Sandstones, Asia Oceania Geosciences Society 2014, 2014.07, [URL].
236. Application of multiphase lattice Boltzmann simulation for the large digital rock models.
237. Time variation of hydrological and elastic properties due to CO2 mineralization in CCS project: Insights from two-phase flow simulation for large digital rock models.
238. Recent surface displacement in Bangkok associated with groundwater recovery.
239. Surface displacement around Hachobaru geothermal field inferred from persistent scatterer SAR interferometry.
240. Ground deformation around Ohaaki geothermal field, New Zealand inferred from persistent scatterer SAR interferometry.
241. Geophysical exploration and monitoring system for subseabed CCS.
242. Pilot Study on CCS in Gundih Gas Field in Central Java, Indonesia: Reservoir Characterization and simulation for site selection.
243. Evolution of hydrological and elastic properties due to mineral precipitation in CCS project: Application of two-phase Lattice-Boltzmann method to large-size digital rock and integration of mineralogical modeling.
244. 辻 健, Reservoir characterization and Monitoring CCS projects in Geological Formations Typical in Japan -CCS projects in Indonesia and Japan-, CCOP CO2 Storage Mapping Program (CCSM) Seminar, 2014.03.
245. 辻 健, Stress state in plate subduction zone and its time variation, Geofluid-3, 2014.03.
246. Takeshi Tsuji, Fei Jiang, Evolution of pore-geometry and relative-permeability due to carbonate precipitation within natural rock sample: Insight from a coupled FVM-LBM method, American Geophysical Union’s 46th annual Fall Meeting, 2013.12.
247. Takeshi Tsuji, Current research status of Gundih CCS pilot project -Progress report from Japanese team -, The 6th Symposium on CCS in Gundih Area, Central Java, Indonesia, 2013.11.
248. Takeshi Tsuji, Teruki Maiguma, Makoto Yamada, Evaluation method for earthquake resistance capacity of smallscale buildings using microtremors, 11th SEGJ International Symposium, 2013.11.
249. Takeshi Tsuji, Estimation and monitoring of crustal stress, Earthquake and Volcano Research Center, Nagoya University, 2013.11.
250. Takeshi Tsuji, Effective stress and pore pressure distribution in the Nankai accretionary prism: Potential rupture propagation from mega-splay fault to décollement, Earthquake Research Institute, University of Tokyo, 2013.09.
251. Takeshi Tsuji, Toshifumi Matsuoka, Toru Takahashi, 北村 圭吾, Kyosuke Onishi, Yasuhiro Yamada, Mohammad Rachmat Sule, Wawan Gunawan A. Kadir, Djedi S. Widarto, Rio I. Sebayang, Agung Prasetyo, Awali Priyono, Eko Widianto, Benyamin Sapiie, Pilot CCS project in Indonesia “Gundih CCS project”: Geological and geophysical surveys for site selection and monitoring, EGU General Assembly, 2013.04.
Membership in Academic Society
  • The Geothermal Research Socity of Japan
  • The society of materials science, Japan
  • The mining and materials processing institute of japan
  • InterPore
  • Japan GeoScience Union (JPGU)
  • European Geophysical Union (EGU)
  • The Seismological Society of Japan
  • American Geophysical Union
  • Society of Exploration Geophysists (SEG)
  • The Society of Exploration Geophysicists of Japan (SEGJ)
  • The Geological Society of Japan
  • Award for the creation of a new method of exploration to study the internal structure of the Earth and its application in the field of disaster management.
  • Tsuji Takeshi has been awarded the Early Career Scientist Award of the International Union of Geodesy and Geophysics (IUGG). IUGG is a non-governmental, scientific organization, established in 1919. IUGG is one of the 40 scientific Unions and Associations presently grouped within the International Council. As a member of the International Science council, it is the largest institution dedicated to the international promotion and coordination of scientific studies of Earth (physical, chemical, and mathematical) and its environment in space. IUGG holds General Assemblies every four years and presents awards to early career scientists who have achieved on excellent performance in their research on Earth and space sciences international research cooperation. Less than 10 scientists from around the world will be chosen for the awards. In 2018, Tsuji is the only Japanese researcher to receive this year’s award.
    Tsuji has been chosen for the Early Career Scientist Award in the field of Seismology for his innovative and interdisciplinary works. He has developed new geophysical exploration methods to estimate earthquake faults, methane hydrate, hydrothermal ore deposits and geothermal reservoirs. He has characterized earthquake faults in the Nankai Trough and in the Japan Trench. His findings contribute to understanding of the hypocenter distribution and tsunami mechanisms. Recently he has been interested in continuous geophysical monitoring of earth crust and resource reservoirs. Indeed, his group succeeded to reveal dynamic behaviors of crust during the earthquake and volcanic eruption. In addition to such geophysical approaches, he has elucidated fluid behaviors within digitalized rock using computational approach (i.e., digital rock physics), because subsurface dynamic behavior is usually related to fluid flow. He further develops a geophysical approach to explore the Moon subsurface structures.
  • Award for Tsuji et al. "Ruptured faults of the 2011 Tohoku-Oki earthquake; Insight from seismic data and submersible observations conducted before and after the earthquake".
  • JSPS Excellent Young Researchers Overseas Visit Program for "Development of rock physics model for various lithologies and evaluation of its scaling effect"
  • Outstanding Presentation Award of 2007 Society of Exploration Geophysicists of Japan (SEGJ) Fall Meeting; Award for "Tsuji, T. and H. Yamaguchi (2007), Improvement of Mineral Mapping Method: Application of Neural Network System to Elemental Maps by Electron Microprobe Analyzer, 2007 SEGJ fall meeting, Hokkaido University, 2007."
  • Incentive Award of 2005 Society of Exploration Geophysicists of Japan (SEGJ); Award for "Tsuji et al. (2004), Physical properties along the plate boundary decollement in the Nankai Trough using seismic attribute anaysis with Kohonen self-organizing map, Butsuri-tansa, 57, 121-134."
Educational Activities
I am supervising students in Department of Earth Resource Engineering department to accomplish their theses. I try to find suitable research topic for each student. Also, I try to have a chance to discuss with students as much as possible. I hope that students are independent when they graduate Kyushu University. In International Institute for Carbon-Neutral Energy Research (I2CNER), I have frequent discussion with young faculties and post-doc scientists. I hope them to be first-class scientists in the world.
Other Educational Activities
  • 2019.12.
  • 2018.11, Evaluate PhD thesis in Yonsei University.
  • 2018.09.
  • 2018.06, Evaluate the PhD thesis of UNIVERSITI BRUNEI DARUSSALAM..
  • 2017.09.
  • 2017.07.
  • 2014.07.
Professional and Outreach Activities
Give a lecture in Institute of Technology of Cambodia under JICA project..