九州大学 研究者情報
論文一覧
松島 健(まつしま たけし) データ更新日:2019.01.18

准教授 /  理学研究院 附属地震火山観測研究センター 地震学・火山学


原著論文
1. Rebecca Coats, Jackie E. Kendrick, Paul A. Wallace, Takahiro Miwa, Adrian J. Hornby, James D. Ashworth, Takeshi Matsushima, Yan Lavallée, Failure criteria for porous dome rocks and lavas
A study of Mt. Unzen, Japan, Solid Earth, 10.5194/se-9-1299-2018, 9, 6, 1299-1328, 2018.11, [URL], The strength and macroscopic deformation mode (brittle vs. ductile) of rocks is generally related to the porosity and pressure conditions, with occasional considerations of strain rate. At high temperature, molten rocks abide by Maxwell's viscoelasticity and their deformation mode is generally defined by strain rate or reciprocally by comparing the relaxation timescale of the material (for a given condition) to the observation timescale - a dimensionless ratio known as the Deborah (De) number. Volcanic materials are extremely heterogeneous, with variable concentrations of crystals, glass-melt, and vesicles (of different sizes), and a complete description of the conditions leading to flow or rupture as a function of temperature, stress and strain rate (or timescale of observation) eludes us. Here, we examined the conditions which lead to the macroscopic failure of variably vesicular (0.09-0.35), crystal-rich (∼ 75 vol %), pristine and altered dome rocks (at ambient temperature) and lavas (at 900°C) from Mt. Unzen volcano, Japan. We found that the strength of the dome rocks decreases with porosity and is commonly independent of strain rate; when comparing pristine and altered rocks, we found that the precipitation of secondary mineral phases in the original pore space caused minor strengthening. The strength of the lavas (at 900°C) also decreases with porosity. Importantly, the results demonstrate that these dome rocks are weaker at ambient temperatures than when heated and deformed at 900°C (for a given strain rate resulting in brittle behaviour). Thermal stressing (by heating and cooling a rock up to 900°C at a rate of 4°C min-1, before testing its strength at ambient temperature) was found not to affect the strength of rocks. In the magmatic state (900°C), the rheology of the dome lavas is strongly strain rate dependent. Under conditions of low experimental strain rate (≤ 10-4 s-1), ductile deformation dominated (i.e. the material sustained substantial, pervasive deformation) and displayed a non-Newtonian shear thinning behaviour. In this regime, the apparent viscosities of the dome lavas were found to be essentially equivalent, independent of vesicularity, likely due to the lack of pore pressurisation and efficient pore collapse during shear. At high experimental strain rates ( ≥ 10-4 s-1) the lavas displayed an increasingly brittle response (i.e. deformation resulted in failure along localised faults); we observed an increase in strength and a decrease in strain to failure as a function of strain rate. To constrain the conditions leading to failure of the lavas, we analysed and compared the critical Deborah number at failure (Dec) of these lavas to that of pure melt (Demelt = 10-3-10-2; Webb and Dingwell, 1990). We found that the presence of crystals decreases Dec to between 6.6×10-4 and 1×10-4. The vesicularity (φ), which dictates the strength of lavas, further controls Dec following a linear trend. We discuss the implications of these findings for the case of magma ascent and lava dome structural stability..
2. Seiji Tsuno, Masahiro Korenaga, Kyosuke Okamoto, Hiroaki Yamanaka, Kosuke Chimoto, Takeshi Matsushima, Local site effects in Kumamoto City revealed by the 2016 Kumamoto earthquake 2016 Kumamoto earthquake sequence and its impact on earthquake science and hazard assessment, Earth, Planets and Space, 10.1186/s40623-017-0622-6, 69, 1, 2017.12, [URL], To evaluate local site effects in Kumamoto City, we installed six temporary seismic stations along a 6-km north-south survey line in the city immediately after the 2016 Kumamoto earthquake foreshock (Mj 6.4), which occurred on April 14, 2016. Seismic data from the 2016 Kumamoto earthquake (Mj 7.3), which occurred on April 16, 2016, were successfully recorded at two sites and indicated large amplitudes in the frequency range of 0.5-3 Hz. Site amplifications estimated from weak ground motion data, with a station at Mt. Kinbo used as a reference, are relatively variable along this survey line; however, site amplification factors in the frequency range of 0.5-3 Hz are not large enough to explain the amplitudes produced by the main shock. Nevertheless, site amplifications estimated from strong ground motion data recorded at the two sites during the main shock are large in the frequency range of 1-3 Hz. These findings reveal that the strong ground motions in the frequency range of 1-3 Hz were enhanced by nonlinear behavior of the subsurface soil in Kumamoto City. Moreover, it is observed that the frequency contents of the main shock data in the frequency range of 0.7-3 Hz differ significantly between the two sites, despite the proximity of these sites (600-m interval). Therefore, we also performed single-station microtremor measurements with an interval distance of approximately 100 m between these two sites. We confirmed that the peak frequencies of the horizontal-to-vertical spectral ratios of microtremors have trends that are similar to those of the site amplification factors between the two sites. However, these results could not explain the differences in strong ground motions observed at the two sites during the 2016 Kumamoto earthquake.[Figure not available: see fulltext.].
3. Koki Aizawa, Hisafumi Asaue, Katsuaki Koike, Shinichi Takakura, Mitsuru Utsugi, Hiroyuki Inoue, Ryokei Yoshimura, Ken'Ichi Yamazaki, Shintaro Komatsu, Makoto Uyeshima, Takao Koyama, Wataru Kanda, Taro Shiotani, Nobuo Matsushima, Maki Hata, Tohru Yoshinaga, Kazunari Uchida, Yuko Tsukashima, Azusa Shito, Shiori Fujita, Asuma Wakabayashi, Kaori Tsukamoto, Takeshi Matsushima, Masahiro Miyazaki, Kentaro Kondo, Kanade Takashima, Takeshi Hashimoto, Makoto Tamura, Satoshi Matsumoto, Yusuke Yamashita, Manami Nakamoto, Hiroshi Shimizu, Seismicity controlled by resistivity structure
The 2016 Kumamoto earthquakes, Kyushu Island, Japan, Earth, Planets and Space, 10.1186/s40623-016-0590-2, 69, 1, 2017.12, [URL], The M JMA 7.3 Kumamoto earthquake that occurred at 1:25 JST on April 16, 2016, not only triggered aftershocks in the vicinity of the epicenter, but also triggered earthquakes that were 50-100 km away from the epicenter of the main shock. The active seismicity can be divided into three regions: (1) the vicinity of the main faults, (2) the northern region of Aso volcano (50 km northeast of the mainshock epicenter), and (3) the regions around three volcanoes, Yufu, Tsurumi, and Garan (100 km northeast of the mainshock epicenter). Notably, the zones between these regions are distinctively seismically inactive. The electric resistivity structure estimated from one-dimensional analysis of the 247 broadband (0.005-3000 s) magnetotelluric and telluric observation sites clearly shows that the earthquakes occurred in resistive regions adjacent to conductive zones or resistive-conductive transition zones. In contrast, seismicity is quite low in electrically conductive zones, which are interpreted as regions of connected fluids. We suggest that the series of the earthquakes was induced by a local accumulated stress and/or fluid supply from conductive zones. Because the relationship between the earthquakes and the resistivity structure is consistent with previous studies, seismic hazard assessment generally can be improved by taking into account the resistivity structure. Following on from the 2016 Kumamoto earthquake series, we suggest that there are two zones that have a relatively high potential of earthquake generation along the western extension of the MTL. [Figure not available: see fulltext.].
4. Miyo Fukui, Takeshi Matsushima, Natsumi Yumitori, Jun Oikawa, Atsushi Watanabe, Takashi Okuda, Taku Ozawa, Yuhki Kohno, Yousuke Miyagi, Pressure sources of the Miyakejima volcano estimated from crustal deformation studies during 2011–2013, Proceedings of the International Symposium on Geodesy for Earthquake and Natural Hazards, GENAH 2014
International Symposium on Geodesy for Earthquake and Natural Hazards (GENAH) - Proceedings of the International Symposium on Geodesy for Earthquake and Natural Hazards (GENAH)
, 10.1007/1345_2015_150, 145, 117-123, 2017.01, [URL], Following the eruption of the Miyakejima Volcano in the Izu Islands, Japan, in the year 2000, a continuous GPS network observed the ongoing contracting crustal deformation. Subsequently, a slight inflation of the island was detected from around 2006, and we initiated a campaign of dense GPS observations around the volcano from 2011. Precise crustal deformation studies indicated inflation in the southern part of the island and deflation around the center of the crater. Using these observations, we estimated that three magma sources (a shallow deflation sill under the crater, a southern inflation dyke, and a deep inflation spherical source) were activated during 2011–2013. In particular, the presence of an inflation dyke at an intermediate depth had not been inferred by previous studies. Accordingly, we posit that the supply of magma from a deep spherical source to the new dyke source has been initiated only recently..
5. Takahiko Murayama, Masaki Kanao, Masa Yuki Yamamoto, Yoshiaki Ishihara, Takeshi Matsushima, Yoshihiro Kakinami, Kazumi Okada, Hiroki Miyamachi, Manami Nakamoto, Yukari Takeuchi, Shigeru Toda, Time-space variations in infrasound sources related to environmental dynamics around Lu¨tzow-Holm Bay, east Antarctica, Polar Science, 10.1016/j.polar.2017.10.001, 2017, [URL], Characteristic features of infrasound waves observed in the Antarctic reflect the physical interaction between the surface environment along the continental margin and the surrounding Southern Ocean. The temporal-spatial variability of the source locations for infrasound excitation during the eight-month period between January and August 2015 was investigated using recordings made by two infrasound arrays deployed along a section of the coast of Lu¨tzow-Holm Bay (LHB), Antarctica. The infrasound arrays clearly detected temporal variations in frequency content and propagation direction during this period. A number of infrasound sources were identified, many located north of the arrays. Many of the events had a predominant frequency content of a few Hz, higher than microbaroms from the ocean. A comparison of the results with MODIS satellite images indicated that these infrasound sources were ice-quakes associated with the calving of glaciers, the breaking off of sea ice, and collisions between this sea ice and icebergs around the LHB. Continuous measurements of infrasound in the Antarctic may serve as a proxy for monitoring the regional surface environment in terms of climate change at high southern latitudes..
6. Masayuki Murase, Fumiaki Kimata, Yoshiko Yamanaka, Shinichiro Horikawa, Kenjiro Matsuhiro, Takeshi Matsushima, Hitoshi Mori, Takahiro Ohkura, Shin Yoshikawa, Rikio Miyajima, Hiroyuki Inoue, Taketoshi Mishima, Tadaomi Sonoda, Kazunari Uchida, Keigo Yamamoto, Harushisa Nakamichi, Preparatory process preceding the 2014 eruption of Mount Ontake volcano, Japan
Insights from precise leveling measurements 5.Volcanology, Earth, Planets and Space, 10.1186/s40623-016-0386-4, 68, 1, 2016.12, [URL], Preparatory activity preceding the 2014 eruption of Mount Ontake volcano was estimated from vertical deformation detected using a precise leveling survey. Notable uplift (2006-2009) and subsidence (2009-2014) were detected on the eastern flank of the volcano. We estimated pressure source models based on the vertical deformation and used these to infer preparatory process preceding the 2014 eruption. Our results suggest that the subsidence experienced between 2009 and 2014 (including the period of the 2014 eruption) occurred as a result of a sill-like tensile crack with a depth of 2.5 km. This tensile crack might inflate prior to the eruption and deflate during the 2014 activity. A two-tensile-crack model was used to explain uplift from 2006 to 2009. The geometry of the shallow crack was assumed to be the same as the sill-like tensile crack. The deep crack was estimated to be 2 km in length, 4.5 km in width, and 3 km in depth. Distinct uplifts began on the volcano flanks in 2006 and were followed by seismic activities and a small phreatic eruption in 2007. From the partially surveyed leveling data in August 2013, uplift might continue until August 2013 without seismic activity in the summit area. Based on the uplift from 2006 to 2013, magma ascended rapidly beneath the summit area in December 2006, and deep and shallow tensile cracks were expanded between 2006 and 2013. The presence of expanded cracks between 2007 and 2013 has not been inferred by previous studies. A phreatic eruption occurred on 27 September 2014, and, following this activity, the shallow crack may have deflated..
7. Tomomi Okada, Toru Matsuzawa, Norihito Umino, Keisuke Yoshida, Akira Hasegawa, Hiroaki Takahashi, Takuji Yamada, Masahiro Kosuga, Tetsuya Takeda, Aitaro Kato, Toshihiro Igarashi, Kazushige Obara, Shinichi Sakai, Atsushi Saiga, Takashi Iidaka, Takaya Iwasaki, Naoshi Hirata, Noriko Tsumura, Yoshiko Yamanaka, Toshiko Terakawa, Haruhisa Nakamichi, Takashi Okuda, Shinichiro Horikawa, Hiroshi Katao, Tsutomu Miura, Atsuki Kubo, Takeshi Matsushima, Kazuhiko Goto, Hiroki Miyamachi, Hypocenter migration and crustal seismic velocity distribution observed for the inland earthquake swarms induced by the 2011 Tohoku-Oki earthquake in NE Japan
Implications for crustal fluid distribution and crustal permeability, Crustal Permeability, 10.1002/9781119166573.ch24, 307-323, 2016.10, [URL], After the occurrence of the 2011 magnitude 9 Tohoku earthquake, seismicity in the overriding plate changed. This chapter considers some possible evidence of the influence of crustal fluid/water on the occurrence of the triggered seismicity after the 2011 Tohoku-Oki earthquake. It estimates the permeability from the observed hypocenter diffusion. Shallow seismic activity and crustal deformation are strongly affected by the water dehydrated and upwelling from the subducting Pacific plate. Spatiotemporal expansion of hypocenter areas of some earthquake swarms can be attributed to fluid diffusion. In the upper crust, the earthquakes seem to be distributed in seismic high-velocity areas rather than in seismic low-velocity areas. In the lower crust, the seismic low-velocity areas appear to be elongated along N-S or NE-SW, the strike of the island arc. The chapter also estimates three-dimensional seismic velocity structure using the double-difference tomography method..
8. Hatakeyama, H., Uchid, N., Matsuzawa, T., Okada, T., Nakajima, J., Matsushima, T., Kono, T., Hirahara, S., Nakayama, T., Variation in high-frequency wave radiation from small repeating earthquakes as revealed by cross-spectral analysis, Geophysical Journal International, 10.1093/gji/ggw313, 207, 2, 1030-1048, 2016.08, We examined the variation in the high-frequency wave radiation for three repeating earthquake sequences (M = 3.1–4.1) in the northeastern Japan subduction zone by waveform analyses. Earthquakes in each repeating sequence are located at almost the same place and show low-angle thrust type focal mechanisms, indicating that they represent repeated ruptures of a seismic patch on the plate boundary. We calculated cross-spectra of the waveforms and obtained the phases and coherences for pairs of events in the respective repeating sequences in order to investigate the waveform differences. We used waveform data sampled at 1 kHz that were obtained from temporary seismic observations we conducted immediately after the 2011 Tohoku earthquake near the source area. For two repeating sequences, we found that the interevent delay times for the two waveforms in a frequency band higher than the corner frequencies are different from those in a lower frequency band for particular event pairs. The phases and coherences show that there are coherent high-frequency waves for almost all the repeaters regardless of the high-frequency delays. These results indicate that high-frequency waves are always radiated from the same vicinity (subpatch) for these events but the time intervals between the ruptures of the subpatch and the centroid times can vary. We classified events in the sequence into two subgroups according to the high-frequency band interevent delays relative to the low-frequency band. For one sequence, we found that all the events that occurred just after (within 11 days) larger nearby earthquakes belong to one subgroup while other events belong to the other subgroup. This suggests that the high-frequency wave differences were caused by stress perturbations due to the nearby earthquakes. In summary, our observations suggest that high-frequency waves from the repeating sequence are radiated not from everywhere but from a long-duration subpatch within the seismic slip area. The variation in high-frequency radiation can be explained by rupture pattern differences that depend on the stress conditions in and around the seismic patches..
9. Ishihara, Y., Kanao, M., Yamamoto, M., Toda, S., Matsushima, T., Murayama, T., Infrasound observations at Syowa Station, East Antarctica: Implications for detecting the surface environmental variations in the polar regions, Geoscience Frontiers, doi/10.1016/j.gsf.2013.12.012 , 6, 2, 285-296, 2015.03, [URL].
10. 九州大学地震火山観測研究センター, 雲仙岳火山活動状況, 火山噴火予知連絡会会報, 117, 182-185, 2015.03.
11. T. Okada, T. Matsuzawa, N. Umino, K. Yoshida, A. Hasegawa, H. Takahashi, T. Yamada, M. Kosuga, T. Takeda, A. Kato, T. Igarashi, K. Obara, S. Sakai, A. Saiga, T. Iidaka, T. Iwasaki, N. Hirata, N. Tsumura, Y. Yamanaka, T. Terakawa, H. Nakamichi, T. Okuda, S. Horikawa, H. Katao, T. Miura, A. Kubo, Takeshi Matsushima, K. Goto, H. Miyamachi, Hypocenter migration and crustal seismic velocity distribution observed for the inland earthquake swarms induced by the 2011 Tohoku-Oki earthquake in NE Japan
Implications for crustal fluid distribution and crustal permeability, Geofluids, 10.1111/gfl.12112, 15, 1-2, 293-309, 2015.01, [URL], After the occurrence of the 2011 magnitude 9 Tohoku earthquake, the seismicity in the overriding plate changed. The seismicity appears to form distinct belts. From the spatiotemporal distribution of hypocenters, we can quantify the evolution of seismicity after the 2011 Tohoku earthquake. In some earthquake swarms near Sendai (Nagamachi-Rifu fault), Moriyoshi-zan volcano, Senya fault, and the Yamagata-Fukushima border (Aizu-Kitakata area, west of Azuma volcano), we can observe temporal expansion of the focal area. This temporal expansion is attributed to fluid diffusion. Observed diffusivity would correspond to the permeability of about 10-15 (m2). We can detect the area from which fluid migrates as a seismic low-velocity area. In the lower crust, we found seismic low-velocity areas, which appear to be elongated along N-S or NE-SW, the strike of the island arc. These seismic low-velocity areas are located not only beneath the volcanic front but also beneath the fore-arc region. Seismic activity in the upper crust tends to be high above these low-velocity areas in the lower crust. Most of the shallow earthquakes after the 2011 Tohoku earthquake are located above the seismic low-velocity areas. We thus suggest fluid pressure changes are responsible for the belts of seismicity..
12. Yoshiaki Ishihara, Masaki Kanao, Masa Yuki Yamamoto, Shigeru Toda, Takeshi Matsushima, Takahiko Murayama, Infrasound observations at Syowa Station, East Antarctica
Implications for detecting the surface environmental variations in the polar regions, Geoscience Frontiers, 10.1016/j.gsf.2013.12.012, 6, 2, 285-296, 2015.01, [URL], Characteristic infrasound waves observed at Antarctic stations demonstrate physical interaction involving environmental changes in the Antarctic continent and the surrounding oceans. A Chaparral-type infrasound sensor was installed at Syowa Station (SYO; 39°E, 69°S), East Antarctica, as one of the projects of the International Polar Year (IPY2007-2008). Data continuously recorded during the three seasons in 2008-2010 clearly indicate a contamination of the background oceanic signals (microbaroms) with peaks between 4 and 10 s observed during a whole season. The peak amplitudes of the microbaroms have relatively lower values during austral winters, caused by a larger amount of sea-ice extending around the Lützow-Holm Bay near SYO, with decreasing ocean wave loading effects. Microbaroms measurements are useful tool for characterizing ocean wave climate, complementing other oceanographic and geophysical data. A continuous monitoring by infrasound sensors in the Antarctic firmly contributes to the Comprehensive Nuclear-Test-Ban Treaty (CTBT) in the southern high latitude, together with the Pan-Antarctic Observations System (PAntOS) under the Scientific Committee on Antarctic Research (SCAR). Detailed measurements of the infrasound waves in Antarctica, consequently, could be a new proxy for monitoring regional environmental change as well as the temporal climate variations in the polar regions..
13. 渡邉篤志, 大湊隆雄, 及川 純, 松島 健, 三本嶽点の記(大野原島観測点新設の記録), 東京大学地震研究所技術研究報告, 20, 19-24, 2014.12, [URL].
14. Murayama, T., Kanao, M., Yamamoto, M., Ishihara, Y., Matsushima, T., Kakinami, Y., Infrasound Array Observations in the Lützow-Holm Bay Region, East Antarctica, Polar Science, 10.1016/j.polar.2014.07.005, 2014.08, The characteristic features of infrasound waves observed in Antarctica reveal a physical interaction involving surface environmental variations in the continent and the surrounding Southern Ocean. A single infrasound sensor has been making continuous recordings since 2008 at Syowa Station (SYO; 69.0S, 39.6E) in the Lützow-Holm Bay (LHB) of East Antarctica. The continuously recorded data clearly show the contamination of background oceanic signals (microbaroms) throughout all seasons. In austral summer 2013, several field stations with infrasound sensors were established along the coast of the LHB. Two infrasound arrays of different diameters were set up: one at SYO (with a 100-m spacing triangle) and one in the S16 area on the continental ice sheet (with a 1000-m spacing triangle). In addition to these arrays, isolated single stations were deployed at two outcrops in the LHB. These newly established arrays clearly detected the propagation direction and frequency content of microbaroms from the Southern Ocean. Microbarom measurements are a useful tool for characterizing ocean wave climates, complementing other oceanographic and geophysical data from the Antarctic. In addition to the microbaroms, several other remarkable infrasound signals were detected, including regional earthquakes, and airburst shock waves emanating from a meteoroid entering the atmosphere over the Russian Republic on 15 February 2013. Detailed and continuous measurements of infrasound waves in Antarctica could prove to be a new proxy for monitoring regional environmental change as well as temporal climate variations in high southern latitudes..
15. 山本 圭吾, 松島 健, 吉川 慎, 大倉 敬宏, 横尾 亮彦, 相澤 広記, 井上 寛之, 三島 壮智, 内田 和也, 園田 忠臣, 関 健次郎, 小松 信太郎, 堀田 耕平, 高橋 温志, 豊福 隆史, 浅野 晴香, 成田 次範, 水準測量によって測定された桜島火山および姶良カルデラ周辺域の地盤上下変動 ―2013年10月および11月測量の結果―, 京都大学防災研究所年報, 第56号B, 116-124, 2014.06.
16. 片尾 浩, 久保 篤規, 山品 匡史, 松島 健, 相澤 広記, 酒井 慎一, 澁谷 拓郎, 中尾 節郎, 吉村 令慧, 木内 亮太, 三浦 勉, 飯尾 能久, 2013年4月13日淡路島付近の地震(M6.3)の余震の発震機構, 京都大学防災研究所年報, 57B, 80-84, 2014.06.
17. 九州大学地震火山観測研究センター, 雲仙岳火山活動状況, 火山噴火予知連絡会会報, 116, 182-185, 2014.03.
18. 九州大学地震火山観測研究センター, 雲仙岳火山活動状況, 火山噴火予知連絡会会報, 115, 127-131, 2014.03.
19. 九州大学地震火山観測研究センター, 雲仙岳火山活動状況, 火山噴火予知連絡会会報, 114, 169-173, 2014.03.
20. 松島 健, 福井 海世, 及川 純, 渡邉 篤志, 大湊 隆雄, 小澤 拓, 宮城 洋介, 河野 裕希, 奥田 隆, 2013 年4 月17 日三宅島大野原島近傍で発生したMJ6.2 の地震, 火山噴火予知連絡会会報, 116, 125-126, 2014.03.
21. 松島 健, 伊豆鳥島の地熱活動, 火山噴火予知連絡会会報, 116, 133-133, 2014.03, [URL].
22. 松島 健, 霧島火山におけるGPS基線長の変化, 火山噴火予知連絡会会報, 113, 173-174, 2014.01, [URL].
23. 九州大学地震火山観測研究センター, 雲仙岳火山活動状況, 火山噴火予知連絡会会報, 113, 144-147, 2014.01.
24. 九州大学地震火山観測研究センター, 雲仙岳火山活動状況, 火山噴火予知連絡会会報, 112, 136-138, 2014.01.
25. Keisuke Yoshida, Akira Hasegawa, Tomomi Okada, Hiroaki Takahashi, Masahiro Kosuga, Takaya Iwasaki, Yoshiko Yamanaka, Hiroshi Katao, Yoshihisa Iio, Atsuki Kubo, Takeshi Matsushima, Hiroki Miyamachi, Youichi Asano, Pore pressure distribution in the focal region of the 2008 M7.2 Iwate-Miyagi Nairiku earthquake, Earth, Planets and Space, 10.1186/1880-5981-66-59, 66, 1, 2014, [URL], The pore fluid pressure distribution in the focal region of the 2008 Iwate-Miyagi Nairiku earthquake was investigated through an analysis of the diversity of focal mechanisms. We inverted stress orientations and focal mechanisms directly from P-wave polarity data obtained from a dense aftershock observation network and other temporarily and routinely operated stations. The estimated stress orientation is consistent with that typical of NE Japan. Specifically, the σ1 axis is oriented WNW-ESE nearly parallel to plate convergence, and the σ3 axis is nearly vertical, consistent with a reverse-faulting stress regime, with some exceptions in the central part of the aftershock area. We obtained 2,497 well-determined focal mechanisms whose average number of P-wave polarity data is more than 70. The spatial distribution of pore fluid pressure was estimated by using the obtained orientations of the principal stresses and earthquake faults. The pore pressure ratio for each earthquake fault was calculated under the assumption that reduced frictional strength was caused by pore fluid pressure. The results showed that the diversity of the focal mechanisms here obtained requires high pore fluid pressures at many of the earthquake faults in the focal region. The spatial pattern of pore pressure ratio shows that areas of higher pore pressure ratio are distributed around the large coseismic slip area near Kurikoma volcano. Immediately beneath these high pore pressure areas, there exists a distinct seismic low-velocity zone that continues down to the mantle wedge below. These observations suggest that crustal fluids supplied from the mantle wedge have contributed to producing high pore pressures and to lowering the frictional strengths of those faults. Crustal fluids may also have contributed to generating the mainshock rupture..
26. 九州大学地震火山観測研究センター, 雲仙岳火山活動状況, 火山噴火予知連絡会会報, 第111号, 110-113, 2013.11.
27. 九州大学地震火山観測研究センター, 松島 健, 霧島火山におけるGPS基線長の変化, 火山噴火予知連絡会会報, 第111号, 141-143, 2013.11.
28. Mori, T., Shinohara, H., Kazahaya, K., Ohwada, M., Hirabayashi, J., Matsushima, T., Mori, T., Odai, M., Iino, H., Miyashita, M., Time-averaged SO2 fluxes of subduction-zone volcanoes: Example of a 32-year exhaustive survey for Japanese volcanoes, Journal of Geophysical Research D: Atmospheres, 10.1002/jgrd.50591, 118, 15, 8662-8674, 2013.08, All available SO2 flux data for 32 years (1975–2006) of Japanese volcanoes, accounting for about 10% of the world's arc volcanoes, were compiled to evaluate the temporal variation of the flux of each volcano and to estimate the time-averaged SO2 flux. The compiled data revealed that 6 volcanoes (Tokachi, Asama, Aso, Sakurajima, Satsuma-Iwojima, and Suwanosejima volcanoes) out of 17 significantly degassing volcanoes usually contributed more than 94% of the total flux. The time-averaged annual flux was 2.2 Tg a−1, which includes intense degassing of Miyakejima volcano after 2000, which raised the figure from 1.4 Tg a−1, indicating that a single huge emitter is capable of significantly skewing regional time-averaged degassing totals and indicating that the time-averaged flux assessments for infrequent huge emitters are important for accurate estimation. The regional SO2 flux distribution in cumulative frequency-flux plot does not obey a power law distribution. It shows a roll-off curve bending at about 500 t d−1, implying that it is misleading to assume the power law distribution for estimation of the global flux. Because the contribution of the major degassing volcanoes including the six volcanoes and additional sporadically degassing volcanoes during eruptive and posteruptive periods to the total flux is more than 95%, measurement of all large flux volcanoes can approximate the global flux..
29. 九州大学地震火山観測研究センター, 雲仙岳火山活動状況, 火山噴火予知連絡会会報, 第110号, 146-149, 2013.07.
30. 山本 圭吾, 園田 忠臣, 高山 鐵朗, 市川 信夫, 大倉 敬宏, 横尾 亮彦, 吉川 慎, 井上 寛之, 諏訪 博之, 松島 健, 藤田詩織, 神薗めぐみ, 水準測量によって測定された桜島火山周辺域の地盤上下変動--2012年11月および12月測量の結果--, 京都大学防災研究所年報, 第56号B, 187-195, 2013.06.
31. Nakao, S., Morita, Y., Yakiwara, H., Oikawa, J., Ueda, H., Takahashi, H., Ohta, Y., Matsushima, T., Iguchi, M., Volume change of the magma reservoir relating to the 2011 Kirishima Shinmoe-dake eruption-Charging, discharging and recharging process inferred from GPS measurements, Earth Planets Space, doi:10.5047/eps.2013.05.017, 65, 6, 505-515, 2013.05, Using GPS data, we evaluate the volume change of the magma reservoir associated with the eruption of Kirishima Shinmoe-dake volcano, southern Kyushu, Japan, in 2011. Because ground deformation around Shinmoe-dake volcano is strongly affected not only by regional tectonic movement but also by inflation of Sakurajima volcano located approximately 30-40 km to the southwest, we first eliminate these unwanted contributions from the observed data to extract the signals from Shinmoe-dake volcano. Then, we estimate the source locations and volume change before, during, and after the highest eruptive activity occurring between January 26 and 31. Our model shows that the magma began to accumulate about one year prior to the sub-Plinian eruption, with approximately 65% of the accumulated magma being discharged during the peak of the eruptive activity, and that magma accumulation continued until the end of November 2011. An error analysis shows that the sources during the three periods indicated above are located in almost the same position: 5 km to the northwest of the summit at a depth of 8 km. The 95% confidence interval of the estimated source depth is from 7.5 to 13.7 km. .
32. Matsumoto, S., Shimizu, H., Matsushima, T., Uehira, K., Yamashita, Y., Nakamoto, M., Miyazaki, M., Chikura, H., Short-term spatial change in a volcanic tremor source during the 2011 Kirishima eruption, Earth, Planets and Space, 10.5047/eps.2012.09.002, 65, 4, 323-329, 2013.05, Volcanic tremors are indicators of magmatic behavior, which is strongly related to volcanic eruptions and activity. Detection of spatial and temporal variations in the source location is important for understanding the mechanism of volcanic eruptions. However, short-term temporal variations within a tremor event have not always been detected by seismic array observations around volcanoes. Here, we show that volcanic tremor sources were activated at both the top (i.e., the crater) and the lower end of the conduit, by analyzing seismograms from a dense seismic array 3 km from the Shinmoedake crater, Kirishima volcano, Japan. We observed changes in the seismic ray direction during a volcanic tremor sequence, and inferred two major sources of the tremor from the slowness vectors of the approaching waves. One was located in a shallow region beneath the Shinmoedake crater. The other was found in a direction N30°W from the array, pointing to a location above a pressure source. The fine spatial and temporal characteristics of volcanic tremors suggest an interaction between deep and shallow conduits. .
33. Hiramatsu, Y., Sawada, A., Yamauchi, Y, Ueyama, S., Nishigami, K., Kurashimo, E., the Japanese University Group of the Joint Seismic Observations at NKTZ, Spatial variation in coda Q and stressing rate around the Atotsugawa fault zone in a high strain rate zone, central Japan, EARTH PLANETS AND SPACE, 10.5047/eps.2012.08.012, 65, 2, 115-119, 2013.05.
34. Keigo Yamamoto,, Tadaomi Yamamoto, Tetsuro Takayama, Nobuo Ichikawa, Takahiro Ohkura, Shin Yoshikawa, Hiroyuki Inoue,, TAKESHI MATSUSHIMA, Kazunari Uchida, Manami Nakamoto, Vertical Ground Deformation Associated with the Volcanic Activity of Sakurajima Volcano, Japan during 1996-2010 as Revealed by Repeated Precise Leveling Surveys, Bull. Volcanol. Soc. Japan, 58, 1, 137-151, 2013.04.
35. Kato, A., Igarashi, T., Obara, K., Sakai, S., Takeda, T., Saiga, A., Iidaka, T., Iwasaki, T., Hirata, N., Goto, K., Miyamachi, H., Matsushima, T., Kubo, A., Katao, H., Yamanaka, Y., Terakawa, T., Nakamichi, H., Okuda, T., Horikawa, S., Tsumura, N., Imaging the source regions of normal faulting sequences induced by the 2011 M9.0 Tohoku-Oki earthquake, Geophysical Research Letters, 10.1002/grl.50104, 40, 2, 273-278, 2013.01, Intense swarm-like seismicity associated with shallow normal faulting was induced in Ibaraki and Fukushima prefectures, Japan, following the 2011 Tohoku-Oki earthquake. This seismicity shows a systematic spatiotemporal evolution, but little is known of the heterogeneity in crustal structure in this region, or its influence on the evolution of the seismicity. Here, we elucidate a high-resolution model of crustal structure in this region and determine precise hypocenter locations. Hypocenters in Ibaraki Prefecture reveal a planar earthquake alignment dipping SW at ~45°, whereas those in Fukushima Prefecture show a more complex distribution, consisting of conjugate sets of aligned small earthquakes. On the north of the hypocenter of the largest earthquake in the sequence (the M7.0 Iwaki earthquake), we imaged a high-velocity body at shallow depths that lacks aftershock seismicity. Based on fault source models, the large-slip region of the Iwaki earthquake is situated along a zone that roughly coincides with this high-velocity body. We delineated a separate low-velocity anomaly directly beneath the hypocenter of the Iwaki earthquake, indicating crustal fluids in this region. We hypothesize that strong crust underwent structural failure due to the infiltration of crustal fluids into the seismogenic zone from deeper levels, causing the Iwaki earthquake..
36. Shigeru Nakao, Yuichi Morita, Hiroshi Yakiwara, Jun Oikawa, Hideki Ueda, Hiroaki Takahashi, Yusaku Ohta, Takeshi Matsushima, Masato Iguchi, Volume change of the magma reservoir relating to the 2011 Kirishima Shinmoe-dake eruption-Charging, discharging and recharging process inferred from GPS measurements, Earth, Planets and Space, 10.5047/eps.2013.05.017, 65, 6, 505-515, 2013, [URL], Using GPS data, we evaluate the volume change of the magma reservoir associated with the eruption of Kirishima Shinmoe-dake volcano, southern Kyushu, Japan, in 2011. Because ground deformation around Shinmoe-dake volcano is strongly affected not only by regional tectonic movement but also by inflation of Sakurajima volcano located approximately 30-40 km to the southwest, we first eliminate these unwanted contributions from the observed data to extract the signals from Shinmoe-dake volcano. Then, we estimate the source locations and volume change before, during, and after the highest eruptive activity occurring between January 26 and 31. Our model shows that the magma began to accumulate about one year prior to the sub-Plinian eruption, with approximately 65% of the accumulated magma being discharged during the peak of the eruptive activity, and that magma accumulation continued until the end of November 2011. An error analysis shows that the sources during the three periods indicated above are located in almost the same position: 5 km to the northwest of the summit at a depth of 8 km. The 95% confidence interval of the estimated source depth is from 7.5 to 13.7 km..
37. 九州大学地震火山観測研究センター, 雲仙岳火山活動状況(2011年3月~5月), 火山噴火予知連絡会会報, 第109号, 134-138, 2012.11.
38. 松島 健, 簡便で低消費電力な地震火山観測データ伝送技術の開発, 月刊地球, 34, 10, 615-619, 2012.10.
39. 九州大学地震火山観測研究センター, 霧島山(新燃岳)調査観測報告, 火山噴火予知連絡会会報, 第108号, 247-259, 2012.07.
40. 九州大学地震火山観測研究センター, 雲仙岳火山活動状況(2010年10月~2011年2月), 火山噴火予知連絡会会報, 第108号, 180-184, 2012.07.
41. 糸谷 夏実, 松島 健, 島原半島地域における微動 H/V スペクトル比を用いた地盤構造推定, 九州大学大学院理学研究院研究報告.地球惑星科学, 23 , 1 , 1-12, 2012.03.
42. Satoshi Matsumoto, Kenji Uehira, TAKESHI MATSUSHIMA, Hiroshi Shimizu, Modeling heterogeneous deviatoric stress field around the hypocentral area of the 2005 Fukuoka earthquake (M7.0) by spatially distributed moment tensors, Journal of Geophysical Research, 10.1029/2011JB008687, 117, B03303, 2012.03.
43. 九州大学地震火山観測研究センター, 雲仙火山活動状況(2010年6月〜2010年9月), 火山噴火予知連絡会会報, 第107号, 150-153, 2011.11.
44. 九州大学地震火山観測研究センター, 雲仙火山活動状況(2010年2月〜2010年6月), 火山噴火予知連絡会会報, 第106号, 125-128, 2011.11.
45. 九州大学地震火山観測研究センター, 阿蘇火山における地球科学的観測, 火山噴火予知連絡会会報, 第106号, 122-124, 2011.11.
46. 九州大学地震火山観測研究センター, 伊豆鳥島火山の火山活動, 火山噴火予知連絡会会報, 第107号, 115-117, 2011.11.
47. 筒井智樹,井口正人,為栗健,及川純,大島弘光,前川徳光,青山裕,植木貞人,平原聡,野上健治,大湊隆雄,市原美恵,辻浩,堀川信一郎,奥田隆,清水洋,松島健,大蔵敬宏,吉川慎,園田忠臣,宮町宏樹,八木原寛,平野舟一郎,斎藤公一滝,末峯宏一,後藤進,池亀孝光,加藤幸司,松末伸一,河野太亮,宇都宮真吾,五藤大仁,渡辺竜一,前原祐樹,佐藤泉,大薮竜童,清水英彦,山下裕亮, 桜島火山における反復地震探査(2010年観測), 京都大学防災研究所年報, 第54号B, 195-208, 2011.06.
48. Aitaro Kato, Shinichi Sakai, Takashi Iidaka, Takaya Iwasaki, Eiji Kurashimo, Toshihiro Igarashi, Naoshi Hirata, Toshihiko Kanazawa, Kei Katsumata, Hiroaki Takahashi, Ryo Honda, Takahiro Maeda, Masayoshi Ichiyanagi, Teruhiro Yamaguchi, Masahiro Kosuga, Tomomi Okada, Junichi Nakajima, Shuichiro Hori, Takashi Nakayama, Akira Hasegawa, Toshio Kono, Syuichi Suzuki, Noriko Tsumura, Yoshihiro Hiramatsu, Katsunori Sugaya, Aiko Hayashi, Tetsuya Hirose, Akihiro Sawada, Keisuke Tanaka, Yoshiko Yamanaka, Haruhisa Nakamichi, Takashi Okuda, Yoshihisa Iio, Kin'Ya Nishigami, Masatoshi Miyazawa, Hiroo Wada, Norio Hirano, Hiroshi Katao, Shiro Ohmi, Kiyoshi Ito, Issei Doi, Shunta Noda, Satoshi Matsumoto, Takeshi Matsushima, Atsushi Saiga, Hiroki Miyamachi, Kazutoshi Imanishi, Tetsuya Takeda, Youichi Asano, Yohei Yukutake, Tomotake Ueno, Takuto Maeda, Takanori Matsuzawa, Shutaro Sekine, Makoto Matsubara, Kazushige Obara, Anomalous depth dependency of the stress field in the 2007 Noto Hanto, Japan, earthquake
Potential involvement of a deep fluid reservoir, Geophysical Research Letters, 10.1029/2010GL046413, 38, 6, 2011.03, [URL], We have elucidated depth variations in the stress field associated with the 2007 Noto Hanto, Japan, earthquake by stress tensor inversion using high-quality aftershock data obtained by a dense seismic network. Aftershocks that occurred above 4 km in depth indicated a strike-slip stress regime. By contrast, aftershocks in deeper parts indicated a thrust faulting stress regime. This depth variation in the stress regime correlates well with that in the slip direction derived from a finite source model using geodetic data. Furthermore, the maximum principal stress (σ1) axis was stably oriented approximately W20N down to the depth of the mainshock hypocenter, largely in agreement with the regional stress field, but, below that depth, the σ1 axis had no definite orientation, indicating horizontally isotropic stress. One likely cause of these drastic changes in the stress regime with depth is the buoyant force of a fluid reservoir localized beneath the seismogenic zone..
49. 松島 健・大湊隆雄・小園誠史・鈴木雄治郎・風早竜之介・三浦大助・宝田晋治・伊藤英之・齋藤武士・金子隆之, 第6回火山都市国際会議 参加報告, 火山, 第55巻, 第6号, 261-271, 2010.12.
50. 山本圭吾・園田忠臣・高山鐵朗・市川信夫・大倉敬宏・吉川 慎・井上寛之・松島 健・内田和也, 桜島火山周辺における水準測量(2009年11月および2010年4月), 京都大学防災研究所年報, 第53号B, 227-232, 2010.10.
51. Atsushi Saiga, Satoshi Matsumoto, Kenji Uehira, Takeshi Matsushima, and Hiroshi Shimizu, Velocity structure in the crust beneath the Kyushu area, Earth Planets Space, Vol. 62, No.5, 449-462, 2010.07.
52. Hiramatsu, Yoshihiro, Iwatsuki, Koichi, Ueyama, Shingo, Iidaka, Takashi, Japanese Univ Grp Joint Seismic Ob, Spatial variation in shear wave splitting of the upper crust in the zone of inland high strain rate, central Japan, EARTH PLANETS AND SPACE, 10.5047/eps.2010.08.003, 62, 9, 675-684, 2010.04.
53. Atsushi Saiga, Satoshi Matsumoto, Kenji Uehira, Takeshi Matsushima, Hiroshi Shimizu, Velocity structure in the crust beneath the Kyushu area, Earth, Planets and Space, 10.5047/eps.2010.02.003, 62, 5, 449-462, 2010, [URL], We present high-resolution three-dimensional tomographic images of the crust beneath the entire Kyushu arc, and particularly the western portion. Our results reveal a velocity anomaly that correlates well with an upper crustal gravity anomaly. Significant low-velocity anomalies exist beneath the Miyazaki plane and along the Beppu-Shimabara Graben. Another extensive low-velocity region near the bottom of the crust is located just below the volcanic front and between active volcanoes. The low-velocity anomalies exhibit low Vp and Vp/Vs characteristics, and the spatial relationship between these anomalies, the Bouguer gravity anomaly, and the Moho suggests that low-density material at the base of the crust is responsible for both the seismic and gravity signatures. We interpret this material to constitute a relict ridge subducting below the Kyushu Mountains..
54. Iinuma, T., M. Ohzono, Y. Ohta, S. Miura, M. Kasahara, H. Takahashi, T. Sagiya, T. Matsushima, S. Nakao, S. Ueki, K. Tachibana, T. Sato, H. Tsushima, K. Takatsuka, T. Yamaguchi, M. Ichiyanagi, M. Takada, K. Ozawa, M. Fukuda, Y. Asahi, M. Nakamoto, Y. Yamashita, and N. Umino, Aseismic slow slip on an inland active fault triggered by a nearby shallow event, the 2008 Iwate-Miyagi Nairiku earthquake (Mw6.8), Geophysical Research Letters, 10.1029/2009GL040063, 36, 20, 2009.10.
55. 大倉敬宏・吉川 慎・井上寛之・宇津木 充・鍵山恒臣・寺田暁彦・加納将行・由井智史・山本圭吾・高山鐵朗・山崎友也・多田光宏・立尾有騎・松島 健・内田和也・中元真美・山下裕亮・平岡喜文・三森庸里江・根本盛行, 阿蘇カルデラにおける水準測量(2008年9月 – 10月), 第4回阿蘇火山の集中総合観測−2008年4月〜2009年3月−, 8-15, 2009.07.
56. Onizawa, S., H. Oshima, H. Aoyama, T. Maekawa, A. Suzuki, H. Miyamachi, T. Tsutsui, T. Matsushima, S. Tanaka, J. Oikawa, N. Matsuwo, K. Yamamoto, T. Shiga, T. Mori, Basement structure of Hokkaido Komagatake Volcano, Japan, as revealed by artificial seismic survey, Journal of Volcanology and Geothermal Research, 183, 245-253, 2009.06.
57. Shin'ya Onizawa, Hiromitsu Oshima, Hiroshi Aoyama, Tokumitsu Maekawa, Atsuo Suzuki, Hiroki Miyamachi, Tomoki Tsutsui, Takeshi Matsushima, Satoru Tanaka, Jun Oikawa, Norimichi Matsuwo, Keigo Yamamoto, Toru Shiga, Takehiko Mori, Basement structure of Hokkaido Komagatake Volcano, Japan, as revealed by artificial seismic survey, Journal of Volcanology and Geothermal Research, 10.1016/j.jvolgeores.2009.03.013, 183, 3-4, 245-253, 2009.06, [URL], We investigate the basement structure of the Hokkaido Komagatake volcano, Japan, by an artificial seismic survey. By inverting first arrival time data, a three-dimensional P-wave velocity model down to 3 km b.s.l. is obtained. The resultant velocity model reasonably reflects regional geological features and is consistent with Bouguer anomalies. Around the Komagatake volcano, the velocity basement deepens to NNW on the whole, reflecting the deepening of the geological basement toward that direction. Higher velocities are observed in Oshima and Kameda Mountains where Neogene volcanic and sedimentary rocks are present. On the contrary, lower velocities are observed in lowlands surrounding the volcano, where Komagatake deposits and Quaternary sediments crop out. At the volcano, a prominent high velocity zone was detected from the surface down to a depth of 1.5 km b.s.l. Above the base, probably a contrast between the core part with higher proportion of massive lavas and intrusions and flank areas dominated by loose pyroclastic deposits caused the prominent high velocity. Below the base, it is thought that solidified intrusive bodies largely contribute to making the high velocity. Further, a high velocity elongates from Kameda Mountains to beneath the summit. This is due to a shallower of the volcano substratum..
58. 河野裕希・松本 聡・松島 健・植平賢司・清水 洋・馬越孝道, 雲仙火山周辺域における相対応力場と1990-1995年噴火活動, 北海道大学地球物理学研究報告, 第72号,363-371, 2009.03.
59. Yoshihisa Iio, Takuo Shibutani, Satoshi Matsumoto, Hiroshi Katao, Takeshi Matsushima, Shiro Ohmi, Fumiaki Takeuchi, Kenji Uehira, Kinya Nishigami, Masatoshi Miyazawa, Bogdan Enescu, Issei Hirose, Yasuyuki Kano, Yuhki Kohno, Ken'ichi Tatsumi, Tomotake Ueno, Hiroo Wada, Yohei Yukutake, Precise aftershock distribution of the 2004 Mid-Niigata prefecture earthquake-Implication for a very weak region in the lower crust, Physics of the Earth and Planetary Interiors, 10.1016/j.pepi.2008.10.014, 172, 3-4, 345-352, 2009.02, [URL], The 2004 Mid-Niigata prefecture Earthquake (Mjma 6.8) occurred in the region of large strain rates (>0.1 ppm/y contraction) in the intraplate region in Japan. The mainshock was followed by four major aftershocks with Mjma >= 6.0. The hypocenters of the mainshock and two large aftershocks that occurred in the central part of the aftershock region were located near the lower limit of the earthquake distribution, while hypocenters of the other two aftershocks near both ends, are located near its upper limit. Furthermore, the fault planes of the latter two aftershocks were confined within the upper half of the upper crust. Also, the lower limit of the aftershock distribution is deepest in the central part and becomes shallower toward the NNE and SSW ends. These data can be explained by the hypothesis that a localized stress concentration occurred near the bottom of the seismogenic region only in the central part. The stress concentration may be generated by the deformation in the very weak region of low strength in the lower crust beneath the central part of the aftershock region..
60. Iinuma, T., Y. Ohta, S. Miura, K. Tachibana, T. Matsushima, H. Takahashi, T. Sagiya, T. Ito, S. Miyazaki, R. Doke, A. Takeuchi, K. Miyao, A. Hirao, T. Maeda, T. Yamaguchi, M. Takada, M. Iwakuni, T. Ochi, I. Meilano, and A. Hasegawa, Postseismic slip associated with the 2007 Chuetsu-oki, Niigata, Japan, Earthquake (M 6.8 on 16 July 2007) as inferred from GPS data, Earth Planets Space, Vol.60, 1087-1091, 2008.12.
61. Ohta, Y., S. Miura, T. Iinuma, K. Tachibana, T. Matsushima, H. Takahashi, T. Sagiya, T. Ito, S. Miyazaki, R. Doke, A. Takeuchi, K. Miyao, A. Hirao, T. Maeda, T. Yamaguchi, M. Takada, M. Iwakuni, T. Ochi, I. Meilano, and A. Hasegawa, Coseismic and postseismic deformation related to the 2007 Chuetsu-oki, Niigata Earthquake, Earth Planets Space, Vol.60, 1081-1086, 2008.12.
62. 河野裕希・松本 聡・松島 健・植平賢司・清水 洋・馬越孝道, 1990〜1995年雲仙火山噴火前に起きた応力場の変化, 月刊地球, 号外,No.60,85-90, 2008.12.
63. 三浦 哲・太田雄策・大園真子・飯沼卓史・立花憲司・植木貞人・高塚晃多・宮尾佳世・佐藤俊也・対馬弘晃・高橋浩晃・山口照寛・笠原 稔・鷺谷 威・小沢和浩・福田真人・朝日友香・松島 健・中元真美・山下裕亮・中尾 茂, 2008年岩手・宮城内陸地震(M7.2)に伴った地震時・地震後地殻変動, 日本地震学会ニュースレター, Vol.20, No.4, 10-14, 2008.11.
64. 山本圭吾・高山鉄朗・山崎友也・多田光宏・大倉敬宏・吉川 慎・松島 健・内田和也・中元真美・平岡喜文・塩谷俊治・根本盛行, 水準測量による桜島火山および姶良カルデラ周辺の地盤上下変動−1996年10月から2007年10月−12月まで−, 京都大学防災研究所年報, 第51号 B,248-252, 2008.11.
65. Kohno, Y., T. Matsushima, and H. Shimizu, Pressure sources beneath Unzen Volcano inferred from leveling and GPS data, Journal of Volcanology and Geothermal Research, Vol.175, 100-109, 2008.07.
66. Yuhki Kohno, Takeshi Matsushima, Hiroshi Shimizu, Pressure sources beneath Unzen Volcano inferred from leveling and GPS data, Journal of Volcanology and Geothermal Research, 10.1016/j.jvolgeores.2008.03.022, 175, 1-2, 100-109, 2008.07, [URL], Unzen Volcano erupted from 1990 to 1995 and the resultant volcanic deformations were measured by GPS, leveling, tilt meter, and EDM. The largest vertical displacement observed was subsidence of 8 cm in the western part of Shimabara Peninsula. Numerous magma chamber models were proposed based on the geodesic data obtained. However, these models could not explain the volcanic deformations observed around Chijiwa Bay after the eruption had finished because previous studies only used data collected during the eruption. We therefore re-examined the magma chamber model using leveling and GPS data, and included measurements collected both during and after the eruption on leveling. We applied the Mogi Model with a height correction applied to the measuring points. There are four parameters for each source: longitude, latitude, depth, and volume change. Each source parameter was estimated using a grid-search scheme. We also used AIC (Akaike Information Criterion) to fix the number of pressure sources beneath Unzen to explain the vertical and horizontal deformations during 1986-2004. The results show that there are four pressure sources under Unzen Volcano and that magma ascended obliquely at an angle of about 45° from beneath Chijiwa Bay to the crater created by this eruption. After the eruption had stopped, magma inflows into deep sources were identified based on our leveling survey conducted after 1996. We compare our source model with several seismic data sets. Before the Unzen eruption, an earthquake swarm occurred from 1989 to 1990 in which pressure sources were detected just below the earthquake hypocenters. Other seismic refraction studies support our estimates of the location of these pressure sources. Using volume change values we inferred that magma supply had continued into this deep source at the rate of 2.0-~ 2.5 m3/yr from at least 1984 until after eruption stopped..
67. 爆破地震動研究グループ, 1998年東北奥羽脊梁山地東麓における稠密屈折・広角反射法探査, 東京大学地震研究所彙報, 第83号,第1冊,43-75, 2008.06.
68. 東海・中部陸域地震探査研究グループ, 東海・中部地方における陸域深部地殻構造探査, 東京大学地震研究所彙報, 2008.06.
69. 2003年九州日奈久断層域構造探査グループ, 九州日奈久断層域における地殻構造探査, 東京大学地震研究所彙報, 第83号,第1冊,103-130, 2008.06.
70. 山本圭吾•高山鐵朗•山崎友也•多田光宏•大倉敬宏•吉川 慎•松島 健•内田和也•中元真美•平岡喜文•塩谷俊治•根本盛行, 桜島火山周辺における水準測量(2007年10月−12月), 第10回桜島火山の集中総合観測(平成19年6月〜平成20年3月), 45-51, 2008.04.
71. 酒井慎一・加藤愛太郎・蔵下英司・飯高 隆・五十嵐俊博・平田 直・岩崎貴哉・金沢敏彦・渡辺 茂・羽田敏夫・小林 勝・三浦勝美・三浦禮子・田上貴代子・荻野 泉・坂  守・渡邉篤志・宮川幸治・勝俣 啓・高橋浩晃・笠原 稔・本多 亮・前田宜浩・一柳昌義・山口照寛・小菅正裕・岡田知己・中島淳一・堀修一郎・中山貴史・新居恭平・長谷川昭・河野俊夫・鈴木秀市・津村紀子・小林里紗・野崎謙治・平松良浩・菅谷勝則・林亜以子・広瀬哲也・澤田明宏・田中敬介・山中佳子・中道治久・奥田 隆・飯尾能久・西上欽也・宮澤理稔・和田博夫・平野憲雄・中尾節郎・片尾 浩・大見士朗・伊藤 潔・澁谷拓郎・加納靖之・土井一生・野田俊太・片木 武・西辻陽平・松本 聡・松島 健・雑賀 敦・宮町宏樹・今西和俊・桑原保人・長 郁夫・干野 真・武田哲也・浅野陽一・行竹洋平・上野友岳・前田拓人・松澤孝紀・関根秀太郎・松原 誠・小原一成, 平成19年(2007年)能登半島地震合同余震観測, 東京大学地震研究所彙報, 第82号,第3冊,225-233, 2008.02.
72. 渡辺秀文・中道治久・大湊隆雄・鍵山恒臣・及川 純・青木陽介・辻  浩・小山悦郎・長田 昇・萩原道徳・竹田豊太郎・小林知勝・大島弘光・青山 裕・前川徳光・鈴木敦生・田中 聡・西村太志・仁田交市・山崎 純・奥田 隆・山田 守・大倉敬宏・須藤靖明・吉川 慎・井口正人・清水 洋・植平賢司・松島 健・八木原 寛・平野舟一郎, 富士山の大学合同稠密地震観測(2002年9月-2005年4月), 東京大学地震研究所彙報, 第82号,第3冊,195-207, 2008.02.
73. 筒井智樹・鬼澤真也・森 健彦・野上健治・平林順一・小川康雄・高木憲朗・鈴木敦生・及川 純・中道治久・吉川 慎・松島 健, 草津白根火山白根火砕丘の地震反射断面−擬似反射記録法による反射断面の推定−, 火山, 第53号,第1号,1-14, 2008.02.
74. 第5回火山都市国際会議実行委員会, 第5回火山都市国際会議, 火山, 53, 51-62, 2008.01.
75. Yusaku Ohta, Satoshi Miura, Takeshi Iinuma, Kenji Tachibana, Takeshi Matsushima, Hiroaki Takahashi, Takeshi Sagiya, Takeo Ito, Shin'ichi Miyazaki, Ryosuke Doke, Akira Takeuchi, Kayo Miyao, Akihiko Hirao, Takahiro Maeda, Teruhiro Yamaguchi, Masamitsu Takada, Makiko Iwakuni, Tadafumi Ochi, Irwan Meilano, Akira Hasegawa, Coseismic and postseismic deformation related to the 2007 Chuetsu-oki, Niigata Earthquake, Earth, Planets and Space, 60, 11, 1081-1086, 2008, An intermediate-strength earthquake of magnitude Mj 6.8 occurred on July 16, 2007, centered beneath the Japan Sea a few kilometers offshore of Niigata Prefecture in central Japan. We constructed a dense GPS network to investigate postseismic deformation after this event, choosing our GPS sites carefully so as to complement the nationwide GPS GEONET array. Coseismic displacements caused by the mainshock detected at some GEONET sites were used to estimate coseismic fault parameters. The results indicate that the geodetic data can be explained by a combination of two rectangular faults dipping northwest and southeast. Minor but definite postseismic deformation was detected largely in the southern part of the dense network. The time series of site coordinates can be characterized by a logarithmic decay function, and the estimated time constant seems to be almost similar in range to that of the 2004 Mid-Niigata Prefecture Earthquake. We also found a possible site instability at 960566 (Izumo-zaki, GEONET) caused by a small, local landslide associated with the mainshock and therefore concluded that the data obtained at this site should not be used for coseismic or postseismic analysis.).
76. Takeshi Iinuma, Yusaku Ohta, Satoshi Miura, Kenji Tachibana, Takeshi Matsushima, Hiroaki Takahashi, Takeshi Sagiya, Takeo Ito, Shin'ichi Miyazaki, Ryosuke Doke, Akira Takeuchi, Kayo Miyao, Akihiko Hirao, Takahiro Maeda, Teruhiro Yamaguchi, Masamitsu Takada, Makiko Iwakuni, Tadafumi Ochi, Irwan Meilano, Akira Hasegawa, Postseismic slip associated with the 2007 Chuetsu-oki, Niigata, Japan, Earthquake (M 6.8 on 16 July 2007) as inferred from GPS data, Earth, Planets and Space, 60, 11, 1087-1091, 2008, Postseismic crustal deformation associated with the 2007 Chuetsu-oki Earthquake, which occurred on 16 July 2007 with a magnitude of 6.8 at the southeastern rim of the Sea of Japan, near the coast of Mid-Niigata Prefecture, Central Japan, are detected by GPS observations. We analyzed continuous GPS data from the sites of the Geographical Survey Institute of Japan (GSI) and another dense temporary network, which we established just after the main shock to reveal spatio-temporal evolution of postseismic slip for 50 days after the main shock by geodetic inversion methods. Four models of faults are configured following Ohta et al. (2008, this issue), and these are optimized based on ABIC (Akaike's Bayesian Information Criterion). The results of the inversion analysis show that the postseismic slip on the faults occurred at a downdip and updip extension of the coseismically slipped portion. The slip in the shallower portion decayed to be negligible within 2 weeks, and the slip in the deeper portion was still large after the slip in the shallower portion had almost terminated..
77. 清水 洋・松本 聡・河野裕希・松島 健・植平賢司, 福岡西方沖地震のその後 -来るべき警固断層地震へむけて-, 長崎県地学会誌, 71, 39-40, 2007.10.
78. 齋藤政城・松島 健・松尾のり道・清水 洋, 阿蘇中岳火山の二酸化硫黄および二酸化炭素ガス放出量の測定, 大学大学院理学研究院 研究報告 地球惑星科学, 第22巻,第2号,51-62, 2007.02.
79. 中尾 茂,高橋浩晃,一柳昌義,松島 健,河野裕希, 福岡県西方沖地震の余効変動観測, 月刊地球, Vol.29,No.2,128-132, 2007.02.
80. 飯尾能久,片尾 浩,上野友岳,Bogdan Enescu,平野憲雄,岡田知巳,内田直希,植平賢司,松本 聡,松島 健,清水 洋, 福岡県西方沖地震の余震の応力降下量の空間分布, 月刊地球, Vol.29,No.2,123-127, 2007.02.
81. Masaki Saito, Takeshi Matsushima, Norimichi Matsuwo, Hiroshi Shimizu, Observation SO2 and CO2 fluxes in and around the active crater of Aso Nakadake Volcano, Science Reports of the Kyushu University, Department of Earth and Planetary Sciences, 22, 2, 51-62, 2007.02, Volatiles of the magma such as H2O, CO2, SO2, H2S and HC1, which are the main components of volcanic explosions, discharge to the surface of the earth as volcanic gases, hot springs, and river waters. The discharge occurs not only in volcanic eruptions but also in non-erupting activities. In order to clarify the mass balance of volatiles, the hydrothermal structure and the volcanic activities, it is very important to characterize the chemical constituents and the amount of the volatiles discharged from volcanoes. It is thought that the volcanic gases reflect immediately the changes of magmatic activity because the mobility of gases is the most abundant among the discharge forms of volatiles. The diffuse degassing from soil is one of the discharge forms paid attention in recent years. As CO2 is hardly influenced by the groundwater due to low solubility in water, the direct information on volcanic activities can be obtained by observing the CO2 flux and its changes. Aso volcano is one of the most active volcanoes in Japan, and magmatic eruptions have occurred several times in historical times. However, the research on the amount of the CO2 flux from the soil in and around the active craters had not been performed at Aso volcano. In this study, we estimated the CO2 fluxes from the Nakadake crater and the circumference soil at Aso volcano and compared the results with the CO2 fluxes at Kusatsu-Shirane volcano. At Aso volcano, the amount of the total CO2 flux from soil was estimated to be about 0.12 ton d-1. While the amount of CO2 flux from the Nakadake First crater was estimated to be 597 ± 95 ton d-1, and thus the CO2 flux from the crater was much larger than that from the soil at Aso volcano. On the contrary, the CO2 flux from the soil was comparable to that from the craters (fumaroles) at Kusatsu-Shirane volcano..
82. Aitaro Kato, Masakatsu Arao, Keisuke Ariyoshi, Youichi Asano, Keiji Doi, Bogdan Enescu, Shinya Fujieda, Hiroko Hagiwara, Toshio Haneda, Akira Hasegawa, Shin'ichi Hashimoto, Satoshi Hirahara, Naoshi Hirata, Yasuhiro Hirata, Issei Hirose, Shusaku Hondo, Kumiko Hori, Shuichiro Hori, Shigeki Horiuchi, Toshihiko Igarashi, Takashi Iidaka, Yoshihisa Iio, Ryoya Ikuta, Takeo Ito, Takaya Iwasaki, Aya Kamimura, Toshihiko Kanazawa, Yasuyuki Kano, Hiroshi Katao, Satoshi Kawamoto, Tomonori Kawamura, Saeko Kita, Masaru Kobayashi, Yuhki Kohno, Toshio Kono, Masahiro Kosuga, Atsuki Kubo, Eiji Kurashimo, Satoshi Matsumoto, Takeshi Matsushima, Toru Matsuzawa, Noa Mitsui, Reiko Miura, Masatoshi Miyazawa, Tomoko Mizukami, Satoko Murotani, Satoru Nagai, Junichi Nakajima, Takashi Nakayama, Hiroaki Negishi, Kinya Nishigami, Izumi Ogino, Shiro Ohmi, Tomomi Okada, Hiroki Onaha, Shantha S.N. Gamage, Mamoru Saka, Shin'ichi Sakai, Katsuhito Sato, Toshiya Sato, Masato Serizawa, Takuo Shibutani, Junpei Shimizu, Junichi Suganomata, Kiyoko Tagami, Keisuke Takahashi, Kaori Takai, Fumiaki Takeuchi, Yasuda Takumi, Kazuo Tanaka, Ken'ichi Tatsumi, Takashi Tonegawa, Hiroaki Tsushima, Naoki Uchida, Kenji Uehira, Tomotake Ueno, Norihito Umino, Hiroo Wada, Kazutoshi Watanabe, Shigeru Watanabe, Yasuo Yabe, Tadashi Yaginuma, Mamoru Yamada, Shunroku Yamamoto, Yoshiko Yamanaka, Futoshi Yamashita, Fumihito Yamazaki, Satoshi Yui, Yohei Yukutake, High-resolution aftershock observations in the source region of the 2004 mid-Niigata Prefecture Earthquake, Earth, Planets and Space, 10.1186/BF03352030, 59, 8, 923-928, 2007.01, [URL], We deployed an extremely dense temporal seismic network in the source region of the 2004 mid-Niigata Prefecture Earthquake (thrust fault) on October 23, 2004, Japan. The seismic network consisted of 145 temporary seismic stations within a 30 km squared and had been kept within approximately a month after the mainshock. High accurate hypocenters of 708 events were determined by inverting the arrival times using double-difference earthquake location algorithm. The aftershocks along the mainshock (Mw = 6.6) and the largest aftershock (Mw = 6.3) rupture zones are distributed on two 60° westward-dipping planes, located approximately 5 km apart. Conversely, the Oct. 27 aftershock (Mw = 5.8) occurred on an eastward dipping plane with a dip angle of 25° that was conjugate to the mainshock fault plane. Most of aftershocks at both northeastern and southwestern edges occurred at shallow depths with eastward-dipping planes. Epicenters of aftershocks in the southwestern region are aligned along N15°E, and rotate approximately 20° counterclockwise from the strike of the mainshock fault. This rotation of the aftershock alignments coincides with the rotation of anticline axes in the southwestern area of the source region. Furthermore, distributions of station corrections for a one-dimensional velocity model suggest that the seismic velocity at the western side of the Muikamachi-fault is lower than that at the eastern side. It is also inferred that the velocity structures in the hangingwall vary along the fault strike. The average velocity in the mainshock rupture area is higher than the periphery in the hangingwall, especially compared with the southwestern side of the hypocenter..
83. 松島 健, 火山観測におけるGPSの利用とWAAS機能について, 測地学会誌, 第52巻,第4号,329-330, 2006.12.
84. 金尾政紀,坪井誠司,松島 健, フロンティア地震学研究の現状と展望, 月刊地球, Vol.28, No.9, 585-591, 2006.09.
85. 飯尾能久・松本 聡・片尾 浩・松島 健・大見士朗・渋谷拓郎・竹内文朗・植平賢司・西上欽也・宮沢理稔・ENESCU Bogdan・広瀬一聖・加納靖之・河野裕希・辰巳賢一・上野友岳・和田博夫・行竹洋平, 北マリアナ諸島アナタハン島における噴火の推移, 月刊地球, Vol.28, No.6, 407-413, 2006.06.
86. 飯尾能久・松本 聡・松島 健・植平賢司・片尾 浩・大見士朗・澁谷拓郎・竹内文朗・西上欽也・Bogdan Enescu・廣瀬一聖・加納靖之・儘田 豊・宮澤理稔・辰己賢一・和田博夫・河野裕希, 2004年新潟県中越地震の発生過程−オンライン合同余震観測結果から−, 地震, 第2輯,第58巻,第4号,463-475, 2006.03.
87. 松島 健・河野裕希, 千々石カルデラと雲仙火山の活動, 月刊地球, Vol.48, No.2, 122-127, 2006.02.
88. Iio, Y., H. Katao, T. Ueno, B. Enescu, N. Hirano, T. Okada, N. Uchida, S. Matsumoto, T. Matsushima, K. Uehira, and H. Shimizu, Spatial distribution of static stress drops for aftershocks of the 2005 West Off Fukuoka Prefecture earthquake, Earth Planets Space, Vol.58, No.12, 1611-1615, 2006.01.
89. Hori, M., S. Matsumoto, K. Uehira, T. Okada, T. Yamada, Y. Iio, M. Shinohara, H. Miyamachi, H. Takahashi, K. Nakahigashi, A. Watanabe, T. Matsushima, N. Matsuwo, T. Kanazawa, and H. Shimizu, Three-dimensional seismic velocity structure as determined by double-difference tomography in and around the focal area of the 2005 West off Fukuoka Prefecture earthquake, Earth Planets Space, Vol.58, No.12, 1621-1626, 2006.01.
90. Matsumoto, S., A. Watanabe, T. Matsushima, H. Miyamachi, and S. Hirano, Imaging S-wave scatterer distribution in southeast part of the focal area of the 2005West Off Fukuoka Prefecture Earthquake (MJMA7.0) by dense seismic array, Earth Planets Space, Vol.58, No.12, 1627-1632, 2006.01.
91. Watanabe, A., S. Matsumoto, T. Matsushima, K. Uehira, N. Matsuwo, and H. Shimizu, Shear wave polarization anisotropy in and around the focal region of the 2005 West off Fukuoka Prefecture earthquake, Earth Planets Space, Vol.58, No.12, 1633-1636, 2006.01.
92. 飯尾能久・松本 聡・片尾 浩・松島 健・大見士朗・渋谷拓郎・竹内文朗・植平賢司・西上欽也・宮沢理稔・ENESCU Bogdan・広瀬一聖・加納靖之・河野裕希・辰巳賢一・上野友岳・和田博夫, 2004年新潟県中越地震発生過程, 月刊地球,号外, 53,217-222, 2006.01.
93. Yamashita, M., H. Miyamachi, M. Kanao, T. Matsushima, S. Toda, M. Takada, and A. Watanabe, Deep Reflection Imaging beneath the Mizuho Plateau, East Antarctica, by SEAL-2002 Seismic Experiment, Antarctica, 147-154, 2006.01.
94. Shimizu, H., H. Takahashi, T. Okada, T. Kanazawa, Y. Iio, H. Miyamachi, T. Matsushima, M. Ichiyanagi, N. Uchida, T. Iwasaki, H. Katao, K. Goto, S. Matsumoto, N. Hirata, S. Nakao, K. Uehira, M. Shinohara, H. Yakiwara, N. Kame, T. Urabe, N. Matsuwo, and T. Yama, Aftershock seismicity and fault structure of the 2005 West Off Fukuoka Prefecture Earthquake (MJMA7.0) derived from urgent joint observations, Earth Planets Space, Vol.58, No.12, 1599-1604, 2006.01.
95. Hiroshi Shimizu, Takeshi Matsushima, Satoshi Matsumoto, Kenji Uehira, Norimichi Matsuwo, Atsushi Watanabe, Takeshi Matsushima, Yuhki Kohno, Masaki Saito, Mio Hori, Hiroaki Takahashi, Masayoshi Ichiyanagi, Satoshi Matsumoto, Naoki Uchida, Toshihiko Kanazawa, Masanao Shinohara, Takaya Iwasaki, Naoshi Hirata, Taku Urabe, Tomoaki Yamada, Kazuo Nakahigashi, Shin’ichi Hashimoto, Takeo Yagi, Yoshihisa Iio, Hiroshi Katao, Bogdan Enescu, Tomotake Ueno, Hiroki Miyamachi, Kazuhiko Goto, Shigeru Nakao, Hiroshi Yakiwara, Syuichiro Hirano, Nobuki Kame, Aftershock seismicity and fault structure of the 2005 West Off Fukuoka Prefecture Earthquake (MJMA7.0) derived from urgent joint observations, Earth, Planets and Space, 10.1186/BF03352668, 58, 12, 1599-1604, 2006.01, [URL], On March 20, 2005, a large MJMA7.0 earthquake occurred in the offshore area, west of Fukuoka prefecture, northern Kyushu, Japan. A series of joint observations were carried out by teams from several universities in Japan with the aim of investigating the aftershock activity. Six online telemetered and 17 offline recording seismic stations were installed on land around the aftershock area immediately followed the occurrence of the mainshock. Because aftershocks were located mainly in offshore regions, we also installed 11 ocean bottom seismometers (OBSs) just above the aftershock region and its vicinity in order to obtain accurate locations of hypocenters. The OBS observation was carried out from March 27 to April 13, 2005. We further conducted temporary GPS observations in which ten GPS receivers were deployed around the aftershock region. The aftershocks were mainly aligned along an approximately 25-km-long NW-SE trend, and the hypocenters of the main aftershock region were distributed on a nearly vertical plane at depths of 2-16 km. The mainshock was located near the central part of the main aftershock region at a depth of approximately 10 km. The largest aftershock of MJMA5.8 occurred near the southeastern edge of the main aftershock region, and the aftershock region subsequently extended about 5 km in the SE direction as defined by secondary aftershock activity. Enlargement of the aftershock region did not occur after the peak in aftershock activity, and the aftershock activity gradually declined. The distribution of hypocenters and seismogenic stress as defined by aftershocks suggest that the 2005 West Off Fukuoka Prefecture Earthquake occurred on the fault that is the NW extension of the Kego fault, which extends NW-SE through the Fukuoka metropolitan area, and that the largest aftershock occurred at the northwestern tip of the Kego fault..
96. Satoshi Matsumoto, Atsushi Watanabe, Takeshi Matsushima, Hiroki Miyamachi, Syuichiro Hirano, Imaging S-wave scatterer distribution in southeast part of the focal area of the 2005 West Off Fukuoka Prefecture Earthquake (MJMA7.0) by dense seismic array, Earth, Planets and Space, 10.1186/BF03352673, 58, 12, 1627-1632, 2006.01, [URL], Spatial distribution of S-wave scatterers in the SE part of the focal area of the 2005 West Off Fukuoka Prefecture Earthquake (M=7.0) has been estimated using dense seismic array data. Waveforms of 22 natural earthquakes were analyzed in a frequency range of 16-24 Hz. It is difficult to estimate the inhomogeneous structure in this wavelength range with ordinary travel time tomography despite the importance of this parameter for understanding the earthquake-generating process. After filtering and gain recovery in the coda part, observed waveforms were semblance-enhanced slant-stacked into various directions from the array. This was followed by diffraction curve summation in order to image the scatterer distribution. The spatial distribution of scatterers thus imaged revealed that higher strengths were distributed at the SE-extension of the fault plane of the event, which corresponds to a region where the rupture process of the main shock stopped..
97. Shigeru Nakao, Hiroaki Takahashi, Takeshi Matsushima, Yuhki Kohno, Masayoshi Ichiyanagi, Postseismic deformation following the 2005 West Off Fukuoka Prefecture Earthquake (M7.0) derived by GPS observation, Earth, Planets and Space, 10.1186/BF03352671, 58, 12, 1617-1620, 2006.01, [URL], We constructed a temporary GPS network around the aftershock area of the 2005 West Off Fukuoka Prefecture Earthquake (M7.0) in order to investigate the characteristics of its postseismic deformation. Our GPS network data, as well as the GEONET data, were analyzed using Bernese GPS software. We detected notable postseismic deformation in horizontal components close to the fault plane. The observed maximum displacement was 5.6 cm at the GNKI site on Genkaijima Island. A logarithmic law was adapted to the coordinate time series data, revealing decay times from 2 to 23 days, similar to those obtained for the 2003 Tokachi-oki Earthquake (M8.0). The amount of postseismic slips on the fault was assessed using the coseismic fault model proposed by the Geographical Survey Institute (GSI). We derived an optimum fault model of postseismic slip on the shallow (less than 3 km depth) portion of the fault. Our findings indicate that postseismic slip occurred only in shallow parts of the coseismic fault..
98. Atsushi Watanabe, Satoshi Matsumoto, Takeshi Matsushima, Kenji Uehira, Norimichi Matsuwo, Hiroshi Shimizu, Shear wave polarization anisotropy in and around the focal region of the 2005 West off Fukuoka Prefecture earthquake, Earth, Planets and Space, 10.1186/BF03352674, 58, 12, 1633-1636, 2006.01, [URL], Crustal shear wave polarization anisotropy is caused by the alignment of vertical microcracks. Leading shear wave polarization directions (LSPDs) are presumed to be consistent with the maximum horizontal compressional axis in many cases. We analyzed shear wave polarization anisotropy in and around the focal region of the 2005 West off Fukuoka Prefecture earthquake. Almost all of the LSPDs are oriented in the E-W direction, which is consistent with the maximum horizontal compressional axis inferred from the mechanism of the main shock. These E-to W-oriented LSPDs are caused by the alignment of stress-induced microcracks. Crack densities at most stations are estimated to be 0.02. Little spacial stress variation around focal region is suspected..
99. M. Hori, Satoshi Matsumoto, K. Uehira, T. Okada, T. Yamada, Y. Iio, M. Shinohara, H. Miyamachi, H. Takahashi, K. Nakahigashi, A. Watanabe, Takeshi Matsushima, N. Matsuwo, T. Kanazawa, Hiroshi Shimizu, Three-dimensional seismic velocity structure as determined by double-difference tomography in and around the focal area of the 2005 West off Fukuoka Prefecture earthquake, Earth, Planets and Space, 10.1186/BF03352672, 58, 12, 1621-1626, 2006.01, [URL], On March 20, 2005 the West off Fukuoka Prefecture earthquake (magnitude of 7.0 on the JMA scale) occurred in southeastern Japan. The earthquake fault was a left-lateral strike-slip having a nearly vertical fault plane and a strike in the WNW-ESE direction. The largest aftershock with a magnitude of 5.8 (JMA) followed 1 month later. To gain more detailed aftershock data, several teams from different Japanese universities jointly installed a number of temporary seismic stations and positioned Ocean Bottom Seismometers (OBSs) immediately above the focal area. Double-difference tomography was used to estimate the three-dimensional (3D) (Zhang and Thurber, 2003) velocity structures in and around the focal area based on the travel time data collected during seismic observations. The high-velocity regions estimated by the inversion are located on the edge of the aftershock area and on the shallow part of asperity, as inferred from the slip distribution. Conversely, the Vp/Vs ratio is not always as high as that found at the location of the asperity. This finding suggests that the construction of the medium is not uniformly elastic but complex, with different relations between elastic constants and strength..
100. Yoshihisa Iio, Hiroshi Katao, Tomotake Ueno, Bogdan Enescu, Norio Hirano, Tomomi Okada, Naoki Uchida, Satoshi Matsumoto, Takeshi Matsushima, Kenji Uehira, Hiroshi Shimizu, Spatial distribution of static stress drops for aftershocks of the 2005 West Off Fukouka Prefecture earthquake, Earth, Planets and Space, 58, 12, 1611-1615, 2006, We investigated the spatial distribution of static stress drops of the aftershocks of the 2005 West Off Fukuoka Prefecture earthquake, with the aim of assessing the possibility that another earthquake will occur on the SE extension of the earthquake fault. The waveforms from six temporary online telemetry stations installed in and around the aftershock region were measured. Small stress drops were estimated for the aftershocks that occurred relatively distant from the SE and NE ends of the earthquake fault. Conversely, the aftershocks that occurred around the SE end of aftershock region are characterized by large stress drops. These results imply the possibility of a stress concentration at the SE edge of the main shock fault..
101. 杉本 健・石橋秀巳・松島 健, 伊豆鳥島火山の岩石学的研究, 火山, Vol.50,No.2, 87-101, 2005.05.
102. Suzuki, S., Sayyed Mahmoud Fatemi Aghda, T. Nakamura, T. Matsushima, Y. Ito, Hossein Sadeghi, Mehdi Maleki, Arash Jafar Gandomi and Sayyed Keivan Hosseini, Temporal Seismic Observation and Preliminary Hypo-center Determination of Aftershocks of the 2003 Bam Earthquake, 東京大学地震研究所彙報, Vol.79, No.3, 37-45, 2005.03.
103. 鬼澤真也・森 健彦・筒井智樹・平林順一・野上健治・小川康雄・松島 健・鈴木敦生, 人工地震探査より推定した草津白根火山白根火砕丘表層のP波速度構造, 火山, Vol.50,No.1, 9-16, 2005.02.
104. 河野裕希・松島 健・清水 洋, 測地学データから推定された雲仙岳下における圧力源, 九州大学大学院理学研究院研究報告(地球惑星科学), Vol.22,No.1, 29-39, 2005.02.
105. Hosseini Sayyed Keivan, T. Matsushima, S. Suzuki, El_Fiky Gamal S., Horizontal Strain Changes in Southwest Japan Using Partitioning Model and GPS Data (1997-2000), 九州大学大学院理学研究院紀要, Vol.31,No.3, 93-104, 2005.02.
106. Takeshi Sugimoto, Takeshi Matsushima, Fumarolic activity in Torishima volcano, Izu islands, Japan, Science Reports of the Kyushu University, Department of Earth and Planetary Sciences, 22, 1, 23-27, 2005.02, Torishima is an active volcanic island located on the Izu Arc, 570 km south of Tokyo at Honshu island. The eruptive activity is divided into two stages; the stratovolcano stage, and the central cone stage. The eruption during the historic period in Torishima volcano has occurred in 1902, 1939, and 2002. We conducted landing observation of Torishima in May, 2004. Temperatures of the fumes and ground and compositions (CO2, SO2, H2S) Of volcanic gases were measured. The current activity of Torishima volcano is as follows: The highest temperature region showing appro)dmately 100°C is distributed along the narrow band inside the westside rim of Torishima caldera. The fume and ground temperatures at the north side in Io-yama, which is the central major cone of Torishima volcano are nearly constant at 100°C from 1957 to present. CO2 concentrations in volcanic gases from the fumaroles of the north side in Io-yama is in levels that have almost unchanged from 1965 to the present. A remarkable change of the fumarolic activity resulting from the eruption in 2002 was not detected in this observation..
107. Yuhki Kohno, Takeshi Matsushima, Hiroshi Shimizu, The pressure sources beneath Unzen Volcano inferred from geodesic data, Science Reports of the Kyushu University, Department of Earth and Planetary Sciences, 22, 1, 29-39, 2005.02, We inferred the pressure sources under Unzen Volcano on Shimabara Peninsula, which erupted during 1990-1995 by using ground deformation data. It has been proposed that there are three pressure sources associated with the 1990-1995 activity beneath Unzen Volcano. But this model can not explain the ground deformation that was observed after the eruption stopped in 1995, because the upheaval was observed in the southwestern part of Shimabara Peninsula. We used 1991-2001 leveling data for searching. And we recalculated the source's parameters (horizontal location, depth, and volume change) by fitting. We modeled using Mogi Model. It was one of the most different points from previous studies that we modeled pressure sources considering the altitude of each observation station. As a result, we could explain the ground deformation around Unzen Volcano by four-source model..
108. 飯尾能久・松本 聡・片尾 浩・松島 健・大見士朗・澁谷拓郎・竹内文朗・植平賢司・西上欽也・Bogdan Enescu・廣瀬一望・加納靖之・河野裕希・是永将宏・儘田 豊・宮澤理稔・辰巳賢一, 2004年新潟県中越地震の発生過程, 京都大学防災研究所年報, No.48 A, 165-170, 2005.01.
109. Nakada, S., T. Matsushima, M. Yoshimoto, T. Sugimoto, T. Kato, T. Watanabe, R. Chong, and J. Camacho, Geological aspects of the 2003-2004 eruption of Anatahan Volcano, Northern Mariana Islands, Journal of Volcanology and Geothermal Research, 10.1016/j.jvolgeores.2004.10.023, 146, 1-3, 226-240, Vol.146, 226-240, 2005.01.
110. Watanabe, T., T. Tabei, T. Matsushima, T. Kato, S. Nakada, M. Yoshimoto, R. Chong, and J. T. Camacho, Geodetic constraints for the mechanism of Anatahan eruption of May 2003, Journal of Volcanology and Geothermal Research, 10.1016/j.jvolgeores.2004.11.033, 146, 1-3, 77-85, Vol.146, 77-85, 2005.01.
111. Okubo, A., Y. Tanaka, M. Utsugi, N. Kitada, H. Shimizu, and T. Matsushima, Magnetization intensity mapping on Unzen Volcano, Japan, determined from high-resolution, low-altitude helicopter-borne aeromagnetic survey, Earth, Planets and Space, 57, 8, 743-753, Vol.57, No.8, 743-753, 2005.01.
112. Kakahashi, H., T. Matsushima, T. Kato, A. Takeuchi, T. Yamaguchi, Y. Kohno, T. Katagi, J. Fukuda, K. Hatamoto, R. Doke, Y. Matsu’ura, and M. Kasahara, A dence GPS observation immediately after the 2004 mid-Niigata prefecture earthquake, Earth Planets Space, 57, 7, 661-665, Vol.57, 661-665, 2005.01.
113. Nakamura, T., S. Suzuki, H. Sadeghi, S. Fatemi Aghda, T. Matsushima, Y. Ito, S. Hosseini, A. Jafar Gandomi, and M. Maleki, Source fault structure of the 2003 Bam earthquake, southeastern Iran, inferred from the aftershock distribution and its relation to the heavily damaged area: Existence of the Arg-e-Bam fault proposed, Geophysical Research Letters, 10.1029/2005GL022631, 32, 9, Vol.32, L09308, doi:10.1029/2005GL022631, 2005.01.
114. Matsumoto, S., Y. Iio, T. Matsushima, K. Uehira, and T. Shibutani, Imaging of S-wave reflectors in and around the hypocentral area of the 2004 mid Niigata Prefecture Earthquake (M6.8), Earth Planets Space, 57, 6, 557-561, Vol.57, 557-561, 2005.01.
115. Shibutani, T., Y. Iio, S. Matsumoto, H. Katao, T. Matsushima, S. Ohmi, F. Takeuchi, K. Uehira, K. Nishigami, B. Enescu, I. Hirose, Y. Kano, Y. Kohno, M. Korenaga, Y. Mamada, M. Miyazawa, K. Tatsumi, T. Ueno, H. Wada, and Y. Yukutake, Aftershock distribution of the 2004 Mid Niigata Prefecture Earthquake derived from a combined analysis of temporary online observations and permanent observations, Earth Planets Space, 57, 6, 545-549, Vol. 57, 545-549, 2005.01.
116. Korenaga, M., S. Matsumoto, Y. Iio, T. Matsushima, K. Uehira, and T. Shibutani, Three dimensional velocity structure around aftershock area of the 2004 mid Niigata prefecture earthquake (M6.8) by the Double-Difference tomography, Earth Planets Space, 57, 5, 429-433, Vol.57, 429-433, 2005.01.
117. 坂東信人・仮屋新一・木股文昭・中尾 茂・及川 純・渡辺秀文・鵜川元雄・藤田英輔・河合晃司・松島 健・宮島力雄・奥田 隆, GPS観測による2000年7月14日三宅島火山噴火に伴う地殻変動, 火山, Vol.50,No.3,173-182, 2005.01.
118. 杉本 健・松島 健, 伊豆鳥島火山の噴気活動, 九州大学大学院理学研究院研究報告(地球惑星科学), Vol.22,No.1, 23-27, 2005.01.
119. 笠原 稔・高橋浩晃・岡崎紀俊・中尾 茂・鷺谷 威・伊藤武男・大谷文夫・佐藤一敏・藤田安良・橋本 学・細 義信・加藤照之・飯沼卓史・福田淳一・松島 健・河野裕希, 稠密GPS観測による2003年十勝沖地震の余効変動観測, 月刊地球, 号外49,105-111, 2005.01.
120. Hiroaki Takahashi, Takeshi Matsushima, Teruyuki Kato, Akira Takeuchi, Teruhiro Yamaguchi, Yuhki Kohno, Takeshi Katagi, Jun'ichi Fukuda, Kazuya Hatamoto, Ryousuke Doke, Yuki Matsu'ura, Minoru Kasahara, A dense GPS observation immediately after the 2004 mid-Niigata prefecture earthquake, Earth, Planets and Space, 10.1186/BF03351844, 57, 7, 661-665, 2005.01, [URL], To investigate the postseismic crustal deformation associated with the 2004 mid-Niigata prefecture earthquake (M6.8), we newly started GPS observation to fill a gap of the nationwide continuous GPS network. Our GPS sites were mainly distributed in the focal region without permanent GPS site, and succeeded in obtaining the postseismic deformation. Coseismic displacements of two aftershocks were clearly detected because of immediate observation. Estimated fault parameters of the aftershock (M5.9) on November 8 occurring just beneath our GPS network indicated that geodetic data could be explained by either east- or west-dipping fault model inferred from detailed aftershock data. Moreover, clear postseismic deformation, which could be characterized by a logarithmic decay function, was observed. This signal probably suggests possible aseismic slip. Our results indicated that dense GPS observation could give important and interesting data to clarify the properties of shallow inland middle-size earthquakes..
121. Takuo Shibutani, Yoshihisa Iio, Satoshi Matsumoto, Hiroshi Katao, Takeshi Matsushima, Shiro Ohmi, Fumiaki Takeuchi, Kenji Uehira, Kin'ya Nishigami, Bogdan Enescu, Issei Hirose, Yasuyuki Kano, Yuhki Kohno, Masahiro Korenaga, Yutaka Mamada, Masatoshi Miyazawa, Ken'ichi Tatsumi, Tomotake Ueno, Hiroo Wada, Yohei Yukutake, Aftershock distribution of the 2004 Mid Niigata Prefecture Earthquake derived from a combined analysis of temporary online observations and permanent observations, Earth, Planets and Space, 10.1186/BF03352590, 57, 6, 545-549, 2005.01, [URL], The 2004 Mid Niigata Prefecture Earthquake (Mj = 6.8) occurred on 23 October 2004 in the northeastern part of the Niigata-Kobe Tectonic Zone where large contraction rates were observed. The mainshock was followed by an anomalously intense aftershock activity that included nine Mj ≥ 5.5 aftershocks. We deployed three temporary online seismic stations in the aftershock area from 27 October, combined data from the temporary stations with those from permanent stations located around the aftershock area, and determined the hypocenters of the mainshock and aftershocks with a joint hypocenter determination (JHD) technique. The resulting aftershock distribution showed that major events such as the mainshock, the largest aftershock (Mj = 6.5), the aftershock on 27 October (Mj = 6.1), etc. occurred on different fault planes that were located nearly parallel or perpendicular to each other. This might be due to heterogeneous structure in the source region. The strain energy was considered to have been enough accumulated on the individual fault planes. These features are probably a cause of the anomalous intensity of the aftershock activity..
122. Satoshi Matsumoto, Takeshi Matsushima, Takeshi Matsushima, Yoshihisa Iio, Takuo Shibutani, Imaging of S-wave reflectors in and around the hypocentral area of the 2004 mid Niigata Prefecture Earthquake (M6.8), Earth, Planets and Space, 10.1186/BF03352592, 57, 6, 557-561, 2005.01, [URL], An S-wave reflector is considered to relate to the existence of liquid in the seismogenic zone of the crust, which plays an important role in understanding the mechanism of earthquakes. We studied a distribution of S-wave reflectors in and around the hypocentral zone of the 2004 mid Niigata Prefecture Earthquake (M6.8). The earthquake was followed by several aftershocks that were greater than M6. Moreover, the aftershocks were not only located on the fault plane of the main shock but also on conjugate fault planes and on a parallel plane to that of the main shock. In order to discuss the relationship between this complex activity and the crustal heterogeneities, we analyzed the seismograms observed at the seismic stations in this region. Normal moveout processing (NMO) was applied to the data of the aftershock. Several S-wave reflectors could be identified from the NMO sections for every station. In particular, relatively strong S-wave reflectors exist in the lower crust at a depth of approximately 20-25 km in the middle part of the aftershock region. Additionally, reflectors were found beneath the fault planes of the main shock and the largest aftershock. This suggests a possibility of the correlation of the crustal heterogeneities to the occurrence of an earthquake..
123. Ayako Okubo, Yoshikazu Tanaka, Mitsuru Utsugi, Naoto Kitada, Hiroshi Shimizu, Takeshi Matsushima, Magnetization intensity mapping on Unzen Volcano, Japan, determined from high-resolution, low-altitude helicopter-borne aeromagnetic survey, Earth, Planets and Space, 10.1186/BF03351853, 57, 8, 743-753, 2005.01, [URL], On September 18, 2002, we conducted a high-resolution, low-altitude helicopter-bome aeromagnetic survey at two flight altitudes, using spiral trajectories for the first time, over Unzen Volcano in the framework of the Unzen Scientific Drilling Project (USDP). This study obtained more detailed and new information than the previous aeromagnetic studies in Unzen volcano about the geological features, for understanding the history and eruption mechanism of the Unzen volcano. Therefore, we conducted a magnetization intensity mapping on the volcano, on the assumption that the magnetic anomalies are caused by the terrain magnetized in the same direction as the present Earth's magnetic field and the magnetization intensity varies only laterally. This map shows good agreement with the geologic features, especially the hydrothermal alteration zone and the collapsed pyroclastic deposits. In addition, even in the area covered by lavas, the magnetization intensities show various values corresponding to each eruption event. It may be considered that the differences in magnetic properties reflect different oxygen fugacity in rocks during their cooling time period. Local magnetization lows on Heisei-Shinzan suggest that the Heisei lava produced by the 1991-1995 eruption has not yet been cooled enough..
124. Masayuki Korenaga, Satoshi Matsumoto, Yoshihisa Lio, Takeshi Matsushima, Kenji Uehira, Takuo Shibutani, Three dimensional velocity structure around aftershock area of the 2004 mid Niigata prefecture earthquake (M6.8) by the Double-Difference tomography, Earth, Planets and Space, 10.1186/BF03351829, 57, 5, 429-433, 2005.01, [URL], The 2004 mid Niigata prefecture earthquake with M6.8 occurred in the north of central part of Japan. It was a reverse fault by the regional compression stress field in NW-SE direction. Several aftershocks with M≥6 were occurred. The large aftershocks occurred on plural fault planes. The plane was either parallel or normal to the main shock one. We estimated three dimensional velocity structures in and around the focal area of the earthquake by using a Double Difference tomography method. The arrival time data were picked from seismograms at the deployed seismic stations settled by Kyoto and Kyushu universities in collaboration, NIED, ERI, and JMA. The velocity structure showed that a low velocity zone existed in the northwest part of the aftershock area. On the contrary, the velocity in the southeast became high. Moreover, the fault plane of the main shock inferred from the aftershock distribution was located at the velocity boundary..
125. 植平賢司・松島 健・清水 洋・安達繁樹・齊藤幸賢, 訂正 衛星電話を利用した地震観測システムの開発 ―無人島における定常地震観測の実現―, 地震2, 57, 70, 2004.08.
126. 筒井智樹・松島 健・清水 洋, 雲仙火山の浅部構造に対する擬似反射記録法の適用の試み, 火山, Vol.49,No.3, 143-151, 2004.06.
127. 大久保綾子・田中良和・宇津木 充・北田直人・清水 洋・松島 健, 雲仙火山における低高度な高密度空中磁気探査, 京都大学防災研究所年報, No.47 B, 735-742, 2004.04.
128. Iwasaki, T., K. Adachi, T. Moriya, H. Miyamachi, T. Matsushima, K. Miyashita, T. Takeda, T. Taira, T. Yamada, K. Ohtake, Upper and middle crustal deformation of an arc-arc collision across Hokkaido, Japan, inferred from seismic refraction/wide-angle reflection experiments, Tectonophysics, 10.1016/j.tecto.2004.03.025, 388, 1-4, 59-73, Vol.388, 59-73, 2004.01.
129. Takahashi, H., S. Nakao, N. Okazaki, J. Koyama, T. Sagiya, T. Ito, F. Ohya, K. Sato, Y. Fujita, M. Hashimoto, Y. Hoso, T. Kato, T. Iinuma, J. Fukuda, T. Matsushima, Y. Kohno, M. Kasahara, GPS observation of the first month of postseismic crustal deformation associated with the 2003 Tokachi-oki earthquake (M JMA 8.0), off southeastern Hokkaido, Japan, Earth, Planets and Space, 56, 3, 377-382, Vol.56, No.3, 377-382, 2004.01.
130. Takahashi, H., S. Nakao, N. Okazaki, J. Koyama, T. Sagiya, T. Ito, F. Ohya, K. Sato, Y. Fujita, M. Hashimoto, Y. Hoso, T. Kato, T. Iinuma, J. Fukuda, T. Matsushima, Y. Kohno, and M. Kasahara, GPS observation of the first month of postseismic crustal deformation associated with the 2003 Tokachi-oki earthquake (MJMA 8.0), off southeastern Hokkaido, Japan, Earth Planets Space, 56, 3, 377-382, Vol.56, 377-382, 2004.01.
131. Hiroaki Takahashi, Shigeru Nakao, Noritoshi Okazaki, Junji Koyama, Takeshi Sagiya, Takeo Ito, Fumio Ohya, Kazutoshi Sato, Yasuyoshi Fujita, Manabu Hashimoto, Yoshinobu Hoso, Teruyuki Kato, Takeshi Iinuma, Jun’ichi Fukuda, Takeshi Matsushima, Yuhki Kohno, Minoru Kasahara, GPS observation of the first month of postseismic crustal deformation associated with the 2003 Tokachi-oki earthquake (MJMA 8.0), off southeastern Hokkaido, Japan, Earth, Planets and Space, 10.1186/BF03353068, 56, 3, 377-382, 2004.01, [URL], To investigate the postseismic crustal deformation associated with the Tokachi-oki earthquake (MJMA=8.0) of 26 September 2003 in Japan Standard Time (JST), off southeastern Hokkaido, Japan, we newly established thirty GPS sites just after the mainshock in the eastern part of Hokkaido. Rapid data analysis for one month after the mainshock clearly indicated postseismic displacements only in the horizontal components. Observed maximum horizontal displacement was 6.6 cm from 28 September to 24 October, 2003. Absence of the vertical suggests that afterslip occurred in and around the coseismic fault rather than at downdip extension. Time series of coordinates are characterized by logarithmic decay functions with 4-11 days relaxation times. This suggests that postseismic deformation was due to afterslip on the fault following the large earthquake..
132. 松島 健・山下幹也・安原達二・堀口 浩・宮町宏樹・戸田 茂・高田真秀・渡邉篤志・渋谷和雄, 投下型地震計(ペネトレータ)の南極・みずほ高原での試験観測 −第43次夏隊報告−, 南極資料, Vol.47, No.3, 395-408p, 2003.11.
133. 高田真秀・戸田 茂・神谷大輔・松島 健・宮町宏樹, JARE−43人工地震探査におけるアイスレーダーによる氷床厚測定, 南極資料, Vol.47, No.3,380-394p, 2003.11.
134. Takeshi Matsushima, Mikiya Yamashita, Tatsuji Yasuhara, Koh Horiguchi, Hiroki Miyamachi, Shigeru Toda, Masamitsu Takada, Atsushi Watanabe, Kazuo Shibuya, Observation tests of the Antarctic penetrator on the Mizuho Plateau in JARE-43 summer operation, Antarctic Record, 47, 3, 395-408, 2003.11, We have developed an Antarctic penetrator that is applicable to seismic explosion experiments along a difficult traverse route on a continental ice sheet with crevasses. In the 43rd Japanese Antarctic Research Expedition (JARE-43, 2001-2002) seismic explosion experiments on the Mizuho Plateau, in East Antarctica, we equipped 22 penetrators for seismic observation. However, due to electrical trouble, we could not apply the penetrators to actual observation. Then, we carried out a running test of the penetrators and acquired much valuable data that cannot be obtained in the domestic environment in Japan, such as the declination angle of a body intruding into the Antarctic ice sheet, impact shock, and daily change of temperature of the body in the snow. These data are not only useful for development of the Antarctic penetrator, but also for development of touchdown-type physical observation equipment for use in Antarctica..
135. Masamitsu Takada, Shigeru Toda, Daisuke Kamiya, Takeshi Matsushima, Hiroki Miyamachi, Radio echo sounding survey along the profile of the JARE-43 seismic exploration on the Mizuho Plateau, East Antarctica, Antarctic Record, 47, 3, 380-394, 2003.11, A seismic exploration was conducted in the austral summer of 2001-2002 by the 43rd Japanese Antarctic Research Expedition (JARE-43) on the Mizuho Plateau, East Antarctica. We carried out the radio echo sounding survey along the seismic line in order to estimate the distribution of bedrock altitude. This report describes the outline of the radio echo sounding sur.vey and the obtained result..
136. 筒井智樹・須藤靖明・森 健彦・勝俣 啓・田中 聡・及川 純・戸松稔貴・松尾のり道・松島 健・宮町宏樹・西 潔・藤原善明・平松秀行, 阿蘇火山中央火口丘山体の3次元地震波速度構造, 火山, Vol.48,No.3,293-307, 2003.07.
137. 松島 健・山下幹也・宮町宏樹・戸田 茂・高田真秀・渡邉篤志・金尾政紀, 南極ペネトレータの開発と投下実験, 月刊地球, Vol.25,461-463, 2003.06.
138. Teruyuki Kato, John Beavan, Takeshi Matsushima, Yoshiko Kotake, Juan T. Camacho, Shigeru Nakao, Geodetic evidence of back-arc spreading in the Mariana Trough, Geophysical Research Letters, 30, 12, 2003.06, Repeated GPS surveys in the Mariana Islands show that the Mariana block is moving apart from the Philippine Sea plate. The velocities of the islands relative to the Philippine Sea plate range from about 15 mm/yr in the northern islands to about 45 mm/yr near Guam. The data also suggest convergence rates for the Mariana forearc with respect to the Pacific plate of 35-45 mm/yr at 19°N increasing to 55-70 mm/yr at 13.5°N. In addition, the velocity vectors show a slight north-south expansion of the arc. The estimated location of the Euler pole of the Mariana forearc with respect to the Philippine Sea plate is well south of the geographical point where the back-arc basin narrows to zero width..
139. 宮町宏樹・戸田 茂・松島 健・高田真秀・高橋康博・神谷大輔・渡邉篤志・山下幹也・柳沢盛雄, 東南極みずほ高原における屈折法および広角反射法地震探査−−観測概要(第43次夏隊報告)−−, 南極資料, Vol.47, No.1, 32-71, 2003.03.
140. Hiroki Miyamachi, Shigeru Toda, Takeshi Matsushima, Masamitsu Takada, Yasuhiro Takahashi, Daisuke Kamiya, Atsushi Watanabe, Mikiya Yamashita, Morio Yanagisawa, A seismic refraction and wide-angle reflection exploration in 2002 on the Mizuho Plateau, East Antarctica - Outline of observations (JARE-43), Antarctic Record, 47, 1, 32-71, 2003.03, A seismic refraction and wide-angle reflection exploration was successfully conducted along a profile crossing the JARE-41 seismic profile on the Mizuho Plateau, in East Antarctica, in the austral summer season of 2001-2002 (JARE-43). One hundred sixty-one seismic stations were temporarily installed along a profile about 151 km long and seven large shots with about 700 kg of dynamite were fired. In addition, one shot with charge size of 20 kg was also arranged along the profile. The obtained seismic records show the clear onsets of the first arrivals at distances of less than 100 km from each large shot. In particular, seismic waves traveling through the ice sheet and dispersed surface waves were clearly observed. Some later reflection phases were also detected. The obtained first travel time data show that the ice sheet is a two-layered structure consisting of an upper layer with a P wave velocity of 2.7-2.9 km/s and a lower layer of 3.7-3.9 km/s. The thickness of the upper layer is estimated to be about 36-45 m. The apparent velocity in the basement rock just beneath the ice sheet is 6.1-6.2 km/s in the central and southern parts of the profile and almost 5.9 km/s in the northern part. This report describes basic outlines of the exploration and the obtained seismic data..
141. 大久保綾子・田中良和・北田直人・宇津木充・清水 洋・松島 健, 雲仙火山における空中磁気測量について, 京都大学防災研究所年報, 第46号 B,739-747, 2003.01.
142. 小竹美子・加藤照之・中尾 茂・松島 健, 西太平洋〜東アジアのGPS連続観測点座標の時系列(1995年7月16日—2000年12月31日), 東京大学地震研究所彙報, 第78冊,第1号,19-56, 2003.01.
143. Kato, T., J. Beavan, T. Matsushima, Y. Kotake, J. T. Camacho, and S. Nakao, Geodetic Evidence of Back-arc Spreading in the Mariana Trough, Geophysical Research Letters, 10.1029/2002GL016757, 30, 12, Vol.30, No.12, 1625, doi:10.1029/2002GL016757, 2003.01.
144. Miyamachi, H., S.Toda, T. Matsushima, M. Takada, A. Watanabe, M. Yamashita, M. Kanao, Seismicrefraction and wide-angle reflection exploration by JARE-43 on Mizuho Plateau, East Antarctica, Polar Geoscience, Vol.16, 1-21, 2003.01.
145. 高橋浩晃・岡崎紀俊・石丸 聡・森 済・松島 健・渡邉篤志・三浦 哲・中尾 茂・加藤照之・木股文昭・笠原 稔, 2周波GPS受信機による2000年有珠山噴火前後の地殻変動観測, 火山, Vol.47, 161-166, 2002.01.
146. Tabei, T., M. Hashimoto, S. Miyazaki, K. Hirahara, F. Kimata, T. Matsushima, T. Tanaka, Y. Eguchi, T. Takaya, Y. Hoso, F. Ohya, and T. Kato, Subsurface Structure and faulting of the Median Tectonic Line, Southwest Japan inferred from GPS velocity field, Earth Planets Space, 54, 11, 1065-1070, Vol. 54, 1065-1070, 2002.01.
147. 勝俣 啓・和田直人・笠原 稔・岡山宗夫・一柳呂義・石川春義・高田真秀・長 郁夫・海野徳仁・岡田知己・中村綾子・掘 修一郎・立花憲司・河野俊夫・仁田交市・橋本恵一・伊藤喜宏, 大学合同臨時地震観測によって決定された島弧一島弧型日高衝突帯付近の震源分布と震源メカニズム解, 東京大学地震研究所彙報, Vol. 77,199-223, 2002.01.
148. 安藤 誠・森谷武男・岩崎貴哉・武田哲也・朴 成実・酒井慎一・飯高 隆・久保篤規・宮町宏樹・田代勝也・松島 健・鈴木貞臣, 九州東部の人工地震から推定された地殻構造, 東京大学地震研究所彙報, Vol. 77,277-285, 2002.01.
149. 爆破地震動研究グループ, 北海道日高衝突帯横断屈折・広角反射法地震探査(大滝−浦幌測線), 東京大学地震研究所彙報, Vol. 77,139-172, 2002.01.
150. 爆破地震動研究グループ, 北海道日高衝突帯前縁部における屈折・広角反射法地震探査(大滝−平取測線), 東京大学地震研究所彙報, Vol. 77,173-198, 2002.01.
151. 宇津木充・田中良和・神田 径・松島 健, 口永良部島火山における空中磁気測量,薩摩硫黄島火山・口永良部島火山の集中総合観測(平成12年8月〜平成13年3月), 全国主要活火山の集中総合観測 (京都大学防災研究所附属火山活動研究センター), 121-127, 2002.01.
152. 安藤 誠・森谷武男・岩崎貴哉・武田哲也・朴 成実・酒井慎一・飯高 隆・久保篤規・宮町宏樹・田代勝也・松島 健・鈴木貞臣, 九州南北測線の地殻構造探査から推定される多重付加体の構造, フィリピン海スラブの沈み込みと島弧・背弧の地球物理・京都大学防災研究所研究集会(一般)13K-7報告書, 215-218, 2002.01.
153. Takao Tabei, Manabu Hashimoto, Shin'ichi Miyazaki, Kazuro Hirahara, Fumiaki Kimata, Takeshi Matsushima, Torao Tanaka, Yasuhide Eguchi, Takashi Takaya, Yoshinobu Hoso, Fumio Ohya, Teruyuki Kato, Subsurface structure and faulting of the Median Tectonic Line, southwest Japan inferred from GPS velocity field, Earth, Planets and Space, 10.1186/BF03353303, 54, 11, 1065-1070, 2002.01, [URL], The Median Tectonic Line (MTL) is the longest arc-parallel fault system in southwest Japan whose right-lateral strike-slip is related to oblique subduction of the Philippine Sea plate (PH). We constructed a dense Global Positioning System network along a 200 km-long traverse line across the MTL in 1998 to estimate deep fault structure and slip distribution. Horizontal velocities were determined at 65 sites through campaign measurements and show crustal shortening in the direction of the plate convergence. Using multi-rectangular segments and depth-dependent coupling at the plate interface, we calculate and remove elastic deformation caused by the PH subduction. The residual velocity field shows right-lateral strike-slip block motion of about 5 mm/yr across the MTL, consistent with geological estimates. However, the block boundary does not coincide with the surface trace of the MTL, being displaced 20-30 km to the north. The residual velocity field is reproduced by a model with a 35-45° northwarddipping fault plane, full locking of the upper portion to a depth of 15 km, and steady slip of 5 mm/yr below. GPS results are supported by imaging of an inclined fault plane revealed by seismic profiling and currently low activity of shallow earthquakes..
154. IWASAKI Takaya, KATO Wataru, MORIYA Takeo, HASEMI Akiko, UMINO Norihito, OKADA Tomomi, MIYASHITA Kaoru, MIZOGAMI Tomoko, TAKEDA Tetsuya, SEKINE Shutaro, MATSUSHIMA Takeshi, TASHIRO Katsuya, MIYAMACHI Hiroki, Extensional structure in northern Honshu Arc as inferred from seismic refraction/wide-angle reflection profiling, Geophysical Research Letters, 10.1029/2000GL012783, 28, 12, 2329-2332, Vol.28,No.12,2329-2332, 2001.01.
155. 呉 新華・田中 穣・松島 健・荒生公雄・大石 哲・小司禎教・島田誠一, 火山地域におけるGPS測位に及ぼす局地的な水蒸気変動の影響について, 電子情報通信学会論文誌, Vol.J84-B,No.12,2149-2159, 2001.01.
156. Teruyuki Kato, Yasuhiro Hirata, Yoshiko Kotake, Shigeru Nakao, John Catane Patrick, Tsutomu Terashima, Toshikazu Chachin, Kunio Fujimori, Kazuro Hirahara, Yoshinobu Hoso, Kajuro Nakamura, Takehide Nakano, Keiichi Tadokoro, Ryuichi Ichikawa, Hiroo Inokuchi, Nobuhiro Isezaki, Tetsuya Iwabuchi, Minoru Kasahara, Fumiaki Kimata, Takashi Okuda, Hiroyuki Kumagai, Yamaoka Koshun, Atsuki Kubo, Takeshi Matsushima, Satoshi Miura, Shigeaki Otsuka, Takao Tabei, Hiroaki Takahashi, Akira Tokuyama, Takeyasu Yamamoto, Global Positioning System Observation before and after the Hyogo-ken Nanbu Earthquake of January 17, 1995, Japan, Journal of the Geodetic Society of Japan, 10.11366/sokuchi1954.43.181, 43, 3, 181-207, 2001.01, [URL], The Hyogo-ken Nanbu earthquake (MJMA 7.2), that took place on January 17th, 1995, in Kobe and Awaji area, caused tremendous disasters in the areas. After the earthquake, the Japanese University Consortium for GPS Research (JUNCO) deployed more than 30 GPS receivers around the hypocentral area to find co-seismic and to monitor post-seismic crustal däformations related to the earthquake. Data have been archived first by on-site recordings and later by tele-communcations at the Disaster Prevention Research Institute, Kyoto Univeristy. Temporary dense array terminated by the end of March, 1995. Further temporary occupations were conducted in May, 1995, in November, 1995, and in March, 1996, as well as long term continuous monitorings at selected several sites. The monitorings ended in August, 1996. Co-seismic offsets were observed at several sites around the source area. The largest offsets amounted to 45cm at Iwaya site which is about 4 km east of the Nojima fault. These data were used for simultaneous inversion together with strong motion data to clarify slip distribution on the buried rectangular faults. Post-seismic deformations were also found at all of sites. They mostly showed temporal decay and amounted to 2 to 3 cm. The largest one was observed at Iwaya site. The areal distribution of post-seismic displacement vectors seems to indicate afterslip on the fault planes, but not the areal visco-elastic readjustments. Relaxation processes at Iwaya and Kawaragi sites were fitted by a logarithmic curve. Application of a theory on the mechanics of afterslip based on the constitutive relationship of a fault surface indicated that the fitting give reasonable estimate on the frictional rate parameter or the thickness of velocity-strengthning layer of the earth's surface. Assuming that the constitutive parameter is ranging from 0.001 to 0.005 based on the results of rock experiments, thicknesses of velocity-strengthning layer at Iwaya and Kawaragi were estimated to be ranging between 500m and 2 km, which is consistent with other seismological data. Monitoring of fault offsets using real-time kinematic GPS (RTK-GPS) were also conducted at two baselines crossing the Nojima fault and the Arima-Takatsuki tectonic line, respectively. Though significant deformation was not observed, it showed a potential capability of real time monitorings of ground deformations in a few centimeter accuracy..
157. 植平賢司,松島 健,清水 洋,安達繁樹,齊藤幸賢, 衛星電話を利用した地震観測システムの開発 —無人島における定常地震観測の実現—, 地震2, Vol.53, No.2, 181-184, 2000.12.
158. Masanori Yoshizaki, Teruyuki Kato, Yoshinobu Tanaka, Hajime Takayama, Yoshinori Shoji, Hiromu Seko, Kimio Arao, Kazuo Manabe, Kazuo Saito, Hisaki Eito, Hajime Nakamura, Yasushi Fujiyoshi, Masayuki Kawashima, Masayuki Ooi, Hiroki Fukushi, Takeshi Matsushima, M. Tanaka, Analytical and numerical study of the 26 June 1998 orographic rainband observed in Western Kyushu, Japan, Journal of the Meteorological Society of Japan, 78, 6, 835-856, 2000.12, On 26 June 1998 during a field experiment called X-BAIU-98, an orographic rainband, called the Nagasaki line in this study, was observed extending northeastward from the Nagasaki Peninsula in western Kyushu, Japan. The convective cells in this rainband, which were about 5 km in horizontal scale and 40 min in duration, propagated northeastward at a speed of about 10 m s-1. They were deep in height in a northeastward direction. Around the Nagasaki line, a moist convectively unstable atmosphere was observed in the lower layer together with environmental winds that included southerly winds near the surface and southwesterly jet at 3-4 km in height. Numerical simulations of the Nagasaki line were conducted using an operational Regional Spectral Model (RSM) of the Japan Meteorological Agency and a Nonhydrostatic Cloud Model (NHM) of the Meteorological Research Institute. While the RSM simulated only a weak precipitation area in western Kyushu, the NHM reproduced many characteristics of the observed Nagasaki line. Sensitivity experiments for topography, humidity and wind profiles showed that a moist convectively unstable atmosphere, mesoscale convergence, and winds having both a strong southwesterly jet at 3-4 km and a strong vertical wind shear in the lower troposphere are essential for the formation of the Nagasaki line. Although small and low, mountains on the Nagasaki Peninsula are capable of forming an organized precipitation band under such environmental fields..
159. Yoshizaki, M, T. Kato, Y. Tanaka, H. Takayama, Y. Shoji, H. Seko, K. Arao, K. Manabe, Member of X-BAIU-98 Observation, Analytical and Numerical Study of the 26 June 1998 Orographic Rainband Observed in Western Kyushu, Japan, Jour. Meteorol. Soc. Japan, Vol.78, 835-856, 2000.01.
160. Matsushima, T. and A. Takagi, GPS and EDM Monitoring of Unzen Volcano Ground Deformation, Earth, Planets and Space, 52, 11, 1015-1018, Vol.52, 1015-1018, 2000.01.
161. Takeshi Matsushima, Akimichi Takagi, GPS and EDM monitoring of Unzen volcano ground deformation, Earth, Planets and Space, 10.1186/BF03352323, 52, 11, 1015-1018, 2000.01, [URL], Following 198 years of dormancy, an eruption started at Mt. Fugen, the main peak of Unzen volcano, in Kyushu, Japan, in November 1990. A dacite lava dome began to grow in May 1991. We installed the surveying points of GPS in 1992 around the lava dome in order to observe the ground deformation that accompanied the growth of the lava dome. In the winters of 1993 and 1994, we observed swift ground deformations that radiated from the vent of the volcano. It was presumed that rising magma accumulated and expanded the volcano body. After the lava effusion stopped in 1995, we also installed surveying points on the lava dome. EDM mirrors were permanently fixed to the large rocks with bolts. A GPS survey was carried out 2 or 3 times each year to estimate the 3-dimensional displacement. The result of the EDM survey showed that the baselines from the flank of the volcano were shortening 5 mm per day, and the result of the GPS survey showed that the displacement vector of the dome was parallel to the direction of the steepest slope of the old volcano body. This indicates that the inside of the lava dome is still very hot, and that deformation of the dome is viscous. Copy right.
162. Yamashina, K. and Matsushima, T., Ground temperature change observed at Unzen Volcano associated with the1990-1995 eruption, JVGR, 10.1016/S0377-0273(98)00123-1, 89, 1-4, 65-71, Vol. 89/1-4, 65-71, 1999.01.
163. Yamashina, K., Matsushima, T. and Ohmi, S., Volcanic deformation at Unzen, Japan, visualized by a time-differential stereoscopy, JVGR, 10.1016/S0377-0273(98)00124-3, 89, 1-4, 73-80, Vol.89/1-4, 73-80, 1999.01.
164. 渡邉篤志・藤井雄志郎・二牟礼勇人・亀 伸樹・竹中博士・植平賢司・鈴木貞臣・松島健, 鹿児島県串木野市の岩盤上における広帯域強震観測, 九州大学理学部研究報告(地球惑星科学), Vol.20,No. 3, 79-88, 1999.01.
165. 田代勝也・鈴木貞臣・松島 健・宮町宏樹・岩崎貴哉・吉井敏剋・武田哲也・朴 成実・酒井慎一・飯高 隆・久保篤規・森谷武男・安藤 誠, 人工地震探査による九州東部の上部地殻構造, 九州大学理学部研究報告(地球惑星科学), Vol.20,No. 3, 111-123, 1999.01.
166. 爆破地震動研究グループ, 東北日本弧横断人工地震探査(釜石−岩城測線), 地震研究所彙報, Vol.74, 63-122, 1999.01.
167. 爆破地震動研究グループ, 九州東部域における爆破地震動の観測1(庄内−串間測線), 地震研究所彙報, Vol.74, 123-140, 1999.01.
168. 爆破地震動研究グループ, 九州東部域における爆破地震動の観測2(安心院−田野測線), 地震研究所彙報, Vol.74, 141-160, 1999.01.
169. 松島健・加藤照之, マリアナ諸島北部の火山について, 火山, Vol.44, No.3,179-182., 1999.01.
170. Atsushi Watanabe, Yushiro Fujii, Hayato Futamure, Nobuki Kame, Hiroshi Takenaka, Sadaomi Skuzuki, Kenji Uehira, Takeshi Matsushima, Broadband strong-motion observation on the hard rock site at Kushikino, Science Reports of the Kyushu University, Department of Earth and Planetary Sciences, 20, 3, 79-88, 1998.12, In 1997, two moderate earthquakes occurred in the northwestern part of Kagoshima Prefecture (Mjma 6.5 on March 26 and Mjma 6.3 on May 13), and a large number of aftershocks occurred in the southern part of the second event focal region. We started the observation of the aftershocks from April 1, 1998, at Kushikino. We used a broadband strong-motion velocity-type seismograph and an accelerograph in order to record the full waveforms of the strong ground motions. Up to April 25, 1999, we observed 74 events, and 3 events were recorded by both seismographs. In this paper, we report the detail of observational conditions and show some waveforms we obtained..
171. Moriya, T., H. Okada, T. Matsushima, S. Asano, T. Yoshii, A. Ikami, Collision Structure in the Upper Crust beneath the Southwestern Foot of the Hidaka Mountains, Hokkaido, Japan as Derived from Explosion Seismic Observations, Tectonophys, 10.1016/S0040-1951(98)00011-0, 290, 3-4, 181-196, Vol.290, 181-196, 1998.01.
172. Tuda, T., K. Heki, S. Miyazaki, A. Aonashi, K. Hirahara, H. Nakamura, M. Tobita, F. Kimata, T. Tabei, T. Matsushima, F. Kimura, M. Satomura, T. Kato, and I. Naito, GPS meteorology project of Japan - Exploring frontiers of geodesy-, Earth Planets Space, 50, 10, I-V, Vol.50, 1-5, 1998.01.
173. 宮町 宏樹・岩切 一宏・津野 拓士・清水 力・福満 修一郎・金子 和弘・関谷 博・角田 寿喜・後藤 和彦・八木原 寛・平野 舟一郎・松島 健・清水 洋, 1997年鹿児島県北西部地震の臨時余震観測, 北海道大学地球物理学研究報告, Vol.61,85-97, 1998.01.
174. 藤井 雄士郎・二牟礼 勇人・竹中 博士・松島 健・馬越 孝道・田代 勝也・鈴木 貞臣, 1997年鹿児島県北西部地震余震の広帯域強震観測, 九州大学理学部研究報告 地球惑星科学, Vol.20,25-46, 1998.01.
175. 儘田 豊・藤井 雄士郎・竹中 博士・松島 健・馬越 孝道, 鹿児島県北西部地域の地震波減衰特性〜Qc-1の測定〜, 自然災害科学, 22, 1998.01.
176. Y. Fujii, H. Futamure, H. Takenaka, Takeshi Matsushima, K. Umakoshi, K. Tashiro, S. Suzuki, Broadband strong-motion observation for aftershocks of the 1997 northwestern Kagoshima earthquakes, Science Reports of the Kyushu University, Department of Earth and Planetary Sciences, 20, 1, 25-46, 1998.01, An earthquake with MJMA 6.5 occurred at the northwest region of Kagoshima prefecture on March 26, 1997. We started observing the aftershocks at KKN (31.9794°N 130.4442°E) on March 28, 1997 using the broadband strong-motion seismometer (VSE 11 C/12 C). The observation was finished on September 30, 1997. Also another VSE 11 C/12 C was installed at the station SIBI (31.9677°N 130.3524°E). After all, we observed 100 events at KKN, including the second large earthquake (MJMA 6.2) on May 13. The purpose of this paper is to describe the detail of observational conditions, and to report the result of the preliminary analysis of the observed seismograms. We transformed the horizontal components of seismograms observed at SIBI into the radial and transverse components, and analyzed the Fourier amplitude spectra for S-wave parts of the aftershocks observed at KKN have a sharp peek at the frequency of 4.0-6.0 Hz, which is not seen for the seismograms observed at SIBI. Also, we integrated the velocity seismograms to get the displacement waveforms. The observation in short epicentral distances made it possible to recognize the near-field term in all of the displacement waveforms..
177. T. Tsuda, K. Heki, S. Miyazaki, K. Aonashi, K. Hirahara, H. Nakamura, M. Tobita, F. Kimata, T. Tabei, Takeshi Matsushima, F. Kimura, M. Satomura, T. Kato, I. Naito, GPS meteorology project of Japan - Exploring frontiers of geodesy, Earth, Planets and Space, 50, 10, 1998.01.
178. Yutaka Mamada, Takashi Okumura, Hiroshi Takenaka, Sadaomi Suzuki, Seiji Saito, Mitsuko Furumura, Tsutomu Sasatani, Takeshi Matsushima, Takashi Furumura, Coda Q-1 in Awaji Island estimated from the aftershock records of the 1995 Hyogo-ken Nanbu earthquake, Journal of Physics of the Earth, 45, 2, 147-154, 1997.12.
179. T. Tabei, T. Kato, J. P.L. Catane, T. Chachin, K. Fujimori, K. Hirahara, A. Kubo, Takeshi Matsushima, T. Nakano, S. Nakao, S. Otsuka, T. Terashima, T. Yamamoto, Crustal deformation associated with the 1995 Hyogo-ken Nanbu earthquake, Japan derived from GPS measurements, Journal of Physics of the Earth, 44, 4, 281-286, 1996.12, A large M=7.2 earthquake occurred just below the western part of the Osaka-Kobe megalopolis, SW Japan on January 17, 1995. The Japanese University Consortium for GPS Research conducted extensive local GPS measurements in and around the hypocentral region to collect near-field data on co-seismic and post-seismic crustal deformation. Adopting old GPS data collected before the earthquake, co-seismic displacement vectors have been obtained at five sites. Horizontal displacements are larger than 0.4 m in the vicinity of the earthquake fault and decay steeply with distance from the fault. The horizontal deformation pattern represents a typical right-lateral slip motion along the fault. In contrast, vertical displacements are rather difficult to interpret probably because of the low precision of old GPS measurements and the complex local site condition..
180. T. Kato, Y. Kotake, S. Nakao, Y. Hirata, T. Chachin, F. Kimata, K. Yamaoka, T. Okuda, H. Kumagai, K. Hirahara, T. Nakano, T. Terashima, J. P.L. Catane, A. Kubo, T. Tabei, T. Iwabuchi, Takeshi Matsushima, Post-seismic crustal deformation associated with the 1995 Hyogo-ken Nanbu earthquake derived from GPS observation
preliminary analysis of Trimble data, Journal of Physics of the Earth, 44, 4, 287-299, 1996.12, Within 1 to 4 days following the 1995 Hyogo-ken Nanbu earthquake (M 7.2) that occurred on January 17, 1995, the Japanese University Consortium for GPS Research deployed more than 30 GPS receivers in the hypocentral area to investigate post-seismic activity. Results suggest that 1) rapid displacements toward the southeast of more than 4 cm/year were found at all of the analyzed sites, which might be part of a post-seismic deformation process, 2) largest of which was found at Rokko Farm site, at which displacement amounted to about 3 cm until the end of February, though its cause were not specified, and 3) local straining seems to be taking place at both Kobe and Awaji areas..
181. T. Okumura, H. Takenaka, S. Suzuki, T. Sasatani, M. Furumura, S. Saito, Takeshi Matsushima, T. Furumura, Aftershock observation of the 1995 Hyogo-ken Nanbu earthquake in Awaji Island
strong motion and broad band observation, Science Reports - Kyushu University, Department of Geology, 19, 1, 103-123, 1995.12, The 1995 Hyogo-ken Nanbu earthquake occurred on January 17 1995. The maximum seismic intensity was seven in Kobe city and a part of Awaji island. The aftershocks were observed at three stations in Awaji island using three strong-motion seismometers and a broad-band seismometer from January 19 to April 4. During this period, 89 events were oberved. In these events, nine events were observed at all of the three stations. Among the nine events, three events were analysed using integration of velocity in the time domain and amplitude spectrum of S-wave for 5 seconds. Amplitude spectral ratios of two events occurring in Kobe side for 20 seconds from P-wave arrival, for 20 seconds from S-wave arrival, and S-wave part for 5 seconds were also analysed. Those amplitude spectra showed predominant frequency around 1-4 Hz for IWY and ABK stations, but TSM predominant frequency around 4-7 Hz. The spectral ratio shows 3-10 times amplification, around 1-2 Hz and 4-7 Hz for TSM/IWY, and around 0.9-2 Hz and 4-7 Hz for ABK/IWY. For TSM/IWY, 2-5 times attenuation was observed around 2-3 Hz..
182. Nakao, S., H. Takahashi, T. Matsushima, Y. Kohno, and M. Ichiyanagi, Postseismic deformation following the 2005West Off Fukuoka Prefecture Earthquake (M7.0) derived by GPS observation, Earth Planets Space, Vol.58, No.12, 1617-1620.
183. 田中良和・橋本武志・北田直人・大久保綾子・宇津木充・清水 洋・松島 健, 雲仙火山における空中磁気測量について, 平成14年度雲仙火山科学掘削成果報告書.

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