Updated on 2026/01/13

Information

 

写真a

 
AIZAWA KOKI
 
Organization
Faculty of Science Institute of Seismology and Volcanology Associate Professor
Faculty of Science Institute of Seismology and Volcanology（Concurrent）
School of Sciences Department of Earth and Planetary Sciences（Concurrent）
Graduate School of Sciences Department of Earth and Planetary Sciences（Concurrent）
Title
Associate Professor
Contact information
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Profile
火山噴火予知・地震予知を究極の目的として、主に電磁気的観測により火山活動や地震のメカニズムを調べています。ローカルなフィールドワークを積み重ねることで、火山活動、地震活動に共通する性質を抽出します。これまでの研究で、火山の地下と、大きな地震が起こる場所の地下は似た性質をもつという考えに至り、火山と地震の区別をあまり意識せず研究しています。 主な研究テーマは以下になります。 (1) 火山地下のマグマ供給系の研究 　マグマ (メルト) やマグマに含まれる水は電気を通しやすいため、火山地下の電気の流れやすさの構造 (比抵抗構造)を推定し，さらに地殻変動や地震等の観測と比較することで、マグマ溜まりの位置や大きさや，そこから地表に至る供給ルートを解明します。最近の研究で、火山性流体の上昇経路は地下構造に異常が見える場所ではなく、そのはじっこの部分 (構造境界) ではないかと考えるようになりました。 (2) 火山体内部の地下水－熱水系の研究 　地下水の流れは地表に電位分布として表れ、火山活動に応じて時間変化します。最近の研究で、火山浅部の地下水の流動が水蒸気噴火を抑制したり、噴火するにしてもその発生を数分間遅らせる働きをしているということを提案しました。 地電位観測が噴火の直前予測の新たなツールとなり得ると考えて研究を行っています。 (3) 内陸地震発生の解明 　比抵抗構造から、大きな地震が発生する場所と最大規模が予測できると考えて、様々な地域で広帯域MT調査を行うことで有効性を検証しています。 地震予知が原理的に可能かどうかは多くの議論がなされていますが、少なくとも場所は絞れるのではないかと比較的、楽観的に考えています。 (4) 地殻構造とテクトニクスの関連の研究 　地殻内は付加体堆積物の中に、マグマだまりが冷え固まった深成岩や、変質した蛇紋岩、流体などが分布し非常に不均質です。これらの不均質は地表の変形や地震の発生と密接に関連しているはずです。主に九州全域を対象に不均質の原因と変形や地震活動との関連を解明します。 (5) 火山雷の研究 　高感度カメラによる可視映像観測と電磁気観測により火山雷の性質や発生条件を研究します。火山雷の観測から、天気が悪いときでも噴火の発生やその規模の即時把握ができることを期待して研究をしています。火山雷は美しいですし、生命の起源にかかわるという説があり興味深い研究対象です。 (6) その他 　特に電磁気観測データに埋もれた新たな現象の発見ができれば新しい道がひらけるはずです。
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Research Areas

  • Social Infrastructure (Civil Engineering, Architecture, Disaster Prevention) / Disaster prevention engineering

  • Natural Science / Solid earth sciences

Degree

  • science

Research History

  • Kyushu University Institute of Seismology and Volcanology Associate Professor 

    2017.4 - Present

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  • 2004年5月－　2005年3月 東京大学 地震研究所 特別研究員 2005年4月－　2008年3月 日本学術振興会特別研究員 (PD) 　　　　　　 (所属:東京工業大学火山流体研究センター) 2008年4月－　2009年3月 京都大学防災研究所火山活動研究センター 研究員(研究機関) 2009年4月－2012年12月　東京大学地震研究所　特任研究員   

Education

  • Kyoto University   理学研究科   地球惑星科学科

    1999.4 - 2004.3

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    Country：Japan

  • Kyoto University   理学部  

    1995.4 - 1999.3

Research Interests・Research Keywords

  • Research theme： Self potential

    Keyword： Self potential

    Research period： 2024

  • Research theme： 爆発

    Keyword： 爆発

    Research period： 2024

  • Research theme： 火山

    Keyword： 火山

    Research period： 2024

  • Research theme： Resistivity

    Keyword： Resistivity

    Research period： 2024

  • Research theme： 地震

    Keyword： 地震

    Research period： 2024

  • Research theme： Geomagnetic field

    Keyword： Geomagnetic field

    Research period： 2024

  • Research theme： Process prior to phreatic eruption

    Keyword： Phreatic eruption, self potential

    Research period： 2016.3 - 2025.3

  • Research theme： Electromagnetic signals by a volcanic lightning

    Keyword： volcanic lightning

    Research period： 2010.3 - 2020.3

  • Research theme： Temporal change of resistivity structure

    Keyword： resistivity magnetotellurics structure change

    Research period： 2008.3 - 2020.3

  • Research theme： Relationship between resistivity structure and earthquakes

    Keyword： resistivity earthquakes

    Research period： 2002.3 - 2020.3

  • Research theme： hydrothermal system of volcanoes

    Keyword： self-potential resistivity hydrothermal system

    Research period： 2002.3 - 2020.3

  • Research theme： Resistivity structure beneath active volcanoes

    Keyword： Resistivity magnetotellurics

    Research period： 2000.4 - 2020.4

Awards

  • 電磁気学的観測・実験・計算に基づく火山噴火準備過程及び噴火現象の総合的研究

    2024.5   The Volcanological Society of Japan  

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    Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

  • SGEPSS論文賞

    2022.11   地球電磁気・地球惑星圏学会   Aizawa et al. 2021, EPS https://link.springer.com/article/10.1186/s40623-020-01340-w に対する論文。 熊本地震を対象に内陸地震ポテンシャル評価に比抵抗構造が貢献できる可能性を示した。

  • 信州フィールド科学賞

    2009.11   信州大学山岳科学総合研究所  

  • 日本火山学会研究奨励賞

    2009.5   日本火山学会   電磁気観測による火山浅部構造の研究

Papers

  • Three-dimensional resistivity structure beneath Beppu and Yufuin geothermal fields imaged by dense broad-band magnetotelluric observations Reviewed

    Aizawa K., Yamamoto Y., Wakabayashi A., Muramatsu D., Aniya S., Tanabe H., Fujita S., Azusa S., Koyama T., Shiozaki I., Ichiki M.

    Earth Planets Space   77 ( 1 )   159   2025.10   （ ISSN:1880-5981 eISSN:1880-5981 ）

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    Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Earth Planets and Space  

    <jats:title>Abstract</jats:title>
    <jats:p>The Beppu and Yufuin geothermal fields are the most famous hot spring areas in Japan, with the highest and second-highest discharge rates, approximately 80,000 and 40,000 L per minute, respectively. These hot springs are located at the foot of three Quaternary active volcanoes: Garan, Tsurumi, and Yufu. To investigate fluid pathways and associated reservoirs supplying the Beppu and Yufuin geothermal fields, we conducted broad-band magnetotelluric (MT) surveys from 2014 to 2025 over an approximately 50 km × 50 km area surrounding these geothermal zones. A total of 161 survey sites' data were analyzed. The resulting 3-D resistivity structure reveals two conductors in the upper crust. One conductor is located beneath the three volcanoes at depths of 2–10 km and extends in an NNE–SSW direction at greater depths. The second conductor is located beneath Beppu Bay at depths of 1–5 km. Earthquakes predominantly occurred in resistive zones near these conductors, including the 2007 earthquake swarm, in which hypocenters migrated from a depth of 10 km within Beppu Bay to a depth of 3 km southwest of Beppu City. We interpret the conductor beneath the volcanoes as a hot zone associated with volcanic fluids, while the conductor beneath Beppu Bay likely represents cold thick sediment. Since eruption sites are positioned around the edge of the conductor beneath the volcanoes, we hypothesize that magmatic fluids preferentially rise along the conductor’s boundaries. Considering the locations of these conductors and the hypocenter migration in 2007, we propose two fluid pathways for the Beppu geothermal fields: one from beneath the three volcanoes and another from beneath Beppu Bay. The primary fluid sources are likely situated to the NNE of the region, based on the locations of deep conductors (&gt; 15 km depth). The hypothesis of dual fluid pathways may explain the significant variations in the chemical composition of Beppu’s hot spring waters. Similarly, the Yufuin hot springs may also be fed by two fluid pathways: one originating beneath the three volcanoes and another from the deep portion of a fault. Among the hot springs in the study region, the northern side of the Beppu hot springs is distinctive in that the conductor beneath the adjacent Garan volcano rises to 2 km beneath the summit, and the shallow layer is approximately one order of magnitude more conductive than that of other hot springs. This indicates that the contribution of fluids from the shallow part of the volcanoes is dominant on the northern side of the Beppu hot springs.</jats:p>
    <jats:p>
    <jats:bold>Graphical Abstract</jats:bold>
    </jats:p>

    DOI： 10.1186/s40623-025-02291-w

    DOI： 10.1186/s40623-025-02291-w

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  • Three-dimensional resistivity structure and its relationship to the rupture of the 1997 Kagoshima earthquake doublet (Mw. 6.1 and 6.0), Japan Reviewed

    Matsunaga K., Aizawa K., Asamori K., Ogawa H., Utsugi M., Yoshimura R., Yamazaki K., Uchida K., Matsushima T., Inoue T., Yonemori K., Shigematsu H.

    Tectonophysics   915   2025.9   （ ISSN:0040-1951 eISSN:1879-3266 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Tectonophysics  

    We estimated the resistivity structure in the region of the 1997 Northwestern Kagoshima earthquake doublet (March 26, Mw6.1; May 13, Mw6.0) by dense magnetotelluric (MT) observations to investigate the influence of low-resistivity zones on the initiation and termination of large inland earthquake ruptures. In addition to MT data from previous studies, we acquired new broadband MT and telluric data at 42 sites. With a total of 86 sites in approximately 50 km × 50 km area, we constructed a high-resolution resistivity structure through 3-D inversion. A comparison between the slip distribution and resistivity structure showed that the rupture of the mainshock in March initiated at the western edge of a low-resistivity zone, propagated westward (with a maximum slip of 0.8 m), and was ultimately arrested by another low-resistivity zone. Based on geological structures and<sup>3</sup>He/<sup>4</sup>He ratios in hot springs, we suggest that magma-derived fluids, located beneath a shallow, low-permeability smectite-rich zone and granodiorite, contributed to the initiation of the mainshock rupture. Another smectite-rich zone, along with underlying high pore pressure fluids, played a role in arresting the rupture. The rupture of the mainshock in May initiated at the edge of another low-resistivity zone and propagated in two directions (with a maximum slip of 0.4 m): one along the edge of the low-resistivity zone and the other toward the low-resistivity zone, before finally stopping within the low-resistivity zone. Our findings are consistent with those from the 2016 Kumamoto earthquake (M7.3), supporting the idea that resistivity structures can help assess the spatial potential of large inland earthquakes.

    DOI： 10.1016/j.tecto.2025.230880

    DOI： 10.1016/j.tecto.2025.230880

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    Open data URL： https://doi.org/10.1016/j.tecto.2025.230880

  • Tilt and self-potential observations of Kibedani Geyser, Japan: Relationship between fluid flow and CO2-driven geyser activity Reviewed

    Tanabe H., Aizawa K., Matsushima T.

    Scientific Reports   15 ( 1 )   1 - 13   2025.5   （ ISSN:2045-2322 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Scientific Reports  

    We conducted multi-parameter, multi-site observations at the Kibedani Geyser, Japan, where cold spring-water eruptions (20 °C) are driven by underground CO<inf>2</inf> pressure. Observations included video, temperature, self-potential (SP), ground tilt, and acoustic measurements. The geyser exhibits a 38-min cycle, consisting of 32 min between eruptions followed by 6 min of eruption. All data revealed changes corresponding to this cycle. Modeling of tilt data indicate that an inclined crack-shaped cavity pressure source expands between eruptions and contracts during eruption, with post-eruption re-expansion beginning ~ 2.5 min after eruption, when ground tremor has ceased. This cavity is interpreted as a bubble trap where CO<inf>2</inf> gas, separated from ascending spring-water, accumulates prior to eruption. SP data modeling suggests that the current source responsible for SP generation, represented by a point and crack-shaped model, is located near this cavity. The correlation between the pressure source and the SP current source suggests that groundwater inflow occurs into the pressure source. Our findings suggest that CO<inf>2</inf> accumulates in the cavity, uplifting water during an eruption and driving groundwater inflow into the cavity. This study highlights the effectiveness of combining tilt and SP methods for analyzing fluid-driven phenomena, providing insights into geyser activity and analogous processes such as volcanic phreatic eruptions. We anticipate that our approach, when applied not only to CO<inf>2</inf>-driven geysers but also to hydrothermal-driven geysers, will contribute to the elucidation of mechanisms underlying phreatic eruptions.

    DOI： 10.1038/s41598-025-04215-w

    DOI： 10.1038/s41598-025-04215-w

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  • Three‐Dimensional Electrical Resistivity Structure Beneath a Strain Concentration Area in the Back‐Arc Side of the Northeastern Japan Arc Reviewed

    Usui Y., Uyeshima M., Hase H., Ichihara H., Aizawa K., Koyama T., Sakanaka S., Ogawa T., Yamaya Y., Nishitani T., Asamori K., Ogawa Y., Yoshimura R., Takakura S., Mishina M., Morita Y.

    Journal of Geophysical Research, Solid Earth   e2023JB028522   2024.5

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    Language：English   Publishing type：Research paper (scientific journal)  

    Other Link： https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023JB028522

  • Vulcanian eruption processes inferred from volcanic glow analysis at Sakurajima volcano, Japan Reviewed International journal

    Dan Muramatsu, Koki Aizawa, Akihiko Yokoo, Takeshi Tameguri, Masato Iguchi

    Bulletin of Volcanology   85 ( 7 )   41   2023.6   （ ISSN:0258-8900 eISSN:1432-0819 ）

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    Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

    Abstract

    Volcanic glow, which is often observed at active craters during nighttime, contains information on high-temperature zones deep in the crater that are hidden from view. We analyzed 90 eruption videos capturing volcanic glow before the onset of Vulcanian eruptions at the Showa crater of Sakurajima volcano (Japan), and found that they show clear temporal changes. The red (R)-value and the green-to-red ratio (GR ratio) are used to track glow intensity and temperature change, respectively. We found two types of temporal change in glow intensity: a short-term change approximately 1 s before the onset of explosions, and a long-term change 3 to 330 s before an explosion. Short-term changes were observed for 28 of 90 eruptions, and coincided with an increase in the GR ratio and with a modest precursory infrasound pressure increase. Since an increasing GR ratio means a temperature increase, we consider that the change was associated with the opening of tensile cracks on the crater floor before an explosion. However, the other 62 eruptions did not show short-term changes, suggesting that the opening of cracks is sporadic. Long-term changes were observed for 73 of 90 eruptions, the GR ratio did not exhibit a significant increase. We suggest that long-term changes are caused by gradual gas leakage, which precedes initiation of Vulcanian eruptions. We hypothesize that the long-term gas leakage causes gradual decompression of the conduit, which induces supersaturation of volatile-rich magma beneath the lava plug causing explosive expansion, thereby triggering an eruption.

    DOI： 10.1007/s00445-023-01656-x

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    Other Link： https://link.springer.com/article/10.1007/s00445-023-01656-x/fulltext.html

  • Vulcanian eruption processes inferred from volcanic glow analysis at Sakurajima volcano, Japan Reviewed International journal

    @Muramatsu D., @Aizawa K., @Yokoo A., @Tameguri T., @Iguchi M.

    Bulletin of Volcanology   85   41   2023.6

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    Language：Japanese   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1007/s00445-023-01656-x

    Other Link： https://doi.org/10.1007/s00445-023-01656-x

  • Multi-parametric observations of intermittent hydrothermal water discharge in West Crater of Iwo-Yama volcano, Kirishima Volcanic Complex, Japan Reviewed International journal

    Harutou Tanabe, Takeshi Matsushima, Koki Aizawa, Dan Muramatsu

    Earth, Planets and Space   75 ( 1 )   2023.5   （ ISSN:1343-8832 eISSN:1880-5981 ）

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    Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Earth, Planets and Space  

    From April to July 2021, West Crater at Iwo-Yama, Kirishima Volcanic Complex, Japan, was repeatedly filled with hydrothermal water and subsequently evacuated. The overall cycle lasted 14–70 h, and the course of a single cycle followed this sequence of phases: (i) steam effusion disappeared 20–40 min before hydrothermal water discharge; (ii) hydrothermal water discharge occurred, generating a hydrothermal water pool; (iii) steam effusion resumed and gradually increased; and (iv) drain-back (evacuation) of the hydrothermal water occurred 1–1.5 h before the onset of the next hydrothermal water discharge. We used multi-parametric observations (optical camera, thermometer, electric self-potential (SP) electrodes, seismometer, acoustic sensor, and tiltmeter) to investigate the cause of the cyclic hydrothermal water discharge. A change in SP data occurred approximately 2 h before the onset of hydrothermal water discharge. However, the change in SP was small when hydrothermal water discharge did not occur. The temporal change in SP is inferred to have been caused by groundwater flow through the region below West Crater, implying that groundwater flow was occurring 2 h before hydrothermal water discharge. The polarity of SP change suggests that groundwater flowed toward the region underlying the vents. Seismic signals in the frequency range of < 20 Hz decreased 15–45 min after the onset of change in SP. This seismic signal pattern is inferred to have been caused by bubble activity in boiling fluid. We interpret that the inflow of cold groundwater inhibited boiling activity in the conduit, which in turn caused the cessation of both steam effusion and seismic activity. SP data suggest that the inflow of cold groundwater gradually decreased before hydrothermal water discharge. Pressurization sufficient to force the water in the upper part of the conduit to ascend could have built up in the lower part of the conduit owing to a decrease in the input of groundwater into the upper part of the conduit and the continuing supply of steam bubbles and hot water. This increase in pressure finally led to hydrothermal water discharge at the surface. We suggest that the inflow of cold groundwater into the geyser conduit was the key control on the occurrence and cyclicity of hydrothermal water discharge in West Crater at Iwo-Yama. Graphical Abstract: [Figure not available: see fulltext.]

    DOI： 10.1186/s40623-023-01830-7

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  • Multi-parametric observations of intermittent hydrothermal discharge in West Crater of Iwo-Yama volcano, Kirishima Volcanic Complex, Japan Reviewed International journal

    #Tanabe H.,@Matsushima T., @Aizawa K., and @Muramatsu D.,

    Earth Planets Space   75   2023.5

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    Language：Japanese   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1186/s40623-023-01830-7

    Other Link： https://doi.org/10.1186/s40623-023-01830-7

  • Magma transport along structural boundaries in the upper crust: insights from broad-band magnetotelluric constraints on the structure beneath Unzen volcano, Japan Reviewed International journal

    #Triahadini A., @Aizawa K., @Hashimoto T. M., @Chiba K., @Uchida K., @Yamamoto Y., @Miyano K., @Muramatsu D., #Aniya S., #Okubo A., #Kawamura Y.

    Geophysical Journal International   234   1268 - 1281   2023.4

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    Language：Japanese   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1093/gji/ggad126

    Other Link： https://doi.org/10.1093/gji/ggad126

  • Magma transport along structural boundaries in the upper crust: insights from broad-band magnetotelluric constraints on the structure beneath Unzen volcano, Japan Reviewed International journal

    Agnis Triahadini, Koki Aizawa, Tasuku M. Hashimoto, Keita Chiba, Kazunari Uchida, Yuto Yamamoto, Kanta Miyano, Dan Muramatsu, Satoru Aniya, Ayumu Okubo, Yuta Kawamura

    Geophysical Journal International   234 ( 2 )   1268 - 1281   2023.3   （ ISSN:0956-540X eISSN:1365-246X ）

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    Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Geophysical Journal International  

    Unzen volcano, located on Shimabara Peninsula, Nagasaki, Japan, is an active volcano that has been intensively monitored since 1989, one year before the most recent eruption in 1990-1995. Previous earthquake and surface deformation studies have revealed that magma is transported obliquely from a magma reservoir beneath Tachibana Bay, to the west of Shimabara Peninsula. Here, we conduct broad-band magnetotelluric (MT) surveys at 99 sites around Shimabara Peninsula to investigate the crustal structure beneath Unzen volcano that is related to magma migration. A 3-D resistivity model that is constructed from 25 broad-band MT sites and 45 telluric sites shows a broad high-resistivity zone beneath Shimabara Peninsula and low-resistivity zones to the west and east of the peninsula. An unexpected observation is the spatial alignment of the high-resistivity zone with a seismic low-velocity zone (LVZ) at 3-15 km depth. Quantitative analysis indicates this high-resistivity zone contains < 0.7 per cent melt under the assumption that the melt is stored in a good porosity network, while < 11 per cent melt in relatively poor pore network. We infer this high-resistivity, LVZ to be a highly crystallized mush zone (HCMZ) with low permeability. The hypocentres and pressure sources of the 1990-1995 eruption are distributed along the boundary between the high- and low-resistivity zones beneath the western part of the peninsula. We therefore conclude that the magma migrated along a structural boundary that possessed a relatively high permeability. Previous studies have suggested that eruptible magma is usually transported vertically upward through the centre of the mush zone, whereas the present results reveal that magma can be transported along the upper boundary of an HCMZ.

    DOI： 10.1093/gji/ggad126

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  • Potential evaluation of supercritical geothermal systems in the Kuju region, central Kyushu, Japan Reviewed International journal

    Kitamura K., Fujii Y., Inagaki H., Saito H., Aizawa K., Ishibashi J., Fujimitsu Y.

    Geothermics   107 ( 107 )   102602   2023.1   （ ISSN:0375-6505 eISSN:1879-3576 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Geothermics  

    We derived the thermal structure of the Kuju region of volcanic activity in central Kyushu, Japan, to assess the potential existence of a supercritical geothermal system. Extrapolation of existing well-logging data suggests the presence of a high-temperature region beneath the area between the Hatchobaru geothermal power plant and Kuju-Iwoyama Volcano, which closely overlaps a low-resistivity body estimated from magnetotelluric data. Based on estimated temperatures exceeding 380 °C at the relatively shallow depth of -3.3 km above sea level, and considering evidence for magmatic fluid transport, this high-temperature region is a potential target for a supercritical geothermal reservoir.

    DOI： 10.1016/j.geothermics.2022.102602

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  • Potential evaluation of supercritical geothermal systems in the Kuju region, central Kyushu, Japan Reviewed International journal

    @Kitamura K., @Fujii Y., @Inagaki H., @Saito H., @Aizawa K., @Ishibashi J., @Fujimitsu Y.

    Geothermics   ( 107 )   102602   2022.11

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1016/j.geothermics.2022.102602

    Other Link： https://doi.org/10.1016/j.geothermics.2022.102602

  • Phreatic volcanic eruption preceded by observable shallow groundwater flow at Iwo-Yama, Kirishima Volcanic Complex, Japan Reviewed International journal

    Aizawa K., Muramatsu D., Matsushima T., Koyama T., Uyeshima M., Nakao S.

    Communications Earth & Environment   3 ( 1 )   2022.8   （ eISSN:2662-4435 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Communications Earth and Environment  

    It is difficult to forecast phreatic eruptions because they are often characterised by an abrupt onset at shallow depths beneath volcanoes. Here we show that temporal changes in the tilt, tremor, and horizontal electric field have occurred repeatedly near the vent of a small phreatic eruption at Iwo-Yama, Kirishima Volcanic Complex, Japan. Such geophysical changes were observed 13 times, with one of these events occurring immediately before the onset of the 2018 phreatic eruption. These observations suggest that shallow hydrothermal intrusions, which are observed as tilt changes with tremors, commonly induce near-surface cold groundwater flow, which is observed as electric-field changes. Near-surface groundwater flows towards the active vent, potentially inhibiting a phreatic eruption. However, explosive phreatic eruptions occur when the intrusion is shallow and cold groundwater flow is depleted. The near-surface groundwater is key in controlling the occurrence of phreatic eruptions and can be monitored using electric-field measurements.

    DOI： 10.1038/s43247-022-00515-5

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  • Phreatic volcanic eruption preceded by observable shallow groundwater flow at Iwo-Yama, Kirishima Volcanic Complex, Japan Reviewed International journal

    @Aizawa K., @Muramatsu D., @Matsushima T., @Koyama T., @Uyeshima M., @Nakao S.

    Communications Earth & Environment   3 ( 187 )   2022.8

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    Language：English   Publishing type：Research paper (scientific journal)  

    It is difficult to forecast phreatic eruptions because they are often characterised by an abrupt
    onset at shallow depths beneath volcanoes. Here we show that temporal changes in the tilt,
    tremor, and horizontal electric field have occurred repeatedly near the vent of a small phreatic
    eruption at Iwo-Yama, Kirishima Volcanic Complex, Japan. Such geophysical changes were
    observed 13 times, with one of these events occurring immediately before the onset of the
    2018 phreatic eruption. These observations suggest that shallow hydrothermal intrusions,
    which are observed as tilt changes with tremors, commonly induce near-surface cold
    groundwater flow, which is observed as electric-field changes. Near-surface groundwater
    flows towards the active vent, potentially inhibiting a phreatic eruption. However, explosive
    phreatic eruptions occur when the intrusion is shallow and cold groundwater flow is depleted.
    The near-surface groundwater is key in controlling the occurrence of phreatic eruptions and
    can be monitored using electric-field measurements.

    DOI： https://doi.org/10.1038/s43247-022-00515-5

    Other Link： https://www.nature.com/articles/s43247-022-00515-5

  • Infrasound–electric-field coupling associated with the 2018 Shinmoe-dake eruptions, Kirishima volcanic complex, Japan Reviewed International journal

    Aniya S., Aizawa K., and Matsushima T.

    Geophysical Research Letters   49 ( 3 )   GRL63677   2022.2   （ ISSN:0094-8276 eISSN:1944-8007 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

    Shinmoe-dake volcano, which is within the Kirishima volcanic complex, Japan, erupted from March to June 2018. The eruptions were recorded by various geophysical instruments that were installed 3.1-5.4 km from the crater. Here we present the first documented evidence of infrasound-induced electric-field changes in the near surface at the time of the explosive eruptions. Significant electric-field changes coincide with the infrasound arrivals. An order-of-magnitude estimation of the electric field indicates that the electrokinetic mechanism induced by pore water movement relative to the host rock, is a plausible cause of the observed infrasound-electric-field coupling. The ground displacement and electric-field particle motions suggest that the infrasound waves from the explosive eruptions produce vertical ground motion, and simultaneously induce horizontal groundwater flow, which subsequently generates electric-field changes due to the propagation of the infrasound wave.Plain Language Summary Infrasound, which is an acoustic wave that propagates through the air at frequencies below 20 Hz, produces ground vibrations. Explosive volcanic eruptions can generate a significant infrasound signal with a clear compressional phase and subsequent rarefaction phase. This infrasound signal travels at the speed of sound while producing vertical ground motion. Coincident infrasound and vertical displacement changes are detected at timescales of a few seconds using observation stations with a collocated microphone and broadband seismometer. Here we provide the first evidence that the infrasound signal from such a volcanic eruption also generates an electric current in the near surface. The electric current, which is measured using a voltmeter and electrode, is very similar to the observed infrasound signal and its associated ground motion. Local infrasound-induced groundwater flow is a plausible cause of the observed electric current generation.

    DOI： 10.1029/2021GL096555

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  • Magmatic fluid pathways in the upper crust: insights from dense magnetotelluric observations around the Kuju Volcanoes, Japan

    Aizawa, K; Utsugi, M; Kitamura, K; Koyama, T; Uyeshima, M; Matsushima, N; Takakura, S; Inagaki, H; Saito, H; Fujimitsu, Y

    GEOPHYSICAL JOURNAL INTERNATIONAL   228 ( 2 )   755 - 772   2022.2   （ ISSN:0956-540X eISSN:1365-246X ）

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    Publisher：Geophysical Journal International  

    Magnetotelluric (MT) observations have revealed subvertical electrical conductors that extend from shallow depths into the mid-crust at various geothermal zones, active volcanoes and active faults worldwide. These deeply rooted subvertical conductors have typically been interpreted to represent entire zones of dedicated fluid transport through the crust. We estimate the high-resolution 3-D crustal resistivity structure below the Kuju Volcanoes, Japan, using dense observations from 153 broad-band MT measurement sites and 40 telluric measurement sites. The resistivity structure highlights subvertical conductors that merge into a deep conductor to the north of the volcanoes, with deep low-frequency earthquakes occurring near the southeastern edge of this subvertical conductor at 10-30 km depth. This deep conductor branches into several subvertical conductors at 2-10 km depth, coinciding with a shallow zone where tectonic earthquakes rarely occur. The surface expressions of active geothermal areas and past volcanic eruptions are all located above the edges of the conductors at 2-6 km depth. Widespread conductive layers exist around the volcanoes above 2 km depth, and their distribution approximately corresponds to a low-gravity-anomaly zone. We discuss the nature of these subvertical conductors, the potential causes of their complex structure and their relationship to local magmatic fluid transport. These subvertical conductors, a shallow clay-rich layer, developed fracture systems and high-strength solidified magma may all contribute to magmatic fluid transport to the surface at the Kuju Volcanoes. In this study, we add the possibility that the edges of these subvertical conductors act as important magmatic fluid pathways.

    DOI： 10.1093/gji/ggab368

    Web of Science

    Scopus

  • Infrasound–electric-field coupling associated with the 2018 Shinmoe-dake eruptions, Kirishima volcanic complex, Japan Reviewed International journal

    #Aniya S., @Aizawa K., and @Matsushima T.

    Geophysical Research Letters   GRL63677   2022.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1029/2021GL096555

    Other Link： https://doi.org/10.1029/2021GL096555

  • Seismic velocity structure of Unzen Volcano, Japan, and relationship to the magma ascent route during eruptions in 1990–1995 Reviewed International journal

    #Miyano K., @Aizawa K., @Matsushima T., @Shito A., and @Shimizu H.

    Scientific Reports   11   22407   2021.11

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1038/s41598-021-00481-6

    Other Link： https://doi.org/10.1038/s41598-021-00481-6

  • Magmatic fluid pathways in the upper crust: Insights from dense magnetotelluric observations around the Kuju Volcanoes, Japan Reviewed International journal

    @Aizawa, K., @Ustugi, M., @Kitamura, K., @Koyama, T., @Uyeshima, M., @Matsuhima, N., @Takakura, S., @Inagaki, H., @Saito, H., @Fujimitsu, Y.

    Geophysical Journal International   228   755 - 772   2021.9

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1093/gji/ggab368

    Other Link： https://doi.org/10.1093/gji/ggab368

  • Hydrothermal and magmatic system of a volcanic island inferred from magnetotellurics, seismicity, self-potential, and thermal image: an example of Miyakejima (Japan) Reviewed International journal

    Marceau Gresse, Makoto Uyeshima, Takao Koyama, Hideaki Hase, Koki Aizawa, Yusuke Yamaya, Yuichi Morita, Derek Weller, Tawat Rung-Arunwan, Takayuki Kaneko, Yoichi Sasai, Jacques Zlotnicki, Tsuneo Ishido, Hideki Ueda, Maki Hata

    Journal of Geophysical Research -Solid Earth-   2021.5

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1029/2021JB022034

    Other Link： https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021JB022034

  • Electrical resistivity structure around the Atotsugawa fault, central Japan, revealed by a new 2‐D inversion method combining Wideband‐MT and Network‐MT datasets Reviewed International journal

    Usui Y., Uyeshima M., Ogawa T., Yoshimura R., Oshiman N., Yamaguchi S., Toh H., Murakami H., Aizawa K., Tanbo T., Ogawa Y., Nishitani T., Sakanaka S. Mishina M., Satoh H., Goto T., Kasaya T., Mogi T., Yamaya Y., Shiozaki I., Honkura Y.

    J. Geophys. Res. Solid Earth   126   e2020JB020904   2021.2

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1029/2020JB020904

    Other Link： https://doi.org/10.1029/2020JB020904

  • Electrical conductive fluid-rich zones and their influence on the earthquake initiation, growth, and arrest processes: observations from the 2016 Kumamoto earthquake sequence, Kyushu Island, Japan Reviewed International journal

    @Koki Aizawa, @Shinichi Takakura, @Hisafumi Asaue, @Katsuaki Koike, @Ryokei Yoshimura, @Ken’ichi Yamazaki, @Shintaro Komatsu, @Mitsuru Utsugi, @Hiroyuki Inoue, @Kaori Tsukamoto, @Makoto Uyeshima, @Takao Koyama, @Wataru Kanda, @Tohru Yoshinaga, @Nobuo Matsushima, @Kazunari Uchida, @Yuko Tsukashima, @Takeshi Matsushima, @Hiroshi Ichihara, #Dan Muramatsu, @Yoshiko @Teguri, @Azusa Shito, @Satoshi Matsumoto & @Hiroshi Shimizu

    Earth Planets Space   1   12   2021.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1186/s40623-020-01340-w

    Other Link： https://link.springer.com/article/10.1186/s40623-020-01340-w

  • Joint seismological–magnetotelluric investigation of shallow and implosive non-DC and DC earthquakes beneath the gravitationally unstable Heisei-Shinzan Lava Dome, Unzen Volcano, Japan Reviewed International journal

    #Tasuku M Hashimoto, Koki Aizawa, #Yuto Hayashida, #Yuhei Yuasa, Takeshi Matsushima, #Yuto Yamamoto, Kaori Tsukamoto, #Kanta Miyano, Satoshi Matsumoto, Hiroshi Shimizu

    Journal of Volcanology and Geothermal Research   2020.9

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1016/j.jvolgeores.2020.107066

  • Three-dimensional electrical resistivity structure of the Kuju volcanic group, Central Kyushu, Japan revealed by magnetotelluric survey data Reviewed International journal

    Sabry Abdallah, Mitsuru Utsugi, Koki Aizawa, Makoto Uyeshima, Wataru Kanda, Takao Koyama, Taro Shiotani

    Journal of Volcanology and Geothermal Research   400   106898   2020.5

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1016/j.jvolgeores.2020.106898

    Other Link： https://www.sciencedirect.com/science/article/pii/S0377027319305414

  • Numerical simulations to explain the coseismic electromagnetic signals: A case study for a M5.4 aftershock of the 2016 Kumamoto earthquake Invited Reviewed International journal

    @Yao-Chong Sun, @Makoto Uyeshima, @Hengxin Ren, @Qinghua Huang, @Koki Aizawa, #Kaori Tsukamoto, @Wataru Kanda, @Kaori Seki, @Takahiro Kishita, @Takao Ohminato, @Atsushi Watanabe, @Jiangjun Ran, @Xiaofei Chen

    Earth Planets and Space   71 ( 143 )   2019.12

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1186/s40623-019-1122-7

    Other Link： https://link.springer.com/article/10.1186%2Fs40623-019-1122-7

  • Magnetotelluric transect of Unzen graben, Japan: Conductors associated with normal faults Reviewed International journal

    #Triahadini A. @Aizawa K., @Teguri Y., @Koyama T., #Tsukamoto K., #Muramatsu D., @Chiba K., and #Uyeshima M.

    Earth Planets Space   71 ( 28 )   2019.2

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： https://doi.org/10.1186/s40623-019-1004-z

    Other Link： https://earth-planets-space.springeropen.com/articles/10.1186/s40623-019-1004-z

  • Estimation of Vent Radii From Video Recordings and Infrasound Data Analysis: Implications for Vulcanian Eruptions From Sakurajima Volcano, Japan Invited Reviewed International journal

    #Dan Muramatsu, @Koki Aizawa, @Akihiko Yokoo, @Masato Iguchi, @Takeshi Tameguri

    Geophysical Research Letters   45 ( 23 )   12829 - 12836   2018.12

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1029/2018GL079898

    Other Link： https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL079898

  • Three-Dimensional Resistivity Structure of Iwo-Yama Volcano, Kirishima Volcanic Complex, Japan: Relationship to Shallow Seismicity, Surface Uplift, and a Small Phreatic Eruption Reviewed International journal

    #K Tsukamoto, @K Aizawa, @K Chiba, @W Kanda, @M Uyeshima, @T Koyama, @M Utsugi, @K Seki, @T Kishita

    Geophysical Research Letters   45 ( 23 )   12821 - 12828   2018.12

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    Language：English   Publishing type：Research paper (scientific journal)  

    Abstract Iwo-yama volcano, part of the Kirishima Volcanic Complex, has recently shown signs of unrest.
    We conducted a hypocenter relocation of shallow earthquakes and broadband magnetotelluric
    measurements around Iwo-yama. Three-dimensional inversion of magnetotelluric data revealed an
    electrically conductive layer that is interpreted as a hydrothermally altered clay-dominated unit. Shallow
    earthquakes occur beneath this layer, suggesting that it controls the location of seismicity. The base of the
    layer corresponds to the depth of a pressure source identified by a leveling survey. These observations
    suggest that the supply of high-temperature fluids has increased over time beneath Iwo-yama, causing an
    increase in pore pressure beneath the clay-rich layer and resulting in tectonic earthquakes and ground
    inflation. Increased upwelling of fluids through a fracture in the clay-rich layer may have caused a vigorous
    liquid-gas phase transition near the surface, which in turn might have led to the small phreatic eruption on 19
    April 2018.

    Plain Language Summary
    Phreatic eruptions result from the sudden release of pressurized fluid
    into the air. Imaging the pressurized region is important to predict future phreatic eruptions. We studied
    Iwo-yama volcano, Kirishima, Japan, where recent volcanic unrest has led to a small phreatic eruption. By
    imaging the subsurface electrical resistivity structure using the magnetotelluric technique, we have identified
    a low-permeability clay-rich layer at depths of 200–700 m below the surface. Earthquake hypocenters and
    one of the sources of surface uplift are located beneath this clay layer, so we conclude that the layer caps
    deep hydrothermal fluids and allows the buildup of pressure beneath it. If this clay-rich layer suddenly breaks,
    or if the fluid supply through the deeper conductor suddenly increases, a larger phreatic eruption could occur
    in the future. Imaging and monitoring of such clay-rich layers is important to our understanding of shallow
    activity beneath volcanoes.

    DOI： 10.1029/2018GL080202

    Other Link： https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL080202

  • Seismicity controlled by resistivity structure: the 2016 Kumamoto earthquakes, Kyushu Island, Japan Invited Reviewed International journal

    Aizawa Koki, H. Asaue, K. Koike, S. Takakura, M. Utsugi, H. Inoue, R. Yoshimura, K. Yamazaki, S. Komatsu, M. Uyeshima, T. Koyama, W. Kanda, T. Shiotani, N. Matsushima, M. Hata, T. Yoshinaga, K. Uchida, Y. Tsukashima, et al.

    Earth Planets and Space   69 ( 4 )   2017.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1186/s40623-016-0590-2

    Other Link： https://earth-planets-space.springeropen.com/articles/10.1186/s40623-016-0590-2

  • Three-dimensional resistivity structure of Asama Volcano revealed by data-space magnetotelluric inversion using unstructured tetrahedral elements Invited Reviewed International journal

    Usui Y., Ogawa Y., Aizawa Koki, Kanda W., Hashimoto T., Koyama T., Yamaya Y., Kagiyama T.

    Geophysical Journal International   208 ( 3 )   1359 - 1372   2016.12

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1093/gji/ggw459

    Other Link： https://academic.oup.com/gji/article/208/3/1359/2666335/Three-dimensional-resistivity-structure-of-Asama

  • 火山電磁気観測の進展 Invited Reviewed International journal

    相澤　広記

    火山   61 ( 2 )   345 - 365   2016.6

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    Language：Japanese   Publishing type：Research paper (scientific journal)  

    Other Link： https://www.jstage.jst.go.jp/article/kazan/61/2/61_345/_pdf

  • Physical properties of volcanic lightning: constraints from magnetotelluric and video observations at Sakurajima volcano, Japan Reviewed International journal

    Aizawa Koki, C. Cimarelli, M. A. Alatorre-Ibargüengoitia, A. Yokoo, D. B. Dingwell, M. Iguchi

    Earth and Planetary Science Letters   444   45 - 55   2016.6

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.epsl.2016.03.024

    Other Link： http://www.sciencedirect.com/science/article/pii/S0012821X1630111X

  • Multiparametric observation of volcanic lightning: Sakurajima Volcano, Japan Reviewed International journal

    C. Cimarelli, M. A. Alatorre-Ibargüengoitia, Koki Aizawa, A. Yokoo, A. Díaz-Marina, M. Iguchi, D. B. Dingwell

    Geophysical Research Letters   43   4221 - 4228   2016.4

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1002/2015GL067445

    Other Link： http://onlinelibrary.wiley.com/doi/10.1002/2015GL067445/abstract;jsessionid=3FBD45B54BFAEA7899CCC871C47CFFBE.f02t03

  • Gas pathways and remotely triggered earthquakes beneath Mt. Fuji, Japan Reviewed International journal

    Aizawa Koki, H. Sumino, M. Uyeshima, Y. Yamaya, H. Hase, H. A. Takahashi, M. Takahashi, K. Kazahaya, Masao OHNO, T. Rung-Arunwan, Y. Ogawa

    Geology   44   127 - 130   2016.2

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1130/G37313.1

    Other Link： http://geology.geoscienceworld.org/cgi/content/full/44/2/127?ijkey=LX6PXeyXqeM7o&keytype=ref&siteid=gsgeology

  • Three-dimensional resistivity structure and magma plumbing system of the Kirishima Volcanoes as inferred from broadband magnetotelluric data Reviewed International journal

    Aizawa Koki, T. Koyama, H. Hase, M. Uyeshima, W. Kanda, M. Utsusgi, R. Yoshimura, Y. Yamaya, T. Hashimoto, K. Yamazaki, S. Komatsu, A. Watanabe, K. Miyakawa, Y. Ogawa

    J. Geophys. Res. Solid Earth   119 ( 1 )   198 - 215   2014.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1002/2013JB010682

    Other Link： http://onlinelibrary.wiley.com/doi/10.1002/2013JB010682/abstract

  • Magnetotelluric and temperature monitoring after the 2011 sub-Plinian eruptions of Shinmoe-dake volcano Reviewed International journal

    Aizawa Koki, T. Koyama, M. Uyeshima, H. Hase, T. Hashimoto, W. Kanda, R. Yoshimura, M. Utsugi, Y. Ogawa, K. Yamazaki

    Earth Planets Space   65 ( 6 )   539 - 550   2013.7

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.5047/eps.2013.05.008

    Other Link： http://link.springer.com/article/10.5047%2Feps.2013.05.008#page-1

  • Temporal changes in electrical resistivity at Sakurajima volcano from continuous magnetotelluric observations Reviewed International journal

    Aizawa Koki, Kanda W., Ogawa Y., Iguchi M., Yokoo A., Yakiwara H., Sugano T.

    Journal of Volcanology and Geothermal Research   199 ( 1-2 )   2011.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    Continuous magnetotelluric (MT) measurements were conducted from May 2008 to July 2009 at Sakurajima,
    one of the most active volcanoes in Japan. Two observation sites were established at locations 3.3 km east and
    3 km west–northwest of the summit crater. At both observation sites, the high-quality component of the
    impedance tensor (Zyx) showed variations in apparent resistivity of approximately ±20% and phase change
    of ±2°, which continued for 20–180 days in the frequency range between 320 and 4 Hz. The start of the
    period of changes in apparent resistivity approximately coincided with the start of uplift in the direction of the
    summit crater, as observed by a tiltmeter, which is one of the most reliable pieces of equipment with which to
    detect magma intrusion beneath a volcano. A 2D inversion of MT impedance suggests that the resistivity
    change occurred at a depth around sea level. One of the possible implications of the present finding is that the
    degassed volatiles migrated not only vertically through the conduit but also laterally through a fracture
    network, mixing with shallow groundwater beneath sea level and thereby causing the observed resistivity
    change.

    DOI： 10.1016/j.jvolgeores.2010.11.003

    Other Link： http://www.sciencedirect.com/science/article/pii/S0377027310003446

  • Magnetotelluric pulses generated by volcanic lightning at Sakurajima volcano, Japan Reviewed International journal

    Aizawa Koki, Yokoo A., Kanda W., Ogawa Y., Iguchi M.

    Geophysical Research Letters   37   2010.9

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1029/2010GL044208

    Other Link： http://onlinelibrary.wiley.com/doi/10.1029/2010GL044208/abstract

  • Magnetotelluric transect across the Niigata-Kobe Tectonic Zone, central Japan: A clear correlation between strain accumulation and resistivity structure Reviewed International journal

    Yoshimura, R., Oshiman, N., Uyeshima, M., Toh, H., Uto, T., Kanezaki, H., Mochido, Y., Aizawa Koki, Ogawa, Y., Nishitani, T., Sakanaka, S., Mishina, M., Satoh, H., Goto, T, Kasaya, T., Yamaguchi, S., Murakami, H., Mogi, T., Yamaya, Y.

    Geophysical Research Letters   36   2009.10

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1029/2009GL040016

  • Structural controls on the 1998 volcanic unrest at Iwate volcano: Relationship between a shallow, electrically resistive body and the possible ascent route of magmatic fluid Reviewed International journal

    Aizawa Koki, Ogawa Y., Mishina M., Takahashi K., Nagaoka S., Takagi N., Sakanaka S., Miura T.

    Journal of Volcanology and Geothermal Research   187 ( 1-2 )   131 - 139   2009.10

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.jvolgeores.2009.08.009

    Other Link： http://www.sciencedirect.com/science/article/pii/S037702730900328X

  • Modification of the Network-MT method and its first application in imaging the deep conductivity structure beneath the Kii Peninsula, southwestern Japan Reviewed International journal

    Yamaguchi, S., Uyeshima, M, Murakami H., Sutoh S., Tanigawa D., Ogawa T., Oshiman N., Yoshimura R., Aizawa Koki, Shiozaki I., Kasaya T.

    Earth, Planets and Space   61 ( 8 )   957 - 971   2009.10

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    Language：English   Publishing type：Research paper (scientific journal)  

  • Groundwater flow and hydrothermal systems within volcanic edifices: Delineation by electric self-potential and magnetotellurics Reviewed International journal

    Aizawa Koki, Ogawa Y., Ishido T.

    Journal of Geophysical Research   114   2009.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1029/2008JB005910

    Other Link： http://onlinelibrary.wiley.com/doi/10.1029/2008JB005910/abstract;jsessionid=F49358E54DB652E1F1865C194AF3F2B9.f02t02

  • Classification of self-potential anomalies on volcanoes and possible interpretations for their subsurface structure Reviewed International journal

    Aizawa Koki

    Journal of Volcanology and Geothermal Research   175 ( 3 )   253 - 268   2008.8

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.jvolgeores.2008.03.011

    Other Link： http://www.sciencedirect.com/science/article/pii/S0377027308001042

  • Shallow resistivity structure of Asama Volcano and its implications for magma ascent process in the 2004 eruption Reviewed International journal

    Aizawa Koki, Ogawa Y., Hashimoto T., Koyama T., Kanda W., Yamaya Y., Mishina M., Kagiyama T.

    Journal of Volcanology and Geothermal Research   173 ( 3-4 )   165 - 177   2008.6

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.jvolgeores.2008.01.016

    Other Link： http://www.sciencedirect.com/science/article/pii/S0377027308000462

  • Zeta potential estimation of volcanic rocks on 11 island arc-type volcanoes in Japan: Implication for the generation of local self-potential anomalies Reviewed International journal

    Aizawa Koki, Uyeshima M., Nogami K.

    Journal of Geophysical Research   113 ( B2 )   2008.2

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1029/2007JB005058

    Other Link： http://onlinelibrary.wiley.com/doi/10.1029/2007JB005058/abstract

  • Hydrothermal system beneath Mt. Fuji volcano inferred from magnetotellurics and electric self-potential Reviewed International journal

    Aizawa Koki, Yoshimura, R., Oshiman, N., Yamazaki, K., Uto, T., Ogawa, Y., Tank, S. B., Kanda, W., Sakanaka, S., Furukawa, Y., Hashimoto, T., Uyeshima, M., Ogawa, T., Shiozaki, I., Hurst, A. W.

    Earth and Planetary Science Letters   235 ( 1-2 )   343 - 355   2005.6

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.epsl.2005.03.023

    Other Link： http://www.sciencedirect.com/science/article/pii/S0012821X05002694

  • Splitting of the Philippine Sea Plate and a magma chamber beneath Mt. Fuji Reviewed International journal

    Aizawa Koki, Yoshimura R., Oshiman N.

    Geophysical Research Letters   31 ( 9 )   2004.5

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1029/2004GL019477

    Other Link： http://onlinelibrary.wiley.com/doi/10.1029/2004GL019477/abstract

  • A Large Self-potential Anomaly and its Changes on the Quiet Mt. Fuji, Japan Reviewed International journal

    Aizawa Koki

    Geophysical Research Letters   ( 31 )   2004.3

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1029/2004GL019462

    Other Link： http://onlinelibrary.wiley.com/doi/10.1029/2004GL019462/abstract

  • Special issue "magma migration and eruptions in a volcanic group: case studies for the 2017-2018 activity of the Kirishima Volcano Group and other global examples"

    Kaneko, T; Ichihara, M; Konstantinou, KI; Costa, A; Miyabuchi, Y; Aizawa, K

    EARTH PLANETS AND SPACE   77 ( 1 )   2025.7   （ ISSN:13438832 eISSN:1880-5981 ）

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    Publisher：Earth Planets and Space  

    (Figure presented.)

    DOI： 10.1186/s40623-025-02209-6

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    researchmap

  • Three‐Dimensional Electrical Resistivity Structure Beneath a Strain Concentration Area in the Back‐Arc Side of the Northeastern Japan Arc

    Yoshiya Usui, Makoto Uyeshima, Hideaki Hase, Hiroshi Ichihara, Koki Aizawa, Takao Koyama, Shin'ya Sakanaka, Tsutomu Ogawa, Yusuke Yamaya, Tadashi Nishitani, Koichi Asamori, Yasuo Ogawa, Ryokei Yoshimura, Shinichi Takakura, Masaaki Mishina, Yuichi Morita

    Journal of Geophysical Research: Solid Earth   129 ( 5 )   2024.5   （ ISSN:2169-9313 eISSN:2169-9356 ）

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    Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

    Abstract

    Intraplate earthquakes occur more frequently in the Japanese islands than in other regions. Large intraplate earthquakes in the island arc preferentially occur in strain concentration zones detected by geological and geodetic studies. Crustal heterogeneity plays a crucial role in generating large intraplate earthquakes and strain concentrations. Thus, we elucidated the crustal heterogeneities beneath a strain concentration area on the back‐arc side of the northeastern Japan Arc based on electrical resistivity, which is sensitive to weak zones in the crust. By deploying wideband magnetotelluric surveys, we revealed the three‐dimensional electrical resistivity structure in the crust, suggesting the coexistence of two different types of strain‐concentration mechanisms in the strain‐concentration area. The shallow conductive layers and lower‐crustal conductors appear to act as low‐elastic‐modulus and low‐viscosity areas, respectively, and are responsible for the strain concentration. We found shallow and lower‐crustal conductors in the strain concentration zone revealed by geological studies. Those conductive areas are considered to act as mechanically weak zones and cause stress loading on the brittle pars of pre‐existing faults, resulting in large intraplate earthquakes. The resultant earthquakes presumably contribute to strain accumulation on a geological timescale. In addition, a spatial correlation between the epicenters of large intraplate earthquakes and edges of lower‐crustal conductors implies the contribution of the fluids in the lower crust to the generation of large earthquakes. We also identified vertical conductors ranging from the lower crust to Quaternary volcanoes, which may indicate trans‐crustal magmatic systems under these volcanoes.

    DOI： 10.1029/2023JB028522

    Web of Science

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  • Steam effusion activity and resistivity structure change in West Crater of Iwo- Yama volcano, Kirishima Volcanic Complex, Japan

    Tanabe Haruto, Matsushima Takeshi, Aizawa Koki, Muramatsu Dan

    Proceedings of the Conductivity Anomaly Workshop   2024 ( 0 )   10 - 17   2024   （ eISSN:27593231 ）

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    Language：Japanese   Publisher：Conductivity Anomaly Research Group  

    DOI： 10.60410/pcaw.2024.0_10

    CiNii Research

  • 1997年鹿児島県北西部地震震源域の3次元比抵抗構造解析（序報）

    松永 佳大, 相澤 広記, 小川 大輝, 宇津木 充, 吉村 令慧, 山崎 健一, 内田 和也

    Proceedings of the Conductivity Anomaly Workshop   2024 ( 0 )   52 - 58   2024   （ eISSN:27593231 ）

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    Language：Japanese   Publisher：Conductivity Anomaly Research Group  

    DOI： 10.60410/pcaw.2024.0_52

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  • Reanalysis of the time-series data obtained by the Network-MT survey in the Kii Peninsula, southwestern Japan for constructing the 3-D electrical resistivity structure

    Watanabe Akira, Uyeshima Makoto, Yamaguchi Satoru, Usui Yoshiya, Murakami Hideki, Ogawa Tsutomu, Oshiman Naoto, Yoshimura Ryokei, Aizawa Koki, Shiozaki Ichiro, Kasaya Takafumi

    Proceedings of the Conductivity Anomaly Workshop   2024 ( 0 )   67 - 74   2024   （ eISSN:27593231 ）

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    Language：Japanese   Publisher：Conductivity Anomaly Research Group  

    DOI： 10.60410/pcaw.2024.0_67

    CiNii Research

  • Analysis of Tilt and Seismic Data During the 2018 Phreatic Eruption of Kirishima Iwoyama

    Katsuyama Asumi, Matsushima Takeshi, Matsumoto Satoshi, Aizawa Koki

    PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN   2024 ( 0 )   195 - 195   2024   （ ISSN:24335320 eISSN:21897190 ）

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    Language：Japanese   Publisher：The Volcanological Society of Japan  

    DOI： 10.18940/vsj.2024.0_195

    CiNii Research

  • Magma pluming system of Kirishima Volcanic Complex

    Aizawa Koki, Nagaoka Yutaka, Kurihara Ryo

    PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN   2024 ( 0 )   189 - 189   2024   （ ISSN:24335320 eISSN:21897190 ）

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    Language：Japanese   Publisher：The Volcanological Society of Japan  

    DOI： 10.18940/vsj.2024.0_189

    CiNii Research

  • Volcanic fluids pathways inferred from electrical methods

    Aizawa Koki

    PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN   2024 ( 0 )   98 - 98   2024   （ ISSN:24335320 eISSN:21897190 ）

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    Language：Japanese   Publisher：The Volcanological Society of Japan  

    DOI： 10.18940/vsj.2024.0_98

    CiNii Research

  • Investigation of High-Temperature Spring Gushing Mechanisms Based on Three-Dimensional Deep Electrical Resistivity Structure in the Kii Peninsula, Southwestern Japan

    Watanabe Akira, Uyeshima Makoto, Yamaguchi Satoru, Usui Yoshiya, Murakami Hideki, Ogawa Tsutomu, Oshiman Naoto, Yoshimura Ryokei, Aizawa Koki, Shiozaki Ichiro, Kasaya Takafumi

    PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN   2024 ( 0 )   168 - 168   2024   （ ISSN:24335320 eISSN:21897190 ）

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    Language：Japanese   Publisher：The Volcanological Society of Japan  

    DOI： 10.18940/vsj.2024.0_168

    CiNii Research

  • Vulcanian eruption processes inferred from volcanic glow analysis at Showa crater, Sakurajima volcano

    Muramatsu Dan, Aizawa Koki, Yokoo Akihiko, Tameguri Takeshi, Iguchi Masato

    PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN   2023   128 - 128   2023   （ ISSN:2433-5320 eISSN:2189-7190 ）

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    Language：Japanese   Publisher：The Volcanological Society of Japan  

    DOI： 10.18940/vsj.2023.0_128

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  • Temporal and spatial variations of helium isotope ratios at Kuju volcano

    Yasuda Yuki, Sumino Hirochika, Obase Tomoya, Toyama Kotaro, Numata Shogo, Yaguchi Muga, Aizawa Koki, Ishibashi Jun-ichiro

    PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN   2023 ( 0 )   210 - 210   2023   （ ISSN:24335320 eISSN:21897190 ）

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    Language：Japanese   Publisher：The Volcanological Society of Japan  

    DOI： 10.18940/vsj.2023.0_210

    CiNii Research

  • Multi-parametric observation of intermittent hydrothermal discharge phenomenon observed at the west crater of Iwo-yama volcano, Kirishima Volcanic Complex, Japan

    Tanabe H., Matsushima T., Aizawa K., Muramatsu D., Aniya S., Yoshinaga K., Watanabe T.

    PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN   2022   79 - 79   2022   （ ISSN:2433-5320 eISSN:2189-7190 ）

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    Language：Japanese   Publisher：The Volcanological Society of Japan  

    DOI： 10.18940/vsj.2022.0_79

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  • Role of fluids for earthquakes and volcanoes growth: Insight from electrical resistivity and fluids geochemistry

    Aizawa Koki

    Abstracts of Annual Meeting of the Geochemical Society of Japan   69 ( 0 )   112   2022

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    Language：Japanese   Publisher：GEOCHEMICAL SOCIETY OF JAPAN  

    <p></p>

    DOI： 10.14862/geochemproc.69.0_112

    CiNii Research

  • Shallow Resistivity Structure of Sakurajima Volcano Revealed by Audio-frequency Magnetotellurics Reviewed

    Kanda W., Yamazaki T., Ogawa Y., Hashimoto T., Sakanaka S., Aizawa Koki, Takakura S., Koyama T., Yamada K., Kobayashi T., Komori S.

    Bulletin of Volcanological Society of Japan   58 ( 1 )   251 - 267   2013.1

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    Language：English   Publishing type：Research paper (scientific journal)  

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Presentations

  • ３次元比抵抗構造から推定される九重火山群の熱供給

    相澤広記・内田和也・塚島祐子・北村圭吾・藤光康宏（九州大学）・宇津木充・塩谷太郎・井上寛之（京都大学）・神田径（東京工業大学）・小山崇夫・上嶋誠（東京大学地震研究所）・稲垣陽大・齋藤博樹・藤井勇樹（西日本技術開発）

    地熱学会  2019.11 

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    Event date： 2019.11

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：熊本   Country：Japan  

  • ２０１６年熊本地震の余震活動と比抵抗構造の関係を詳細にみることで考えられること Invited

    相澤広記

    地球電磁気・地球惑星圏学会  2019.10 

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    Event date： 2019.10

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：熊本   Country：Japan  

  • 2016年熊本地震震源域の比抵抗構造と震源分布の関係性

    相澤 広記、麻植 久史、小池 克明、高倉 伸一、吉永 徹、上嶋 誠、小山 崇夫、吉村 令慧、山崎 健一、小松 信太郎、山下 裕亮、市原 寛、宇津木 充、塚本 果織、村松 弾、手操 佳子、内田 和也、長谷 英彰、志藤 あずさ、松本 聡、松島 健、清水 洋

    日本地球惑星科学連合 2019年大会  2019.5 

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    Event date： 2019.5

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：千葉幕張   Country：Japan  

  • 霧島火山での広帯域MT観測

    相澤広記・#塚本果織・#A. Triahadini・#村松弾・#林田祐人・#湯浅雄平・#A. Luthfian・@手操佳子・#武石貢佑・@神田径・@木下貴裕・@関香織・@宇津木充・@小山崇夫・@上嶋誠

    日本火山学会2018年度秋季大会  2018.9 

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    Event date： 2018.9

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：秋田   Country：Japan  

  • 桜島・霧島・富士山・九重山での広帯域MT連続観測により推定される比抵抗構造時間変化

    相澤　広記・上嶋 誠・小山　崇夫・長谷 英彰・山谷 祐介・宇津木 充・神田　径・橋本 武志・塚本 果織・村松 弾・吉村　令慧・山崎　健一

    地球惑星科学連合大会  2018.5 

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    Event date： 2018.5

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：千葉幕張   Country：Japan  

  • Three dimensional resistivity structure around the rupture zone of the 2016 Kumamoto earthquake

    2016年熊本地震比抵抗構造研究グループ・相澤　広記

    地球電磁気･地球惑星圏学会  2017.10 

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    Event date： 2017.10

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：京都宇治   Country：Japan  

  • 火山の比抵抗構造研究の進展と課題 Invited

    相澤広記

    火山学会  2017.9 

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    Event date： 2017.9

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：熊本   Country：Japan  

  • 2016 年熊本地震周辺域の比抵抗構造

    2016年熊本地震比抵抗構造研究グループ

    地球電磁気･地球惑星圏学会  2016.10 

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    Event date： 2016.10

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：福岡   Country：Japan  

  • 別府―万年山断層帯の比抵抗構造

    相澤 広記、小山 崇夫、志藤 あずさ、若林 翌馬、宮崎 真大、内田 和也、塚島 祐子、塚本 果織、高島 奏、近藤 健太郎、河本 洋輝、藤田 詩織、山本 有人、緒方 美季、上嶋 誠

    地球惑星科学連合大会  2016.5 

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    Event date： 2016.5

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：千葉幕張   Country：Japan  

  • 2016年熊本―九州中部地震活動領域の電気比抵抗構造

    相澤 広記、 麻植 久史、小池 克明、高倉 伸一、松島 喜雄、畑 真紀、吉永 徹、橋本 武志、宇津木 充、井上 寛之、塩谷 太郎、上嶋 誠、小山 崇夫、神田 径、内田 和也、塚島 祐子、志藤 あずさ、藤田 詩織、若林 翌馬、塚本 果織、松島 健、吉村 令慧、山崎 健一、小松 信太郎、田村 慎、2016年熊本地震 合同地震観測グループ

    地球惑星科学連合大会  2016.5 

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    Event date： 2016.5

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：千葉幕張   Country：Japan  

  • 比抵抗構造と地下水同位体比測定から推測する2011年富士山Mw5.9地震の発生メカニズム

    相澤　広記, 角野 浩史, 上嶋 誠, 山谷 祐介, 長谷 英彰, 大野 正夫, 高橋 正明, 風早 康平, Tawat Rung-Arunwan, 小川 康雄

    地球惑星科学連合大会 

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    Event date： 2015.5

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：千葉幕張   Country：Japan  

  • 地電位差計を用いた大分県中南部の広帯域MT観測

    相澤　広記, 上嶋 誠, 高村 直也, 宇津木 充, 井上 寛之, 塩谷 太郎, 内田　和也, 塚島 祐子, 若林 翌馬, 藤田 詩織, 松島　健, 小山 崇夫, 神田 径, 吉村 令慧, 山崎 健一, 小松 信太郎, 志藤 あずさ

    地球惑星科学連合大会  2015.5 

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    Event date： 2015.5

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：千葉幕張   Country：Japan  

    Other Link： https://confit.atlas.jp/guide/event/jpgu2015/subject/02735_PG/date?cryptoId=

  • MT連続観測による霧島硫黄山北の比抵抗変化（口頭）

    相澤 広記, 小山崇夫, 長谷英彰, 上嶋誠, 橋本武志, 宇津木充, 吉村令慧, 神田径, 小川康雄

    日本地球惑星科学連合2012年大会  2012.5 

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    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：千葉幕張   Country：Japan  

  • 広帯域MT探査による富士山の比抵抗構造 (序報)

    相澤 広記, 山谷祐介, 上嶋誠, 長谷英彰

    日本地球惑星科学連合2012年大会  2012.5 

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    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：千葉幕張   Country：Japan  

  • 広帯域MT探査による霧島火山群の3次元比抵抗構造（口頭）

    相澤 広記, 小山崇夫, 上嶋誠, 長谷英彰, 山谷祐介, 橋本武志, 神田径, 小川康雄, 宇津木充, 吉村令慧, 山崎健一

    日本火山学会秋季大会  2012.10 

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    Language：Japanese  

    Venue：御代田   Country：Japan  

  • MT連続観測による桜島火山の3次元比抵抗構造とその時間変化(2010年2月~6月)

    相澤 広記, 小山崇夫, 長谷英彰, 上嶋誠

    日本火山学会秋季大会  2012.10 

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    Language：Japanese   Presentation type：Oral presentation (general)  

    Country：Japan  

  • 広帯域MT探査による富士山の比抵抗構造：2次元解析と3次元解析の違いと問題点

    相澤 広記, 上嶋誠, 山谷祐介, 長谷英彰

    日本火山学会秋季大会  2012.10 

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    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：御代田   Country：Japan  

  • 広帯域MT連続観測による桜島火山の3次元比抵抗構造とその時間変化（ポスター）

    相澤 広記, 小山崇夫, 長谷英彰, 上嶋誠

    地球電磁気・地球惑星圏学会  2012.10 

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    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：札幌   Country：Japan  

  • 広帯域MT探査による霧島火山群の3次元比抵抗構造

    相澤　広記, 小山 崇夫, 長谷 英彰, 上嶋 誠, 神田 径, 宇津木 充, 吉村 令慧, 山谷 祐介, 橋本 武志, 山崎 健一, 小松 信太郎, 渡邉 篤志, 小川 康雄

    地球惑星科学連合大会  2013.5 

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    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：幕張、千葉   Country：Japan  

  • 浅間山山頂域電磁気構造探査序報

    小山 崇夫, 相澤　広記, 辻浩, 神田 径, 長谷 英彰, 山谷 祐介, 渡邉 篤志, 橋本 武志, 田中 良, 高倉 伸一, 小川 康雄, 上嶋 誠, 長竹 宏之, 吉村 令慧, 武尾 実

    地球惑星科学連合大会  2013.5 

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    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：幕張、千葉   Country：Japan  

  • 桜島爆発1 秒前の火映の明るさ変動

    相澤広記, 横尾亮彦, 為栗健, 井口正人

    日本地球惑星科学連合大会  2013.5 

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    Language：Japanese  

    Venue：幕張、千葉   Country：Japan  

  • Three dimensional resistivity structure of Kirishima volcanoes inferred from magnetotelluric data International conference

    Koki Aizawa, et al.

    IAVCEI 2013 Scientific Assembly  2013.7 

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    Language：English   Presentation type：Oral presentation (general)  

    Venue：Kagoshima   Country：Japan  

  • Magnetotelluric monitoring at Sakurajima volcano, Japan International conference

    Koki Aizawa, Takao Koyama, Hideaki Hase, Makoto Uyeshima

    IAVCEI 2013 Scientific Assembly  2013.7 

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    Language：English   Presentation type：Oral presentation (general)  

    Country：Japan  

  • MT探査装置を用いた桜島火山雷観測

    相澤　広記

    Conductivity Anomaly研究会  2014.1 

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    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：東京   Country：Japan  

  • 電位差観測をメインにした九州内陸部でのMT探査計画

    相澤　広記, 上嶋 誠, 高村 直也

    Conductivity Anomaly研究会  2014.1 

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    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：東京   Country：Japan  

  • 地磁気－地電流(MT) 連続観測と可視映像連続観測による桜島火山雷の性質

    相澤　広記, 横尾　亮彦

    JPGU  2014.4 

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    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：横浜   Country：Japan  

  • 地下水同位体比測定と比抵抗構造から推測する2011年富士山Mw5.9地震の発生メカニズム

    相澤　広記, ・角野浩史・上嶋誠・山谷祐介・長谷英彰・大野正夫・高橋正明・風早康平・TaWaT Rung-Arunwan・小川康雄

    日本火山学会  2014.11 

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    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：福岡   Country：Japan  

  • Resistivity structure around the 2011 earthquakes bellow Mt. Fuji volcano, Japan

    相澤　広記, Makoto Uyeshima; Yusuke Yamaya; Hideaki Hase; Yasuo Ogawa

    sgepss  2014.11 

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    Language：Japanese   Presentation type：Oral presentation (general)  

    Country：Japan  

  • 高サンプリング磁場観測と高速度撮影から推定する桜島火山雷の性質

    相澤　広記, C. Cimarelli, M. A. Alatorre-Ibargüengoitia, 横尾亮彦, B. Scheu, S. Mueller, 井口正人

    日本火山学会秋季大会  2015.9 

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    Language：Japanese   Presentation type：Oral presentation (general)  

    Country：Japan  

  • 別府―万年山断層帯の比抵抗構造（序報）

    相澤　広記, 小山　崇夫, 志藤　あずさ, 若林　翌馬, 宮崎　真大, 内田　和也, 塚島　祐子, 塚本　果織, 高島　奏, 近藤　健太郎, 河本　洋輝, 藤田　詩織, 緒方　美季, 山本　有人, 上嶋　誠

    Conductivity Anomaly研究会  2016.1 

    　More details

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：東京大学地震研究所   Country：Japan  

  • 比抵抗構造と地下水同位体比測定から推測する2011年富士山Mw5.9地震の発生メカニズム

    相澤　広記, 角野 浩史, 上嶋 誠, 山谷 祐介, 長谷 英彰, 大野 正夫, 高橋 正明, 風早 康平, Tawat Rung-Arunwan, 小川 康雄

    Conductivity Anomaly研究会  2016.1 

    　More details

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：東京大学地震研究所   Country：Japan  

  • Shallow Low-frequency Tremor in the Hyuga-nada region, western Nankai Trough subduction zone, observed by ocean bottom seismographic experiment

    Yamashita Y., H. Yakiwara, H. Shimizu, K. Uchida, M. Kamizono, M. Nakamoto, M. Fukui, S. Fujita, K. Aizawa, H. Miyamachi, S. Hirano, K. Umakoshi, T. Yamada, H. Kanehara, T. Aoshima

    AGU Fall Meeting  2013.12 

    　More details

    Language：English  

    Venue：San Francisco, CA, USA   Country：Japan  

  • 広帯域MT探査による九重連山周辺の比抵抗構造推定

    塩谷　太郎, 宇津木 充, 相澤　広記, 上嶋 誠, 小山 崇夫, 神田 径

    地球惑星科学連合大会  2015.5 

    　More details

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：千葉幕張   Country：Japan  

  • 雲仙火山の最近の火山活動について

    松島 健, 馬越 孝道, 清水 洋, 松本 聡, 相澤　広記, 神薗　めぐみ

    地球惑星科学連合大会  2015.5 

    　More details

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：千葉幕張   Country：Japan  

▼display all

MISC

  • 電磁気的観測で地下構造を探る―マグマ性ガスの上昇と電気比抵抗構造 Reviewed

    相澤広記

    岩波科学   2022.7

    　More details

    Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

    Other Link： https://www.iwanami.co.jp/kagaku/

  • 電磁気観測で探る火山浅部の浸透率構造と地下水流動, 火山, 55巻6号, 251-259.

    相澤広記

    2010.10

    　More details

    Language：Japanese  

  • 火山爆発に伴うインフラサウンドの研究と南極研究への応用に関す る展望 (総特集 雪氷圏地震学 (下) 極域表層環境の新指標), 月刊地球＝Chikyu monthly：カラー版, 海洋出版, 40(10), pp558-564, 2018. （査読なし）

    #村松弾, @松島健, @相澤広記

    月刊地球＝Chikyu monthly   2018.10

    　More details

    Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

  • MT連続観測による桜島地下3次元比抵抗構造とその時間変化

    相澤　広記, 小山　崇夫, 長谷　英彰, 上嶋　誠

    桜島火山における多項目観測に基づく火山噴火準備過程解明のための研究（課題番号1809) 報告書   2015.2

    　More details

    Language：Japanese   Publishing type：Internal/External technical report, pre-print, etc.  

  • 富士山内部の水の流れを地表の電気の流れから探る,

    相澤広記・小川康雄・石戸恒雄

    財団法人山田科学振興財団事業報告書, No.34 p. 60-63, 2011.   2011.3

  • MT連続観測による桜島地下浅部の比抵抗変化（２）

    相澤広記・小山崇夫・長谷英彰・上嶋誠

    地震及び火山噴火予知観測研究計画報告書「桜島火山における多項目観測に基づく火山噴火準備過程解明のための研究」   2011.3

    　More details

    Language：Japanese   Publishing type：Internal/External technical report, pre-print, etc.  

  • 電磁気観測で推定する火山体内部の地下水流動

    相澤広記

    地質ニュース   2010.1

    　More details

    Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

  • MT連続観測による桜島浅部の比抵抗変化

    相澤広記・神田径・小川康雄・井口正人・横尾亮彦・八木原寛・菅野貴之

    , 第11回桜島火山の集中総合観測報告書   2008.3

    　More details

    Publishing type：Internal/External technical report, pre-print, etc.  

▼display all

Professional Memberships

  • sgepss

  • The volcanological society of Japan

  • AGU

  • The seismological society of japan

Committee Memberships

  • 火山調査研究推進本部 総合基本施策・調査観測計画部会   調査観測計画検討分科会委員  

    2025.4 - 2027.4   

  • 火山調査研究推進本部 火山調査委員会   機動調査観測部会委員  

    2024.4 - 2027.4   

  • 文部科学省科学技術・学術審議会専門委員 火山研究推進委員会   委員  

    2022.4 - Present   

Academic Activities

  • 学術論文等の審査

    Role(s)： Review, evaluation,　Peer review

    2024.4 - 2025.3

    　More details

    Type：Scientific advice/Review 

  • Screening of academic papers International contribution

    Role(s)： Peer review

    2023.4 - 2024.4

    　More details

    Type：Peer review 

    Number of peer-reviewed articles in foreign language journals：8

    Number of peer-reviewed articles in Japanese journals：0

    Proceedings of International Conference Number of peer-reviewed papers：0

    Proceedings of domestic conference Number of peer-reviewed papers：0

  • Screening of academic papers

    Role(s)： Peer review

    2023

    　More details

    Type：Peer review 

    Number of peer-reviewed articles in foreign language journals：7

    Number of peer-reviewed articles in Japanese journals：0

    Proceedings of International Conference Number of peer-reviewed papers：0

    Proceedings of domestic conference Number of peer-reviewed papers：0

  • Earth, Planets and Space International contribution

    2022.1 - 2027.1

    　More details

    Type：Academic society, research group, etc. 

  • Screening of academic papers

    Role(s)： Peer review

    2022

    　More details

    Type：Peer review 

    Number of peer-reviewed articles in foreign language journals：9

    Number of peer-reviewed articles in Japanese journals：0

    Proceedings of International Conference Number of peer-reviewed papers：0

    Proceedings of domestic conference Number of peer-reviewed papers：0

  • 科学技術・学術審議会測地学分科会専門委員

    Role(s)： Review, evaluation

    文部科学省  2021.5 - 2027.2

    　More details

    Type：Scientific advice/Review 

  • Screening of academic papers

    Role(s)： Peer review

    2021

    　More details

    Type：Peer review 

    Number of peer-reviewed articles in foreign language journals：4

    Number of peer-reviewed articles in Japanese journals：0

    Proceedings of International Conference Number of peer-reviewed papers：0

    Proceedings of domestic conference Number of peer-reviewed papers：0

  • 科学技術・学術審議会測地学分科会火山研究推進委員会/委員

    Role(s)： Review, evaluation

    文部科学省  2020.4 - 2021.3

    　More details

    Type：Scientific advice/Review 

  • Screening of academic papers

    Role(s)： Peer review

    2020

    　More details

    Type：Peer review 

    Number of peer-reviewed articles in foreign language journals：2

    Number of peer-reviewed articles in Japanese journals：0

    Proceedings of International Conference Number of peer-reviewed papers：0

    Proceedings of domestic conference Number of peer-reviewed papers：0

  • コンビーナー

    日本地球惑星科学連合 2019年大会  （ Japan ） 2019.5

    　More details

    Type：Competition, symposium, etc. 

  • Screening of academic papers

    Role(s)： Peer review

    2019

    　More details

    Type：Peer review 

    Number of peer-reviewed articles in foreign language journals：4

    Number of peer-reviewed articles in Japanese journals：0

    Proceedings of International Conference Number of peer-reviewed papers：0

    Proceedings of domestic conference Number of peer-reviewed papers：0

  • コンビーナー

    日本地球惑星科学連合 2018年大会  （ Japan ） 2018.5

    　More details

    Type：Competition, symposium, etc. 

  • Screening of academic papers

    Role(s)： Peer review

    2018

    　More details

    Type：Peer review 

    Number of peer-reviewed articles in foreign language journals：1

    Number of peer-reviewed articles in Japanese journals：2

    Proceedings of International Conference Number of peer-reviewed papers：0

    Proceedings of domestic conference Number of peer-reviewed papers：0

  • Screening of academic papers

    Role(s)： Peer review

    2017

    　More details

    Type：Peer review 

    Number of peer-reviewed articles in foreign language journals：2

    Number of peer-reviewed articles in Japanese journals：2

    Proceedings of International Conference Number of peer-reviewed papers：0

    Proceedings of domestic conference Number of peer-reviewed papers：0

  • 火山学会誌

    2014.7 - 2018.6

    　More details

    Type：Academic society, research group, etc. 

  • 座長（Chairmanship）

    日本地球惑星科学連合2013年大会  （ Japan ） 2013.5

    　More details

    Type：Competition, symposium, etc. 

▼display all

Research Projects

  • 傾斜変動と電場変動の同時観測による水蒸気噴火直前予測可能性の検討

    Grant number：23K25971  2023.4 - 2026.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    相澤 広記, 松島 健

    　 More details

    Grant type：Scientific research funding

    傾斜と電場(地電位差)の同時観測から水蒸気噴火を直前予測できるか検証する。電場観測では他の物理観測で計測できない地下水流動を間接的に推定できる。本研究の最初のステップとして２か所の間欠泉において傾斜、電場、可視映像の同時観測を２週間程度行い、地下圧力源と電場変動の時空間関係を明らかにする。次に３つの火山において傾斜と電場の長期観測(２年程度)を行い「傾斜変動を伴う火山性微動」により電場変動が観測されるか、されるとしたら地下圧力源とどのような時空間関係があるか確認する。以上の観測により得られた知見から、最終的に傾斜と電場観測による水蒸気噴火直前予測の有用性について結論を得る。

    CiNii Research

  • 傾斜変動と電場変動の同時観測による水蒸気噴火直前予測可能性の検討

    Grant number：23H01275  2023 - 2025

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    相澤 広記, 松島 健

    　 More details

    Authorship：Principal investigator  Grant type：Scientific research funding

    傾斜と電場(地電位差)の同時観測から水蒸気噴火を直前予測できるか検証する。電場観測では他の物理観測で計測できない地下水流動を間接的に推定できる。本研究の最初のステップとして２か所の間欠泉において傾斜、電場、可視映像の同時観測を２週間程度行い、地下圧力源と電場変動の時空間関係を明らかにする。次に３つの火山において傾斜と電場の長期観測(２年程度)を行い「傾斜変動を伴う火山性微動」により電場変動が観測されるか、されるとしたら地下圧力源とどのような時空間関係があるか確認する。以上の観測により得られた知見から、最終的に傾斜と電場観測による水蒸気噴火直前予測の有用性について結論を得る。

    CiNii Research

  • Imaging fossil magma pluming system by broad-band magnetotelluric observation: root of the Okueyama volcano-plutonic complex

    Grant number：20K04132  2020 - 2022

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

    Aizawa Koki

    　 More details

    Authorship：Principal investigator  Grant type：Scientific research funding

    In the area around Mt. Okue, Japan, a granitic batholith and surrounding ring dikes, which intruded 14 Ma and later, are exposed on the surface (Takahashi, 1984). The granitic batholith (33 x 23 km), which is a fossil of a magma reservoir, has little pore space and fracture, and therefore, show electrical high resistivity. We conducted broadband MT observations around Mt. Okue in 2015, 2017 and 2020, 2021, and estimated the 3-D resistivity structure. A high resistivity (>3000 Ωm) body, which exceeds 3000 km3, is imaged beneath the ring dike. We interpreted the high resistivity body as solidified magma. The volume of the erupted magma is only 10 % of that of the magma solidified underground. The correspondence between the high resistivity body and the ring dyke is not perfect. There are regions without high resistivity zone beneath the ring dike. This finding is not consistent with the simple idea that the ring dyke intrusion uniformly occurred at the margin of the magma chamber.

    CiNii Research

  • 災害の軽減に貢献するための地震火山観測研究計画 (第２次)

    2019.4 - 2024.3

    　 More details

    Authorship：Coinvestigator(s) 

  • 研究課題番号HKD_04 電磁気・熱・ガス観測に基づく火山活動推移モデルの構築

    2019 - 2023

    災害の軽減に貢献するための地震火山観測研究計画（第2次）

    　 More details

    Authorship：Coinvestigator(s)  Grant type：Contract research

  • 研究課題番号KYU_01 地震火山相互作用下の内陸地震空間ポテンシャル評価 参加機関　北海道大学・東京大学・九州大学・鹿児島大学 協力機関　名古屋大学

    2019 - 2023

    災害の軽減に貢献するための地震火山観測研究計画（第2次）

    　 More details

    Authorship：Principal investigator  Grant type：Contract research

  • 超臨界地熱発電技術研究開発

    2018.9 - 2026.3

    　 More details

    Authorship：Coinvestigator(s) 

  • 平成２８年熊本地震を踏まえた総合的な活断層調査

    2017.10 - 2019.3

    　 More details

    Authorship：Coinvestigator(s) 

  • 平成２８年熊本地震を踏まえた総合的な活断層調査

    2017.4 - 2019.3

    Research commissions

    　 More details

    Authorship：Coinvestigator(s)  Grant type：Other funds from industry-academia collaboration

  • 2016 年熊本地震と関連する活動に関する総合調査

    Grant number：16H06298  2016 - 2017

    Japan Society for the Promotion of Science・Ministry of Education, Culture, Sports, Science and Technology  Grants-in-Aid for Scientific Research  Grant-in-Aid for Special Purposes

    　 More details

    Authorship：Coinvestigator(s)  Grant type：Scientific research funding

  • 雲仙普賢岳溶岩ドームの地すべり的運動の研究

    2015 - 2017

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Young Scientists (B)

    　 More details

    Authorship：Principal investigator  Grant type：Scientific research funding

  • 別府－万年山断層帯（大分平野－由布院断層帯東部）における重点的な調査観測

    2014.10 - 2016.3

    　 More details

    Authorship：Coinvestigator(s) 

  • 災害の軽減に貢献するための地震火山観測研究計画

    2014.4 - 2019.3

    　 More details

    Authorship：Coinvestigator(s) 

  • 別府－万年山断層帯（大分平野－由布院断層帯東部）における重点的な調査観測

    2014.4 - 2017.3

    Research commissions

    　 More details

    Authorship：Coinvestigator(s)  Grant type：Other funds from industry-academia collaboration

  • 研究課題番号1003 多項目観測に基づく火山熱水系の構造の時空間変化の把握と異常現象の検知

    2014 - 2018

    文部科学省委託研 究・災害の軽減に貢 献するための地震火 山観測研究計画・H26 ～30・配分機関 東京 大学地震研究所

    　 More details

    Authorship：Coinvestigator(s)  Grant type：Contract research

  • 研究課題番号2201 地震・火山相互作用下の内陸地震・火山噴火発生場解明およびモデル化の研究

    2014 - 2018

    文部科学省委託研 究・災害の軽減に貢 献するための地震火 山観測研究計画・H26 ～30・配分機関 東京 大学地震研究所

    　 More details

    Authorship：Coinvestigator(s)  Grant type：Contract research

  • 別府－万年山断層帯（大分平野－由布院断層帯東部）における重点的な調査観測

    2014 - 2016

    文部科学省委託研究 「別府－万年山断層帯（大分平野－由布院断層帯東部）における重点的な調査観測」

    　 More details

    Authorship：Coinvestigator(s)  Grant type：Contract research

  • 機動的電場観測装置の開発

    2014

    東京大学地震研究所平成26　年度一般共同研究

    　 More details

    Authorship：Principal investigator  Grant type：Contract research

  • 長期モニタリング観測による火山雷発生メカニズム推定

    2011 - 2013

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Young Scientists (B)

    　 More details

    Authorship：Principal investigator  Grant type：Scientific research funding

  • ひずみ集中帯の重点的調査観測・研究プロジェクト

    2009.4 - 2013.3

    　 More details

    Authorship：Coinvestigator(s) 

  • 広帯域ＭＴ連続観測による桜島比抵抗変動源の推定

    2009

    東京大学地震研究所平成21年度一般共同研究

    　 More details

    Authorship：Principal investigator  Grant type：Contract research

  • 富士山内部の水の流れを地表の電気の流れから探る

    2008 - 2010

    山田科学振興財団2008年度研究援助

    　 More details

    Authorship：Principal investigator  Grant type：Contract research

  • 電磁気的観測による島弧成層火山の浅部構造と活動様式との関連性

    2005 - 2007

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for JSPS Fellows

    　 More details

    Authorship：Principal investigator  Grant type：Scientific research funding

▼display all

Educational Activities

  • 基幹教育セミナー
    基幹物理学IA演習 (力学)
    地球惑星科学Ⅱ(分担)
    観測火山学(分担)
    火山科学(分担)
    伊都、島原観測所で行われるセミナー。

Class subject

  • 観測地震学

    2023.10 - 2024.3   Second semester

  • 力学概論演習

    2023.4 - 2023.9   First semester

  • 地震火山数理演習

    2023.4 - 2023.9   First semester

  • 地震火山計測演習

    2023.4 - 2023.9   First semester

  • 火山科学

    2023.4 - 2023.9   First semester

  • 観測火山学

    2022.10 - 2023.3   Second semester

  • 観測地震学

    2022.10 - 2023.3   Second semester

  • 力学概論演習

    2022.4 - 2022.9   First semester

  • 力学概論演習

    2022.4 - 2022.9   First semester

  • 火山科学

    2022.4 - 2022.9   First semester

  • 地球惑星科学ⅠA

    2022.4 - 2022.6   Spring quarter

  • 演習Ⅱ

    2021.10 - 2022.3   Second semester

  • 観測火山学

    2021.10 - 2022.3   Second semester

  • 基幹教育セミナー

    2021.6 - 2021.8   Summer quarter

  • 基幹教育セミナー

    2021.6 - 2021.8   Summer quarter

  • 火山科学 (分担)

    2021.4 - 2021.9   First semester

  • 地球惑星科学Ⅱ

    2021.4 - 2021.9   First semester

  • 観測火山学

    2020.10 - 2021.3   Second semester

  • 地球惑星科学Ⅱ

    2020.4 - 2020.9   First semester

  • 火山科学

    2020.4 - 2020.9   First semester

  • 地球惑星科学Ⅱ

    2019.10 - 2020.3   Second semester

  • 基幹物理学ⅠＡ演習

    2019.4 - 2019.9   First semester

  • 観測火山学

    2019.4 - 2019.9   First semester

  • 火山科学

    2019.4 - 2019.9   First semester

  • 地球惑星科学Ⅱ

    2018.10 - 2019.3   Second semester

  • 観測火山学

    2018.10 - 2019.3   Second semester

  • 基幹物理学ⅠＡ演習

    2018.4 - 2018.9   First semester

  • 火山科学

    2018.4 - 2018.9   First semester

  • 観測火山学

    2017.10 - 2018.3   Second semester

  • 地球惑星科学Ⅱ

    2017.4 - 2017.9   First semester

  • 火山科学

    2017.4 - 2017.9   First semester

  • 観測火山学

    2016.10 - 2017.3   Second semester

  • 火山科学

    2016.4 - 2016.9   First semester

  • 火山科学

    2015.4 - 2015.9   First semester

  • 観測火山学(分担)

    2014.10 - 2015.3   Second semester

  • 火山科学

    2014.10 - 2015.3   Second semester

  • 火山科学(分担)

    2013.10 - 2014.3   Second semester

  • 観測地震学

    2025.10 - 2026.3   Second semester

  • 観測火山学

    2025.10 - 2026.3   Second semester

  • 地震火山数理演習

    2025.4 - 2025.9   First semester

  • 火山科学

    2025.4 - 2025.9   First semester

  • 地震火山計測演習

    2025.4 - 2025.9   First semester

  • 観測地震学

    2024.10 - 2025.3   Second semester

  • 観測火山学

    2024.10 - 2025.3   Second semester

  • 地球惑星科学特別研究Ⅰ（１年）

    2024.4 - 2025.3   Full year

  • 地球惑星科学特別研究Ⅱ（２年）

    2024.4 - 2025.3   Full year

  • 地震火山数理演習

    2024.4 - 2024.9   First semester

  • 火山科学

    2024.4 - 2024.9   First semester

  • 地震火山計測演習

    2024.4 - 2024.9   First semester

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Teaching Student Awards

  • 日本火山学会学生優秀論文賞

    Year and month of award：2024.5

    Classification of award-winning students：Postgraduate student   Name of award-winning student：田辺暖柊

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Media Coverage

  • Live News it! 火山雷についての電話解説 TV or radio program

    フジテレビ  2024.5

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    Live News it! 火山雷についての電話解説

  • 予測難しい水蒸気噴火、直前に「地中の電流が強まる」兆候…九大など研究チーム発見 Newspaper, magazine

    読売新聞　福岡  2022.10

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    予測難しい水蒸気噴火、直前に「地中の電流が強まる」兆候…九大など研究チーム発見

  • 水蒸気噴火発生、冷たい地下水の動きが鍵握る 直前予測に期待 九州大など

    サイエンスポータル  2022.9

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    水蒸気噴火発生、冷たい地下水の動きが鍵握る 直前予測に期待 九州大など

  • 噴火予測の精度向上へ「大地の電流」　九州大学などの研究グループが硫黄山の噴火を分析し新発見 TV or radio program

    MRT宮崎放送  2022.9

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    噴火予測の精度向上へ「大地の電流」　九州大学などの研究グループが硫黄山の噴火を分析し新発見

  • 「水蒸気噴火」噴火前に強い電流発生九大研究グループなど発見 TV or radio program

    NHK福岡  2022.9

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    「水蒸気噴火」噴火前に強い電流発生九大研究グループなど発見

  • 熊本地震と地下比抵抗構造の関係を地球電磁気・地球惑星圏学会で発表した紹介。 TV or radio program

    NHK福岡  2016.11

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    熊本地震と地下比抵抗構造の関係を地球電磁気・地球惑星圏学会で発表した紹介。

  • 導電性の差、地震生む？ 地盤 危険性予測に活用 九大 熊本地震受け分析 Newspaper, magazine

    西日本新聞  2016.11

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    導電性の差、地震生む？
    地盤 危険性予測に活用
    九大 熊本地震受け分析

  • 鹿児島、宮崎県境のえびの高原で、地表に湧き出ている湯の温度が上昇していることが分かった。 Newspaper, magazine

    毎日新聞  2015.4

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    鹿児島、宮崎県境のえびの高原で、地表に湧き出ている湯の温度が上昇していることが分かった。

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Activities contributing to policy formation, academic promotion, etc.

  • 2022.4 - 2027.4   文部科学省

    科学技術・学術審議会専門委員 火山研究推進委員会

  • 2021.4 - 2024.4   地震・火山噴火予知研究協議会

    文部科学省「災害の軽減に貢献するための地震火山観測研究計画（第2次）の推進について」の運営のため、年12回程度の会議および、そこで割り当てられたデスクワーク。
    https://www.eri.u-tokyo.ac.jp/YOTIKYO/H31-R5/member_suisin.html