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Keisuke Yoshida

Section

Graduate School of Science

Job title

Associate Professor

Degree

博士（理学）（東北大学）
修士（理学）（東北大学）

researchmap

https://researchmap.jp/k-yoshida999

J-GLOBAL ID

201701005916602203

Research History 6

2024/10 - Present

Tohoku University　Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science
2025/05 - 2027/04

Tohoku University
2023/02 - 2025/01

Tohoku University
2016/09 - 2024/09

Tohoku University　Graduate School of Science　Assistant professor
2014/09 - 2016/08

国立研究開発法人防災科学技術研究所　契約研究員
2014/04 - 2014/08

日本学術振興会　特別研究員

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Education 2

Tohoku University　Graduate School, Division of Natural Science　地球物理学専攻

2009/04 - 2014/03/31
Tohoku University　Faculty of Science　宇宙地球物理学科

2005/04 - 2009/03

Committee Memberships 4

日本地震学会　「地震」編集委員

2025/04 - Present
Earth, Planets and Space, Editorial Board

2025 - Present
日本地震学会　代議員

2024/04 - Present
日本地震学会　普及行事委員

2020/04 - Present

Professional Memberships 4

米国地震学会
米国地球物理学連合
日本地球惑星科学連合
日本地震学会

Research Interests 9

fault structure
seismic radiation
震源過程
テクトニクス
地震活動
地殻流体
断層強度
crustal stress
地震発生機構

Research Areas 1

Natural sciences / Solid earth science /

Awards 13

2024 Editor’s Citation for Excellence in Refereeing

2025/05　American Geophysical Union (AGU)　Outstanding Service to the Authors and Readers of JGR: Solid Earth
Minister of Education, Culture, Sports, Science and Technology Award for Young Scientists in the Field of Science and Technology」

2025/04　Minister of Education, Culture, Sports, Science and Technology
Top Cited Article Among Work Published between January 1, 2023 and December 31, 2023 (Journal of Geophysical Research: Solid Earth)

2025/03　Wiley　Upward Earthquake Swarm Migration in the Northeastern Noto Peninsula, Japan, Initiated From a Deep Ring‐Shaped Cluster: Possibility of Fluid Leakage From a Hidden Magma System
Outstanding Reviewer 2024 (Geophysical Journal International)

2024　The Royal Astronomical Society
Young Scientist Award, Seismological Society of Japan

2020/10　The Seismological Society of Japan
AOGS Kamide Lecture Award

2019/08　Asia Oceania Geosciences Society (AOGS)
Top Viewed Article Among Work Published between January 1, 2023 and December 31, 2023 (Journal of Geophysical Research: Solid Earth)

2025/04　Wiley　Upward Earthquake Swarm Migration in the Northeastern Noto Peninsula, Japan, Initiated From a Deep Ring‐Shaped Cluster: Possibility of Fluid Leakage From a Hidden Magma System
Top Viewed Article Among Work Published between January 1, 2023 and December 31, 2023 (Geophysical Research Letters)

2025/04　Wiley　Updip Fluid Flow in the Crust of the Northeastern Noto Peninsula, Japan, Triggered the 2023 Mw 6.2 Suzu Earthquake During Swarm Activity
2018 Research Paper Award of the Seismological Society of Japan

2019/10　Seismological Society of Japan
Student Outstanding Presentation Award in the Solid Earth Sciences Section at the Japan Geoscience Union Meeting

2013
Student Outstanding Presentation Award at the Seismological Society of Japan

2012
Best Student Poster Award, G-COE Symposium 2012, "Seismic wave propagation and crustal heterogeneity & The 2011 Tohoku earthquake and earthquake cycle"

2012
Student Outstanding Presentation Award in the Solid Earth Sciences Section at the Japan Geoscience Union Meeting 2012

2012　JpGU

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Papers 70

Highly Systematic Response of Seismic Rupture Patterns to Background Loading Rate: Insights From Repeating Earthquakes Peer-reviewed

Keisuke Yoshida, Satoshi Ide

Geophysical Research Letters　52　(10)　e2025GL115207　2025/05

DOI： 10.1029/2025GL115207 　
Nonplanar 3D fault geometry controls the spatiotemporal distributions of slip and uplift: evidence from the Mw 7.5 2024 Noto Peninsula, Japan, Earthquake Invited Peer-reviewed

Ryosuke Ando, Yo Fukushima, Keisuke Yoshida, Kazutoshi Imanishi

Earth, Planets and Space　77　(1)　2025/04/29
Publisher: Springer Science and Business Media LLC
DOI： 10.1186/s40623-025-02187-9 　

eISSN： 1880-5981

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Abstract The 2024 Mw 7.5 Noto Peninsula Earthquake broke through a previously documented active fault system over 150 km in the northern central Japanese Island. This fault system is characterized by geometrical complexity. It is important to understand the physical mechanism underlying the multi-fault rupture. We conduct fully dynamic rupture simulations and identify that the 3D fault geometry controls the observed rupture process and heterogeneous spatiotemporal patterns of the fault slip, seismic radiation and crustal deformation exhibiting about five meters of the maximum uplift. Aiming to examine the effect of the 3D fault geometry, we exclude the heterogeneity arising from the frictional properties. We also avoid retrospective frictional parameter tunings to fit the coseismic observations to test whether it is possible for our forward modeling to reproduce the coseismic observations. The 3D nonplanar geometry model is built based on the previously documented surface fault traces, and we use the regional stress field determined by the stress tensor inversion. As a result, the dynamic rupture simulation reasonably reproduces the observed characteristics of the heterogeneous deformation patterns. We find the rupture is accelerated, and slip is increased, where the fault is bent and optimally oriented to the regional stress orientations. Remarkably, the spatial distribution of surface displacement captured by the Synthetic Aperture Radar imageries is quantitatively reproduced, as characterized by two areas of large and small peaks of uplifts. Our findings may contribute to better constraining future earthquake rupture scenarios. Graphical Abstract
Systematic Differences in Energy Radiation Processes Between Regular and Intraplate Low‐Frequency Earthquakes Around the Focal Area of the 2008 Mw6.9 Iwate‐Miyagi, Japan, Earthquake Peer-reviewed

Masaki Orimo, Keisuke Yoshida, Toru Matsuzawa, Taka'aki Taira, Kentaro Emoto, Akira Hasegawa

Journal of Geophysical Research: Solid Earth　130　(3)　e2024JB030750　2025/03/24
Publisher: American Geophysical Union (AGU)
DOI： 10.1029/2024jb030750 　

ISSN： 2169-9313

eISSN： 2169-9356

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Abstract Many unknowns exist regarding the energy radiation processes of intraplate low‐frequency earthquakes (LFEs), which are frequently observed beneath volcanoes. To evaluate their energy radiation characteristics, we estimated scaled energy () for LFEs and regular earthquakes around the focal area of the 2008 6.9 Iwate‐Miyagi, Japan, earthquake. Their source spectra were first obtained by correcting for the site and path effects from direct S‐waves. We then estimated the radiated energy and seismic moment and obtained the for the 1,421 regular earthquakes, 62 deep LFEs, and 46 shallow LFEs. The for the regular earthquakes is in the order of to , typical for crustal earthquakes and tends to be smaller near volcanoes and the shallow LFEs. In contrast, the is in the order of and for the deep and shallow LFEs, respectively, one to three orders of magnitude smaller than that for the regular earthquakes. The systematically lower suggests that LFEs are associated with a much lower stress drop and (or) slower deformation than regular earthquakes. While the energy magnitudes derived from radiated energy generally show good agreement with the local magnitudes for the three types of earthquakes, the moment and local magnitudes show a large discrepancy for the LFEs. This suggests that the local magnitude based only on the maximum amplitude of the observed seismic records may not provide good information on the static sizes of LFEs whose is substantially different from that for regular earthquakes.
Fault material heterogeneity controls deep interplate earthquakes Peer-reviewed

Yihe Huang, Satoshi Ide, Aitaro Kato, Keisuke Yoshida, Chengxin Jiang, Peng Zhai

Science Advances　11　(9)　eadr9353　2025/02/28
Publisher: American Association for the Advancement of Science (AAAS)
DOI： 10.1126/sciadv.adr9353 　

eISSN： 2375-2548

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Earthquakes may seem random, but are often concentrated in some localized areas. Thus, they are likely controlled by fault materials and stress heterogeneity, which are little understood. Here, we provide high-resolution observations of fault material and stress heterogeneity in the Japan subduction zone through an integration of material and source imaging with numerical simulations. Our results present evidence for localized, anisotropic structures with a near-zero Poisson’s ratio in the medium surrounding 1 to 2 kilometer–sized earthquake clusters, suggesting that the fault medium is damaged, foliated, and enriched with fluid. Such localized structures may cause stress perturbations on faults that in turn favor the frequent occurrence of deep interplate earthquakes at depths of 60 to 70 kilometers. Therefore, identifying the distribution and properties of fault material heterogeneity is important for more informed assessment of earthquake hazards.
Coseismic slip distribution of the 2024 Noto Peninsula earthquake deduced from dense global navigation satellite system network and interferometric synthetic aperture radar data: effect of assumed dip angle Peer-reviewed

Taisuke Yamada, Yusaku Ohta, Takuya Nishimura, Keisuke Yoshida, Yoshihiro Hiramatsu, Yohei Kinoshita

Earth, Planets and Space　77　(1)　19　2025/02/21
Publisher: Springer Science and Business Media LLC
DOI： 10.1186/s40623-025-02154-4 　

eISSN： 1880-5981

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Abstract The Mw 7.5 Noto Peninsula earthquake, which occurred on January 1, 2024, was considerably hazardous to the peninsula and surrounding regions owing to a strong motion, large-scale crustal deformation, and subsequent tsunami. Significant surface displacement was observed by the dense global navigation satellite system (GNSS) stations, including universities and SoftBank corporation sites, and synthetic aperture radar (SAR). To estimate reliable coseismic slip distribution and its uncertainties for this event, we used the dense GNSS and the line-of-sight displacements from the SAR based on the Bayesian optimization framework. Considering the listric fault structure of this source fault, we validated the fault dip angles using the grid-search approach in the slip estimation. The acquired models indicated reverse fault motion, including a right-lateral slip component, and two slip peaks were estimated in the eastern and western regions of the fault in the central peninsula, independent of the assumed dip angles. These locations correspond to regions of significant uplift and westward displacement. The dip angle assumption affects the horizontal and vertical component of the calculated displacements: a higher dip angle model (≥ 45°) well reproduces vertical components of GNSS and synthetic aperture radar displacements, whereas a lower dip angle model (< 45°) well reproduces horizontal displacements. Overall, a fault dip of 45° is plausible, although it is not consistent with the listric structure suggested by the seismic reflection survey and the aftershock distribution below the central part of the peninsula. To test such a listric fault model, we conducted a coseismic slip estimation assuming a relatively high (60°) and low (25°) dip angles for the shallow and deep sections of the fault, respectively. Even in this case, we acquired a slip model similar to that of a plain fault, which reasonably reproduced each component of the surface displacements as well as the simple plane fault models. These results suggest that listric geometry is also acceptable for the source faults of this event, although the flat geometry similarly explains the observations. Graphical Abstract
Near‐Field Imaging of Near‐Identical M_w5.9 Earthquakes in the Crust of Ibaraki, Japan Peer-reviewed

Keisuke Yoshida, Yo Fukushima, Yoshihiro Kaneko

Journal of Geophysical Research: Solid Earth　130　(2)　e2024JB029791　2025/02/21
Publisher: American Geophysical Union (AGU)
DOI： 10.1029/2024jb029791 　

ISSN： 2169-9313

eISSN： 2169-9356

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Abstract Understanding the physical mechanisms of intraplate earthquakes requires a better understanding of the earthquake cycle and aseismic slip. A potential short‐term repetition of intraplate earthquakes has been documented from interferometric synthetic aperture radar (InSAR) observations of two M_w5.9 events in northern Ibaraki Prefecture, Japan, which occurred on 19 March 2011 and 28 December 2016. However, our understanding based on surface geodetic measurements remains limited, particularly in terms of spatial resolution at depth. Here, we used the near‐field seismic waveform data to complement InSAR data, thereby improving the spatial resolution of the coseismic slip distributions. First, we confirmed that the aftershocks of both events occurred along a common fault area. We then conducted a joint inversion that successfully reconciled near‐identical surface displacements with the different seismic waveforms. Our results indicate that while the 2011 event mainly ruptured just updip of the hypocenter at 6 km depth, the 2016 rupture initiated deeper, at 10 km, and propagated to the shallow, northern side, causing large slip near the 2011 rupture area. The slip distributions of two events were complementary in the deeper portion (3 < z < 6 km), whereas those on the shallower side (z < 3 km) largely overlapped, resulting in nearly identical surface displacements. Small earthquakes rarely occur shallower than 3 km, suggesting that this shallow segment releases accumulated strain aseismically. The two events repeatedly triggered seismic slip on this typically aseismic shallow segment, possibly due to dynamic stress changes.
Landscape changes caused by the 2024 Noto Peninsula earthquake in Japan. International-journal Peer-reviewed

Yo Fukushima, Daisuke Ishimura, Naoya Takahashi, Yoshiya Iwasa, Luca C Malatesta, Takayuki Takahashi, Chi-Hsien Tang, Keisuke Yoshida, Shinji Toda

Science advances　10　(49)　eadp9193　2024/12/06

DOI： 10.1126/sciadv.adp9193 　

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Landscapes are shaped by tectonic, climatic, and surface processes over geological timescales, but we rarely witness the events of marked landscape change. The moment magnitude 7.5 Noto Peninsula earthquake in central Japan was caused by a large thrust faulting, up to nearly 10 meters of slip, that expanded more than 150 kilometers along the fault zone. The deformation field reconstructed from satellite data and field surveys reveals up to 4.4 meters of uplift and associated coastal advance along the entire northern coast of the peninsula, meter-scale systematic movement of the mountain slopes consistent with slip on flexural faults, and activation of secondary inland faults, suggesting synchronized ruptures. The findings show excellent consistency between the coseismic deformation and geomorphic features and provide a vivid example of the role of a major earthquake in landscape formation.
Quasi-Real-Time Earthquake Relocation and Monitoring in the Northeastern Noto Peninsula Peer-reviewed

Ryuta Matsumoto, Keisuke Yoshida

Earth Planets Space　76　(131)　131　2024/10

DOI： 10.1186/s40623-024-02079-4 　
Near-Source Waveform Modeling to Estimate Shallow Crustal Attenuation and Radiated Energy of Mw 2.0-4.5 Earthquakes Peer-reviewed

Keisuke Yoshida, Kentaro Emoto, Shunsuke Takemura, Toru Matsuzawa

Journal of Geophysical Research: Solid Earth　129　(9)　e2023JB028523　2024/09

DOI： 10.1029/2023JB028523 　
"Role of a Hidden Fault in the Early Process of the 2024 Mw7.5 Noto Peninsula Earthquake Peer-reviewed

Yoshida, K, Takagi, R, Fukushima, Y, Ando, R, Ohta, Y, Hiramatsu, Y.

Geophysical Research Letters　51　(16)　e2024GL110993　2024/08

DOI： 10.1029/2024GL110993 　
Spatial Variation in Stress Orientation around Türkiye: Rupture Propagation across the Stress Regime Transition in the 2023 Mw 7.8 Türkiye Earthquake Peer-reviewed

Keisuke Yoshida

Geophysical Journal International　2024/06

DOI： 10.1093/gji/ggae230 　
Direct Evidence for Diverse Source Complexity in Small Earthquakes (Mw 3.3–5.0) Obtained from Near-Source Borehole Seismic Data Peer-reviewed

Keisuke Yoshida

Seismological Research Letters　95　(4)　2409-2421　2024/04/10
Publisher: Seismological Society of America (SSA)
DOI： 10.1785/0220230431 　

ISSN： 0895-0695

eISSN： 1938-2057

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Abstract Small earthquakes (Mw &lt;5) may have a similar degree of complexity as large earthquakes. However, their seismic waveforms are strongly distorted during wave propagation, making their complexity challenging to resolve. In many cases, the source parameters of small events are determined based on models that assume their source patterns are simple. In this study, to directly examine the source complexities in small events, we examined high-quality near-source (&lt;8 km) seismic waveforms recorded by two excellent downhole sensors in Japan. The results show that the P waveforms of microearthquakes (Mw &lt;2) are always simple at the sensors and agree well with the synthetic waveforms based on a 1D structure up to 20 Hz. The microearthquake waveforms in this frequency band essentially represent path effects besides the static source effect, suggesting that the contribution of structural inhomogeneity to the observed waveforms is small. Taking advantage of this, we inferred the moment rate functions of 164 Mw 3.3–5.0 events from the shapes of the direct P waves. They showed diversity in their complexity, and even conservatively estimated, 25% of the events had multiple subevents. The results suggest that methods that account for complexity, rather than those that assume a simple source pattern, are required to characterize even small events.
Shear wave splitting and seismic velocity structure in the focal area of the earthquake swarm and their relation with earthquake swarm activity in the Noto Peninsula, central Japan International-journal International-coauthorship Peer-reviewed

Tomomi Okada, Martha K. Savage, Shin’ichi Sakai, Keisuke Yoshida, Naoki Uchida, Ryota Takagi, Shuutoku Kimura, Satoshi Hirahara, Ayaka Tagami, Ryotaro Fujimura, Toru Matsuzawa, Eiji Kurashimo, Yoshihiro Hiramatsu

Earth, Planets and Space　76　24　2024/02/04

DOI： 10.1186/s40623-024-01974-0 　

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Preprint https://doi.org/10.21203/rs.3.rs-3271539/v1
Updip Fluid Flow in the Crust of the Northeastern Noto Peninsula, Japan, Triggered the 2023 Mw6.2 Suzu Earthquake During Swarm Activity Peer-reviewed

Keisuke Yoshida, Naoki Uchida, Yoshiaki Matsumoto, Masaki Orimo, Tomomi Okada, Satoshi Hirahara, Shuutoku Kimura, Ryota Hino

Geophysical Research Letters　50　(21)　e2023GL106023　2023/11

DOI： 10.1029/2023GL106023 　
Upward Earthquake Swarm Migration in the Northeastern Noto Peninsula, Japan, Initiated From a Deep Ring‐Shaped Cluster: Possibility of Fluid Leakage From a Hidden Magma System Peer-reviewed

Keisuke Yoshida, Masaoki Uno, Toru Matsuzawa, Yohei Yukutake, Yusuke Mukuhira, Hiroshi Sato, Takeyoshi Yoshida

Journal of Geophysical Research: Solid Earth　128　(6)　2023/06/12
Publisher: American Geophysical Union (AGU)
DOI： 10.1029/2022jb026047 　

ISSN： 2169-9313

eISSN： 2169-9356

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Abstract This study describes an ongoing intense earthquake swarm in the crust of the northeastern Noto Peninsula, Japan, that began around the end of 2019. Fluid movement related to volcanic activity is often involved in earthquake swarms in the crust. However, no volcanic activity has occurred in this region since the Middle Miocene (15.6 Ma). This study investigates the cause of this earthquake swarm based on the spatiotemporal evolution of earthquake hypocenters and seismic reflectors. The hypocenter relocation of 10,940 earthquakes (M > 1) reveals that they are all crustal and migrated upward, activating a complex network of faults at depths shallower than 20 km. The initiation of this earthquake swarm occurred at a locally deep depth (z = 17 km), and the local hypocenter distribution shows a characteristic circular pattern. We find a distinctive S‐wave reflector in the immediate vicinity. A low‐velocity anomaly exists below the reflector, and a high helium isotope ratio and a low‐gravity anomaly were observed at the surface. These observations suggest that the current seismicity is associated with fluids released by ancient or possibly unrecognized modern magmatic activity, although no volcanic activity has been documented in this area for 15 million years. Significant crustal deformation was observed during this swarm and is probably related to the fluid movement and aseismic deformation that contributed to this earthquake swarm. The strongest M5.4 earthquake (as of October 2022) occurred near the migration front on the largest planar structure, leaving the shallow extension unruptured.
Time-domain source parameter estimation of Mw 3–7 earthquakes in Japan from a large database of moment-rate functions Peer-reviewed

Keisuke Yoshida, Hiroo Kanamori

Geophysical Journal International　234　(1)　243-262　2023/02

DOI： 10.1093/gji/ggad068 　
The Mw 6.0-6.8 quasi-repeating earthquakes off Miyagi, Japan, with variable moment release patterns due to a hidden adjacent slip patch Peer-reviewed

Keisuke Yoshida

Journal of Geophysical Research: Solid Earth　128　(2)　e2022JB025654　2023

DOI： 10.1029/2022JB025654 　
Hidden magma system causing intense earthquake swarm in the northeastern Noto Peninsula, Japan

Keisuke Yoshida, Masaoki Uno, Toru Matsuzawa, Yohei Yukutake, Yusuke mukuhira, Hiroshi Sato, Takeyoshi Yoshida

2022/11/19

DOI： 10.1002/essoar.10512876.1 　
Slab-derived fluid storage in the crust elucidated by earthquake swarm Peer-reviewed

Yusuke Mukuhira, Masaoki Uno, Keisuke Yoshida

Communications Earth & Environment　3　(1)　2022/11/19
Publisher: Springer Science and Business Media LLC
DOI： 10.1038/s43247-022-00610-7 　

eISSN： 2662-4435

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Abstract Slab-derived fluids control crustal dynamics in the subduction zone. However, the slab-derived fluid budget has never been quantified beyond a geophysical and geological spatiotemporal resolution. Here, we target an intense earthquake swarm associated with the M9 Tohoku earthquake, which represented the critical dynamic behavior of slab-derived fluid. The fluid volume involved has been quantified, with a plausible range of 10⁶−10⁸ m³, by utilizing injection-induced seismicity insights. Comparisons with geological proxies suggest that the estimated fluid volume can be accumulated via supply from the lower crust within 10²–10⁴ y. Our study demonstrated such amount of aqueous fluid stored at the midcrustal level, which triggered consecutive swarm activity for ~2 y with the Tohoku earthquake, suggesting a possible link between earthquake swarms to M9 class earthquakes (10³ y cycle) and mineral veins and deposits. This study has shed light on the quantitative understanding of the dynamic slab-derived fluid budget.
The 2021 Mw7.0 and Mw6.7 Miyagi-Oki earthquakes nucleated in a deep seismic/aseismic transition zone: Possible effects of transient instability due to the 2011 Tohoku earthquake Peer-reviewed

Keisuke Yoshida, Toru Matsuzawa, Naoki Uchida

Journal of Geophysical Research: Solid Earth　127　(8)　e2022JB024887　2022/08

DOI： 10.1029/2022JB024887 　

ISSN： 2169-9313

eISSN： 2169-9356
Seismic Data from Temporary Seismic Observation in the Northeast Noto Peninsula, Central Japan

Shin'ichi Sakai, Eiji Kurashimo, Takashi Iidaka, Naoki Uchida, Keisuke Yoshida, Tomomi Okada

Zenodo　2022/06

DOI： 10.5281/zenodo.6767362 　
Interaction Between Aseismic Slip and Fluid Invasion in Earthquake Swarms Revealed by Dense Geodetic and Seismic Observations Peer-reviewed

Y. Yukutake, K. Yoshida, R. Honda

Journal of Geophysical Research: Solid Earth　127　(4)　2022/04
Publisher: American Geophysical Union (AGU)
DOI： 10.1029/2021jb022933 　

ISSN： 2169-9313

eISSN： 2169-9356
中小地震の破壊伝播指向性と応力降下量－東北沖地震後に活発化した福島－茨城県境の地震活動の解析－

池田里奈, 吉田圭佑, 松澤暢

東北地域災害科学研究　58　2022/03
セントロイドモーメントテンソルインバージョンへのベイズ最適化の適用 Peer-reviewed

久保久彦, 木村武志, 吉田圭佑

AI・データサイエンス論文集　3　(J2)　2022

DOI： 10.11532/jsceiii.3.J2_209 　
Prevalence of updip rupture propagation in interplate earthquakes along the Japan trench Peer-reviewed

Keisuke Yoshida, Naoki Uchida, Hisahiko Kubo, Ryota Takagi, Shiqing Xu

Earth and Planetary Science Letters　578　117306-117306　2022/01
Publisher: Elsevier BV
DOI： 10.1016/j.epsl.2021.117306 　

ISSN： 0012-821X
Improving the Constraint on the M w 7.1 2016 Off‐Fukushima Shallow Normal‐Faulting Earthquake With the High Azimuthal Coverage Tsunami Data From the S‐Net Wide and Dense Network: Implication for the Stress Regime in the Tohoku Overriding Plate Peer-reviewed

Tatsuya Kubota, Hisahiko Kubo, Keisuke Yoshida, Naotaka Y. Chikasada, Wataru Suzuki, Takeshi Nakamura, Hiroaki Tsushima

Journal of Geophysical Research: Solid Earth　126　(10)　2021/10/13
Publisher: American Geophysical Union ({AGU})
DOI： 10.1029/2021JB022223 　

ISSN： 2169-9313

eISSN： 2169-9356
Backward earthquake ruptures far ahead of fluid invasion: Insights from dynamic earthquake-sequence simulations Peer-reviewed

Keisuke Yoshida, Hiroyuki Noda, Masao Nakatani, Bunichiro Shibazaki

Tectonophysics　816　229038-229038　2021/10
Publisher: Elsevier BV
DOI： 10.1016/j.tecto.2021.229038 　

ISSN： 0040-1951
Seismic evidence of fluid migration in northeastern Japan after the 2011 Tohoku-Oki earthquake Peer-reviewed

Qing-Yu Wang, Michel Campillo, Florent Brenguier, Albanne Lecointre, Tetsuya Takeda, Keisuke Yoshida

Earth and Planetary Science Letters　563　116894-116894　2021/06
Publisher: Elsevier {BV}
DOI： 10.1016/j.epsl.2021.116894 　

ISSN： 0012-821X
Focal mechanisms and the stress field in the aftershock area of the 2018 Hokkaido Eastern Iburi earthquake (M-JMA=6.7) Peer-reviewed

Yuki Susukida, Kei Katsumata, Masayoshi Ichiyanagi, Mako Ohzono, Hiroshi Aoyama, Ryo Tanaka, Masamitsu Takada, Teruhiro Yamaguchi, Kazumi Okada, Hiroaki Takahashi, Shin'ichi Sakai, Satoshi Matsumoto, Tomomi Okada, Toru Matsuzawa, Hiroki Miyamachi, Shuichiro Hirano, Yoshiko Yamanaka, Shinichiro Horikawa, Masahiro Kosuga, Hiroshi Katao, Yoshihisa Iio, Airi Nagaoka, Noriko Tsumura, Tomotake Ueno, Koji Miyakawa, Shin'ichi Tanaka, Miwako Ando, Naoki Uchida, Ryosuke Azuma, Ryota Takagi, Keisuke Yoshida, Takashi Nakayama, Satoshi Hirahara, Toshiko Terakawa, Yuta Maeda, Hiroki Miyamachi, Hiroshi Yakiwara

EARTH PLANETS AND SPACE　73　(1)　2021/01

DOI： 10.1186/s40623-020-01323-x 　

eISSN： 1880-5981
Studies about the Impacts of Upward Fluid Migration on the Earthquake Occurrence: Constraints from Seismicity Triggered by the 2011 Tohoku-Oki Earthquake Invited Peer-reviewed

Keisuke Yoshida

Zisin 2　74　95-116　2021

DOI： 10.4294/zisin.2020-20 　
Fault-valve behavior estimated from intensive foreshocks and aftershocks of the 2017 M 5.3 Kagoshima Bay earthquake sequence, Kyushu, southern Japan Peer-reviewed

Yoshiaki Matsumoto, Keisuke Yoshida, Toru Matsuzawa, Akira Hasegawa

Journal of Geophysical Research - Solid Earth　126　(5)　2021

DOI： 10.1029/2020JB020278 　

ISSN： 2169-9313

eISSN： 2169-9356
Detection of Temporal Change in Near-Source Attenuation during Intense Fluid-Driven Seismicity Following the 2011 Tohoku-Oki Earthquake Peer-reviewed

Keisuke Yoshida

Geophysical Journal International　224　(1)　138-150　2021/01

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筆頭
Stagnant forearc mantle wedge inferred from mapping of shear-wave anisotropy using S-net seafloor seismometers Peer-reviewed

Naoki Uchida, Junichi Nakajima, Kelin Wang, Ryota Takagi, Keisuke Yoshida, Takashi Nakayama, Ryota Hino, Tomomi Okada, Youichi Asano

Nature Communications　11　(1)　2020/12
Publisher: Springer Science and Business Media LLC
DOI： 10.1038/s41467-020-19541-y 　

eISSN： 2041-1723

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<title>Abstract</title> Shear-wave anisotropy in Earth’s mantle helps constrain the lattice-preferred orientation of anisotropic minerals due to viscous flow. Previous studies at the Japan Trench subduction zone using land-based seismic networks identified strong anisotropy in the mantle wedge, reflecting viscous flow induced by the subducting slab. Here we map anisotropy in the previously uninvestigated offshore region by analyzing shear waves from interplate earthquakes that are recorded by a new seafloor network (the S-net). The newly detected anisotropy is not in the mantle wedge but only in the overlying crust (∼0.1 s time delay and trench-parallel fast direction). The distinct lack of anisotropy indicates that the forearc mantle wedge offshore is decoupled from the slab and does not participate in the viscous flow, in sharp contrast with the rest of the mantle wedge. A stagnant forearc mantle wedge provides a stable and cold tectonic environment that is important for the petrological evolution and earthquake processes of subduction zones.
Low-frequency earthquakes observed in close vicinity of repeating earthquakes in the brittle upper crust of Hakodate, Hokkaido, northern Japan Peer-reviewed

Keisuke Yoshida, Akira Hasegawa, Shinako Noguchi, Keiji Kasahara

Geophysical Journal International　223　(3)　1724-1740　2020/09/03
Publisher: Oxford University Press (OUP)
DOI： 10.1093/gji/ggaa418 　

ISSN： 0956-540X

eISSN： 1365-246X

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SUMMARY We conducted a detailed investigation of an earthquake cluster distributed from the lower crust to the upper crust beneath Hakodate, Hokkaido, which included both low-frequency earthquakes (LFEs) and regular earthquakes. Relocated hypocentres clearly show that both the LFEs and regular earthquakes occurred close to each other in the brittle upper crust of this non-volcanic area, while only LFEs occurred in the lower crust. This observation indicates that LFEs can occur not only in the ductile lower crust, but also in the brittle upper crust, which suggests that LFEs can occur in an environment similar to that of regular earthquakes. Regular earthquakes that occur in close vicinity of LFEs have very similar waveforms and nearly overlapping source regions, which indicate that they reflect the repeated rupture of the same asperity patch on a fault. Temporally, the intervals between events in the repeating earthquake sequence were very short, thus suggesting that they were caused by a sudden increase in pore pressure. The cluster of LFEs and repeating earthquakes, which has a rod-like distribution extending from the bottom of the crust to the surface and tilted slightly eastward, might represent a pathway of aqueous fluid movement sourced from the subducting slab.
Late Cenozoic Igneous Activity and Crustal Structure in the NE Japan Arc: Background of Inland Earthquake Activity Peer-reviewed

Takeyoshi YOSHIDA, Reishi TAKASHIMA, Takeshi KUDO, Oky Dicky Ardiansyah PRIMA, Sumire MAEDA, Keisuke YOSHIDA, Tomomi OKADA, Satoshi MIURA, Tomohiro TAKAHASHI, Yoshitaka NAGAHASHI, Kyoko KATAOKA

Journal of Geography (Chigaku Zasshi)　129　(4)　529-563　2020/08/25
Publisher: Tokyo Geographical Society
DOI： 10.5026/jgeography.129.529 　

ISSN： 0022-135X

eISSN： 1884-0884
2019 M6.7 Yamagata-Oki earthquake in the stress shadow of 2011 Tohoku-Oki earthquake: Was it caused by the reduction in fault strength? Peer-reviewed

Keisuke Yoshida, Naoki Uchida, Satoshi Hiarahara, Takashi Nakayama, Toru Matsuzawa, Tomomi Okada, Yoshiaki Matsumoto, Akira Hasegawa

Tectonophysics　793　(20)　228609-228609　2020/08

DOI： 10.1016/j.tecto.2020.228609 　

ISSN： 0040-1951

eISSN： 1879-3266
Heterogeneity in stress field in NE Japan and its implication for the fault strength and the earthquake occurrence mechanism Invited Peer-reviewed

Keisuke Yoshida, Toru Matsuzawa

Journal of Geography (Chigaku Zasshi)　129　(4)　451-471　2020/08

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Stress release process along an intraplate fault analogous to the plate boundary: a case study of the 2017 M5.2 Akita-Daisen earthquake, NE Japan Peer-reviewed

Keisuke Yoshida, Taka'aki Taira, Yoshiaki Matsumoto, Tatsuhiko Saito, Kentaro Emoto, Toru Matsuzawa

Journal of Geophysical Research - Solid Earth　125　(5)　e2020JB019527-e2020JB019527　2020/05

DOI： 10.1029/2020JB019527 　

ISSN： 2169-9313

eISSN： 2169-9356
Prevalence of asymmetrical rupture in small earthquakes and its effect on the estimation of stress drop: a systematic investigation in inland Japan Peer-reviewed

Keisuke Yoshida

Geoscience Letters　6　(1)　2019/12/12
Publisher: Springer Science and Business Media LLC
DOI： 10.1186/s40562-019-0145-z 　

eISSN： 2196-4092

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Abstract Stress drops of small earthquakes have been estimated under the assumption that the rupture propagates symmetrically within a circular fault. However, recent studies have observed directivity effects on seismic waves even for small earthquakes. In this study, rupture directivity was investigated systematically for small-to-moderate-sized earthquakes (M 3.5–5.5) that occurred beneath inland Japan from 2004 to April 2019. Apparent moment rate functions were determined for 1463 earthquakes, and their corner frequencies were inverted for their rupture parameters. The results indicate that most of the analyzed earthquakes (1217 of 1463) are characterized by significantly asymmetrical rupture propagation. The stress drops of the earthquakes estimated by considering asymmetrical rupture propagation were 16.8 MPa, which are almost twice the estimates based on the commonly used symmetrical rupture model. This shows the importance of recognizing the diversity of ruptures, even for small earthquakes, for extracting information about earthquake sources and the Earth’s structure. The prevailing rupture directivity can provide useful information on source parameters including the fault size, fault geometry, and rupture velocity of small earthquakes.
Stress Tensor Inversion Using Seismological Data Invited Peer-reviewed

Takaki IWATA, Keisuke YOSHIDA, Yukitoshi FUKAHATA

Journal of Geography (Chigaku Zasshi)　128　(5)　797-811　2019/10/25

DOI： 10.5026/jgeography.128.797 　
Rupture directivity, stress drop, and hypocenter migration of small earthquakes in the Yamagata-Fukushima border swarm triggered by upward pore-pressure migration after the 2011 Tohoku-Oki earthquake

Keisuke Yoshida, Tatsuhiko Saito, Kentaro Emoto, Yumi Urata, Daisuke Sato

Tectonophysics　769　228184-228184　2019/10
Publisher: Elsevier BV
DOI： 10.1016/j.tecto.2019.228184 　

ISSN： 0040-1951
Causes of the N-S compressional aftershocks of the E-W compressional 2008 Iwate-Miyagi Nairiku earthquake (M7.2) in the northeastern Japan arc Peer-reviewed

Sumire Maeda, Toru Matsuzawa, Keisuke Yoshida, Tomomi Okada, Takeyoshi Yoshida

EARTH PLANETS AND SPACE　71　(1)　94　2019/09

DOI： 10.1186/s40623-019-1073-z 　

ISSN： 1880-5981
The 2018 Hokkaido Eastern Iburi earthquake (M-JMA=6.7) was triggered by a strike-slip faulting in a stepover segment: insights from the aftershock distribution and the focal mechanism solution of the main shock Peer-reviewed

Kei Katsumata, Masayoshi Ichiyanagi, Mako Ohzono, Hiroshi Aoyama, Ryo Tanaka, Masamitsu Takada, Teruhiro Yamaguchi, Kazumi Okada, Hiroaki Takahashi, Shin'ichi Sakai, Satoshi Matsumoto, Tomomi Okada, Toru Matsuzawa, Shuichiro Hirano, Toshiko Terakawa, Shinichiro Horikawa, Masahiro Kosuga, Hiroshi Katao, Yoshihisa Iio, Airi Nagaoka, Noriko Tsumura, Tomotake Ueno, Koji Miyakawa, Shin'ichi Tanaka, Miwako Ando, Naoki Uchida, Ryosuke Azuma, Ryota Takagi, Keisuke Yoshida, Takashi Nakayama, Satoshi Hirahara, Yoshiko Yamanaka, Yuta Maeda, Shuichiro Hirano, Hiroki Miyamachi, Hiroshi Yakiwara, Takuto Maeda, Masahiro Shimazaki, Youichi Asano

EARTH PLANETS AND SPACE　71　(1)　53　2019/05

DOI： 10.1186/s40623-019-1032-8 　

ISSN： 1880-5981

eISSN： 1880-5981
Stable forearc stressed by a weak megathrust: Mechanical and geodynamic implications of stress changes caused by the M=9 Tohoku‐oki earthquake Peer-reviewed

Wang, K, L Brown, Y Hu, K Yoshida, J He, T Sun

Journal of Geophysical Research: Solid Earth　124　(3)　6179-6194　2019/05

DOI： 10.1029/2018JB017043 　
Heterogeneities in stress and strength in Tohoku and its relationship with earthquake sequences triggered by the 2011 M9 Tohoku-Oki earthquake Invited Peer-reviewed

Keisuke Yoshida, Akira Hasegawa, Takeyoshi Yoshida, Toru Matsuzawa

Pure and Applied Geophysics　176　(3)　1335-1355　2019/03

DOI： 10.1007/s00024-018-2073-9 　

ISSN： 0033-4553

eISSN： 1420-9136
Complex microseismic activity and depth-dependent stress field changes in Wakayama, southwestern Japan Peer-reviewed

Sumire Maeda, Toru Matsuzawa, Shinji Toda, Keisuke Yoshida, Hiroshi Katao

Earth, Planets and Space　70　(1)　2018/12

DOI： 10.1186/s40623-018-0788-6 　

ISSN： 1880-5981

eISSN： 1880-5981
Shear Strain Energy Change Caused by the Interplate Coupling Along the Nankai Trough: An Integration Analysis Using Stress Tensor Inversion and Slip-Deficit Inversion Peer-reviewed

Tatsuhiko Saito, Akemi Noda, Keisuke Yoshida, Sachiko Tanaka

Journal of Geophysical Research: Solid Earth　123　(7)　5975-5986　2018/07

DOI： 10.1029/2018JB015839 　

ISSN： 2169-9313

eISSN： 2169-9356
Hypocenter Migration and Seismicity Pattern Change in the Yamagata-Fukushima Border, NE Japan, Caused by Fluid Movement and Pore Pressure Variation Peer-reviewed

Keisuke Yoshida, Akira Hasegawa

Journal of Geophysical Research: Solid Earth　123　(6)　5000　2018/06
Publisher: American Geophysical Union ({AGU})
DOI： 10.1029/2018JB015468 　

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Sendai-Okura earthquake swarm induced by the 2011 Tohoku-Oki earthquake in the stress shadow of NE Japan: Detailed fault structure and hypocenter migration Peer-reviewed

Keisuke Yoshida, Akira Hasegawa

Tectonophysics　733　132-147　2018/05/09
Publisher: Elsevier B.V.
DOI： 10.1016/j.tecto.2017.12.031 　

ISSN： 0040-1951
Temporal Changes in Stress Drop, Frictional Strength, and Earthquake Size Distribution in the 2011 Yamagata-Fukushima, NE Japan, Earthquake Swarm, Caused by Fluid Migration Peer-reviewed

Keisuke Yoshida, Tatsuhiko Saito, Yumi Urata, Youichi Asano, Akira Hasegawa

Journal of Geophysical Research: Solid Earth　122　(12)　10-397　2017/12/01
Publisher: Blackwell Publishing Ltd
DOI： 10.1002/2017JB014334 　

ISSN： 2169-9356 2169-9313
Real-Time Earthquake Monitoring during the Second Phase of the Deep Fault Drilling Project, Alpine Fault, New Zealand Peer-reviewed

Calum J. Chamberlain, Carolin M. Boese, Jennifer D. Eccles, Martha K. Savage, Laura-May Baratin, John Townend, Anton K. Gulley, Katrina M. Jacobs, Adrian Benson, Sam Taylor-Offord, Clifford Thurber, Bin Guo, Tomomi Okada, Ryota Takagi, Keisuke Yoshida, Rupert Sutherland, Virginia G. Toy

SEISMOLOGICAL RESEARCH LETTERS　88　(6)　1443-1454　2017/11

DOI： 10.1785/0220170095 　

ISSN： 0895-0695

eISSN： 1938-2057
3-D dynamic rupture simulations of the 2016 Kumamoto, Japan, earthquake Peer-reviewed

Yumi Urata, Keisuke Yoshida, Eiichi Fukuyama, Hisahiko Kubo

EARTH PLANETS AND SPACE　69　(1)　150　2017/11

DOI： 10.1186/s40623-017-0733-0 　

ISSN： 1880-5981
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

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

Crustal Permeability　307-323　2016/10/31
Publisher: wiley
DOI： 10.1002/9781119166573.ch24 　
Stress rotations due to the M6.5 foreshock and M7.3 main shock in the 2016 Kumamoto, SW Japan, earthquake sequence Peer-reviewed

Keisuke Yoshida, Akira Hasegawa, Tatsuhiko Saito, Youichi Asano, Sachiko Tanaka, Kaoru Sawazaki, Yumi Urata, Eiichi Fukuyama

GEOPHYSICAL RESEARCH LETTERS　43　(19)　10097-10104　2016/10

DOI： 10.1002/2016GL070581 　

ISSN： 0094-8276

eISSN： 1944-8007
Temporal variation of frictional strength in an earthquake swarm in NE Japan caused by fluid migration Peer-reviewed

Keisuke Yoshida, Akira Hasegawa, Takeyoshi Yoshida

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH　121　(8)　5953-5965　2016/08

DOI： 10.1002/2016JB013022 　

ISSN： 2169-9313

eISSN： 2169-9356
Heterogeneous stress field in the source area of the 2003 M6.4 Northern Miyagi Prefecture, NE Japan, earthquake Peer-reviewed

Keisuke Yoshida, Akira Hasegawa, Tomomi Okada

GEOPHYSICAL JOURNAL INTERNATIONAL　206　(1)　408-419　2016/07

DOI： 10.1093/gji/ggw160 　

ISSN： 0956-540X

eISSN： 1365-246X
Heterogeneous stress state of island arc crust in northeastern Japan affected by hot mantle fingers Peer-reviewed

Bunichiro Shibazaki, Tomomi Okada, Jun Muto, Takumi Matsumoto, Takeyoshi Yoshida, Keisuke Yoshida

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH　121　(4)　3099-3117　2016/04

DOI： 10.1002/2015JB012664 　

ISSN： 2169-9313

eISSN： 2169-9356
Unusual stress rotations within the Philippines possibly caused by slip heterogeneity along the Philippine fault Peer-reviewed

Keisuke Yoshida, Nelson Pulido, Eiichi Fukuyama

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH　121　(3)　2020-2036　2016/03

DOI： 10.1002/2015JB012275 　

ISSN： 2169-9313

eISSN： 2169-9356
Preceding seismic activity and slow slip events in the source area of the 2011 Mw 9.0 Tohoku-Oki earthquake: a review Peer-reviewed

Akira Hasegawa, Keisuke Yoshida

Geoscience Letters　2　(1)　2015/12/01
Publisher: SpringerOpen
DOI： 10.1186/s40562-015-0025-0 　

ISSN： 2196-4092
Spatially heterogeneous stress field in the source area of the 2011 M-w 6.6 Fukushima-Hamadori earthquake, NE Japan, probably caused by static stress change Peer-reviewed

Keisuke Yoshida, Akira Hasegawa, Tomomi Okada

GEOPHYSICAL JOURNAL INTERNATIONAL　201　(2)　1062-1071　2015/05

DOI： 10.1093/gji/ggv068 　

ISSN： 0956-540X

eISSN： 1365-246X
Spatial variation of stress orientations in NE Japan revealed by dense seismic observations Peer-reviewed

Keisuke Yoshida, Akira Hasegawa, Tomomi Okada

TECTONOPHYSICS　647　63-72　2015/04

DOI： 10.1016/j.tecto.2015.02.013 　

ISSN： 0040-1951

eISSN： 1879-3266
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 Peer-reviewed

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, T. Matsushima, K. Goto, H. Miyamachi

GEOFLUIDS　15　(1-2)　293-309　2015/02

DOI： 10.1111/gfl.12112 　

ISSN： 1468-8115

eISSN： 1468-8123
Changes in the stress field after the 2008 M7.2 Iwate-Miyagi Nairiku earthquake in northeastern Japan Peer-reviewed

Keisuke Yoshida, Akira Hasegawa, Tomomi Okada, Takeshi Iinuma

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH　119　(12)　9016-9030　2014/12

DOI： 10.1002/2014JB011291 　

ISSN： 2169-9313

eISSN： 2169-9356
Pore pressure distribution in the focal region of the 2008 M7.2 Iwate-Miyagi Nairiku earthquake Peer-reviewed

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

EARTH PLANETS AND SPACE　66　(1)　59　2014/06

DOI： 10.1186/1880-5981-66-59 　

ISSN： 1880-5981
Stress fields in NE Japan before and after the 2011 Tohoku-oki Earthquake Peer-reviewed

Keisuke Yoshida, Akira Hasegawa, Tomomi Okada, Junnichi Nakajima, Takeshi Iinuma, Yoshihiro Ito, Youichi Asano

Proceedings of the 11th SEGJ International Symposium　2013/11
Publisher: Society of Exploration Geophysicists
DOI： 10.1190/segj112013-126 　

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An intraslab seismic sequence activated by the 2011 Tohoku-oki earthquake: Evidence for fluid-related embrittlement Peer-reviewed

Junichi Nakajima, Keisuke Yoshida, Akira Hasegawa

Journal of Geophysical Research: Solid Earth　118　(7)　3492-3505　2013/07/01
Publisher: Blackwell Publishing Ltd
DOI： 10.1002/jgrb.50246 　

ISSN： 2169-9356 2169-9313
Change in stress field after the 2011 great Tohoku-Oki earthquake Peer-reviewed

Akira Hasegawa, Keisuke Yoshida, Youichi Asano, Tomomi Okada, Takeshi Iinuma, Yoshihiro Ito

EARTH AND PLANETARY SCIENCE LETTERS　355　231-243　2012/11

DOI： 10.1016/j.epsl.2012.08.042 　

ISSN： 0012-821X

eISSN： 1385-013X
Stress before and after the 2011 great Tohoku-oki earthquake and induced earthquakes in inland areas of eastern Japan Peer-reviewed

Keisuke Yoshida, Akira Hasegawa, Tomomi Okada, Takeshi Iinuma, Yoshihiro Ito, Youichi Asano

GEOPHYSICAL RESEARCH LETTERS　39　L03302　2012/02

DOI： 10.1029/2011GL049729 　

ISSN： 0094-8276

eISSN： 1944-8007
Nearly complete stress drop in the 2011 M-w 9.0 off the Pacific coast of Tohoku Earthquake Peer-reviewed

Akira Hasegawa, Keisuke Yoshida, Tomomi Okada

EARTH PLANETS AND SPACE　63　(7)　703-707　2011

DOI： 10.5047/eps.2011.06.007 　

ISSN： 1343-8832
Shallow inland earthquakes in NE Japan possibly triggered by the 2011 off the Pacific coast of Tohoku Earthquake Peer-reviewed

Tomomi Okada, Keisuke Yoshida, Sadato Ueki, Junichi Nakajima, Naoki Uchida, Toru Matsuzawa, Norihito Umino, Akira Hasegawa

EARTH PLANETS AND SPACE　63　(7)　749-754　2011

DOI： 10.5047/eps.2011.06.027 　

ISSN： 1343-8832

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Misc. 11

Relocated Hypocenters and Repeating Earthquake Candidates Around the 2003 Mw 7.0 Miyagi-Oki Intraslab Earthquake and Overlying Plate Boundary

Keisuke Yoshida

Zenodo　2025/06
Joint Inversion Results and InSAR data for the 2011 and 2016 Mw5.9 Northern Ibaraki Earthquakes

Yoshida, Keisuke, Fukushima, Yo, Kaneko, Yoshihiro

Zenodo　2025/01

DOI： 10.5281/zenodo.14772367 　
Relocated Earthquake Catalog near the Hypocenter of the 2024 Mw7.5 Noto Peninsula, Japan, Earthquake (from March 2003 to March 2024)

Yoshida, Keisuke, Takagi, Ryota, Fukushima, Yo, Ando, Ryosuke, Ohta, Yusaku, Hiramatsu, Yoshihiro

Zenodo　2024/07

DOI： 10.5281/zenodo.12799165 　
Hypocenters, Focal Mechanisms, and Radiated Energy of Small Earthquakes in Northern Ibaraki Prefecture, Japan

Yoshida, Keisuke, Emoto, Kentaro, Takemura, Shunsuke, Matsuzawa, Toru

Zenodo　2024/06

DOI： 10.5281/zenodo.11626607 　
Earthquake Data for the 2023 Mw6.2 Suzu Earthquake in the Northeastern Noto Peninsula, Japan

Yoshida, Keisuke, Uchida, Naoki, Matsumoto, Yoshidki, Orimo, Masaki, Okada, Tomomi, Hirahara, Satoshi, Kimura, Shuutoku, Hino, Ryota

Zenodo　2023/10

DOI： 10.5281/zenodo.10019859 　
Fault-valve behavior estimated from intensive foreshocks and aftershocks of the 2017 M 5.3 Kagoshima Bay earthquake sequence, Kyushu, southern Japan

Yoshiaki Matsumoto, Keisuke Yoshida, Toru Matsuzawa, Akira Hasegawa

Zenodo　2021/04

DOI： 10.5281/zenodo.4702524 　
2011 年東北地方太平洋沖地震の誘発地震の解析に基づく地震の発生機構の研究 Invited

吉田圭佑

東日本大震災発災 10 年事業「若手研究者からの報告」　2021/03
Data for: 2019 M6.7 Yamagata-Oki earthquake in the stress shadow of 2011 Tohoku-Oki earthquake: Was it caused by the reduction in fault strength?

Keisuke Yoshida

Zenodo　2020/04

DOI： 10.17632/d48gyz4zts.1 　
近年の地震観測により得られた東北日本の応力場の空間不均質性と，その偏差応力・断層強度状態・地震発生機構への示唆 Invited

吉田圭佑

地震予知連絡会会報　103　335-338　2020/03
地震を生じさせる2つの要因ー2011年東北地方太平洋沖地震による誘発地震活動ー Invited

吉田圭佑

なゐふる　114　2-3　2018/07
臨時地震観測データを用いて推定した東北日本の応力場 Invited

吉田圭佑

地震予知連絡会会報　92　436-438　2014/09

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Presentations 139

Predictable and Unpredictable Aspects of Earthquakes from P-wave Onsets: Vigorous Ruptures Finish Quickly

Satoshi Ide, Keisuke Yoshida

JpGU 2025 Annual meeting　2025/05/26
小地震の断層破壊過程とモーメントマグニチュードとローカルマグニチュードの系統的乖離の関係

織茂雅希, 吉田圭佑, 松澤暢, 長谷川昭, 山本希

日本地球惑星科学連合2025年大会　2025/05/29
Abrupt Change in Stress Field Near the Deep Plate Interface: Investigation Using Short-Period Moment Tensor Inversion

Keisuke Yoshida

JpGU 2025 Annual meeting　2025/05/26
Distinct Patterns in Earthquake Occurrence along the Megathrust and within the Slab: Implications for False Detection of Repeaters

Keisuke Yoshida

JpGU 2025 Annual meeting　2025/05/30
Deconvolution Approach to Estimate Radiation Process of Large (Mw7.0-9.0) Earthquakes

Keisuke Yoshida

JpGU 2025 Annual meeting　2025/05/30
Source Characterization of Complex Earthquakes via Subevent Decomposition: Application to Apparent-repeating Earthquakes

Keisuke Yoshida

Seismological Society of America 2025 Annual Meeting　2025/04/16
The 2024 Mw7.5 Noto Peninsula Earthquake and Recent Earthquake Swarms in Japan Triggered by the Upward Migration of Deep Crustal Fluids Invited

Keisuke Yoshida

Seismological Society of America 2025 Annual Meeting　2025/04/15
Earthquake Swarms in Japan Triggered by Upward Fluid Migration following the 2011 M9 Tohoku Earthquake and the 2024 Mw7.5 Noto Peninsula Earthquake International-presentation Invited

Keisuke Yoshida

International Workshop on: Swarm-like Seismicity …What We Know, What We Don’t Know, and What We Need to Learn　2024/10/24
Relationship between Final Size Diversity and Initial Rupture Process in Earthquake Cycles International-presentation

Keisuke Yoshida, Satoshi Ide

EARTHQUAKES: nucleation, triggering, rupture, and relationships to aseismic processes – 4th edition　2024/10/14
東北地方の上部地殻におけるS波偏向異方性の起因推定（３）

藤村遼太郎, 岡田知己, 水田達也, Savage Martha, 高木涼太, 吉田圭佑, 酒井慎一, 勝俣啓, 大園真子, 小菅正裕, 前田拓人, 山中佳子, 片尾浩, 松島健, 八木原寛, 田上綾香, 木村洲徳, 平原聡, 河野俊夫, 松澤暢

日本地震学会2024年度秋季大会　2024/10/21
S-netデータを用いた精密震源決定による2021年M6.0茨城県沖地震の前震活動の時空間分布

松本圭晶, 吉田圭佑, 内田直希, 日野亮太

日本地震学会2024年度秋季大会　2024/10/21
動的破壊シミュレーションが明らかにした2024年能登半島地震の滑り及び地殻変動分布における非平面断層形状の効果

安藤亮輔, 福島洋, 吉田圭佑, 今西和利

日本地震学会2024年度秋季大会　2024/10/21
稠密GNSS観測網に基づく2024年能登半島地震のすべり分布および断層幾何の網羅的評価

山田太介, 太田雄策, 西村卓也, 平松良浩, 木下陽平, 吉田圭佑

日本地震学会2024年度秋季大会　2024/10/21
稠密測地観測にもとづく2024年能登半島地震の地震時すべり分布と断層幾何の定量評価

山田太介, 太田雄策, 西村卓也, 平松良浩, 木下陽平, 吉田圭佑

日本測地学会第１４２回講演会　2024/10
Initial and Total Rupture Processes of Earthquakes: Re-considering P-wave First Motions

Satoshi Ide, Keisuke Yoshida

International Joint Workshop on Slow-to-Fast Earthquakes　2024/09/17
Initial Rupture Momentum Diversify Final Size in Earthquake Cycles International-presentation

Keisuke Yoshida, Satoshi Ide

International Joint Workshop on Slow-to-Fast Earthquakes 2024　2024/09/17
Rupture Initiation of the 2024 Mw7.5 Noto Peninsula, Japan, Earthquake that Occurred within a Complex Fault Network International-presentation

Keisuke Yoshida

International Joint Workshop on Slow-to-Fast Earthquakes 2024　2024/09/18
Extreme coseismic uplift and faulting complexity during the January 1, 2024, Mw 7.5 Noto Peninsula earthquake

Chi-Hsien Tang, Yo Fukushima, Shinji Toda, Keisuke Yoshida, Naoya Takahashi, Takayuki Takahashi

JpGU 2024 Annual meeting　2024/05/31
Relationship between the preceding earthquake swarm and the 2024 Mw7.5 Noto Peninsula earthquake inferred from a detailed three-dimensional S-wave velocity structure

Ryota Takagi, Keisuke Yoshida, Tomomi Okada

JpGU 2024 annual meeting　2024/05/28
Evaluation of favorable to slip of the fault – in the case of the 2024 Noto Peninsula Earthquake

Ayaka Tagami1, Tomomi Okada1, Martha K Savage2, Toru Matsuzawa1, Ryotaro Fujimura1, Kazuya Tateiwa1, Keisuke Yoshida1, Shuutoku Kimura1, Satoshi Hirahara1, Ryota [Ayaka Tagami, Tomomi Okada, Martha K Savage, Toru Matsuzawa, Ryotaro Fujimura, Kazuya Tateiwa, Keisuke Yoshida, Shuutoku Kimura, Satoshi Hirahara, Ryota Takagi, Taisuke Yamada, Yusaku Ohta

JpGU 2024 annual meeting　2024/05/28
Hypocenter determination using S-net data of shallow earthquakes off Fukushima and Ibaraki prefectures, Japan Invited

Yoshiaki Matsumoto, Keisuke Yoshida, Naoki Uchida, Tatsuya Kubota, Ryota Hino, Toru Matsuzawa

JpGU 2024 Annual meeting　2024/05/27
Spatio-temporal variation of the aftershock activity following the 2021 and 2022 intraslab earquakes in off-Fukushima prefecture

Ryo Osawa, Keisuke Yoshida, Ryota Hino

JpGU 2024 Annual meeting　2024/05/26
Resolve the source process of repeating earthquakes Invited

Keisuke Yoshida

JpGU 2024 annual meeting　2024/05/26
Masaki Orimo, Keisuke Yoshida, Akira Hasegawa, Mare Yamamoto, Toru Matsuzawa

Systematic changes, in, seismic radiated energy in the foreshock activities o, Kumamoto earthquake

JpGU 2024 annual meeting　2024/05/26
Intersource-Distance Dependence of Seismic Waveform Similarity and Validity of Repeating Earthquake Detection

Keisuke Yoshida

JpGU 2024 annual meeting　2024/05/28
Generation Process of the 2024 Mw7.5 Noto Peninsula earthquake Inferred from Microearthquake Migration that Continued for a Few Years on the Fault

Keisuke Yoshida, Ryota Takagi, Yo Fukushima, Ryosuke Ando, Yusaku Ohta, Naoki Uchida, Satoshi Hirahara, Shuutoku Kimura, Tomomi Okada, Ryota Hino, Shin'ichi Sakai, Yoshihiro Hiramatsu, Satoshi Matsumoto

JpGU 2024 annual meeting　2024/05/28
Recent crustal earthquakes in Japan related to fluid movement Invited

Keisuke Yoshida

JpGU 2024 Annual meeting　2024/05/29
On the causality of fluid for the series of earthquakes in Noto peninsula

Takaaki Kawahito, Yusuke Mukuhira, Keisuke Yoshida, Masaoki Uno, Takatoshi Ito

JpGU 2024 Annual meeting　2024/05/26
Relationship between the coseismic slip distribution and its assumed fault geometry in the 2024 Noto Peninsula earthquake derived from very dense geodetic observation data

Taisuke Yamada, Yusaku Ohta, Takuya NISHIMURA, Yoshihiro Hiramatsu, Yohei Kinoshita, Keisuke Yoshida

JpGU 2024 annual meeting　2024/05/28
Landscape changes caused by the 2024 Noto peninsula earthquake and its relation to the long-term landscape evolution

Ayaka Tagami1, Tomomi Okada1, Martha K Savage2, Toru Matsuzawa1, Ryotaro Fujimura1, Kazuya Tateiwa1, Keisuke Yoshida1, Shuutoku Kimura1, Satoshi Hirahara1, Ryota [Ayaka Tagami, Tomomi Okada, Martha K Savage, Toru Matsuzawa, Ryotaro Fujimura, Kazuya Tateiwa, Keisuke Yoshida, Shuutoku Kimura, Satoshi Hirahara, Ryota Takagi, Taisuke Yamada, Yusaku Ohta

JpGU 2024 annual meeting　2024/05/28
Spatial variation in the origin of S-wave polarization anisotropy in the upper crust of the Tohoku region, NE Japan.

Ryotaro Fujimura, Tomomi Okada, Tatsuya Mizuta, Savage Martha, Ryota Takagi, Keisuke Yoshida, Shinichi Sakai, Kei Katsumata, Mako Ohzono, Masahiro Kosuga, Takuto Maeda, Yoshiko Yamanaka, Hiroshi Katao, Takeshi Matsushima, Hiroshi Yakiwara, Shuutoku Kimura, Satoshi Hirahara, Toshio Kono, Toru Matsuzawa, Ayaka Tagami

JpGU 2024 annual meeting　2024/05/30
Shear wave splitting and seismic velocity structure in the focal area of the 2024 M7.6 Noto Peninsula earthquake, central Japan

Tomomi Okada, Martha Savage, Ryota Takagi, Keisuke Yoshida, Satoshi Matsumoto, Kentaro Emoto, Yoshiko Yamanaka, Kei Katsumata, Takuto Maeda, Motoko Ishise, Shinichi Sakai, Masatoshi Miyazawa, Toshiko Terakawa, Mako Ohzono, Hiroshi Yakiwara, Kazutoshi Imanishi, Naoki Uchida, Ayaka Tagami, Ryotaro Fujimura, Satoshi Hirahara, Shuutoku Kimura, Takuo Shibutani, Hiroyuki Noda, Tomoaki Nishikawa, Airi Nagaoka, Yuki Funabiki, Yoshihiro Hiramatsu

JpGU 2024 annual meeting　2024/05/28
Effects of the 3D fault geometry, regional stresses and earthquake history on the 2024 Noto Peninsula earthquake: Insight from dynamic rupture simulations

Ryosuke Ando, Yo Fukushima, Keisuke Yoshida, Kazutoshi Imanishi

JpGU 2024 Annual meeting　2024/05/28
A clearer view of seismicity offshore NE Japan through deep-learning-based analysis of S-net data: evidence for the role of forearc fluids in interplate coupling

Naoki Uchida, Rintaro Suzuki, Weiqiang Zhu, Gregory Beroza, Takashi NAKAYAMA, Genti Toyokuni, Ryota Takagi, Ryosuke Azuma, Keisuke Yoshida, Akira Hasegawa

JpGU 2024 Annual meeting　2024/05/28
The 2024 Mw7.5 Noto Peninsula, Japan, Earthquake initiated in Fluid-Driven Swarm Activity International-presentation Invited

Keisuke Yoshida

Seismological Society of America 2024 Annual Meeting　2024/05/03
地震波放射エネルギーに基づいた 2016 年熊本地震の前駆的地震活動の評価: 間隙水圧と載荷速度変化の影響

織茂雅希, 吉田圭佑, 松澤暢, 長谷川昭

日本地震学会2023年度秋季大会　2023/11/02
Spatial Variation of Stress Field around Turkey Estimated from Earthquake Focal Mechanisms and the 2023 Mw7.8 and Mw7.7 earthquakes

Keisuke Yoshida

SSJ 2023 Fall Meeting　2023/10/31
The 2023 M6.5 Suzu, Japan, Earthquake that occurred during a Fluid-Induced Swarm Activity

Keisuke Yoshida

SSJ 2023 annual meeting　2023/11/01
2016年に福島-茨城沖で発生したMw7.0の正断層型地震周辺における高精度震源決定: S-netデータを用いた解析

松本圭晶, 吉田圭佑, 内田直希, 久保田達矢, 松澤暢

日本地震学会2023年度秋季大会　2023/11/01
Double-difference relocation of a large number of events: toward real-time monitoring

Keisuke Yoshida, Yoshiaki Matsumoto, Masaki Orimo

JpGU Meeting 2023　2023/05
Moment-rate functions of repeating earthquakes of varying magnitude and surrounding earthquake distribution

Keisuke Yoshida

JpGU Meeting 2023　2023/05
Near-field Waveform Modeling and Source Characterization of Small Earthquakes in Northern Ibaraki Prefecture

Keisuke Yoshida, Kentaro Emoto, Shunsuke Takemura, Toru Matsuzawa

JpGU Meeting 2023　2023/05
Possibility of shallow repeating aseismic slip associated with the 2011 Mw5.8 and 2016 Mw5.9 crustal earthquakes in northern Ibaraki Prefecture, Japan

Keisuke Yoshida, Yo Fukushima

JpGU Meeting 2023　2023/05
2008年岩手・宮城内陸地震震源域周辺の通常地震および低周波地震の震源スペクトルと地震波放射エネルギー

織茂雅希, 吉田圭佑, 松澤暢, 平貴昭, 江本賢太郎, 長谷川昭

日本地震学会2022年度秋季大会　2022/10/25
石川県能登半島北東部の群発地震：マグマ活動に起因する構造と流体供給

2022/10/25
同一アスペリティで発生する地震破壊の多様性と共通点： 2015年宮城沖の Mw6.8地震と Mw6.0-6.4の準繰り返し地震

吉田圭佑

日本地震学会2022年度秋季大会　2022/10/24
東北沖地震後に福島-茨城沖で多発している正断層型地震の震源分布・断層構造: sP depth-phase を用いた推定

松本圭晶, 吉田圭佑, 豊国源知, 松澤暢

日本地震学会2022年度秋季大会　2022/10/15
石川県能登半島群発地震震源域におけるS波スプリッティングと地震波速度構造

岡田知己, Savage Martha, 酒井慎一, 吉田圭佑, 内田直希, 髙木涼太, 木村洲徳, 平原聡, 松澤暢

日本地震学会2022年度秋季大会　2022/10/14
What controls earthquake rupture complexity?: implications from the comparison of the rupture process of repeating earthquakes and other earthquakes.

Keisuke Yoshida, Naoki Uchida

JpGU Meeting 2022　2022/05/29
S波スプリッティング解析による東北地方の地震波速度異方性測定（５）

水田達也, 岡田知己, Savage Martha, 高木涼太, 吉田圭佑, 酒井慎一, 勝俣啓, 大園真子, 小菅正裕, 前田拓人, 山中佳子, 片尾浩, 松島健, 八木原寛, 中山貴史, 平原聡, 河野俊夫, 松澤暢, 年東北地方太平洋沖地震, 緊急観測グループ

日本地球惑星科学連合2022年大会　2022/05/27
2008年岩手・宮城内陸地震震源域周辺の通常地震と深部低周波地震の震源スペクトルと地震波放射エネルギー: 類似点と相違点

織茂雅希, 吉田圭佑, 平貴昭, 江本賢太郎, 松澤暢, 長谷川昭

日本地球惑星科学連合2022年大会　2022/05/25
The 2021 Mw7.0 and Mw6.7 Miyagi-Oki earthquakes, northeastern Japan, nucleated at a seismic/aseismic transition zone in the postseismic period of the 2011 M9 Tohoku earthquake

Keisuke Yoshida, Toru Matsuzawa, Naoki Uchida

Japan Geoscience Union Meeting 2022　2022/05/24
Rupture complexity of Mw3-7 earthquakes in Japan and its appearance in the time and frequency domains Invited

Keisuke Yoshida

Japan Geoscience Union Meeting 2022　2022/05/23
Time-domain Source Parameter Estimation of Mw3-7 Earthquakes in Japan

Yoshida Keisuke, Kanamori Hiroo

Seismological Society of America 2022　2022/04/20
2011年東北沖地震後から福島-茨城県境周辺で活発化した地震活動に見られる内陸の繰り返し地震とその原因

池田里奈, 吉田圭佑, 高橋諒, 福島洋, 松澤暢, 長谷川昭

日本地震学会2021年秋季大会　2021/10/15
Radiated energy and source complexity of small earthquakes estimated from a large source time function data base in Japan

Keisuke Yoshida, Hiroo Kanamori

SSJ fall meeting 2021　2021/10/14
Initiation of the M~9 earthquake cycle: the 2021 Miyagi-Oki Mw7.0 earthquake at the deep seismic/aseismic transition

Keisuke Yoshida, Toru Matsuzawa, Naoki Uchida

SSJ fall meeting 2021　2021/10/14
地震学分野におけるブラックボックス最適化問題へのベイズ最適化の適用：セントロイドモーメントテンソルインバージョンでの例

久保久彦, 吉田圭佑, 木村武志

日本地震学会2021年秋季大会　2021/10/14
S波スプリッティング解析による東北地方の地震波速度異方性測定（４）

水田達也, 岡田知己, Savage Martha, 高木涼太, 吉田圭佑, 酒井慎一, 勝俣啓, 大園真子, 小菅正裕, 前田拓人, 山中佳子, 片尾浩, 松島健, 八木原寛, 中山貴史, 平原聡, 河野俊夫, 松澤暢, 年東北地方太平洋, 沖地震, 緊急観測グループ

日本地球惑星科学連合2021年大会　2021/10/14
日本列島内陸域の通常地震と低周波地震の震源スペクトルの形状の推定

織茂雅希, 吉田圭佑, 平貴昭, 松澤暢, 長谷川昭, 江本賢太郎

日本地震学会2021年度秋季大会　2021/10/14
Prevailing updip ruptures in small interplate earthquakes along the Japan Trench revealed from land-based;offshore observations

Keisuke Yoshida, Naoki Uchida, Hisahiko Kubo, Ryota Takagi, Shiqing Xu

Japan Geoscience Union Meeting 2021　2021/05
Measurement of seismic velocity anisotropy in the Tohoku region, NE Japan by shear wave splitting analysis (3)

Tatsuya Mizuta, Tomomi Okada, Martha Savage, Ryota Takagi, Keisuke Yoshida, Shin'ichi Sakai, Mako Ohzono, Masahiro Kosuga, Yoshiko Yamanaka, Hiroshi Katao, Takeshi Matsushima, Hiroshi Yakiwara, Takashi NAKAYAMA, Satoshi Hirahara, Toshio Kono, Toru Matsuzawa, Group for, the aftershock observations of th, off the Pacific coast, of, Tohoku Earthquake

Japan Geoscience Union Meeting 2021　2021/05
Comparison of the spectral characteristics of deep low-frequency earthquakes with regular earthquakes around the Gifu-Nagano prefectural border

Masaki Orimo, Keisuke Yoshida, Taka'aki Taira, Toru Matsuzawa, Akira Hasegawa

Japan Geoscience Union Meeting 2021　2021/05
Improving the constraint of the 2016 Off-Fukushima shallow normal-faulting earthquake with the high-coverage tsunami data from the S-net wide network: implication on the crustal stress in the overriding plate

Tatsuya Kubota, Hisahiko Kubo, Naotaka Yamamoto Chikasada, Keisuke Yoshida, Wataru Suzuki, Takeshi Nakamura

Japan Geoscience Union Meeting 2021　2021/05
Intraplate repeating earthquakes in the Fukushima-Ibaraki border region following the 2011 Tohoku-Oki earthquake

Rina Ikeda, Keisuke Yoshida, Ryo Takahashi, Toru MAtsuzawa, Akira Hasegawa

Japan Geoscience Union Meeting 2021　2021/05
Aseismic process driving the earthquake swarm, revealed by the dense seismic observation

Yohei Yukutake, Keisuke Yoshida, Ryo Honda

Japan Geoscience Union Meeting 2021　2021/05
Inverse analysis of seismic swarm induced by slab-derived fluids

Yusuke Mukuhira, Masaoki Uno, Keisuke Yoshida

Japan Geoscience Union Meeting 2021　2021/05
Systematic examination of rupture directivities of small earthquakes offshore eastern Japan from 2003 to 2021

Keisuke Yoshida

Japan Geoscience Union Meeting 2021　2021/05
Low-frequency earthquakes in close vicinity of repeating earthquakes in the brittle upper crust of Hakodate, Hokkaido, northern Japan Invited

Keisuke Yoshida, Akira Hasegawa, Shinako Noguchi, Keiji Kasahara

Keisuke Yoshida, Akira Hasegawa, Shinako Noguchi, Keiji Kasahara　2021/05
Simultaneous estimation of stress drop and rupture directivity of small earthquakes in Japan: prevalence of asymmetrical rupture leads to systematic estimation error of stress

Keisuke Yoshida

AGU fall meeting 2020　2020/12
Detection of Temporal Change in Seismic Attenuation near Earthquake Source during Intense Fluid-Driven Seismicity following 2011 Tohoku-Oki earthquake

吉田圭佑

日本地震学会2020年秋季大会　2020/10/30
2011年東北地方太平洋沖地震後の地震活動の活発化と剪断ひずみエネルギー変化

田中佐千子, 齊藤竜彦, 野田朱美, 吉田圭佑

日本地震学会2020年秋季大会　2020/10/30
2011年東北沖地震後から福島-茨城県境周辺で活発化した地震活動に見られる内陸の繰り返し地震

2020/10/30

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自然地震データに基づく応力と断層強度に関する研究 Invited

吉田圭佑

日本地震学会2020年秋季大会　2020/10/29
小中地震の破壊伝播指向性を考慮した応力降下量の推定;福島-茨城県境の地震活動への適用

池田里奈, 吉田圭佑, 髙橋諒, 松澤暢, 長谷川昭

JpGU-AGU Joint Meeting 2020　2020/07
東北地方太平洋沖で発生した小中地震の破壊伝播指向性と応力降下量： S-netを用いた解析

吉田圭佑, 高木涼太, 内田直希, 池田里奈

JpGU-AGU Joint Meeting 2020　2020/07
流体圧変化に同期した震源近傍の Qの時間変化: 山形-福島県境の群発地震活動の例

吉田圭佑

JpGU-AGU Joint Meeting 2020　2020/07
A systematic investigation of rupture directivity, stress drop, fault geometry, and radiation efficiency of small inland earthquakes in Japan

Keisuke Yoshida

JpGU-AGU Joint Meeting 2020　2020/07
鹿児島湾の M 5.3 の地震の前駆的活動及び余震活動の背後にある非地震過程の可能性

松本圭晶, 吉田圭佑, 松澤暢, 長谷川昭

日本地震学会2019年秋季大会　2019/09
地震学的データを用いた応力インバージョン手法の比較

深畑幸俊, 岩田貴樹, 吉田圭佑

日本地震学会2019年秋季大会　2019/09
Stress release process ongoing along a crustal fault examined through the foreshock-mainshock-aftershock sequence of the 2017 M5.2 Akita-Daisen, NE Japan, earthquake

Keisuke Yoshida, Tatsuhiko Saito, Taka’aki Taira, Kentaro Emoto, Toru Matsuzawa

日本地震学会2019年秋季大会　2019/09
2019年山形沖 M6.7地震の余震の詳細な震源分布とその時空間発展

吉田圭佑, 平原聡, 中山貴史, 内田直希, 岡田知己, 松澤暢

日本地震学会2019年秋季大会　2019/09
2011年東北沖地震後の流体圧変化に伴う内陸の群発地震震源域近傍の速度構造の時間変化

吉田圭佑, 長谷川昭, 行竹洋平, 松澤暢

日本地震学会2019年秋季大会　2019/09
鹿児島湾で発生した M 5.3 の地震の前駆的活動及び余震活動にみられる震源 migration とその背後の非地震的過程,

松本圭晶, 吉田圭佑, 松澤暢, 長谷川昭

日本地球惑星科学連合2019年大会　2019/05
・

2019/05
2011年東北沖地震後に活発化した茨城県北部の地震活動：内陸地震の繰り返し

高橋諒, 吉田圭佑, 長谷川昭, 松澤暢

日本地球惑星科学連合2019年大会,　2019/05
北海道函館周辺の深部低周波地震と内陸の繰り返し地震,

吉田圭佑, 長谷川昭, 野口科子, 笠原敬司

日本地球惑星科学連合2019年大会　2019/05
Estimation of rupture directivity, fault planes, and stress drop of small- and moderate-sized earthquakes

2019/05
Earthquake Activities Induced by the 2011 Tohoku-Oki Earthquake Related to the Heterogeneities in Stress and Strength in the Tohoku District

Yoshida, K, A. Hasegawa, T. Yoshida, T. Matsuzawa

International Symposium Crustal Dynamics (ISCD-2): Toward Integrated View of Island Arc Seismogenesis　2019/03
Heterogeneities in Stress and Strength in Tohoku and its Relationship with Earthquake Sequences Triggered by the 2011 M9 Tohoku-Oki Earthquake Invited

Keisuke Yoshida

AOGS　2019
Hypocenter migration and its cause in the precursory activity and aftershocks of the 2017 M 5.3 Kagoshima Bay earthquake International-presentation

Matsumoto, Y, Yoshida, K, Matsuzawa, T, Hasegawa, A

AGU Fall Meeting 2018　2018/12
Source process, rupture directivity, and stress drop of the 2018 M5.2 Southern Akita earthquake, and its implication to deviatoric stress in Tohoku

YOSHIDA Keisuke, Tatsuhiko Saito, Kentaro Emoto, Toru Matsuzawa

SSJ annual meeting　2018/10/11
Simulation of the migration swarms triggered after the 2011 Tohoku-Oki earthquake due to the pore pressure change

YOSHIDA Keisuke, Hiroyuki Noda, Bunichiro Shibazaki, Masao Nakatani

SSJ annual meeting　2018/10/10
Detailed hypocenter distribution and fault structure in the 2017 M 5.3 Kagoshima Bay earthquake sequence

Matsumoto, Y, Yoshida, K, Matsuzawa, T, Hasegawa, A

SSJ annual meeting　2018/10
Rupture directivities of small- and moderate-sized earthquakes in the Yamagata-Fukushima swarm triggered by the fluid migration after the 2011 Tohoku-Oki earthquake International-presentation

YOSHIDA Keisuke, Tatsuhiko Saito, Kentaro Emoto

10th ACES International Workshop　2018/09/26
Hypocenter migration and its cause in the precursory activity and aftershocks of the 2017 M 5.3 Kagoshima Bay earthquake, Kyusyu, SW Japan International-presentation

Matsumoto, Y, Yoshida, K, Matsuzawa, T, Hasegawa, A

10th ACES International Workshop　2018/09/25
A detailed view of the earthquake swarms triggered by the pore pressure change after the 2011 Tohoku-Oki earthquake: Rupture directivity and frictional strength variation on faults

YOSHIDA Keisuke, Tatsuhiko Saito, Kentaro Emoto

JpGU annual Meeting　2018/05/22
A detailed hypocenter distribution along the upper boundary of the Philippine Sea plate beneath Kanto and its implications for the cause of repeating earthquakes

YOSHIDA Keisuke, Akira Hasegawa

JpGU annual Meeting　2018/05/20
Detailed hypocenter distribution and fault structure in the 2017 M 5.3 Kagoshima Bay earthquake sequence

Matsumoto, Y, Yoshida, K, Matsuzawa, T, Hasegawa, A

JpGU annual meeting　2018/05
Details of hypocenter migration of aftershocks of the 2011 Tohoku-Oki earthquake caused in the stress shadow probably due to the fluid pressure change International-presentation Invited

YOSHIDA Keisuke

Workshop: Frontiers in Studies of Earthquakes and Faults　2017/11/29
東北沖地震に stress shadowで誘発された群発地震活動の発生機構

SSJ fall meeting　2017/10/25
Details of hypocenter migration in the Yamagata-Fukushima border earthquake swarm probably caused by fluid pressure change after the 2011 Tohoku-Oki earthquake International-presentation Invited

Keisuke Yoshida, Akira Hasegawa

JpGU-AGU Joint Meeting　2017/05/20

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2011年東北沖地震で誘発された仙台大倉ダム周辺の群発地震活動－詳細な震源分布と微細断層構 International-presentation

吉田圭佑, 長谷川昭

JpGU-AGU Joint Meeting　2017/05/20

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Heterogeneities of Stress and Strength and its Relationship With Induced Seismic Activities Associated With the Tohoku-Oki Earthquake International-presentation Invited

Keisuke Yoshida, Akira Hasegawa, Toru Matsuzawa

SSA 2017 Annual Meeting　2017/04/18

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東北沖地震で誘発された山形-福島県境群発地震の震源域における応力降下量および b値の時間変化と摩擦強度

吉田圭佑, 齊藤竜彦, 浅野陽一, 長谷川昭

SSJ fall meeting　2016/10/05

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S-wave anisotropy in the crust of east Japan before and after the 2011 Tohoku-oki earthquake International-presentation

Keisuke Yoshida, Akira Hasegawa, Tomomi Okada, Junnichi Nakajima, Group for Aftershock Observations of the, Tohoku-Oki Earthquake

International Symposium Crustal Dynamics 2016　2016/07/19

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Stress and Strength Heterogeneities and its Relationship With Induced Seismic Activities Associated With the Tohoku-Oki Earthquake International-presentation

Keisuke Yoshida, Akira Hasegawa, Toru Matsuzawa

International Symposium Crustal Dynamics 2016　2016/07/19

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東北日本の応力不均質と2011年東北沖地震による誘発地震活動

吉田圭佑, 長谷川昭, 松澤暢

JpGU annual meeting　2016/05/20

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中央構造線の活動のモデル化に向けた西南日本の応力方向の詳細な空間分布の推定

吉田圭佑, 福山英一

JpGU annual meeting　2016/05/20

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2016年熊本地震震源域周辺の応力場

吉田圭佑, 長谷川昭, 齋藤竜彦, 浅野陽一, 田中佐千子, 澤崎郁, 浦田優美, 福山英一

JpGU annual meeting　2016/05/20

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Spatially heterogeneous stress orientation in the Philippines caused by the slip heterogeneity along the Philippine fault International-presentation

K. Yoshida, P. Nelson, E. Fukuyama

AGU fall meeting　2015/12/14

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2015 年5 月30 日に小笠原西方沖で発生したMw8.5 の深発地震周辺域のメカニズム解の推定

吉田圭佑, 福山英一

SSJ fall meeting　2015/10/26

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2011 年東北沖地震後に福島- 山形県境で多発する誘発地震活動に見られるメカニズム解の多様性と応力・摩擦強度の時空間発展

吉田圭佑, 長谷川昭

SSJ fall meeting　2015/10/26

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NIED国際地震観測網データを用いて推定したフィリピン地殻内応力場の空間変化: フィリピン断層の不均質すべりによる影響

吉田圭佑, ネルソン・プリード, 福山英一

JpGU annual meeting　2015/05/24

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稠密合同余震観測データを用いて推定した 2008年岩手・宮城内陸地震余震の応力降下量：断層強度との比較

吉田圭佑, 長谷川昭, 岡田知己, 内田直希

JpGU annual meeting　2015/05/24

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Second-Order Pattern of Stress in NE Japan Revealed by Dense Seismic Observation: Topography Effect and Its Implication for Absolute Stress State International-presentation

Keisuke Yoshida, Akira Hasegawa, Tomomi Okada

International Symposium on Geodesy for Earthquake and Natural Hazards　2014/07/22

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2011年福島県浜通りの地震震源域の応力場：静的応力変化に起因すると推定される顕著な空間不均質

吉田圭佑, 長谷川昭, 岡田知己

JpGU annual meeting　2014/04/28

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Stress fields in NE Japan before and after the 2011 Tohoku-oki Earthquake International-presentation

Keisuke Yoshida, Akira Hasegawa, Tomomi Okada, Junichi Nakajima, Yoshihiro Ito, Takeshi Iinuma, Youichi Asano, Group for the aftershock observations of th, off the Pacific coast, of, Tohoku Earthquake

the 11th SEGJ International Symposium　2013/11/18
臨時観測データを用いて推定した 2011年東北沖地震前後での東日本地殻内のS波偏向異方性構造

吉田圭佑, 長谷川昭, 岡田知己, 中島淳一, 年東北地方太平洋沖地震合同余震観測グループ

SSJ fall meeting　2013/10/07

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2008年岩手・宮城内陸地震震源域における応力場の顕著な空間不均質

吉田圭佑, 長谷川昭, 岡田知己, 飯沼卓史

SSJ fall meeting　2013/10/07

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臨時観測データを用いて推定した東北日本の応力場 - プレート収束と地形効果 -

吉田圭佑, 長谷川昭, 岡田知己

JpGU annual meeting　2013/05/19

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2011年東北地方太平洋沖地震に伴い応力場が変化した領域の広がりと応力・強度の推定

吉田圭佑, 長谷川昭, 岡田知己, 中島淳一, 伊藤喜宏, 佐藤忠弘, 浅野陽一, 飯沼卓史

JpGU annual meeting　2013/05/19

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Did stress field change after the 2011 Tohoku Did stress field change after the 2011 Tohoku-Oki earthquake in the inland areas of Tohoku-Oki earthquake in the inland areas of Tohoku? International-presentation

K. Yoshida, A. Hasegawa, T. Okada, Y. Ito, T. Iinuma, Y. Asano

AGU fall meeting　2012/12/03

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2011 年東北地方太平洋沖地震に伴う東日本内陸域における応力場の変化

吉田圭佑, 長谷川昭, 岡田知己, 飯沼卓史, 伊藤喜宏, 浅野陽一

SSJ fall meeting　2012/10/16

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Stress change after the 2011 Tohoku-Oki earthquake in the inland areas of Tohoku International-presentation

K. Yoshida, A. Hasegawa, T. Okada, J. Nakajima, Y. Ito, T. Iinuma, Y. Asano

Global COE Program Symposium 2012　2012/09

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2011年東北沖地震に伴う応力変化と東北日本内陸における誘発地震活動 2

吉田圭佑, 長谷川昭, 岡田知己, 中島淳一, 伊藤喜宏, 飯沼卓史, 浅野陽一

JpGU annual meeting　2012/05/20

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Stress change by the 2011 great Tohoku earthquake and induced earthquake activity in the inland areas of northeastern Japan International-presentation

K. Yoshida, A. Hasegawa, T. Okada, Y. Ito, T. Iinuma, Y. Asano

AGU fall meeting　2011/12/05

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2011 年東北地方太平洋沖地震に伴う応力変化と東北日本内陸における誘発地震活動

吉田圭佑, 長谷川昭, 岡田知己, 飯沼卓史, 伊藤喜宏, 浅野陽一

SSJ fall meeting　2011/10/12

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2011年東北地方太平洋沖地震前後の応力

吉田圭佑, 長谷川昭, 岡田知己, 伊藤喜宏, 飯沼卓史, 浅野陽一

JpGU annual meeting　2011/05/24

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メカニズム解から推定した 2008 年岩手・宮城内陸地震震源域の起震応力場と間隙水圧

吉田圭佑, 岡田知己, 伊藤喜宏, 飯沼卓史, 海野徳仁, 長谷川昭, 年岩手, 宮城内陸地震合同余震観測グループ

JpGU annual meeting　2011/05/24

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Spatial heterogeneity of stress and pore-pressure estimated from aftershocks of the 2008 Iwate-Miyagi Nairiku earthquake International-presentation

K. Yoshida, T. Okada, Y. Ito, T. Iinuma, N. Umino, A. Hasegawa, Group for the aftershock observations of, the, Iwate-Miyagi Nairiku Earthquake

IGRS International Geo-Hazards Research Society　2010/08

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Stress field and pore-pressure distribution inferred from the focal mechanisms of aftershocks of the 2008 Iwate-Miyagi Nairiku (inland) earthquake International-presentation

K. Yoshida, T. Okada, Y. Ito, T. Iinuma, N. Umino, A. Hasegawa, Group for the aftershock observations of, the, Iwate-Miyagi Nairiku Earthquake

G-COE symposium 2010: Dynamic Earth and Heterogeneous Structure　2010/07

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Estimation of postseismic stress field and pore-pressure distribution inferred from the focal mechanisms of aftershocks of the 2008 Iwate-Miyagi Nairiku (inland) earthquake International-presentation

K. Yoshida, T. Okada, Y. Ito, T. Iinuma, N. Umino, A. Hasegawa

Western Pacific Geophysics Meeting　2010/06

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稠密観測データから得られた余震のメカニズム解による2008年岩手・宮城内陸地震震源域の応力場と摩擦係数の空間変化

吉田圭佑, 岡田知己, 伊藤喜宏, 飯沼卓史, 海野徳仁, 長谷川昭, 年岩手, 宮城内陸地震合同余震観測グループ

JpGU annual meeting　2010/05/23

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Spatial heterogeneity of tectonic stress and friction in and around the source area of the 2008 M7.2 Iwate-Miyagi Nairiku earthquake, NE Japan, inferred from the aftershock focal mechanisms International-presentation

K. Yoshida, T. Okada, Y. Ito, T. Iinuma, N. Umino, A. Hasegawa, Group for the aftershock observations of, the, Iwate-Miyagi Nairiku Earthquake

Global COE Program Symposium 2010　2010/02

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Heterogeneity of stress field in and around the source area of the 2008 M7.2 Iwate-Miyagi Nairiku earthquake, NE Japan, inferred from the aftershock focal mechanisms International-presentation

K. Yoshida, T. Okada, Y. Ito, T. Iinuma, N. Umino, A. Hasegawa, Group for the aftershock observations of, the, Iwate-Miyagi Nairiku Earthquake

AGU fall meeting　2009/12/14

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2008年岩手宮城内陸地震の余震のメカニズム解および起震応力場

吉田圭佑, 岡田知己, 伊藤喜宏, 飯沼卓史, 海野徳仁, 長谷川昭, 年岩手宮城内陸地震合同余震観測グループ

SSJ fall meeting　2009/10/21

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2008年岩手・宮城内陸地震の余震のメカニズム解および起震応力場

吉田圭佑, 岡田知己, 伊藤喜宏, 飯沼卓史, 趙大鵬, 海野徳仁, 長谷川昭, 年岩手, 宮城内陸地震合同余震観測グループ

JpGU annual meeting　2009/05/16

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Focal mechanisms of aftershocks of the 2008 M7.2 Iwate-Miyagi Nairiku earthquake and the stress field in its aftershock area International-presentation

K. Yoshida, T. Okada, Y. Ito, T. Iinuma, D. Zhao, N. Umino, A. Hasegawa

Global COE International Symposium 2009 Circum-Pacific Subduction Zones – Insights from geodesy, seismology, and volcanology –　2009/02

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Research Projects 13

微小地震解析に基づく，スラブ内起源流体がプレート境界すべりに与える影響の研究

吉田圭佑

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 基盤研究(C)

Institution: 東北大学

2024/04/01 - 2028/03/31
Postseismic model for predicting crustal deformation and seismicity after the 7Tohoku-oki earthquake

Jun Muto, Takeshi IInuma, Tomomi Okada, Yusaku Ohta, Keisuke Yoshida

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: Tohoku University

2025/04 - 2027/03
繰り返し地震の破壊過程の解像による地震の複雑性の支配要因の研究

吉田圭佑

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 学術変革領域研究(A)

Institution: 東北大学

2024/04/01 - 2026/03/31
小地震の破壊過程を用いた断層状態の情報抽出に基づく地震発生機構の解明

吉田圭佑

Offer Organization: 日本学術振興会

System: 科学研究費助成事業若手研究

Category: 若手研究

Institution: 東北大学

2020/04/01 - 2024/03/31

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今年度は、 (1) 日本海溝沿いに展開された海域観測網を活用して、2016-2020年の間に発生した Mw3.5-5の東北沖プレート境界地震に対して、様々な観測点でのみかけの震源時間関数 (apparent source time function)を推定した。それらのみかけ震源時間関数の方向依存性に基づき、破壊伝播方向を系統的に推定した。解析機関である 2016年以降に発生したプレート境界地震の破壊が深部側から浅部側に伝播する特徴を持つことを見出した。 (2) 流体移動が生じた際の破壊伝播方向の傾向を数値シミュレーションにより調べた。その結果から、破壊伝播方向から、地震の臨界核サイズの情報が得られる可能性を示した。 (3) 2021年3月20日および 5月 1日に発生した Mw7.0と Mw6.7のプレート境界型地震の破壊過程、放射エネルギーを推定した。宮城沖のプレート境界で網羅的に繰り返し地震を検出することにより、この地域で東北沖地震の余効すべりが継続しており、地震発生に大きな影響を与えていることを見出した。2021年3月20日の地震の破壊が、平時には地震破壊を生じさせない摩擦特性を持つ領域から開始した可能性を示した。 (4) 内陸域で発生した地震の震源時間関数を精査し、放射エネルギー・破壊の複雑性を系統的に調べた。既存の観測網で、Mw>2の地震の破壊の特徴を従来よりも遥かに詳細に抽出できることを明らかにした。単純な破壊過程が仮定されることが多い小地震についても、各々の空間スケールでは、大地震と同等の複雑性を示す結果が得られた。
2023年5月5日の地震を含む能登半島北東部陸海域で継続する地震と災害の総合調査

平松良浩, 岡田知己, 吉田圭佑, 高木涼太, 篠原雅尚, 酒井慎一, 藏下英司, 西村卓也, 太田雄策, 木下陽平, 宮崎真一, 後藤忠徳, 笠谷貴史, 吉村令慧, 田中愛幸, 宮澤理稔, 荒木英一郎, 森下知晃, 鹿児島渉悟, 石山達也, 立石良, 安江健一, 廣内大助, 松多信尚, 宍倉正展, 岩田知孝, 浅野公之, 大堀道広, 村田晶, 石川浩一郎, 山岸邦彰, 須田達, 山崎新太郎, 青木賢人, 林紀代美, 武田公子, 田中純一, 井口克郎, 佐々木大輔, 原裕太, 吉田浩

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 特別研究促進費

Institution: 金沢大学

2023/06 - 2024/03
2023年トルコ南部の地震と災害に関する総合調査

楠浩一, 青木陽介, 西村卓也, 小林知勝, 近藤久雄, Adriano Bruno, 王功輝, Bhandary NetraPrakash, 加藤愛太郎, 山本揚二朗, 吉田圭佑, 八木勇治, 内田直希, 汐見勝彦, 山中浩明, 高井伸雄, 吉見雅行, 地元孝輔, 中村洋光, 目黒公郎, 久田嘉章, 森伸一郎, 清田隆, 小野祐輔, 後藤浩之, 日比野陽, 毎田悠承, 大西直毅, SHEGAY ALEKSEY, 阪本真由美, 金田義行, 木村周平, 牧紀男

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 特別研究促進費

Institution: 東京大学

2023/03 - 2024/03
能登半島北東部において継続する地震活動に関する総合調査

平松良浩, 藏下英司, 酒井慎一, 飯高隆, 勝間田明男, 岡田知己, 吉田圭佑, 西村卓也, 太田雄策, 木下陽平, 吉村令慧, 後藤忠徳, 笠谷貴史, 田中愛幸, 宮澤理稔, 森下知晃, 鹿児島渉悟, 石山達也, 安江健一, 廣内大助, 松多信尚, 大堀道広, 村田晶, 岩田知孝

Offer Organization: 日本学術振興会

System: 科学研究費助成事業特別研究促進費

Category: 特別研究促進費

Institution: 金沢大学

2022/07/22 - 2023/03/31

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能登半島北東部で長期間継続する地震活動の原因及び全体像、また2022年6月19日のマグニチュード5.4、最大震度６弱の地震による災害像を明らかにするために、地震観測、測地観測、電磁気観測、重力観測、温泉成分測定、活構造調査、強震観測からなる総合調査を2022年7月から2023年3月まで実施した。これらの観測で得られたデータの解析により、複数の断層面で地震が発生していることや震源が時空間的に移動していること、震源域南部の深部に流体の存在を示す地震波速度構造や比抵抗構造が存在すること、地震波の反射波から推定される反射面も深部の流体の存在と整合的であること、地殻変動源の位置が時間的に変化するとともに地殻変動源のモデルが開口割れ目から開口を伴う逆断層に変化したこと、震源域北部において重力値が減少し、地殻変動源のモデルと概ね一致すること、温泉成分の陰イオン濃度が複数地点で同時期に時間変化をし、地殻流体の影響を反映した可能性が考えられること、年代指標となる火山灰に基づき海成段丘面の年代を特定し、その分布高度と合わせて隆起速度を推定したこと、地震活動域の東部から南部にかけての海成段丘面で新たな変動地形を見出したこと、震度６弱の記録地点周辺において、工学的基盤面での速度コントラストの大きさが地震動増幅に大きく寄与していることや卓越周波数の空間変化があること、を研究成果として得ることができた。これらの成果は非火山地域における群発地震活動の要因を考える上で重要なものであり、また当該地域における地震防災に役立つ知見も得られており、科学的・社会的にも意義がある成果である。
坑井検層による地球物理データが導く微小地震き裂面方向逆解析のベイズ統計学的展開

椋平祐輔, 吉田圭佑

Offer Organization: 日本学術振興会

System: 科学研究費助成事業基盤研究(C)

Category: 基盤研究(C)

Institution: 東北大学

2020/04/01 - 2023/03/31

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本年度は，前年度，研究分担者と本研究で提案する手法に周辺の応用分野や，現象についても議論を深めた結果，有望な本技術の応用先である群発地震に関してより理解を深めることとした。研究分担者が，精力的に研究を行なっている東北地方の群発地震に対して，これまで注水時の誘発地震の解析で蓄積されてきた知識や解析手法を応用することで，群発地震を励起させたと考えられる流体の量を逆推定することができた。ここでは，群発地震発生領域の時間発展をモデリングし，その進展から求めた水理学的パラメータを用いて，流体の量を逆推定することに成功した。一方で，誘発地震分野でハザード予測に用いられている，流体と地震活動を結びつける法則を用いて群発地震活動から流体量を逆推定した。得られた流体量を地質学的な知見から議論し，蓄積されていた流体量がどれくらいの年月の脱水過程で供給されるかを検討した。上記は，本来の研究実施計画に必ずしも沿ったものではないが，近年の誘発地震研究分野の蓄積が可能にした大変斬新なアプローチであるため，実施した。なお，本研究にそったフレームワーク部分も，着実に進捗を重ね，対象フィールドに対してモーメントテンソルインバージョンのコードの書き換え等も終了し，基礎解析を進めている。ベイズ理論の応用に関しても様々な学会や，論文等からベイズ統計学の地震学分野での実際の応用状況を把握し，実装に向けた知識を蓄積することができた。
微小地震への短周期地震波解析手法の適用による地震発生準備過程の解明

吉田圭佑

Offer Organization: 日本学術振興会

System: 科学研究費助成事業若手研究(B)

Category: 若手研究(B)

Institution: 東北大学

2017/04/01 - 2020/03/31

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平成30年度の研究では，1) 微小地震の震源過程の推定手法を確立し，その適用を 2)日本国内で近年発生し，顕著な前震活動を伴った 3つの地震活動，および 3) 2011年東北沖地震による内陸の誘発地震活動に対して行った。 1) 微小地震の地震波形解析アルゴリズムを構築し，微小地震の多くが顕著な破壊伝播指向性を示すことを明らかにした。短周期波形を用いて，小中地震の断層面解を効率的かつ高精度に推定する手法も確立した。これらのことにより，通常直接的な推定が困難である小中地震の断層方向や破壊伝播速度について情報が得られるようになった (学術誌に投稿中)。 <BR> 2) 日本国内で近年発生し，顕著な前震活動を伴った 3つの地震 a) 2016年鳥取県中部地震，b) 2017年鹿児島湾の地震，c) 2017年秋田県大仙市の地震についての解析を行った。前震震源の移動現象や震源過程などから、地震発生に関わる非地震性過程について情報抽出することができた。これらの地震活動について，本震発生前の顕著な応力場の擾乱は検出されなかった。このことは，地震発生場の偏差応力の大きさが，非地震性過程によるそれに比べて大きいことを示唆する。(b)について解析と研究発表を行った修士学生の松本圭晶さんは，その発表により2018年地震学会学生優秀発表賞を受賞した (上記 3つの解析結果について学術雑誌への投稿準備中)。 <BR> 3) 小中地震の震源の移動現象・応力場の情報に基づき，2011年東北沖地震後の内陸の誘発地震活動の発生機構を統一的に説明することに成功した。その成果は，2本の学術誌および 1本の広報紙に掲載された。
Clarification of strength and stress of the inland crust

Matsuzawa Toru, IWASAKI takaya, TERAKAWA toshiko, KAGAWA takao

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

Category: Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

Institution: Tohoku University

2014/07/10 - 2019/03/31

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We estimated the differential stress in the seisimic zones beneath the Japanese Islands from the precise hypocenter locations and focal mechanism solutions in this study. We found that some active faults cannot slip unless the strength is very small there. We have developed a method to estimate accurate stress fields using P wave initial motion data and verified its effectiveness. Based on the correlation between the topography and the focal mechanism solutions and the stress rotations around the source areas after large earthquakes, we found that the differential stress in the seismic zone is less than 100 MPa, which corresponds to an extremely small frictional coefficient of about 0.1-0.3 assuming hydrostatic pore pressure. We also obtained some evidences showing that such low strength is caused by high pore pressure for earthquake swarms at least.
地球の非地震的変形過程と地震活動の関係の解明

内田直希, 金亜伊, 北佐枝子, 高木涼太, 吉田圭佑, 富田史章, Roland Burgmann, Manoochehr Shirzaei, Robert Nadeau, Paul Segall, Kaj Johnson, Yehuda Ben-Zion, Brent Delbridge

Offer Organization: 日本学術振興会

System: 二国間交流事業

Institution: 東北大学

2017/04 - 2019/03
ミクロからマクロスケールにおけるアルパイン断層の力学特性の評価

重松紀生, 岡田知己, 西川治, 松本則夫, 林為人, 坂口有人, Horst Zwingmann, 高木涼太, 森宏, 吉田圭佑, 米谷優佑, John Townend, Rupert Sutherland, Virginia Toy, Simon Cox, Timothy Little, Phaedra Upton, Martha Savage, Kasper van Wijk, Ludmila Adam, Carolin Boese, Jennifer Eccles Lucie Capova, Cecile Massio, Risa Matsumura

Offer Organization: 日本学術振興会

System: 二国間交流事業

Institution: 国立研究開発法人産業技術総合研究所

2015/04 - 2017/03
日本列島周辺における地震発生深度での応力場・摩擦強度の絶対値に関する研究

吉田圭佑

Offer Organization: 日本学術振興会

System: 科学研究費助成事業特別研究員奨励費

Category: 特別研究員奨励費

Institution: 東北大学

2013/04/01 - 2015/03/31

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今年度の研究において、本研究の目的を東北日本において達成した。本研究の目的とは、次のようなものであった：「日本国内での地震を発生する原因となる地殻内の応力場・断層強度の絶対値の推定を多面的に行い，統合的な知見を得る．また，そもそもの地殻内の応力場の形成原因を量的に検討する」具体的には、「地震発生深度での絶対応力・強度の推定」を、次の二通りのアプローチにより行った。 (1) アプローチの一つ目では、前年度までに検出することに成功していた東北日本の応力方向の空間変化と地形分布との相関を利用して行った (2) アプローチの二つ目では、2008年岩手・宮城内陸地震と2011年福島県浜通りの地震と言う二つの大地震震源域において応力方向の空間不均質性を検出し、それを大地震の擾乱と関係付けることにより行ったいずれの場合も、東北日本地殻内の差応力が 20 MPaと言う、通常の岩石に摩擦滑りを引き起こすには、非常に小さな値が得られた。このことは、地震発生の際に地殻流体などの要因が岩石の強度を低下させていることを示唆する。

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Teaching Experience 4

Exercises in mechanics　Tohoku University
Exercises in Mechanics of Elastic Body　Tohoku University
宇宙地球物理学研究　東北大学
Experiments in Geophysics　Tohoku University

Social Activities 1

地殻内流体の移動と2011年東北地方太平洋沖地震による誘発地震活動，そして能登半島の地震活動

地震・火山研究の最前線に迫る第6回～誘発地震活動と地殻内流体の移動～

2024/03/17 -

Media Coverage 3

〝最悪のシナリオ〟超えた能登地震鍵となる地下流体の正体

産業経済新聞社　産経新聞

2024/01

Type: Newspaper, magazine
その地震、原因は「水」？知られざる地下流体、見えてきた姿

毎日新聞社　毎日新聞　https://mainichi.jp/articles/20230905/k00/00m/040/112000c

2023/09

Type: Newspaper, magazine
Deadly Earthquake Swarm Caused by Ancient Dead Volcano

Newsweek　https://www.newsweek.com/deadly-earthquake-swam-ancient-dead-volcano-1816969

2023/08

Type: Newspaper, magazine