Seismic velocity structure in the source region of the 2016 Kumamoto earthquake sequence, Japan

Azusa Shito; Satoshi Matsumoto; Hiroshi Shimizu; Takahiro Ohkura; Hiroaki Takahashi; Shinichi Sakai; Tomomi Okada; Hiroki Miyamachi; Masahiro Kosuga; Yuta Maeda; Masayuki Yoshimi; Youichi Asano; Makoto Okubo

doi:10.1002/2017GL074593

Seismic velocity structure in the source region of the 2016 Kumamoto earthquake sequence, Japan

Azusa Shito, Satoshi Matsumoto, Hiroshi Shimizu, Takahiro Ohkura, Hiroaki Takahashi, Shinichi Sakai, Tomomi Okada, Hiroki Miyamachi, Masahiro Kosuga, Yuta Maeda, Masayuki Yoshimi, Youichi Asano, Makoto Okubo

SCI - Research Center for Prediction of Earthquakes and Volcanic Eruptions (RCPEVE)

Research output: Contribution to journal › Article › peer-review

20 Citations (Scopus)

Abstract

We investigate seismic wave velocity structure and spatial distribution of the seismicity in the source region of the 2016 Kumamoto earthquake sequence. A one-dimensional mean velocity shows that the seismogenic zone has a high-velocity and low-Vp/Vs ratio relative to the average velocity structure of Kyushu Island. This indicates that the crust is relatively strong, capable of sustaining sufficiently high strain energy to facilitate two large (M_j > 6.5) earthquakes in close proximity to one another in rapid succession. Three-dimensional tomography of the seismogenic zone around the source of the 2016 Kumamoto earthquake sequence yields Vp = 6 km/s and Vs = 3.5 km/s. Most large-displacement areas (asperities) of the M_j 7.3 event overlap with the seismogenic zone and the overlying surface layer. Aftershock seismicity is distributed deeper than the conventional seismogenic zone, which suggests decreased strength due to fluids or increased stress, both caused by coseismic slip.

Original language	English
Pages (from-to)	7766-7772
Number of pages	7
Journal	Geophysical Research Letters
Volume	44
Issue number	15
DOIs	https://doi.org/10.1002/2017GL074593
Publication status	Published - 2017 Aug 16

Keywords

double-difference tomography
the 2016 Kumamoto earthquakes
velocity structure

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10.1002/2017GL074593

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@article{8114686a1f0c4e9880b0e3af2df9740d,

title = "Seismic velocity structure in the source region of the 2016 Kumamoto earthquake sequence, Japan",

abstract = "We investigate seismic wave velocity structure and spatial distribution of the seismicity in the source region of the 2016 Kumamoto earthquake sequence. A one-dimensional mean velocity shows that the seismogenic zone has a high-velocity and low-Vp/Vs ratio relative to the average velocity structure of Kyushu Island. This indicates that the crust is relatively strong, capable of sustaining sufficiently high strain energy to facilitate two large (Mj > 6.5) earthquakes in close proximity to one another in rapid succession. Three-dimensional tomography of the seismogenic zone around the source of the 2016 Kumamoto earthquake sequence yields Vp = 6 km/s and Vs = 3.5 km/s. Most large-displacement areas (asperities) of the Mj 7.3 event overlap with the seismogenic zone and the overlying surface layer. Aftershock seismicity is distributed deeper than the conventional seismogenic zone, which suggests decreased strength due to fluids or increased stress, both caused by coseismic slip.",

keywords = "double-difference tomography, the 2016 Kumamoto earthquakes, velocity structure",

author = "Azusa Shito and Satoshi Matsumoto and Hiroshi Shimizu and Takahiro Ohkura and Hiroaki Takahashi and Shinichi Sakai and Tomomi Okada and Hiroki Miyamachi and Masahiro Kosuga and Yuta Maeda and Masayuki Yoshimi and Youichi Asano and Makoto Okubo",

note = "Funding Information: Data used in this study were partly obtained by the Group for Urgent Joint Seismic Observation of the 2016 Kumamoto Earthquakes. We used phase data from Shimizu et al. [2016] with permission from the authors. This work was partly supported by JSPS KAKENHI grant JP15J40067, MEXT KAKENHI grant JP16H06298, MEXT under its Earthquake and Volcano Hazards Observation and Research Program, and the Earthquake Research Institute cooperative research program. We thank Junichi Nakajima of Tokyo Institute of Technology and three anonymous reviewers for their con structive comments. Publisher Copyright: {\textcopyright}2017. American Geophysical Union. All Rights Reserved.",

year = "2017",

month = aug,

day = "16",

doi = "10.1002/2017GL074593",

language = "English",

volume = "44",

pages = "7766--7772",

journal = "Geophysical Research Letters",

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TY - JOUR

T1 - Seismic velocity structure in the source region of the 2016 Kumamoto earthquake sequence, Japan

AU - Shito, Azusa

AU - Matsumoto, Satoshi

AU - Shimizu, Hiroshi

AU - Ohkura, Takahiro

AU - Takahashi, Hiroaki

AU - Sakai, Shinichi

AU - Okada, Tomomi

AU - Miyamachi, Hiroki

AU - Kosuga, Masahiro

AU - Maeda, Yuta

AU - Yoshimi, Masayuki

AU - Asano, Youichi

AU - Okubo, Makoto

N1 - Funding Information: Data used in this study were partly obtained by the Group for Urgent Joint Seismic Observation of the 2016 Kumamoto Earthquakes. We used phase data from Shimizu et al. [2016] with permission from the authors. This work was partly supported by JSPS KAKENHI grant JP15J40067, MEXT KAKENHI grant JP16H06298, MEXT under its Earthquake and Volcano Hazards Observation and Research Program, and the Earthquake Research Institute cooperative research program. We thank Junichi Nakajima of Tokyo Institute of Technology and three anonymous reviewers for their con structive comments. Publisher Copyright: ©2017. American Geophysical Union. All Rights Reserved.

PY - 2017/8/16

Y1 - 2017/8/16

N2 - We investigate seismic wave velocity structure and spatial distribution of the seismicity in the source region of the 2016 Kumamoto earthquake sequence. A one-dimensional mean velocity shows that the seismogenic zone has a high-velocity and low-Vp/Vs ratio relative to the average velocity structure of Kyushu Island. This indicates that the crust is relatively strong, capable of sustaining sufficiently high strain energy to facilitate two large (Mj > 6.5) earthquakes in close proximity to one another in rapid succession. Three-dimensional tomography of the seismogenic zone around the source of the 2016 Kumamoto earthquake sequence yields Vp = 6 km/s and Vs = 3.5 km/s. Most large-displacement areas (asperities) of the Mj 7.3 event overlap with the seismogenic zone and the overlying surface layer. Aftershock seismicity is distributed deeper than the conventional seismogenic zone, which suggests decreased strength due to fluids or increased stress, both caused by coseismic slip.

AB - We investigate seismic wave velocity structure and spatial distribution of the seismicity in the source region of the 2016 Kumamoto earthquake sequence. A one-dimensional mean velocity shows that the seismogenic zone has a high-velocity and low-Vp/Vs ratio relative to the average velocity structure of Kyushu Island. This indicates that the crust is relatively strong, capable of sustaining sufficiently high strain energy to facilitate two large (Mj > 6.5) earthquakes in close proximity to one another in rapid succession. Three-dimensional tomography of the seismogenic zone around the source of the 2016 Kumamoto earthquake sequence yields Vp = 6 km/s and Vs = 3.5 km/s. Most large-displacement areas (asperities) of the Mj 7.3 event overlap with the seismogenic zone and the overlying surface layer. Aftershock seismicity is distributed deeper than the conventional seismogenic zone, which suggests decreased strength due to fluids or increased stress, both caused by coseismic slip.

KW - double-difference tomography

KW - the 2016 Kumamoto earthquakes

KW - velocity structure

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DO - 10.1002/2017GL074593

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VL - 44

SP - 7766

EP - 7772

JO - Geophysical Research Letters

JF - Geophysical Research Letters

IS - 15

ER -

Seismic velocity structure in the source region of the 2016 Kumamoto earthquake sequence, Japan

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Keywords

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