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.
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U2 - 10.1002/2017GL074593
DO - 10.1002/2017GL074593
M3 - Article
AN - SCOPUS:85028390726
VL - 44
SP - 7766
EP - 7772
JO - Geophysical Research Letters
JF - Geophysical Research Letters
SN - 0094-8276
IS - 15
ER -