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Seismic velocity structure in the source region of the 2016 Kumamoto earthquake sequence, Japan
Author(s) -
Shito Azusa,
Matsumoto Satoshi,
Shimizu Hiroshi,
Ohkura Takahiro,
Takahashi Hiroaki,
Sakai Shinichi,
Okada Tomomi,
Miyamachi Hiroki,
Kosuga Masahiro,
Maeda Yuta,
Yoshimi Masayuki,
Asano Youichi,
Okubo Makoto
Publication year - 2017
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl074593
Subject(s) - seismology , geology , aftershock , induced seismicity , crust , slip (aerodynamics) , seismic velocity , hypocenter , sequence (biology) , p wave , geophysics , physics , genetics , biology , thermodynamics , medicine , cardiology , atrial fibrillation
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.