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Stress rotations due to the M 6.5 foreshock and M 7.3 main shock in the 2016 Kumamoto, SW Japan, earthquake sequence
Author(s) -
Yoshida Keisuke,
Hasegawa Akira,
Saito Tatsuhiko,
Asano Youichi,
Tanaka Sachiko,
Sawazaki Kaoru,
Urata Yumi,
Fukuyama Eiichi
Publication year - 2016
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 - 10.1002/2016gl070581
Subject(s) - foreshock , seismology , clockwise , geology , aftershock , fault plane , shock (circulatory) , fault (geology) , focal mechanism , stress (linguistics) , geodesy , shear (geology) , geophysics , rotation (mathematics) , geometry , petrology , medicine , linguistics , philosophy , mathematics
A shallow M 7.3 event with a M 6.5 foreshock occurred along the Futagawa‐Hinagu fault zone in Kyushu, SW Japan. We investigated the spatiotemporal variation of the stress orientations in and around the source area of this 2016 Kumamoto earthquake sequence by inverting 1218 focal mechanisms. The results show that the σ 3 axis in the vicinity of the fault plane significantly rotated counterclockwise after the M 6.5 foreshock and rotated clockwise after the M 7.3 main shock in the Hinagu fault segment. This observation indicates that a significant portion of the shear stress was released both by the M 6.5 foreshock and M 7.3 main shock. It is estimated that the stress release by the M 6.5 foreshock occurred in the shallower part of the Hinagu fault segment, which brought the stress concentration in its deeper part. This might have caused the M 7.3 main shock rupture mainly along the deeper part of the Hinagu fault segment after 28 h.