Stress rotations due to the M6.5 foreshock and M7.3 main shock in the 2016 Kumamoto, SW Japan, earthquake sequence

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

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)

Abstract

A shallow M7.3 event with a M6.5 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 σ3 axis in the vicinity of the fault plane significantly rotated counterclockwise after the M6.5 foreshock and rotated clockwise after the M7.3 main shock in the Hinagu fault segment. This observation indicates that a significant portion of the shear stress was released both by the M6.5 foreshock and M7.3 main shock. It is estimated that the stress release by the M6.5 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 M7.3 main shock rupture mainly along the deeper part of the Hinagu fault segment after 28 h.

Original languageEnglish
Pages (from-to)10,097-10,104
JournalGeophysical Research Letters
Volume43
Issue number19
DOIs
Publication statusPublished - 2016 Oct 16
Externally publishedYes

Keywords

  • fault strength
  • focal mechanisms
  • stress field
  • stress magnitude
  • the 2016 Kumamoto earthquake

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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