Imaging the heterogeneous source area of the 2003 M6.4 northern Miyagi earthquake, NE Japan, by double-difference tomography

Tomomi Okada, Akira Hasegawa, Jun'ichi Suganomata, Norihito Umino, Haijiang Zhang, Clifford H. Thurber

研究成果: Article

18 引用 (Scopus)

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A shallow M6.4 inland earthquake occurred on 26 July 2003 in the northern part of Miyagi Prefecture, northeastern Japan. This earthquake was a typical inland thrust earthquake, a type that is common in NE Japan. We obtained a detailed seismic velocity structure in the focal area of this earthquake by the double-difference tomography method. Arrival-time data came from temporary seismic stations deployed above the mainshock fault plane. Both the P-wave and S-wave velocities in the hanging wall were lower than those in the footwall. Aftershocks were aligned along a zone where the seismic velocity changes rapidly. This is consistent with the interpretation that the 2003 northern Miyagi earthquake occurred along a fault that acted as a normal fault in the Miocene and has been reactivated as a reverse fault under the present compressional stress regime. The large slip area by the main shock rupture (asperity) corresponds to an area with relatively high P- and S-wave velocities. A zone with low Vp/Vs was detected along the aftershock area. One of the possible causes of this low-Vp/Vs zone is the existence of high-aspect-ratio pores that contain water. Hypocenters of the main shock, largest foreshock, and largest aftershock are also located within the low-Vp/Vs zone.

元の言語English
ページ(範囲)67-81
ページ数15
ジャーナルTectonophysics
430
発行部数1-4
DOI
出版物ステータスPublished - 2007 2 5

ASJC Scopus subject areas

  • Geophysics
  • Earth-Surface Processes

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