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Prevalence of updip rupture propagation in interplate earthquakes along the Japan Trench
  • +2
  • Keisuke Yoshida,
  • Naoki Uchida,
  • Hisahiko Kubo,
  • Ryota Takagi,
  • Shiqing Xu
Keisuke Yoshida
Tohoku University

Corresponding Author:keisuke.yoshida.d7@tohoku.ac.jp

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Naoki Uchida
Tohoku University
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Hisahiko Kubo
National Research Institute for Earth Science and Disaster Resilience, Tsukuba, Japan
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Ryota Takagi
Tohoku University
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Shiqing Xu
Southern University of Science and Technology
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Abstract

The development of seafloor seismic observations facilitates reliable estimation of the rupture directivities of offshore earthquakes. We used seismic waveforms obtained by a new seafloor seismic network (S-net) and onland stations to systematically examine the rupture directivities of interplate earthquakes along the Japan trench. We estimated the rupture directions of 206 (M w 3.5-5) events, most of which occurred near the base of the seismogenic zone. We found that most earthquake ruptures (>~80 %) were directional, primarily propagating in the updip direction. This tendency cannot be explained by the effect of the bimaterial interface. The prevalence of updip rupture in the data suggests that deep, steady creep and upward fluid migration along the plate interface affected earthquake ruptures in the subduction zone. The updip ruptures redistributed the accumulated shear stress from the base of the seismogenic zone to the shallow large seismic patches. Furthermore, the updip ruptures may open up ways for deeper fluids to migrate further upward along the plate interface. Both the stress redistribution and the upward fluid migration facilitate the occurrence of shallow megathrust earthquakes.
Jan 2022Published in Earth and Planetary Science Letters volume 578 on pages 117306. 10.1016/j.epsl.2021.117306