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DOI	10.1016/j.tecto.2020.228609
	2019 M6.7 Yamagata-Oki earthquake in the stress shadow of 2011 Tohoku-Oki earthquake: Was it caused by the reduction in fault strength?
	Yoshida K.; Uchida N.; Hiarahara S.; Nakayama T.; Matsuzawa T.; Okada T.; Matsumoto Y.; Hasegawa A.
发表日期	2020
ISSN	00401951
卷号	793
英文摘要	Earthquake occurrence in the stress shadow provides a unique opportunity for extracting information about the physical processes behind earthquakes because it highlights processes other than the ambient stress change in earthquake generation. In this study, we examined the fault structure and the spatiotemporal distribution of the aftershocks of the 2019 M6.7 Yamagata-Oki earthquake, which occurred in the stress shadow of the 2011 M9.0 Tohoku-Oki earthquake, to better understand the earthquake generation mechanism. The detection and hypocenter relocation of the aftershocks led to the delineation of three planar earthquake structures consitent with their focal mechanisms. The results suggest that individual aftershocks were caused by a slip on these macroscopic planar structures. Aftershock hypocenters rapidly migrated upward from the deeper part of the major plane (fault), similar to the recent earthquake swarm sequences following the Tohoku-Oki earthquake in the upper plate. Moreover, we investigated the temporal evolution of the surface strain rate distribution in the source region using GNSS data. The east–west contraction strain rate in the source region of the Yamagata-Oki earthquake, with an E–W compressional reverse fault mechanism, changed to an E–W extension as a result of the Tohoku-Oki earthquake, and it continued until the occurrence of the Yamagata-Oki earthquake. The upward hypocenter migrations, together with the earthquake occurrence in the stress shadow and in the E–W extension strain rate field, suggest that a reduction in the fault strength due to uprising fluids contributed to the occurrence of this earthquake sequence. Localized aseismic deformations, such as aseismic creeps, beneath the fault zone may also have contributed to the earthquake occurrence. The results support the hypothesis that aseismic processes in the deeper part of the fault play crucial roles in the occurrence of shallow intraplate earthquakes. © 2020 Elsevier B.V.
关键词	2016 Yamagata-Oki earthquake Aftershock Aseismic process Fluid migration Hypocenter relocation Stress shadow
英文关键词	Faulting; Strain rate; Transport properties; 2011 Tohoku-Oki earthquakes; Earthquake generation mechanism; Earthquake occurrences; Extracting information; Hypocenter relocation; Intraplate earthquakes; Spatiotemporal distributions; Tohoku-Oki earthquakes; Earthquakes; aftershock; earthquake hypocenter; earthquake swarm; fault zone; focal mechanism; stress analysis; Tohoku earthquake 2011; Chugoku; Honshu; Japan; Oki Islands; Shimane; Tohoku; Yamagata [Tohoku]
语种	英语
来源期刊	Tectonophysics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/207906
作者单位	Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, Sendai, Japan
推荐引用方式 GB/T 7714	Yoshida K.,Uchida N.,Hiarahara S.,et al. 2019 M6.7 Yamagata-Oki earthquake in the stress shadow of 2011 Tohoku-Oki earthquake: Was it caused by the reduction in fault strength?[J],2020,793.
APA	Yoshida K..,Uchida N..,Hiarahara S..,Nakayama T..,Matsuzawa T..,...&Hasegawa A..(2020).2019 M6.7 Yamagata-Oki earthquake in the stress shadow of 2011 Tohoku-Oki earthquake: Was it caused by the reduction in fault strength?.Tectonophysics,793.
MLA	Yoshida K.,et al."2019 M6.7 Yamagata-Oki earthquake in the stress shadow of 2011 Tohoku-Oki earthquake: Was it caused by the reduction in fault strength?".Tectonophysics 793(2020).