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Kinematic Rupture Characterization of Large Compressional Intraslab Earthquakes Along the Tohoku Region, Japan
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  • Kenichi Tsuda,
  • Shohei Yoshida,
  • Chen Ji,
  • Ralph Archuleta,
  • Toshiaki Sato
Kenichi Tsuda
Shimizu Corporation

Corresponding Author:[email protected]

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Shohei Yoshida
Ohsaki Research Institute Inc.
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Chen Ji
UC Santa Barbara
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Ralph Archuleta
RJA Ground Motion Analysis Inc.
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Toshiaki Sato
Ohsaki Research Institute Inc.
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We examine the source parameters of four Mw≥7.0 intraslab earthquakes that occurred near the Tohoku coast over the past two decades: 2003, 2011, 2021, and 2022. By analyzing the finite fault slip histories constrained by inland strong motion observations, we found that these earthquakes occurred within the upper plane of the subducted Pacific Plate due to downdip compression caused by plate unbending. These earthquakes have a more compact fault area and higher stress drop compared to shallow crustal earthquakes. Additionally, intraslab earthquakes have much slower relative rupture velocity than shallow crustal earthquakes. Good spatial correlations between the static stress drop and slip rate are found, which may suggest the compatibility between dynamic stress drop and static stress drop. The rupture area, average slip, asperity area, average static stress drop over the entire fault, and asperities are consistent with the reported scaling relationship for global intraslab earthquakes within a similar depth range. Using plate unbending, we found the recurrence intervals of these intraslab earthquakes are around 600 years, which is comparable with that of the 2011 Tohoku earthquake. A visual spatial-correlation between the locations of these earthquakes and seismicity in the lower plane is reported. These findings provide insights into the tectonic background and source parameters of intraslab earthquakes in the Tohoku region and contribute to better seismic hazard assessment.
21 Apr 2023Submitted to ESS Open Archive
30 Apr 2023Published in ESS Open Archive