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A possible long-term and very-deep aseismic slip event activating seismicity off Tohoku
  • Fumiaki Tomita
Fumiaki Tomita
IRIDeS, Tohoku University

Corresponding Author:[email protected]

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Various slips at plate interfaces in subduction zones have been documented, and the role of aseismic slips in strain release and stress re-distribution has been revealed. Prior to the M9 2011 Tohoku earthquake in Japan, various small-scale aseismic slip events which possibly affected the occurrence of the 2011 Tohoku earthquake had been reported. However, the small-scale aseismic slip behaviors after the M9 2011 Tohoku earthquake have not been well-clarified because the dominant postseismic deformation of the 2011 Tohoku earthquake has hidden minor aseismic slips. In this study, we performed trajectory models for the GNSS time-series after eliminating the postseismic deformation of the 2011 Tohoku earthquake, and we extracted afterslips followed by M7 class earthquakes, and an ongoing long-term aseismic slip event (L-ASE) since late 2019. The spatial extent of these aseismic slips was also clarified, and the 2019 L-ASE was estimated to be in the down-dip area of the seismogenic zone. As a similar L-ASE was also found before the 2011 Tohoku earthquake, a comparison of these L-ASEs suggests that the repeated L-ASEs promoted strain accumulation in the shallow plate interface, including the M9 rupture area, and may be markers preceding M7 class seismicity. Because L-ASEs are key phenomena in assessing sequential seismic behaviors in the Tohoku subduction zone, monitoring the ongoing L-ASE and investigating its physical interaction with other slip behaviors is important.
14 Jun 2023Submitted to ESS Open Archive
23 Jun 2023Published in ESS Open Archive