[S-SS07] Fault Rheology and Earthquake Physics

[SSS07-P15] Modeling of tsunami earthquakes that occur at the shallow plate boundary along the Japan Trench

*Ryoko Nakata¹, Ryota Hino¹ (1.Graduate School of Science, Tohoku University)

Seismic and geodetic studies have demonstrated that the large coseismic slip in the shallow area which caused the 2011 Tohoku-Oki earthquake (Mw9.0) was limited to the middle segment of the Japan Trench [e.g., Iinuma et al., 2012; Tomita et al., 2020]. On the other hand, tsunami data suggested that the source area of the 1869 Sanriku-Oki earthquake (Mw8.0) also ruptured during the Tohoku-Oki earthquake [Satake et al., 2013]. In this study, we assumed that the large slip of the Tohoku-Oki earthquake did not reach the Sanriku-Oki source. Then, we conducted numerical simulation of earthquake generation cycles along the Japan Trench to investigate the rupture area of these two “tsunami earthquakes”. In the shallow part of the northern segment, the frictional models of velocity-strengthening (A-B>0) were assumed. We assume A-B>0 at the spot of the decreasing in smectite [Fujie et al., 2020].
Then, we obtained a situation in which a M~9 earthquake at the middle segment and a M~8 earthquake at the northern segment have occurred independently even though their source areas are adjacent to each other. We are investigating what kind of frictional conditions are appropriate for the coexistence of the M~8 earthquake in the north and the M~9 earthquake in the middle.

Acknowledgments
This work was supported partly by JSPS KAKENHI (Grant Numbers JP19H05596, JP19H00708, and JP26000002). The computational resources of the Earth Simulator provided by JAMSTEC and of Cyberscience Center, Tohoku University were used for all simulations.