[S13-P] Poster

[S13-P-18] A Possible Dynamic Rupture Scenario of the Nankai-trough Earthquakes, southwest Japan

^○Yumi Urata¹, Eiichi Fukuyama¹, Chihiro Hashimoto² (1.National Research Institute for Earth Science and Disaster Resilience (NIED), Tsukuba, Japan, 2.Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan)

We investigated possible dynamic rupture scenarios of anticipated megathrust earthquakes along the Nankai-trough, southwest Japan, taking into account the stress accumulation due to tectonic loading driven by relative plate motion. For the plate interface geometry, we used a realistic 3D non-planar plate interface geometry in and around Japan constructed by Hashimoto et al. (2004, Pageoph). The quasi-static stress accumulation was simulated according to Hashimoto et al. (2014, Pageoph), assuming an elastic surface layer overlying Maxwell-type viscoelastic half-space. We used the slip- and time-dependent constitutive law (Aochi & Matsu'ura, 2002, Pageoph) for the plate interface frictional property. Using the shear stress distribution for 150 years after the Nankai-Tonankai-like earthquake (Hashimoto et al., 2017, JpGU-AGU Joint Meeting 2017), we computed the dynamic rupture propagation by the boundary integral equation method with triangular elements (Hok & Fukuyama, 2011, GJI). A hypocenter location is one of the most uncertain parameters in the simulation. Therefore we examined various hypocenter locations and nucleation sizes to test whether or not a rupture can propagate. Under a given distribution of slip deficit and constitutive parameters, the rupture was not initiated in the Tonankai area, in the eastern Nankai area, nor in the western Nankai area at depth. In contrast, the rupture was initiated in the shallow part of the western Nankai area and propagated toward the deep portion of the western Nankai area and toward the eastern Nankai area along the edge of the asperity. The rupture then broke the Tonankai asperity and the slip evolved in the shallow portions of the eastern Nankai area. Such possible dynamic rupture scenario could not be achieved by traditional experience-based kinematic modeling approaches; thus the procedure shown in this study is quite important to constructing a physics-based earthquake generation model.