[S13-P] Poster

[S13-P-16] Estimation of the dynamic rupture parameters for the 2016 Tottoriken-chubu earthquake

^○Keisuke Sato¹, Shoichi Yoshioka², Hideo Aochi^3,4 (1.Graduate School of Science, Kobe University, Kobe, Japan, 2.Research Center for Urban Safety and Security/Graduate School of Science, Kobe University, Kobe, Japan, 3.Ecole Normale Superieure Paris, Geological Laboratory, Paris, France, 4.Bureau de Recherches Geologiques et Minieres, Orleans, France)

We performed dynamic rupture simulations for the 2016 Tottoriken-chubu earthquake (M6.6). We used a boundary integral equation method, and supposed slip-weakening law as a frictional constitutive law. We assumed a vertical rectangular fault plane whose depth of the upper edge is 0.5 km, and the fault size is 19.5 km (strike) and 18 km (dip). We attempted to obtain spatial distributions of initial stress and critical slip weakening distance (hereafter referred to as Dc), which can fit better the slip distribution obtained from an inversion analysis performed by Kobayashi et al. (2016). The inverted final slip distribution has an area whose slip amount is large just above the hypocenter, reaching 1.3 m. We divided the fault plane into two areas; one is the area with a large slip amount (hereafter referred to as asperity), and the other is the surrounding one with a small slip amount. We fixed values of residual stress, peak stress, and Dc in both areas. We attempted to obtain initial stress values so as to minimize the residual between the simulated and inverted final slip distributions by a try-and-error method. As a result, we obtained 10 MPa as the optimal value of initial stress at the asperity. Next, we attempted to estimate spatial distribution of Dc values. For this purpose, we assumed the value to be 0.25 m in the surrounding area, and divided the asperity into four areas in the depth direction (the deepest one included the rupture initiation point (hypocenter)). We estimated Dc values, by using the same method to estimate initial stress values. As a result, we found that the Dc values became larger toward the direction of the ground surface. Comparing the inverted slip distribution with obtained heterogeneous distributions of initial stress and Dc, we found that initial stress values at the asperity were larger than those of the surrounding area, and Dc value was the smallest in the area including the rupture initiation point than the other upper three areas.