81011531

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断層の動的破壊パラメータの空間不均質分布の推定 : 2016年鳥取県中部地震を例にして

Estimation of the dynamic rupture parameters for the 2016 Tottoriken-chubu earthquake

Japanese (日本語)

神戸大学都市安全研究センター研究報告

21

1-15

神戸大学都市安全研究センター

2017-03

2019-05-30

In this study, 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; the fault size is 19.5 km (strike)-18 km (dip). We attempted to obtain spatial distributions of initial stress and critical slip weakening distance (called Dc hereafter), which can fit better the slip distribution obtained from inversion analysis performed by Kobayashi et al. (2016). The inverted final slip distribution has an area whose slip amount is very large just above the hypocenter, reaching 1.33 m. We divided the fault plane into two areas; one is the area with a large slip amount (hereafter called asperity), and the other is the surrounding one with a small slip amount. We fixed the residual stress, peak stress, and Dc values in both areas. We attempted to obtain an initial stress value so as to minimize the residual between the simulated and maximum slip amount by Kobayashi et al. (2016) by a try-and-error method. As a result, we obtained 10.6 MPa as the optimal initial stress value on the asperity, and found that an initial stress value on the asperity was larger than that of the surrounding,. 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, and divided the asperity into four areas in the depth direction (the deepest one included the rupture initiation point). We estimated Dc values by the same method that used to estimate initial stress value. As a result, we found there is a trend that the Dc value becomes larger toward the direction of the ground surface.

紀要論文