[SCG57-P23] Construction of a dynamic fault model of the 2016 Tottoriken-chubu earthquake based on kinematic source inversion
Using thus obtained spatial distribution of the stress drop amount, numerical simulations of dynamic fault rupture and seismic wave field are carried out to obtain values of peak stress and critical slip weakening distance which satisfy the observed seismic waveforms. We employed the boundary integral equation method (Aochi et al., 2000) for dynamic fault rupture calculation, and finite difference method (Aochi and Madariaga, 2003) for seismic wave field calculation, respectively. The initial crack was assumed ot be a circle with a radius of 1.0 km, and the values of fault size, physical property and spatiotemporal increment were the same as those for obtaining temporal change of shear stress from temporal change of slip amount. The distribution of stress drop amount obtained above was taken as the initial stress distribution, and the values of peak stress and residual stress were set to be constant on the fault plane. The value of the critical slip weakening distance was set so that the hypocenter was the smallest and the other part increased in proportion to the distance from the hypocenter. We assume the value of residual stress as 0 MPa. We changed the value of peak stress between 10 and 20 MPa, and the value (minimum value) of critical slip weakening distance between 0.10 and 0.20 m, respectively, to obtain the values which satisfy the observed seismic waveforms by a trial-and-error method. As a result, the value of peak stress and the critical slip weakening distance became 14 MPa and 0.12 m, respectively. Comparing the seismic waveforms obtained from the numerical simulations with the observed ones, the amplitudes were almost the same at the observation points located in the south of the fault. However, the amplitudes of the simulated seismic waveforms were smaller than those of the observed ones at the observation points located in the north of the fault. This suggests that slip also occurred in the north part of the fault in addition to the slip area in the central part of the fault, as can be seen in the kinematic inversion result.