SEGJ Technical Conference

Simulation of seismic wave propagation in focal area of the 2003 Northern Miyagi Prefecure Earthquake using a large scale parallel-computer

Abstract In 2003 Northern Miyagi Prefecture Earthquake, damage of wooden houses was observed in the focal area. The ground motion characteristics in the focal area are not clearly understood, because there are a few seismic stations near the focal area. It is expected that the ground motion in the area were affected by the sediments with low S-wave velocity near the surface. Actually, the record of the main shock observed at Ishinomaki in the area shows a 1-sec period dominant peak of later phases. In order to clarify the mechanism of the characteristics, we tried to estimate the underground structure by waveform inversion of S-wave of the aftershock data observed by Yamanaka et al. [2004].Estimated Underground structure represents locality according to surface geology, Therefore, we made a 3D subsurface structure model from the inversion results with gravity anomaly [GSJ, 2000].We, then, simulate ground motion by finite difference method, using the subsurface structure model. We found the significant later phases in the synthetic motions and concluded that the later phases in the 2003 Northern Miyagi Prefecture Earthquake is surface waves converted from S-wave by the irregularity of sediment.