SOURCE CHARACTERIZATION FOR AN INLAND LARGE EARTHQUAKE AND NEAR-SOURCE STRONG GROUND MOTION SIMULATION

摘要

We simulate strong ground motions during (be 1948 Fukui earthquake, Japan with the JMA magnitude 7.1 based on a heterogeneous souce model and the hybrid simulation technique. Most of the source models have been assumed to have uniform slip distribution on rectangular fault plane. Such models could generate ground motions only available longer than several seconds, underestimating shorter period motions (<1 sec) of engineering interest. We assume two source models of reverse (Model-1) and normal (Model-2) types with a heterogeneous slip distribution on fault plane based on the self-similar scaling relationships of seismic moment versus asperity areas and slips by [Somerville et al.,1999]. Simulations have been carried out by the hybrid scheme combined the 3-D Finite Difference Method with the stochastic simulation technique. Large ground motions from both models are spread over the Fukui basin, although peak velocity distributions are slightly difference each other. Areas over 30% collapse ratio during the Fukui earthquake correspond to those with peak velocity over 60 cm/sec for Model-1 and over 80 cm/sec for Model-2. The level of the peak velocity in the areas with more than 30% collapse ratio are estimated to be over 80 cm/sec based on the previous studies by [Moroi et al., 1998] and [Miyakoshi and Hayashi, 1998]. From this result and the comparison of pseudo velocity response spectral level with those within the damage belt during the 1995 Hyogo-ken Nanbu earthquake, we conclude that the damage distribution during the Fukui earthquake is well explained by strong ground motions simulated for Model-2 combined the normal fault model by [Kikuchi et al., 1999] with a standardized heterogeneous source model developed by [Somerville et al.,1999].