Source Modeling of Recent Large Inland Crustal Earthquakes in Japan and Source Characterization for Strong Motion Prediction

Abstract eng:
Dense strong motion observation networks provided us valuable data for studying strong motion generation from large earthquakes. In recent years, several large earthquakes occurred in Japan, and a large amount of strong motion data is recorded. It is important for advancement of source modeling in scenario-based strong motion prediction to quantify detailed source characteristics of past earthquakes. We have estimated the source rupture process of these earthquakes by the kinematic waveform inversion using strong motion data. The asperity, where slip is relatively large compared to average slip over the fault, is quantified following the criteria proposed by Somerville et al. (1999). The stress changes during these earthquakes are cestimated from the detailed slip distributions obtained by the kinematic waveform inversion. The stress drops on and off asperities are characterized based on the stress change distributions obtained here. The stress drop on asperity is one of key parameters in source modeling, because stress drop is related to slip velocity of the source fault and associated ground motion. We compiled the stress drop on the asperities together with data set of previous studies for other inland earthquakes in Japan and others. The static stress drop on asperity depends on its depth, and we obtained an empirical relationship between static stress drop and asperity’s depth. Moreover, surface breaking asperities appeared to have smaller stress drop than buried asperities.

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