やや長周期地震動を構成する堆積層表面波の生成伝播過程に関する研究

概要

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Significant later phases following the S-wave arrivals in horizontal components often appear in the ground motions recorded in the sedimentary plain. In this paper, we discuss the propagation process of ground motions generated by a shallow earthquake through the analysis of seismograms recorded on rock and sediment sites. To accomplish it, we first deployed a temporary stations for seismic refraction prospecting to clear up the boundary between the mountain range and the edge of the sedimentary plain in the southwestern edge of the Kanto Plain. Accordingly, we employed the recordings of seismic waves generated by explosions to model the subsurface structures applying travel time analysis. We also applied 2D finite difference method to simulate the later phases during an earthquake observed at the sediment sites using the subsurface structures derived from the seismic prospecting process. The results indicate that when considering basin-excited waves, the characteristics of the simulated waveforms including the later phases display good agreement with the observed seismograms.
2007-09-30