関東平野におけるやや長周期地震動のシミュレーション

概要

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Long period (2.5-12 sec) seismic motions on the Kanto sedimentary basin, Japan, are simulated by a two dimensional basin shaped underground model. We treat three shallow seismic sources located near the Izu Peninsula (their epicentral distances from Tokyo are 100-150 km). Simulations are carried out by the 2-D boundary element method with the Haskell-type dislocation source using known underground data and fault parameters. Comparing simulated motions with observed seismograms inside and outside of the basin, the following conclusions are obtained. 1) Main parts of the long period seismic motions in the basin are simulated well, with regard to their amplitudes and phases, by the 2-D basin shaped underground model. However, coda parts of the motions in the basin are not simulated. 2) The main phases in the basin are local Love waves excited in the layer of Vs=0.7 km/sec, and their characteristics are mainly controlled by the underground structure rather than the source mechanism.
1990-11-30