観測記録と数値シミュレーションから推定される1995年兵庫県南部地震によるやや長周期地震動の伝播特性

概要

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To deepen our understanding on long period ground motion used for seismic design, the ground motion in the Osaka basin due to the 1995 Hyogo-ken Nanbu earthquake is studied. First, peak frequencies observed at Fukushima in Osaka city are discussed with the underground structure. Then, direction and velocity of wave propagation are estimated, using up-down component observed at very densely spaced stations in Osaka city. The velocities are close to the phase velocity of the fundamental mode of Rayleigh wave. Propagating direction is about N30W, indicating that the long period ground motion is predominated by the surface waves affected by 3-D topographical conditions. Using boundary element analysis, the 3-D effects on the ground motion is investigated, with a result that the long period ground motion is propagated from N40W direction with surface wave velocity.
1997-08-30