地盤の震動特性評価の際の地形の影響

Abstract

The influence of topographic features on earthquake motions at the rock outcrop was studiedfrom examining the nature of particle motions of P waves. The apparent angles of P waves, estimated from particle motions diagrams in the vertical plane, vary in dependence of thedirections of seismic arrivals.The evaluation of the topographical effect on the motions at the point on the irregular surfacewas made, by applying the method studied by Aki and Larner to calculate the scattered wavefield in a layer with an irregular interface. The calculated values of the apparent angles ofP waves' motions explain well the observed values. Some problems were discussed to obtainthe input motions to the base rock from the observation at the rock outcrop.