重力異常を用いた3次元地盤モデルの構築と地震波伝播シミュレーション

抄録

This article presents a technique to build 3 dimensional underground structure for earthquake ground motion estimation directly from gravity anomaly. The local gravity anomaly is evaluated by subtracting the regional gravity anomaly from the Bouguer anomaly, and the depth of irregular shaped bedrock is regressed assuming linear dependency to the local gravity anomaly along reflection survey lines and at outcrops. Since gravity anomaly around Japan is well studied, this method is effective especially for the regrion where few underground surveys are conducted. We apply this method to construct 3D underground model around the epicentral region of the 1997 Northwestern Kagoshima prefecture earthquake. Three dimensional finite difference method with this 3D underground structure model simulates the observed records better than that with simple 1D underground structure model.