地震波的散射与盆地的场地效应

根据射线理论对二维盆地型试场地与Ｐ波波列特征的关系，波列中震相的性质及其产生的原因等进行了研究，对决定震相振幅大小的散射系数，几何扩散和波阻抗３个因子等的研究表明，因界面弯曲引起的广角反射和聚焦分别Ｐ波波阵中出现大能量团的第一和第二位的重要因素，在层内纵，横波波速比和层间波速比大范围变动的条件下，对界面散射系数的计算表明，介质内界面上Ｐ到Ｓ的反射转换波是指示界面两侧速度反差强弱以及入射波所在介质层

Scattering of Seismic Waves and Site Effects of Basin-Like Models

The relationship between site structures and the characteristics of P-wave-trains, and the nature of the coda waves in P-wave-trains are studied in this paper according to asymptotic ray theory. By studying the amplitude factors of scattering coefficents, geometrical spreading, and wave impedence, seperately, it is found that the supercritical reflection and caustic owing to curved boundaries are the first and second important causes for the large amplitude coda waves to come into being. The systematical computation of scattering coe-fficents shows that P to S reflected-conversion waves are the best indicator to the contrast of seismic wave impedances at the PS wave generated boundary. It is demonstrated by using synthetic seismogram method and an example that the characteristics of P-wave-trains can be used to estimate the site structures under stations.