内源作用下盆地倾角对地表地震动放大特征的影响

Effect of basin slope angle on ground motion amplification characteristics under internal point source

基于二维盆地模型和内置震源,利用高精度谱元法,探究了近场点源作用下,盆地倾角对盆地地面运动时、频域放大特征的影响。结果表明:内源作用下盆地地震效应及其随盆地参数的变化特征与平面波入射情况显著不同。从时域分析角度,盆地倾角对盆地内地震波的传播过程影响显著。盆地边缘效应依然明显,最大放大系数出现在盆地边缘,其值与盆地倾角无线性关系,但较小倾角下盆地中心的聚焦效应显著,形成另一强烈放大区。从频域分析角度,相比一维水平成层模型,盆地倾角的变化主要影响盆地边缘区域的放大,最大放大系数3左右,且最大放大系数有随盆地倾角减小而增大的趋势;盆地中心区域整体放大作用不明显,但对高频段仍有1.2倍左右放大。

Based on the two-dimensional basin model and the internal point source,the influence of the basin slope angle on the amplification characteristics of the ground motion in time and frequency domain analysis was investigated by using the high-accuracy spectral element method.The results show that the influence of basin slope angle on seismic wave propagation is significant from the time domain view.The effect of the basin edge is still obvious,and the maximum amplification coefficient appears at the basin edge,which has a non-linear relationship with the basin slope angle,but the focusing effect at the center of the basin under a small slope angle is significant,forming another strong amplification area.On frequency domain aspects,compared with the one-dimensional horizontal stratification model,the change of basin slope angle mainly affects the amplification of the basin edge region,with the maximum amplification coefficient around 3,and the maximum amplification coefficient tends to increase with the decrease of basin slope angle.The magnification of the central region of the basin is not obvious,but there is still about 1.2 times magnification of the high frequency band.