【摘要】 产生地震动空间效应的主要原因是地质构造的变化会极大地改变复杂场地条件下到达不同观测点的地震波,因此地震波振幅和相位发生明显变化。本文利用有限元和边界元耦合的方法,通过建立雷克子波入射时的非线性响应模型求解复杂场地条件下的波动积分方程,进行复杂近地表构造中地震波场数值模拟,旨在分析复杂场地条件下入射方向不同的地震波的动力响应规律。研究结果显示近地表会极大地改变地震波传播特征,导致地震波传播趋向不一致性的因素是由于复杂场地条件重建了地震波的传播路径,尤其须指出的是非一致性地表位移响应源于软土层中低频子波的传播。在地震响应分析中导致系统不同动力响应的其他原因是主频和地震波速度结构的改变,同时地震波入射角度的改变会引起到达观测点的时间滞后,地表位移响应随着入射角度的增大而增加,地震动的空间效应随着入射角度的减小而愈趋明显。更多还原

【Abstract】 The main factor to cause the spatially varying ground motions is that the complex of the geological structure can greatly change the propagation of seismic waves at different sites,which will result in the anomalous variation of the amplitude and phase.In this study,a previously developed coupled Boundary Elements-Finite Elements algorithm is employed for simulating the Ricker wave propagation in the complex near surface structure by solving the wave propagation equation with site conditions.The result reveals that the soft site conditions and soft local sites rebuild the propagation routes of the seismic waves,which will result in the tendency of the non-uniform of the propagation.The importance is that the low frequency Ricker waves of the soft local sites will lead to the obvious non-uniform of the ground displacement responses.In the analysis of the seismic responses,the other main factors resulting in different dynamic responses are the dominant frequency and wave velocity.Due to the incident wave angles,the arrival time of the seismic waves will be different.,the ground displacement is increased with an increment of the incident angle;on the other hand,with a decrement of the incident angle,the non-uniformity will be more obvious.更多还原