含流体层的河谷场地对地震波散射的间接边界元法模拟

IBEM simulation of seismic wave scattering by valley topography with fluid layer

结合单相介质动力格林函数和流体域格林函数,将间接边界元方法拓展到含流体层河谷对地震波散射的求解,并结合具体算例进行大量参数分析。研究结果表明,含流体层河谷地形对平面P波、SV波入射时的地震响应受控于入射波频率、入射波角度及流体深度等多种因素。总体来看:(1)在低频域内,含流体河谷底部及附近地表的频谱特性与不含流体的河谷反应基本一致;(2) P波入射时在水层体系共振频率处,河谷底部位移缩小效应显著,而此频率处流体表面位移达到最大;(3)流体层具有吸收地震波能量的作用,流体深度越大,河谷表面及附近地表的地震动位移越小。研究成果可在一定程度上为河谷地形附近地震动效应的评估及防震减灾工作提供理论依据。

Combined with the dynamic Green’s function of single-phase medium and the Green’s function in the fluid domain,the indirect boundary element method is developed to solve the scattering of valley topography with fluid on plane P and SV waves,and the parameter analysis is carried out in combination with specific examples. The results show that the seismic response of valley topography with fluid layer to plane P and SV waves is controlled by many factors,such as incident wave frequency,incident wave angle and the depth of fluid.Generally speaking:(1) In the low frequency domain,the frequency spectrum characteristics of the valley bottom and the nearby surface are basically the same in the valley with or without water.(2) When P wave incidents,at the resonance frequency of this aquifer system,the displacement at the bottom of the valley decreases significantly,but the displacement of fluid surface reaches the maximum.(3) The fluid layer has the function of absorbing seismic wave energy.The larger the fluid depth is,the smaller the ground motion displacement of the valley surface and nearby ground is. The results can provide a theoretical basis for the evaluation of the ground motion effect near the valley terrain and the work of earthquake prevention and mitigation.