断层下方地壳分层结构对地震动模拟结果的影响研究

Research on influences of crust layered structure beneath fault on seismic ground motion simulation

考虑震源破裂过程的三维地震动数值模拟一般需将震源包含在计算区域中,这样的计算模型区域大,计算量大,尤其是对于断层埋深较大的情况。本文对破裂断层下地壳分层结构引起的反射波的影响进行了分析,分别对改变断层下方介质的密度和波速两个参数的模拟结果进行了对比,结果表明:断层下方地壳分层结构引起的反射波对地表观察点地震动时程的影响很小,可以忽略。因此进行三维地震动数值模拟可以不考虑断层下介质的影响,从而可以大大减小计算区域,提高计算效率。

Three dimensional seismic ground motion simulation considering source rupture process generally in- cludes source in the computational domain, in which the computation region and amount are quite large, especially in the case of large buried depth of the fault. Analysis of the influences of reflected wave cause^l by the crust lay- ered structure beneath fault has been made in this paper, and the simulation results are compared when medium density and wave velocity under the fault are changed respectively. The results show that the effect of reflected wave caused by the crust layered structure beneath fault on the ground motion of surface observation points is small and negligible. So we can ignore the effect of medium under the fault in 3D numerical simulation of strong ground mo- tion, which will reduce the calculation region significantly and the calculation efficiency is improved as well.