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在模拟地震波在介质中传播过程的研究中,正演模拟是一个重要的方面。该文采用间接边界元法(IBEM)对横观各向同性(TI)不同参数介质的凸起场地中入射SH波的散射问题进行了正演模拟,研究了TI凸起场地对SH波的放大效应。放大效应是通过地表位移与基岩露头位移幅值的比值来体现的。该间接边界元法结合了层状TI半空间精确动力刚度矩阵和均布斜线荷载动力格林函数,具有较高的精度。该文分别给出了TI介质凸起中SH波散射问题在频域和时域内的解答。频域内研究分析表明,土体TI介质参数的变化会对场地位移幅值的放大谱和空间分布产生显著的影响,即改变了凸起部分和土层的动力特性,使得两者动力相互作用发生改变。时域内研究表明,SH波在凸起周围的传播同时依赖于TI介质参数的具体取值和传播方向。时域位移幅值云图清晰地展示入射波、透射波、反射波和散射波的传播过程,凸起角点产生的散射波在TI介质中传播呈现“半椭圆”型,而在各向同性介质中呈现“半圆”型。
In simulating the propagation of seismic waves in a medium, forward modeling is an important aspect. In this paper, the indirect boundary element method (IBEM) was used to simulate the scattering of incident SH wave in the convexity field of transversely isotropic (TI) media with different parameters. The amplification of SH wave at TI raised site effect. The amplification effect is reflected by the ratio of the surface displacement to the amplitude of the outcrop of bedrock. This indirect boundary element method combines the precise dynamic stiffness matrix in layered TI half-space and the uniformly distributed diagonal load dynamics Green’s function with high accuracy. In this paper, the solutions of SH-wave scattering in TI media bumps are given in the frequency and time domains, respectively. The analysis in the frequency domain shows that the change of the TI media parameters will have a significant effect on the magnification spectrum and spatial distribution of the displacement amplitude of the soil, ie, the dynamic characteristics of the raised part and the soil layer are changed so that the dynamic interaction between the two occurs change. The study in the time domain shows that the propagation of SH waves around the bumps depends on the specific values and propagation directions of the TI medium parameters. The time-domain displacement amplitude cloud clearly shows the propagation of incident, transmitted, reflected and scattered waves. The scattered waves generated at the raised corners appear “semi-elliptical” in the TI medium, whereas in all directions The same sex medium presents “semi-circle ” type.