SH波在表面多层介质中传播的精确模拟

Precise Modelling of SH Wave Propagation in Subsurface Multi-layer Media

针对地震横波在地表低速层内的振幅放大效应问题 ,提出了一种模拟SH波在地表层状介质中传播的递推算法 ,并用它模拟了新西兰Alfredton盆地A10场址的SH波地震动响应特性。这个方法适用于具线性吸收性质的粘弹性介质。由于方法不受介质层厚薄制约 ,层厚可以无限薄化 ,实践上可以用许多薄层逼近的办法来模拟纵向上任意变化的连续介质。通过求取不同频率不同波数平面简谐波解并按实际问题加权迭加可求解具特定波形和传播方向组合的任意SH波场。此方法在计算上具有解析解特有的精确性 ,稳定性和方便性 ,特别适用于模拟薄层介层 ,次波长现象及需要进行大量而又精确模拟计算的情形。

A recurrence algorithm is presented in this paper for modelling SH waves in subsurface multi-layer media. The ground motion amplification due to SH waves at Site A10 in the Alfredton Basin, New Zealand, is modelled using this approach. The approach is applicable to linear attenuation media. The thickness of the layers can be infinitely thin. Hence the approach can practically be applied to vertically continuous media by using many thin layers to approximate the continuous media. General SH waves with arbitrary waveforms can be modelled by stacking of all the fundamental harmonic plane wave solutions obtained using the approach. As it is analytical the solution is stable and precise. Thus it is suitable for modelling wavefields in very thin layers, sub-wavelength phenomena, or for cases in which computation is heavy while precision is crucial.