黏弹性与弹性介质中Rayleigh面波特性对比研究

Rayleigh面波的频散特性可以用来研究地表浅层结构. 本文使用时域有限差分法来模拟复杂黏弹性介质中的Rayleigh面波,研究了Q值对面波频散特性的影响.文中采用旋转交错网格有限差分,以非分裂卷积形式的完全匹配层为吸收边界,推出了求解二阶位移-应力各向同性黏弹性波动方程的数值方法.为了检验数值解的精度,首先将简单模型的正演结果与解析解对比,验证了方法的正确性;然后模拟了横向缓变层状介质和含有洞穴的介质中的面波,对弹性和黏弹性介质中的面波的频散特性进行对比分析.模拟结果表明浅层Q值对面波的频散特性有显著的影响;强吸收情况下,高阶面波的能量相对低阶面波能量显著增强.

Comparison of the Rayleigh wave in elastic and viscoelastic media

Dispersion properties of Rayleigh-type surface waves can be used for imaging and characterizing the shallow subsurface.This paper models Rayleigh waves in complex viscoelastic media by using the time-domain finite difference method on the rotated staggered grid.We compared the dispersion properties of the viscoelastic Rayleigh wave with the elastic one.We proposed a method to model the Rayleigh wave based on the second-order displacement-stress viscoelastic wave equations and the unsplit convolutional perfectly matched layer absorbing boundary condition.The validity of our method is tested by two examples.Then,the wave fields are calculated in a laterally heterogeneous media and a media with cavity.We analyzed the dispersion properties of the Rayleigh waves.The dispersion curve varies considerably with quality factor Q in shallow subsurface;the higher modes of Rayleigh waves are generated and possess significant amounts of energy for strong attenuation.