Scattering of elastic waves in geometrically anisotropic random media and its implication to sounding of heterogeneity in the Earth's deep interior
Scattering of elastic waves in geometrically anisotropic random media and its implication to sounding of heterogeneity in the Earth's deep interior
复制标题
弹性波在几何各向异性随机介质中的散射及其对地球深处非均质性探测的影响
DOI：
10.1111/j.1365-246x.2005.02760.x
复制
发表时间：
2005
影响因子：
2.8
通讯作者：
R. Wu
中科院分区：
文献类型：
--
作者：
T. Hong;R. Wu
摘要
从散射衰减、尾波电平和散射方向性方面研究了几何各向异性介质中弹性波的散射特征。使用多重前向散射和单一后向散射近似来公式化散射衰减随归一化波数 (ka) 的理论变化。从数值模拟中获得的估计值与理论预测非常吻合。散射水平受各向异性（纵横比、方向）和波入射方向的影响。散射水平对波入射方向的尺度变化不敏感，但对切线方向的尺度变化高度敏感。当波沿几何各向异性非均质性的主方向入射时，前向散射占主导地位；当波沿次要方向入射时，后向散射占主导地位。在具有各向异性非均质性的介质中，散射能量不是各向同性分布的，早期尾波的水平随波入射角的变化而变化。晚期尾波由多散射和多路径波组成，并表现出随机稳定的能级。波的入射角是早期尾波变化的关键参数，在从地震尾波和前兆研究地球深处的各向异性不均匀性时，需要一种对入射角进行分类的地震数据的方法。
SUMMARY
The scattering features of elastic waves in media with geometrically anisotropic heterogeneities are investigated in terms of scattering attenuation, coda level and scattering directivity. The theoretical variation of scattering attenuation with normalized wavenumber (ka) is formulated using the multiple forward scattering and single backscattering approximation. Estimates obtained from numerical simulations agree with the theoretical predictions well. The level of scattering is influenced by the anisotropy (aspect ratio, direction) and the wave incidence direction. The scattering level is not sensitive to the scale variation in the wave incidence direction, but is highly sensitive to the scale variation in the tangential direction. Forward scattering is dominant when waves are incident along the major direction of geometrically anisotropic heterogeneity, and backward scattering is dominant when the waves are incident in the minor direction. The scattered energy is not distributed isotropically in media with anisotropic heterogeneity, and the level of early coda varies with the wave incidence angle. The late coda is composed of multiscattered and multipathing waves, and displays a stochastically stable energy level. The incidence angle of waves is a key parameter in the early coda variation, and an approach with classified seismic data for incidence angle is desired in the study of anisotropic heterogeneity in Earth's deep interior from seismic coda and precursor.