Characterizing Seismic Scattering in 3D Heterogeneous Earth by a Single Parameter
Characterizing Seismic Scattering in 3D Heterogeneous Earth by a Single Parameter
复制标题
通过单一参数表征 3D 非均质地球中的地震散射
DOI：
--
复制
发表时间：
2020
期刊：
影响因子：
--
通讯作者：
P. Mai
中科院分区：
文献类型：
--
作者：
J. Vyas;M. Galis;P. Mai
我们推导出一个理论参数为三个地震散射制度，地震波长是短得多，类似的，或长得多的相关长度的小尺度地球的异质性。我们的分析集中在冯卡门自相关函数（ACF）的功率谱密度（PSD）上，用于表征弹性岩石参数的小尺度变化引起弹性地震波散射的空间非均匀性。我们的分析是基于这样的假设，即在相应的波数的介质不均匀性的PSD是相关的波场散射。数值模拟验证了我们的理论研究结果。在我们的模拟地震散射效应进行评估，通过检查峰值地面加速度的衰减。我们发现：（1）在所有三个区域中，地震波的散射与速度变化的标准差成正比;（2）在地震波波长短于相关长度的区域中，散射与相关长度成反比，而在其它两个区域中，散射与相关长度成正比，以及（3）散射效应由于非均匀性而弱，所述非均匀性的特征在于对于地震波长类似于或远长于相关长度的区域，冯卡门ACF的温和衰减。
We derive a theoretical parameter for three seismic scattering regimes where seismic wavelengths are either much shorter, similar, or much longer than the correlation length of small-scale Earth heterogeneities. We focus our analysis on the power spectral density (PSD) of the von Karman autocorrelation function (ACF), used to characterize the spatial heterogeneity of small-scale variations of elastic rock parameters that cause elastic seismic-wave scattering. Our analysis is based on the assumption that the PSD of the medium heterogeneities at the corresponding wavenumber is related to the wavefield scattering. Our theoretical findings are verified by numerical simulations. The seismic scattering effects in our simulations are assessed by examining attenuation of peak ground acceleration. We discover (1) that seismic scattering is proportional to the standard deviation of velocity variations in all three regimes, (2) that scattering is inversely proportional to the correlation length for the regime where seismic wavelengths are shorter than correlation length, but directly proportional to the correlation length in the other two regimes, and (3) that scattering effects are weak due to heterogeneities characterized by a gentle decay of the von Karman ACF for regimes where seismic wavelengths are similar or much longer than the correlation length.