各向异性介质qP波传播描述Ⅱ:分离纯模式标量波

Description of qP-wave propagation in anisotropic media,Part II:Separation of pure-mode scalar waves

在各向异性地震波场中,qP波与qS波常常是耦合在一起的.多分量地震数据处理中一个关键环节就是波型分离(即模式解耦),以纵波成分为主的常规单分量地震数据的成像则需要合理描述标量qP波的传播算子.本文作者曾构建了在运动学上同弹性波动方程等价,动力学上突出标量qP波的伪纯模式波动方程.为了彻底消除qS波残余,本文根据波矢量与qP波偏振矢量之间的偏差,提出从伪纯模式波场提取纯模式标量qP波的方法.数值分析展示了投影偏差算子在波数域和空间域的特征.基于不同复杂程度理论模型的试验结果表明,联合"伪纯模式传播算子"与"投影偏差校正"可为各向异性介质分离模式波场传播过程提供一种简便的描述工具.

In anisotropic seismic wavefields,qP and qS waves are generally coupled.Mode decoupling or separation is the most important step for processing of multi-component seismic data,while a scalar qP-wave propagator is prerequisite for imaging of the conventional single component seismic data that predominantly record compressional waves.The authors had formerly built a pseudo-pure-mode wave equation that is kinematically equivalent to the original elastic wave equation and highlights the energy of scalar qP-waves for arbitrary anisotropic media.To remove the residual qS-waves,we propose an approach to extract pure-mode scalar qPwaves from the pseudo-pure-mode wavefields according to the deviation between wave and polarization vectors. Numerical analysis demonstrates the characteristics of the projection deviation operators in wavenumber and space domains respectively.Examples of synthetic models of different complexity show that,pseudo-pure-mode wave propagator plus correction of the projection deviation can provide an effective tool to describe propagation of separated wave modes in anisotropic media.