VTI介质中的波场分离

Wave-field Separation in VTI Media

波场延拓得到的多分量波场中既包含纵波信息也包含横波信息。能否在全波场中实现横纵波的分离对于逆时偏移具有重要意义。利用散旋度的传统波场分离方法在各向同性介质中可以将纵横波场完全分开,但这种方法在各向异性介质的波场分离中不再有效。通过求解Christoffel方程,在波数域得到随波数变化的偏振方向,进行傅立叶反变换得到空间域的波场分离算子。该算子随空间域各点弹性参数的变化而变化,通过使用该算子来进行各向异性介质中的波场分离,从全波场中可得到分离完全的纵波与横波。为验证算法的有效性,分别使用均匀VTI介质模型和层状VTI介质模型进行试算。计算结果表明,波场分离方法能够有效实现VTI介质中的波场分离。

The extrapolated multi-component wavefield contains both compressional wave and shear wave.Whether compressional wave and shear wave can be separated from wavefield makes differences in reverse-time migration.The traditional wave-separation methods based on divergence and curl perform well in isotropic media,while it is not the case in anisotropic media,In this paper,through solving the christoffel equation,we can get the polarization vector changing with wave number in wave-number domain,then an inverse fourier transform is exerted to get a wavefield separation operator in space domain.This wavefield separation operator varied with the elastic parameters in space domain can be used to implement the wave-separation in anisotropic media.To test the efficiency of the algorithm,a test is implemented by a homogeneous and layered VTI anisotropic model.The result shows that the wave-separation methods proposed here can achieve the complete wave separation in VTI media effectively.