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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 multi-component wavefield obtained by the wavefield extension contains both longitudinal and transverse wave information. Whether the separation of transverse and longitudinal waves can be realized in the full wave field is of great significance to reverse time migration. The traditional wavefield separation method using helicity can completely separate the longitudinal and transverse wavefields in isotropic media, but this method is no longer effective in the wavefield separation of anisotropic media. By solving the Christoffel equation, the direction of polarization with the wavenumber is obtained in the wavenumber domain, and the inverse Fourier transform is used to obtain the wavefield separation operator in the space domain. The operator changes with the change of the elastic parameters of each point in the space domain. By using the operator to separate the wave fields in the anisotropic medium, the complete separation of the longitudinal and shear waves can be obtained from the full wave field. In order to verify the validity of the algorithm, a uniform VTI media model and a layered VTI media model are used for trial calculation. The calculation results show that the wave field separation method can effectively separate the wave field in VTI media.