三维VTI介质中波动方程深度偏移的最优分裂Fourier方法

从含Thomsen各向异性参数的qP波相速度表示式出发，建立并求解三维VTI介质中的频散方程，得到三维VTI介质中的相移算子，进而将以相移算子为基础的最优分裂Fourier方法推广到三维VTI介质，发展了一个三维VTI介质的深度偏移方法.文中使用的各向异性介质的速度模型与现行的各向异性构造的速度估计方法一致，将各向同性、弱各向异性及强各向异性统一在一个模型中.文中提出的偏移算法对相移法引入了高阶校正项来补偿介质横向变化的影响，使该方法可应用于横向非均匀VTI介质的陡角度成像，文中给出的偏移脉冲响应很好地证明了这一点.

Wave equation depth migration with optimum split-step Fourier method in 3-D VTI media

A Dispersion equation for the transversely isotropic media with a vertical symmetry axis (VTI) is derived from the phase velocity expressed in terms of Thomsen parameters. Based on the vertical wavenumber solved from the dispersion equation, the optimum split-step Fourier 3-D wave equation depth migration method in isotropic media is extended to 3-D VTI media. The macro velocity model used for describing VTI media is consistent with current velocity estimation method, and can simultaneously accommodate the isotropy, weak anisotropy and strong anisotropy. Involving higher order correction terms added to the phase-shift method, the proposed algorithm can model wider-angle wavefield with a high accuracy in the presence of severe lateral velocity variations in 3-D VTI media. The accuracy of the proposed algorithm is demonstrated by 2-D and 3-D migration impulse responses.