Ignoring anisotropy characteristic of subsurface media may lead to misplaced images and low resolution of the target for the reverse-time migration (RTM). The mature anisotropic RTM methods are mainly based on the pseudoacoustic wave approximation. Although these schemes have high computational efficiency, most of pseudo-acoustic wave equations (PWEs) inevitably encounter SV-wave artifacts or instability for anisotropic modeling and imaging. To improve the anisotropic RTM quality, we develop a combination of optimal pure acoustic wave and complex wavefield separation to conduct anisotropic RTM for both surface and vertical seismic profiling (VSP) acquisition geometries. Among the proposed scheme, we derive an optimal pure acoustic wave dispersion relation, and solve the corresponding wave equation by incorporating finite-difference and Poisson solver. The modified equation can remove SV-wave artifacts and instability of PWEs. Wavefield separation approach can choose desired wavefield components along different directions to carry out the final imaging, which can effectively suppress low-frequency imaging noise. Moreover, the hybrid absorbing boundary condition is adopted to suppress artificial boundary reflections during wavefield extrapolation. Basic theory and modeling examples demonstrate that the developed schemes can generate RTM results with high accuracy.

忽略地下介质的各向异性特征可能导致逆时偏移（RTM）图像错位和目标分辨率低。成熟的各向异性 RTM 方法主要基于拟声波近似。尽管这些方案具有较高的计算效率，但大多数伪声波方程（PWE）不可避免地会遇到 SV 波伪影或各向异性建模和成像的不稳定性。为了提高各向异性 RTM 质量，我们开发了最佳纯声波和复杂波场分离的组合，以针对表面和垂直地震剖面 (VSP) 采集几何进行各向异性 RTM。在所提出的方案中，我们推导出了一个最优的纯声波色散关系，并通过结合有限差分和泊松求解器求解相应的波动方程。修改后的方程可以消除 SV 波伪影和 PWE 的不稳定性。波场分离方法可以选择沿不同方向的所需波场分量进行最终成像，可以有效抑制低频成像噪声。此外，在波场外推过程中，采用混合吸收边界条件抑制人工边界反射。基础理论和建模实例表明，所开发的方案可以生成高精度的 RTM 结果。能有效抑制低频成像噪声。此外，在波场外推过程中，采用混合吸收边界条件抑制人工边界反射。基础理论和建模实例表明，所开发的方案可以生成高精度的 RTM 结果。能有效抑制低频成像噪声。此外，在波场外推过程中，采用混合吸收边界条件抑制人工边界反射。基础理论和建模实例表明，所开发的方案可以生成高精度的 RTM 结果。