Pure‐mode wave propagation is important for applications ranging from imaging to avoiding parameter tradeoff in waveform inversion. Although seismic anisotropy is an elastic phenomenon, pseudo‐acoustic approximations are routinely used to avoid the high computational cost and difficulty in decoupling wave modes to obtain interpretable seismic images. However, such approximations may result in inaccuracies in characterizing anisotropic wave propagation. We propose new pure‐mode equations for P‐ and S‐waves resulting in an artefact‐free solution in transversely isotropic medium with a vertical symmetry axis. Our approximations are more accurate than other known approximations as they are not based on weak anisotropy assumptions. Therefore, the S‐wave approximation can reproduce the group velocity triplications in strongly anisotropic media. The proposed approximations can be used for accurate modelling and imaging of pure P‐ and S‐waves in transversely isotropic media.

中文翻译：

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横向各向同性介质中的纯P波和S波方程

纯模式波传播对于从成像到避免波形反转中的参数折衷的应用非常重要。尽管地震各向异性是一种弹性现象，但通常使用伪声近似来避免高计算成本和解耦波模式以获得可解释地震图像的困难。但是，这样的近似可能导致表征各向异性波传播的准确性。我们为P和S波提出了新的纯模式方程，从而在具有垂直对称轴的横观各向同性介质中产生了无伪像的解。我们的近似值比其他已知的近似值更准确，因为它们不是基于弱各向异性假设。因此，S波近似可以在强各向异性介质中再现群速度三重。