In a series of papers, Kawakatsu et al. (2015) and Kawakatsu (2016a, b, 2017) introduced and discussed a new parameter, ηκ, that characterizes the incidence angle dependence (relative to the symmetry axis) of seismic body wave velocities in a transverse isotropy (TI) system. With the properly defined new set of parameters, Kawakatsu (2016b) further demonstrated that sensitivities of those parameters to Rayleigh wave phase velocity made much more sense and thus they were useful for long-period seismology. More recently, Kawakatsu (2017) showed how the reflection and transmission coefficients behaved in terms of ηκ. During the course of these exercises, several nontrivial consequences of transverse isotropy are realized and summarized as follow: (1) a trade-off exists between ηκ and Vp/Vs-ratio if assumed for isotropy; (2) P-wave velocity (anisotropy) strongly influences the conversion efficiency of P-to-S and S-to-P, as much as S-wave velocity perturbation does; (3) Rayleigh wave phase velocity has substantially sensitivity to P-wave anisotropy near the surface. These findings, especially the last two, might deserve careful attention in interpretation of results of popular seismic analysis methods, such as receiver function analyses and ambient noise Rayleigh wave dispersion measurements. Especially, the strong influence of P-wave anisotropy to P-to-S and S-to-P conversion may be essential to the receiver function analysis, because, for isotropic media, we typically attribute the primary receiver function signals to S-wave velocity changes. Considering that the receiver function analysis has become a popular and powerful tool to investigate the crustal and upper mantle structures, it seems important to fully investigate to what extent and under what circumstances the effect might be significant.

中文翻译：

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横向各向同性的意外后果

在一系列论文中，Kawakatsu 等人。(2015) 和 Kawakatsu (2016a, b, 2017) 介绍并讨论了一个新参数 ηκ，它表征横向各向同性 (TI) 系统中地震体波速度的入射角依赖性（相对于对称轴）。有了正确定义的新参数集，Kawakatsu (2016b) 进一步证明这些参数对瑞利波相速度的敏感性更有意义，因此它们对长周期地震学很有用。最近，Kawakatsu (2017) 展示了反射系数和透射系数在 ηκ 方面的表现。在这些练习过程中，横向各向同性的几个重要后果被实现并总结如下：（1）如果假设各向同性，则在 ηκ 和 Vp/Vs 比之间存在权衡；(2) P波速度（各向异性）对P-to-S和S-to-P的转换效率影响很大，与S波速度扰动一样；(3)瑞利波相速度对地表附近的纵波各向异性有很大的敏感性。这些发现，尤其是最后两个发现，在解释流行的地震分析方法的结果时可能值得认真关注，例如接收器函数分析和环境噪声瑞利波色散测量。特别是，P 波各向异性对 P 到 S 和 S 到 P 转换的强烈影响可能对接收函数分析至关重要，因为对于各向同性介质，我们通常将主要接收函数信号归因于 S 波速度变化。