The critical angle plays a crucial role in data processing for refraction seismology. In the context of three-dimensional data, the critical angle exhibits azimuthal dependence, particularly in the presence of an anisotropic model. In this paper, we propose a method to determine the critical angle (phase angle) and analyse the sensitivity of the critical angle to the model parameters and the available azimuthal range for both transversely isotropic medium with a vertical symmetry axis and orthorhombic models. For more complex orthorhombic models, the critical angle can be computed while considering changes in azimuth. In a numerical example, we apply sensitivity analysis to examine the existence of the critical angle and determine its corresponding values to variations in model parameters and the azimuthal range. Additionally, we conduct computations of the critical angle for the simplified acoustic and elliptical orthorhombic models. This analysis can be extended to encompass all model parameters for different wave modes (pure and converted waves), and they provide generalized predictions for the available range of data in seismic data processing applications.

中文翻译：

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弹性斜方介质中临界角的敏感性研究

临界角在折射地震学数据处理中起着至关重要的作用。在三维数据的背景下，临界角表现出方位角依赖性，特别是在存在各​​向异性模型的情况下。在本文中，我们提出了一种确定临界角（相位角）的方法，并分析了具有垂直对称轴的横观各向同性介质和正交模型的临界角对模型参数的敏感性以及可用的方位角范围。对于更复杂的正交模型，可以在考虑方位角变化的同时计算临界角。在数值示例中，我们应用敏感性分析来检查临界角的存在，并确定其与模型参数和方位角范围的变化相对应的值。此外，我们还计算了简化的声学模型和椭圆正交模型的临界角。这种分析可以扩展到涵盖不同波模式（纯波和转换波）的所有模型参数，并且它们为地震数据处理应用中的可用数据范围提供通用预测。