Stress-induced seismic anisotropy is usually difficult to be separated or decoupled from intrinsic or fracture-induced anisotropy in the subsurface. To distinguish the effects of fracture and stress on azimuthal reflection amplitudes in an anisotropic medium, a feasible approximation for decoupled fracture- and stress-induced PP-wave reflection coefficient is presented used for azimuthal seismic inversion. Following nonlinear acoustoelastic theory, we first present the relationship between horizontal uniaxial stress and decoupled fracture- and stress-induced PP-wave reflection coefficient for an interface between two stressed horizontal transversely isotropic (HTI) media based on weak-contrast, weak-anisotropy and small-stress assumptions. Next, we present an inversion method of amplitude variations with angles of incidence and azimuth to estimate decoupled fracture- and stress-induced anisotropy using the seismic amplitude differences between different azimuths. Finally, both synthetic and real data sets are used to validate our proposed inversion method, and it can provide an alternative way to estimate the decoupled fracture- and stress-induced anisotropic parameters in stressed shale gas reservoir with HTI symmetry from azimuthal reflection amplitude data.

应力引起的地震各向异性通常很难与地下固有的或裂缝引起的各向异性分离或解耦。为了区分各向异性介质中裂缝和应力对方位角反射振幅的影响，提出了一种用于方位角地震反演的解耦裂缝和应力引起的 PP 波反射系数的可行近似。遵循非线性声弹性理论，我们首先基于弱对比度、弱各向异性和小应力假设。接下来，我们提出了一种振幅随入射角和方位角变化的反演方法，以利用不同方位角之间的地震振幅差来估计解耦断裂和应力引起的各向异性。最后，使用合成数据集和实际数据集来验证我们提出的反演方法，它可以提供一种替代方法，根据方位反射振幅数据估计具有 HTI 对称性的应力页岩气储层中解耦裂缝和应力引起的各向异性参数。