In microseismic monitoring, obtaining reliable information about event properties, such as the location, origin time, and moment-tensor components, is critical for evaluating the success of fluid-injection programs. Elastic wavefield-based migration approaches can robustly image microseismic sources by extrapolating data through an earth model and evaluating an imaging condition. The success of these imaging methods, though, primarily depends on the elastic model’s accuracy. The previously developed extended PS energy imaging condition can provide valuable information about the accuracy of the elastic model parameters including vertical P- and S-wave velocities as well as anisotropy coefficients. Using the SEG advanced modeling Barrett Unconventional model, we have assessed the influence of errors in the anisotropy parameters by conducting a sensitivity analysis in three types of 3D models: transversely isotropic with a vertical symmetry axis, transversely isotropic with a horizontal symmetry axis, and orthorhombic media. Our analysis on zero-lag and extended PS energy images computed with perturbed anisotropy models shows that event images exhibit different moveout patterns of misfocused energy with respect to the distorted Thomsen parameters $ϵ$ and $\delta$; however, for this model, the $\gamma$ parameters have almost no influence on images regardless of the applied perturbations, which are reflected in the minimal traveltime differences in the data. The dependence of microseismic source images on these parameters provides essential insights into anisotropic model accuracy, and it suggests that misfocused energy on extended image gathers may be used as a criterion for updating earth models through anisotropic elastic image-domain inversion.

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微地震数据的PS能量成像条件—第2部分：3D各向异性介质中的灵敏度分析

在微地震监测中，获得有关事件属性的可靠信息，例如位置，起始时间和矩张量分量，对于评估流体注入程序的成功至关重要。基于弹性波场的迁移方法可以通过地球模型外推数据并评估成像条件，从而对微震源进行可靠的成像。但是，这些成像方法的成功主要取决于弹性模型的准确性。先前开发的扩展PS能量成像条件可以提供有关弹性模型参数准确性的有价值的信息，包括垂直P波和S波速度以及各向异性系数。使用SEG高级建模Barrett非常规模型，我们通过对三种类型的3D模型进行敏感性分析来评估各向异性参数误差的影响：3种3D模型：具有垂直对称轴的横观各向同性，具有水平对称轴的横观各向同性和正交晶体。我们对通过各向异性模型计算的零延迟和扩展PS能量图像的分析表明，相对于变形的Thomsen参数，事件图像表现出不同的散焦能量偏移模式$ϵ$ 和 $\delta$; 但是，对于此模型，$\gamma$无论施加什么扰动，参数对图像几乎没有影响，这反映在数据的最小传播时间差异上。微震源图像对这些参数的依赖性为各向异性模型的准确性提供了重要的见解，并且表明扩展图像集上的聚焦能量可能被用作通过各向异性弹性图像域反演更新地球模型的标准。