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首页> 外文期刊>Journal of geophysics and engineering >Moveout-based geometrical-spreading correction for PS-waves in layered anisotropic media
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Moveout-based geometrical-spreading correction for PS-waves in layered anisotropic media

机译：分层各向异性介质中基于波的基于位移的几何扩展校正

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This paper is devoted to pre-stack amplitude analysis of reflection seismic data from anisotropic (e.g., fractured) media. Geometrical-spreading correction is an important component of amplitude-variation-with-offset (AVO) analysis, which provides high-resolution information for anisotropic parameter estimation and fracture characterization. Here, we extend the algorithm of moveout-based anisotropic spreading correction (MASC) to mode-converted PSV-waves in VTI (transversely isotropic with a vertical symmetry axis) media and symmetry planes of orthorhombic media. While the geometrical-spreading equation in terms of reflection traveltime has the same form for all wave modes in laterally homogeneous media, reflection moveout of PS-waves is more complicated than that of P-waves (e.g., it can become asymmetric in common-midpoint geometry). Still, for models with a horizontal symmetry plane, long-spread reflection traveltimes of PS waves can be well approximated by the Tsvankin-Thomsen and Alkhalifah-Tsvankin moveout equations, which are widely used for P-waves. Although the accuracy of the Alkhalifah-Tsvankin equation is somewhat lower, it includes fewer moveout parameters and helps to maintain the uniformity of the MASC algorithm for P- and PS-waves. The parameters of both moveout equations are obtained by least-squares traveltime fitting or semblance analysis and are different from those for P-waves. Testing on full-waveform synthetic data generated by the reflectivity method for layered VTI media confirms that MASC accurately reconstructs the plane-wave conversion coefficient from conventional-spread PS data. Errors in the estimated conversion coefficient, which become noticeable at moderate and large offsets, are mostly caused by the offset-dependent transmission loss of PS-waves.
机译：本文致力于对各向异性（例如裂缝）介质反射地震数据的叠前振幅分析。几何扩展校正是偏移幅度变化（AVO）分析的重要组成部分，它为各向异性参数估计和裂缝表征提供高分辨率信息。在这里，我们将基于运动的各向异性展宽校正（MASC）算法扩展到VTI（垂直对称轴为横观各向同性）介质和正交晶面对称平面中的模式转换PSV波。尽管在横向均质介质中所有波模的反射传播时间的几何扩展方程具有相同的形式，但PS波的反射移动比P波的反射移动更为复杂（例如，在公共中点可能会变得不对称）几何）。不过，对于具有水平对称平面的模型，PS波的长传播反射传播时间可以通过Tsvankin-Thomsen和Alkhalifah-Tsvankin漂移方程很好地近似，后者广泛用于P波。尽管Alkhalifah-Tsvankin方程的精度略低，但它包含的偏移参数较少，有助于维持P波和PS波的MASC算法的均匀性。这两个时差方程的参数是通过最小二乘旅行时间拟合或相似性分析获得的，与P波的参数不同。对通过反射率法针对分层VTI介质生成的全波形合成数据进行的测试证实，MASC可从常规扩展的PS数据准确地重建平面波转换系数。估计的转换系数中的误差在中，大偏移量时变得很明显，这主要是由PS波与偏移量有关的传输损耗引起的。

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