Wide‐azimuth angle gathers for anisotropic wave‐equation migration
Wide‐azimuth angle gathers for anisotropic wave‐equation migration
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DOI：
10.1111/j.1365-2478.2012.01024.x
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发表时间：
2013-01
影响因子：
2.6
通讯作者：
P. Sava;T. Alkhalifah
中科院分区：
文献类型：
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作者：
P. Sava;T. Alkhalifah
通过宽方位角TI波方程迁移构建的扩展共像点集（CIP）包含了作为地下选定位置反射角和方位角函数的角度分解所需的所有信息。孔径和方位角是从扩展图像中导出的，利用空间和时间滞后扩展之间的分析关系，利用迁移时已经可用的信息，即各向异性模型参数。cip的计算成本很低，因为它们可以分布在图像中最相关的位置，正如地质结构所表明的那样。如果CIP位置的反射器倾角已知，则只需计算空间滞后矢量的两个分量即可减少计算成本。从扩展图像到角度集的变换是一个依赖于局部介质参数的平面Radon变换。这种转换允许我们在一个给定的实验中分离所有的照明方向，或者在不同的实验之间。我们不需要分解重构波场，也不需要选择能量最高的方向进行分解。该方法的应用包括在基于射线的方法失败的复杂区域的照明研究，以及假设地下照明足够密集，研究振幅随孔径和方位角的变化。
Extended common‐image‐point gathers (CIP) constructed by wide‐azimuth TI wave‐equation migration contain all the necessary information for angle decomposition as a function of the reflection and azimuth angles at selected locations in the subsurface. The aperture and azimuth angles are derived from the extended images using analytic relations between the space‐ and time‐lag extensions using information which is already available at the time of migration, i.e. the anisotropic model parameters. CIPs are cheap to compute because they can be distributed in the image at the most relevant positions, as indicated by the geologic structure. If the reflector dip is known at the CIP locations, then the computational cost can be reduced by evaluating only two components of the space‐lag vector. The transformation from extended images to angle gathers is a planar Radon transform which depends on the local medium parameters. This transformation allows us to separate all illumination directions for a given experiment, or between different experiments. We do not need to decompose the reconstructed wavefields or to choose the most energetic directions for decomposition. Applications of the method include illumination studies in complex areas where ray‐based methods fail, and assuming that the subsurface illumination is sufficiently dense, the study of amplitude variation with aperture and azimuth angles.