The subsurface steeply-dipping structures, such as buried hills, fault zones, and salt flanks, are difficult to accurately image in seismic exploration due to weak illumination from large incident angles. To mitigate this issue, we propose an angle-related imaging condition for acoustic and elastic reverse-time migration (ERTM) to improve the image quality of steeply-dipping structures. We first use the wavefield decomposition method based on the Hilbert transform to decompose the extrapolated wavefield into up–down-left–right going components. We observed that the left- and right-going wavefields can accurately image steeply-dipping structures, while the up- and down-going wavefields mainly contribute to the layers with small dipping angles. Then, an angle-related imaging condition is developed to use the decomposed directional wavefields to enhance the image quality of both flat layers and steeply-dipping structures. In ERTM, after the directional wavefield decomposition, the vector Helmholtz decomposition is used to decouple PS waves to produce PP and PS images. Numerical examples demonstrate that the proposed method produces more accurate images than conventional RTM for steeply-dipping structures.

中文翻译：

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具有角度相关成像条件的声学和弹性逆时偏移，用于对陡倾结构进行成像


潜山、断裂带、盐翼等地下急倾构造由于大入射角光照弱，难以在地震勘探中准确成像。为了缓解这个问题，我们提出了一种用于声学和弹性逆时偏移（ERTM）的与角度相关的成像条件，以提高陡倾结构的图像质量。我们首先使用基于希尔伯特变换的波场分解方法将外推波场分解为上下左右分量。我们观察到，左行和右行波场可以准确地成像陡倾结构，而上行和下行波场主要对小倾角地层有贡献。然后，开发了与角度相关的成像条件，以使用分解的定向波场来增强平坦层和陡倾结构的图像质量。在ERTM中，在定向波场分解之后，使用矢量亥姆霍兹分解来解耦PS波以产生PP和PS图像。数值例子表明，对于陡倾结构，所提出的方法比传统 RTM 产生更准确的图像。