Summary

The multicomponent seismic data processing in areas with complex topography and subsurface geological formation is becoming a challenge. In this paper, an accurate PP and polarity-corrected PS beam migration method withoout slant stack based on surface dip information under complex topography conditions is proposed. Compared to the conventional elastic beam migration with the vector planewave decomposition processing, our method without the following processing can obtain higher imaging quality: (1) elevation statics; (2) phase correction; (3) approximate substitution of velocity and surface dip angle between receivers and the beam center. Numerical results reach our expectation that our method can effectively remedy the imaging energy error caused by the large distance between the beam center and detectors, which usually occurs in the conventional elastic beam migration method.

Introduction

With the development trends from regular to irregular surface and from acoustic to elastic media, the multicomponent data processing under complex topography condition becomes a challenge. Under complex topography condition, conventional statics processing can’t meet the requirements of imaging quality. Gray (2005) proposed an acoustic Gaussian beam migration (GBM) method based on local statics correction. However, the drawbacks to Gray’s method are that, rapid near-surface velocity variations can compromise the accuracy of a slant stack that has a large spatial extent and rapid elevation variations can make static shifts a poor approximation to wavefields extrapolation. In order to avoid these problems, Yue et al. (2010) presented a relatively amplitudepreserved acoustic GBM method that directly decomposed the records into local plane-wave components on the irregular surface. Yuan et al. (2014) realized an accurate acoustic GBM method without the local plane-wave decomposition for irregular surface and obtained improved image result. Huang et al. (2013) applied local slant stack theory proposed by Hill (1990, 2001) to elastic GBM under complex topography condition. However, this method characterizes backward-continuation vector wavefields by compensating for phase changes from vector beam centers to receivers. When receivers are not in some neighborhood of the beam center, this treatment will lead to amplitude error due to inaccurate Green’s function. Moreover, the differences of near-surface velocity and surface dip angle from the beam center to receivers and the poor spatial sampling of land data lead to inaccuracy and aliasing of the slant stack, respectively.

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