Diffraction separation and imaging using ensemble empirical mode decomposition and multichannel singular spectrum analysis

Abstract

Seismic diffracted wavefield has substantial potential for high-resolution subsurface imaging of discontinuous geological structures; however, they are often masked by higher amplitude reflection, thus requiring separation. According to the low-rank nature of a seismic wavefield, the diffracted wavefield can be extracted using the rank-reduction method. The traditional low-rank diffraction separation suffers from a threshold selection problem, especially for field data. To improve threshold accuracy, we propose a method in the common-offset or poststack domains based on the f-x ensemble empirical mode decomposition and multichannel singular spectrum analysis. We demonstrate that such decomposition allows the determination of the diffraction threshold according to the difference between the singular values of the data before and after it. Synthetic and field data examples prove that the decomposition can effectively predict and suppress the horizontal reflected signal, while attenuating the energy of the dipping reflected signal. The following multichannel singular spectrum analysis suppresses the dipping reflection and separates the diffraction according to the precise threshold obtained earlier. The proposed method effectively improves the accuracy of the diffraction threshold selection, enhances diffraction and attenuates reflection, resulting in an enhanced image of small-scale geological structures.