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1

Improving the plane‑wave destruction method by parameterizing the local slope for VSP wavefield separation

Guo Yinling, Peng Suping, Du Wenfeng, Li Dong, Li Chuangjian

Acta Geophysica

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2023

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Vol. 71, no. 4

1659--1673

EN

High-precision seismic exploration has attracted a great deal of attention. Vertical seismic profiles have the advantages of high exploration accuracy and ideal imaging effects, making them an effective tool for mine exploration. The separation of upgoing and downgoing waves is a vital step in vertical seismic profile processing. However, wavefield separation processing in the frequency–wavenumber domain often leads to aliasing in the time–distance domain. In addition, it is likely to result in incomplete wavefield separation in the sparse domain because of inaccurate threshold selection. As an effective time–distance domain wavefield separation method, the plane-wave destruction method can effectively avoid these problems. However, the traditional local slope estimation in plane-wave destruction is data-driven, making it difficult to distinguish linear upgoing and downgoing waves. Therefore, the velocity-based local slope parameterization method is proposed to construct a plane-wave destruction filter that can be used to separate the vertical seismic profile wavefield. Synthetic and field data show that the proposed separating strategy has higher separation accuracy than traditional methods when separating the upgoing and downgoing waves of vertical seismic profile data.

2

Diffraction enhancement using the double sparse dictionary method

Wang Tao, Peng Suping, Lin Peng, Cui Xiaoqin, Zhou Jiawei

Acta Geophysica

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2023

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Vol. 71, no. 3

1259--1271

EN

Seismic diffraction delivers high-precision imaging of subsurface discontinuities and objects. As diffraction is characterised by weak energy, separating diffraction from full wavefields is an essential pre-imaging step. However, traditional diffraction separation methods generally produce unsatisfactory separation results for datasets with low signal-to-noise ratios. Accordingly, we propose a novel diffraction separation method that incorporates plane-wave destruction and the double sparse dictionary algorithm to improve separation quality. The plane-wave destruction method is used to suppress strong reflection, whereas the double sparse dictionary can simultaneously extract diffracted signals. A robust plane-wave destruction method using the Hilbert transform is employed to improve the stability and accuracy of slope estimation. The double sparse dictionary algorithm has better performance when sparsely representing seismic signals and can effectively extract weak diffraction with a high signal-to-noise ratio. Synthetic and field examples demonstrate the effectiveness of the proposed method in removing strong reflection and enhancing weak diffraction. Overall, the proposed method is conducive to detect small structures and offers a new resource for seismic structural interpretation.

3

Low-rank difraction separation using an improved MSSA algorithm

Lin Peng, Zhao Jingtao, Peng Suping

Acta Geophysica

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2021

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Vol. 69, no. 5

1651--1665

EN

Diffraction separation is a vital key step for high-resolution imaging of small-scale geologic discontinuities. The multichannel singular-spectrum analysis (MSSA) algorithm has exhibited adequacy for diffraction separation and refection suppression. However, the traditional MSSA algorithm is expensive because of the singular-value decomposition (SVD) operator. In addition, the common rank misidentification renders the diffraction separation highly rank-sensitive. Random noise caused by energy leakage is another problem for diffraction separation that is unresolved by the conventional MSSA. In this study, we propose a prestack diffraction separation method involving an improved MSSA algorithm. The new algorithm enables faster singular value estimation relative to the conventional SVD, with a diagonal Hankelization operator for artificial linear and random noise suppression, thereby enhancing the signal-to-noise ratio. Rank misidentification is alleviated by lowering the sensitivity to rank of the separated diffractions. Synthetic and field data are utilized to demonstrate the feasibility and superiority of the proposed method in computational efficiency and noise suppression compared with the conventional method.