Extraction of amplitude-preserving angle gathers based on vector wavefield reverse-time migration |
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| Authors: | Jia-Jia Yang Xi-Wu Luan Bing-Shou He Gang Fang Jun Pan Wei-Min Ran Tao Jiang |
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| Institution: | 1.The Key Laboratory of Marine Hydrocarbon Resource and Environment Geology, Ministry of Land and Resources,Qingdao Institute of Marine Geology,Qingdao,China;2.Function Laboratory for Marine Mineral Resource Geology and Exploration,National Laboratory for Marine Science and Technology,Qingdao,China;3.Key Lab of Submarine Geosciences and Prospecting Techniques, Ministry of Education,Ocean University of China,Qingdao,China |
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| Abstract: | Angle-domain common-image gathers (ADCIGs) transformed from the shotdomain common-offset gathers are input to migration velocity analysis (MVA) and prestack inversion. ADCIGs are non-illusion prestack inversion gathers, and thus, accurate. We studied the extraction of elastic-wave ADCIGs based on amplitude-preserving elastic-wave reversetime migration for calculating the incidence angle of P-and S-waves at each image point and for different source locations. The P-and S-waves share the same incident angle, namely the incident angle of the source P-waves. The angle of incidence of the source P-wavefield was the difference between the source P-wave propagation angle and the reflector dips. The propagation angle of the source P-waves was obtained from the polarization vector of the decomposed P-waves. The reflectors’ normal direction angle was obtained using the complex wavenumber of the stacked reverse-time migration (RTM) images. The ADCIGs of P-and S-waves were obtained by rearranging the common-shot migration gathers based on the incident angle. We used a horizontally layered model, the graben medium model, and part of the Marmousi-II elastic model and field data to test the proposed algorithm. The results suggested that the proposed method can efficiently extract the P-and S-wave ADCIGs of the elastic-wave reverse-time migration, the P-and S-wave incident angle, and the angle-gather amplitude fidelity, and improve the MVA and prestack inversion. |
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