Extraction of amplitude-preserving angle gathers based on vector wavefield reverse-time migration
Yang Jia-Jia1,2, Luan Xi-Wu1,2, He Bing-Shou2,3, Fang Gang1,2, Pan Jun1,2, Ran Wei-Min1,3, and Jiang Tao1
1. The Key Laboratory of Marine Hydrocarbon Resource and Environment Geology, Ministry of Land and Resources, Qingdao Institute of Marine Geology, Qingdao 266071, China.
2. Function Laboratory for Marine Mineral Resource Geology and Exploration, National Laboratory for Marine Science and Technology, Qingdao 266071, China.
3. Key Lab of Submarine Geosciences and Prospecting Techniques, Ministry of Education, Ocean University of China, Qingdao 266071, China.
Abstract：
Angle-domain common-image gathers (ADCIGs) transformed from the shot-domain 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 reverse-time 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.
. Extraction of amplitude-preserving angle gathers based on vector wavefield reverse-time migration[J]. APPLIED GEOPHYSICS, 2017, 14(4): 492-504.
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2017, Vol. 14 
