Extraction of P- and S-wave angle-domain common-image gathers based on first-order velocity-dilatation-rotation equation
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Extraction of P- and S-wave angle-domain common-image gathers based on first-order velocity-dilatation-rotation equations* Li Kai-Rui1,2 and He Bing-Shout1,2,3 Abstract: Accuracy of angle-domain common-image gathers (ADCIGs) is the key to multiwave AVA inversion and migration velocity analysis, and of which Poynting vectors of pure P- and S-wave are the decisive factors in obtaining multi-component seismic data ADCIGs. A Poynting vector can be obtained from conventional velocity-stress elastic wave equations, but it focused on the propagation direction of mixed P- and S-wave fields, and neither on the propagation direction of the P-wave nor the direction of the S-wave. The Poynting vectors of pure P- or pure S-wave can be calculated from first-order velocity-dilatation-rotation equations. This study presents a method of extracting ADCIGs based on first order velocitydilatation-rotation elastic wave equations reverse-time migration algorithm. The method is as follows: calculating the pure P-wave Poynting vector of source and receiver wavefields by multiplication of P-wave particle-velocity vector and dilatation scalar, calculating the pure S-wave Poynting vector by vector multiplying S-wave particle-velocity vector and rotation vector, selecting the Poynting vector at the time of maximum P-wave energy of source wavefield as the propagation direction of incident P-wave, and obtaining the reflected P-wave (or converted S-wave) propagation direction of the receiver wavefield by the Poynting vector at the time of maximum P-(S-) wave energy in each grid point. Then, the P-wave incident angle is computed by the two propagation directions. Thus, the P- and S-wave ADGICs can obtained Numerical tests show that the proposed method can accurately compute the propagation direction and incident angle of the source and receiver wavefields, thereby achieving high-precision extraction of P- and S-wave ADGICs. Keywords: first-order velocity-dilatation-rotation equations, RTM, Poynting vector, ADCIGs
Introduction Angle-domain common-image gathers (ADCIGs) of P- and S-wave can be used in multi-wave AVA inversion
and migration velocity analysis (Li et al., 2003; Liu et al., 2007, 2008; Zhang et al., 2010; Du et al., 2011). The method of extracting P- and S-wave ADCIGs based on elastic reverse-time migration (ERTM) has become a research hotspot due to its high amplitude preservation
Manuscript received by the Editor February 08, 2018; revised manuscript received January 27, 2020. * The research was financially supported by the Fundamental Research Funds for the Central Universities (No. 201822011), the National Key R&D Program of China (No. 2018YFC1405900), the National Natural Science Foundation of China (Nos. 41674118 and 41574105) and the National Science and Technology Major Project (No.2016ZX05027002). 1. Ocean University of China, Qingdao 266100, China. 2. Evaluation and Detection Technology Laboratory of Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China. 3. Key Laboratory of S
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