The imaging result of prestack depth migration (Pre‐SDM) is quite sensitive to migration velocity field. Reasonable migration velocity modeling becomes the key to obtain the Pre–SDM imaging with high quality. Firstly, common imaging point (CIP) gathers are extracted by using wave equation Pre‐SDM with high imaging precision. Then, based on the perturbation method, the quantitative relationship between the errors in migration velocity and those in imaged depths is established through a parameterized velocity function and the modified residual curvature analysis (RCA). Finally, migration velocity modeling is realized by using single/multi parameter joint‐iteration inversion. The test on the Marmousi model shows that the method proposed in this paper has a stronger adaptability and better modeling and imaging results for a complex geological body, and it needs only to analyze and control the main reflectors through 3 to 4 iterations to meet the required precision.
The common-reflection-surface (CRS) stacking is a new seismic imaging method, which only depends on seismic three parameters and near-surface velocity instead of macro-velocity model. According to optimized three parameters obtained by CRS stacking, we derived an analytical relationship between three parameters and migration velocity field, and put forward CRS gather migration velocity modeling method, which realize velocity estimation by optimizing three parameters in CRS gather. The test of a sag model proved that this method is more effective and adaptable for velocity modeling of a complex geological body, and the accuracy of velocity analysis depends on the precision of optimized three parameters.
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