Wave-equation Migration Velocity Analysis Using Radon-Domain Common-Image Gathers

The accuracy of the background velocity analysis is critical to image the subsurface structure in seismology. Wave-equation migration velocity analysis using source-domain common-image gathers requires picking the relative moveouts based on semblance analysis. However, the picking process is complex and time-consuming. To avoid picking and maintain efficiency in generating CIGs, an automatic wave-equation migration velocity analysis method is proposed utilizing the focusing properties of the Radon-domain common-image gathers. <br>Seismic events in the Radon-domain common-image gathers appear focused if an accurate migration velocity model is used; otherwise, the resultant events will be unfocused. The objective function is defined in the Radon domain to measure focus of the common image gathers automatically. The proposed migration velocity analysis method links the defocusing information to the migration velocity update under the assumption that model perturbations only result in slope shifts in the common-image gathers. This method provides a reasonably accurate background velocity model for imaging and full-waveform inversion without requiring an accurate initial velocity model. Tests on synthetic and field data demonstrate the effectiveness of the method. This method is tolerable to both inaccurate initial velocity models and the lack of low-frequency data.