Differential Semblance Velocity Analysis by Reverse Time Migration: Image Gathers and Theory

Velocity models can be automatically updated by differential semblance velocity analysis (DSVA). To overcome the dip limitations associated with the one-way wave equation based imaging algorithms, we propose in this study that the common image gathers can be defined other than in horizontal offset domain within the reverse time migration(RTM) framework, where two-way wave equation is solved as the wave propagator. A function to be minimized in differential semblance analysis is set up and the principle in DSVA is verified in this study that the velocity is correct when the function is minimized. We also show a detailed derivation of an algorithm that the velocity model can be updated automatically through the differential semblance analysis in the RTM frame work.