THE GEOMETRY SPREADING OF WAVEFIELD EXTRAPOLATION FOR REVERSE TIME MIGRATION

Theoretical analysis about the amplitude of wavefield propagation for reverse time migration plays an important role in the development of true-amplitude migration methods and the improvement of the accuracy of imaging results. We analyze how the geometry spreading influence the amplitude of reverse time migration in this paper. Based on the high-frequency asymptotic theory, we express the forward and backward wavefield in its WKBJ approximate representations. Using stationary phase principle, we proved that the geometry spreading will be automatically compensated during the process of wavefield backward propagation for reverse time migration. The theoretical derivations are verified by numerical tests, and the results from numerical experiments are consistent with the theoretical analysis. Our theoretical derivations provide a fundamental basis for developing true-amplitude reverse time migration algorithm.