Circumventing velocity uncertainty in imaging complex structures

In areas with complex near-surface with irregular topography and structurally complex subsurface, there is much uncertainty in rms velocity estimation for prestack time migration, whereas interval velocity estimation for prestack depth migration is despairingly challenging. We often attribute the velocity uncertainty to various factors, including strong lateral velocity variations, heterogeneity, anisotropy, and three-dimensional behavior of complex structures. Nevertheless, it is not easy to identify the cause of and account for the ucertainty as it often is a combination of the various factors. And the analyst struggles with much difficulty when estimating a velocity field whether it is for prestack time or depth migration.