Migration

The state-of-the-art in migration methodology is represented by migration using downward continuation (24). Such methods are accurate, robust, and capable of handling models with large and sharp velocity variations. These methods naturally handle multipathing occurring in complex geology. However, migration by downward continuation limits angular accuracy since it is designed for energy propagating mainly in the vertical direction.

A first goal of this thesis is to eliminate the dip limitation of wave-equation migration. The solution proposed involves wavefield extrapolation in general Riemannian coordinates which follow the general direction of wave propagation in the physical space. In this case, extrapolation is done forward relative to the direction of wave propagation, and not in the arbitrary downward direction as in conventional migration.