Three common-shot migration methods

It has long been recognized that conventional CDP processing degrades in geologic areas with steeply dipping beds and strong lateral velocity variation. As a result commonshot processing has been suggested as an alternative in such regions. A requisite for successful processing of this type is a common-shot migration method which can be used with arbitrary velocity variation. In this paper we describe three common-shot migration methods which should perform well in such complicated areas. The first migration algorithm is a ray tracing method which maps digitized horizons from x-t space x-z space. The other two methods operate on common-shot gathers and map time sections into depth sections. The common departure point for the three methods is an imaging principle which replaces the exploding reflector model used in the migration of stacked sections. We describe the three migration methods and present synthetic examples which shed light on their features.