f 3D Prestack Migration with Cross-Spreads

Data acquired with parallel geometry can be described as a collection of common-offset gathers. Prestack migration of such data can be conveniently considered as the repeated application of the migration process to all common-offset gathers. In contrast, data acquired with orthogonal geometry in land or OBC surveys do not allow the construction of common-offset gathers. Instead, the data of an orthogonal geometry 3D survey can be described as a collection of cross-spreads. Each cross-spread has illuminated its own little part of the subsurface which can be imaged by migration. This paper introduces some of the problems associated with migration of cross-spreads.