Migration of common-shot gathers

Three depth migration methods which operate on common-shot data are presented. The first migration method maps digitized horizons from the X-T domain to the X-Z domain. Because this method is based on ray tracing, its computation time is short; it is suggested for iterative velocity analysis. The other two migration methods map the entire common-shot gather into a depth section. The common-shot migration requires calculation of the arrival time of the direct wave from the source to all the depth points, and is done through a direct solution of the eikonal equation. All three methods are suitable for areas with both lateral and vertical velocity variation.