Migration Velocity Analysis Using Residual Diffraction Moveout in the Pre-stack Depth Domain

In this paper we present a methodology for migration velocity improvement and diffraction localisation based on a moveout analysis of over- or undermigrated diffraction events in the depth domain. The method does not depend on any requirement apart from a fairly arbitrary initial velocity model as input. We demonstrate that the method can be applied in both the pre- or post-stack domains without any restrictions. For each iteration, the method provides an update to the velocity model and consequently to the diffraction locations. The algorithm is based on the focusing of remigration velocity rays from uncollapsed migrated diffraction curves. These velocity rays are constructed from a ray-tracing like approach applied to the image-wave equation for velocity continuation. After choosing and picking the diffraction events in the pre-stack migrated domain, the method has a very low computational cost, and the diffraction points are located automatically. We demonstrate the feasibility of our method using a synthetic nonzero-offset data example.