Kinematical Properties of Migrated Images: A Guide For Prestack Interpretation

Migration velocity analysis (van Trier, 1990, Grau and Lailly, 1993, Stork, 1992) is an approach dedicated to imaging of complex geological structures. This analysis requires interpretation of individual migrated images that have been obtained using a probably erroneous velocity model of the subsurface. Thus, the images do not show the correct shape of the geological structures and, moreover, the reflector geometries can change drastically from one image to another. Thus, geological knowledge is only of very limited help for interpretation of individual migrated images obtained with erroneous velocity models. We propose a solution to overcome this difficulty in the context of shot record migration. This solution is based on image-theoretical considerations which complement geological ones and thus make interpretation possible. The theoretical concepts for interpretation can be obtained from a high frequency (asymptotic) description of seismic modeling and migration. Although the results obtained with this theory are classical, they have never been practically employed for interpretation. In this paper we recall these theoretical results, present them from the viewpoint of interpretation and apply them to a synthetic data example.