Residual moveout and residual radii of curvature from approximate prestack depth migrations

Abstract

For the case that a prestack depth migration has been performed with inaccurate velocities and with approximate offset migrations, it is demonstrated how the residual moveout after the application of a full downward continuation may be estimated. If both a common shot and a common receiver migration and the respective moveout analyses have been performed, it is possible to estimate the residual moveout and the residual radii of curvature at zero offset with little additional raytracing. For the case that just one approximate migration has been performed, reflective events are constructed for the interpolated dips estimated in the residual moveout analysis. The residual radii are obtained by the downward continuation of wavefronts along zero offset rays and may be inverted. The approach is verified for a homogeneous model and for an illustrative model exhibiting distinct lateral variations of propagation velocities. For the investigated depth model the iterative application of the suggested procedure converges rapidly to a satisfactory solution.