Velocity Model Update Using Migration to Residual Time

Abstract

The Common-Reflection-Surface stack extracts kinematic wavefield attributes from pre-stack data which can be used for a tomographic inversion scheme to determine smooth velocity models for depth migration. These kinematic wavefield attributes give a second-order approximation of the diffraction traveltimes. Thus, the obtained velocity models can only explain the pre-stack data up to second order. In this paper I present a technique to update these models. The method makes use of residual traveltime information picked in CIG gathers and is, therefore, beyond second order. Migration is performed only for selected depth points and directly to residual time. The picking of residual moveout does not need to follow a specific trend. Moreover, there is no pulse stretch phenomenon in migration to residual time. The inversion algorithm is demonstrated on a synthetic data example.