A Velocity Analysis Procedure for Multicomponent Data with Topographic Variations

We have modified the normal-moveout (NMO) equation for both P-wave and converted-wave (C-wave) data to handle surface elevation changes, and we have implemented this equation in our velocity analysis and NMO correction programs. For the C-wave case, we have also developed a new velocity analysis method that combines NMO correction and common conversion point (CCP) binning with a set of trial γ (Vp/Vs) values, thereby reducing errors introduced by the approximate asymptotic conversion point (ACP) binning method. This procedure has been successfully applied to P-wave and C-wave field data from western Canada and the Colombian Foothills. The benefits are both prestack and poststack. Stacked sections from synthetic and field data that have been processed using these modified equations show better focusing and event continuity. Furthermore, since the events on the moveout-corrected gathers are flatter, longer offsets can be retained for AVO analysis. The improved gathers also enable a more robust residual statics calculation.