Conclusion

We have presented a method to estimate the error in the migration velocity. It is based on the analysis of the residual move-out in 3-D angle-domain common-image gathers. The 3-D ADCIGs are functions of the aperture angle and the reflection azimuth angle. We tested a 2-D and a 3-D RMO function that led to an estimation of the velocity error and made it possible to update the velocity model. Because of 3-D events, the 2-D estimation of the velocity error is not accurate enough. The 3-D approach accounted for 3-D events and improved the resolution of the error. All the parameters required to estimate precisely the RMO function (the dips of the reflectors, the azimuth of the reflectors, and, to a minor extent, the reflection azimuth) can be estimated from the migrated data. The method can be automated and can serve as a basis for migration velocity analysis.