Conclusions

We presented an anisotropic migration velocity analysis (MVA) method based on the computation and analysis of angle-domain common-image gathers (ADCIGs) in conjunction with anisotropic wavefield-continuation migration. This method is based on the assumption of flat reflectors and vertically transversely isotropic (VTI) media but could also be generalized to dipping reflectors and tilted transversely isotopic (TTI) media. Our method has the great advantage of being based on migrated gathers and allows the iterative estimation of anisotropic parameters. We analyzed synthetic data to determine the accuracy and convergence of the estimation method. We showed that vertical velocities could not be resolved by our method but that even if we used a first-order approximation of the RMO function, picking the anisotropic migration velocities in semblance panels improves the overall anisotropic parameter estimation. We performed anisotropic MVA on a real data set acquired in the North Sea. Starting from an isotropic velocity model, we demonstrated the validity of our estimation method by showing it indicates the presence of anellipticity in the layers that are stratigraphically interpreted as anisotropic and for which well data do not match seismic data migrated under isotropy assumption.