Conclusions

The methodology for computing and analyzing ADCIGs that has been recently developed for isotropic media can be generalized to prestack images computed using anisotropic prestack migration. The transformation to angle domain performed by slant-stacking the subsurface-offset axis generates angle gathers that are approximately function of the phase aperture angle. In VTI media the approximation is exact for flat reflectors, and even for dipping reflectors it seems to be sufficiently accurate for practical applications with realistic anisotropic parameters.

The linearized analysis of ADCIGs obtained by anisotropic migration shows that the RMO function observed when the migration velocity is inaccurate is function of both the phase aperture angle and the group aperture angle. The numerical examples show that the linearized expression of the RMO function accurately predicts the actual RMO function measured after wavefield migration.

A simple modification of the analysis that yields the expression of the RMO function leads also to a linearized relationship between depth errors measured in ADCIGs and traveltime errors accumulated along the wavepaths. This relationship should enable the development of migration velocity analysis methods based on tomographic velocity-updating procedures.