We examined the sensitivity of the AVO response due to the presence of a overburden with complex velocity anomalies using a synthetic data set. We observed that AVO attributes calculated after prestack depth migration using the true velocity model are sensitive to the velocity anomalies. Introducing errors in the migration-velocity, we found that the AVO gradient attribute is much more sensitive to velocity errors than AVO intercept attribute. For velocity errors up to 5%, we can see a maximum of AVO intercept errors of , whereas for velocity errors of only 1%, the inversion of AVO gradient attribute has an error of 185%. These results are specific for the synthetic data used; different results could be obtained by modeling different velocity anomalies.
We observed some boundary artifacts in the modeled data and we noted that amplitude values after migration are more sensitive to these boundary artifacts than amplitude values before migration. These boundary artifacts become worse when we introduce velocity errors in the migration-velocity. We need to do further work to evaluate the influence of boundary artifacts on the amplitudes; we also would like to compare the results using other migration methods, such as Kirchhoff prestack migration.