1. A seismic imaging method that comprises: migrating seismic survey data with an anisotropic velocity model to obtain common angle image gathers; processing the common angle image gathers to obtain depth residuals along one or more horizons; determining angle-domain sensitivity kernels for the horizons based on the anisotropic velocity model; inverting the depth residuals using sensitivity kernels to obtain velocity errors; applying the updates to the velocity model; and displaying a representation of the survey region to a user based at least in part on the updated velocity model.