1. A migration velocity analysis method comprising the steps of: a) establishing a seismic data set and a velocity model corresponding to a seismic exploration volume; b) performing migration on the seismic data set using the velocity model to generate a set of common image gathers for the volume; c) computing a set of residual velocity values each corresponding to one of the common image gathers; d) tying a residual velocity value from the set of residual velocity values to a geological horizon; and e) updating the velocity model using the residual velocity value tied to the geological horizon.