DEPTH MIGRATION OPERATOR UPDATE

The obvious question: is it possible to limit the need for costly and complicated back projection by using our picks for $\gamma$ to update our focusing operator? In the case where we have a significant (DC) error in our initial velocity model, the answer is yes. A systematic error in our velocity model will result in a systematic bias in our maximum focusing $\gamma$. If we apply a constant scaling to our travel-time field, such as the median focusing $\gamma$, we are not changing ray-paths, so back projection is not required. We can then rescan the $\gamma$ parameter, further refining our focusing operator.