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The obvious question: *is it possible to
limit the need for costly and complicated back
projection by using
our picks for 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 .
If we apply a constant scaling to our travel-time field, such as the
median focusing , we are not changing ray-paths, so back projection
is not required. We can then rescan the parameter, further
refining our focusing operator.

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Stanford Exploration Project

11/11/1997