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Preliminary results are encouraging. The data focuses at the predicted
when given an inaccurate velocity model. In addition, for the
case of a DC error in global travel-times, can be found iteratively,
reducing the need for costly back projections.
A theory
relating how to actually to map perturbations to changes in
the focusing operator needs to be developed.
Building
a linear operator relating travel-time pertubations to change in reponse seems to be the next step.
Changing the focusing operator is at best a first order approximation.
At some stage we must back project the focusing operator to the
the velocity field, recalculate travel-times and repeat the focusing
analysis. An open question is *what
is the best method for back projection, is the central ray
approach of Audebert1996
sufficient?*
Another potential area of research is to see if
we can avoid going back to the data when scanning over .*Is it possible to apply a small convolution operator, similar
to residual migration, on the image space that simulates changes in ?*

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Stanford Exploration Project

11/11/1997