Equations 53 and 54
exchange
the and terms. The source term
is removed,
and the
boundary condition
* bc*
is applied every time step. This backward in time
migration of seismic data is called * Reverse Time Migration*.
The modeling finite difference equation is

The imaging finite difference equation is

where

The three seismic models which were generated using the
exploding reflector model are migrated using Equation 55.
The * dipping layer*, * reef*, and
* salt models* have all been computed using the initial known
velocity model
and are shown in Figures 22,
25,
and 28,
respectively.
Study the moving wave fields and see if the
recorded reflections move into the earth in an understandable way.
As you might want to compare the migration process with the modeling
process, notice that waves exiting the model sides do not
appear in the migration. What does this do to the image
reconstruction? Would any other imaging method be more
successful in reconstruction
of the missing data?