Residual Migration
, by Daniel Rothman, Stewart Levin, and Fabio Rocca
Roccan and Salvador (1982) showed that migration velocity can be modified by
applying a residual migration to previously migrated data, rather than having
to remigrate the original data with the corrected velocity field. The effective
velocity entiering this residual processing is usually smaill comparted to the
original migration velocity. This decreases computational cost compared to a
full migration, and allows the inital migration to be done with a less accurate
but faster algorithm than would otherwise be required.
The possible advantages are many. The overall cost of migration may be reduced,
a consideration especially important when migrating 3-D datasets. Migration
quality may also be improved, both form the corrected location of mispositioned
reflectors and the freedom to initially migrate with a high dip, low dispersion
algorithm such as Stolt migration. Interactive residual sharpening of the migrated
image also becomes feasible.
The theoretical and practical limitations of residual migration are discussed.
The related reductions of effective dip, veloicty, and frequency after initial
migration are quantified. We determine how accurate the initial migration ve-
locity needs to be to justify use of this approach. Aliasing and numerical
artifacts are also analyzed. Field data examples using Kirchhoff summantion
migration are shown to illustrate the features and drawbacks of the method.
STANFORD