Elastic prestack migration of two comonent data
, by John T. Etgen
P and SV waves recorded with two component geophones can be migrated before stack to form
images of the subsurface. If the source contains only P waves, the recorded wave field
(for land data) will contain both P and SV waves. If the data are separated into P and SV
potentials, separate migration equations can be written, one for P-P reflections and one
for P-SV reflections (mode conversions). Separate migration of P and SV waves may have some
advantages over fully coupled P-SV migration. Separated P-P and P-SV wave migrations allow
for more inaccuracy in the velocity model than fully coupled migration. Some care must be
given to the imaging condition to avoid problems with polarity reversals of the SV potential
across zero offset. When the data are collected on a regular grid, a verson of Stolt's W,
Kh, Km migration technique can be applied. When the shot sampling is not uniform, it may
be advantageious to migrate individual shot profiles and stack the results. For the Stolt
algorithm, a P-P wave velocity space and a P-SV wave velocity space can be built allowing
the estimation of P and SV wave velocities from the migrated images.
STANFORD