Inversion of Refraction Data by Wave-Field Migration
, by Robert W. Clayton and George A. McMechan
The process of wave equation migration is adapted for refraction
data in order to produce velocity-depth models directly from the
recorded data. The procedure consists of two linear transformations:
a slant stack of the data produces a wave field in the p-tao plane
which is then migrated using tao = 0 as the imaging condition. The
result is that the data wave field is linearly transformed from the
time-distance fomain into the slowness-depth domain, where the
velocity profile can be picked directly. No traveltime picking is
involved, and all the data are present throughout the inversion.
The method is iterative because it is necessary to specify a velocity
function for the migration. The solution produced by a given
iteration is used as the migration velocity function for the next step.
Convergence is determined when the migrated wave field images the same
velocity-depth function as was input to the migration.
The method obviates the problems associated with determiing the envelope
of solutions that are consistent with the observations, since the time
resolution in the data becomes transformed into a depth resolution in the
slowness-depth domain.
STANFORD