Weighting and Extrapolation Schemes for Stacking
, by Jeff Thorson
Among the things that influence the suppression of multiples on a stack,
the finite width of the CDP gather, and the corresponding truncation effects,
is significant. Truncation of strong muliplies a the edge of a gather
widens the sidelobes of the multiples in the velocity spectral domain to
the point where they may overlap the desired primary components. Analagous
to taper and transform methods of spectral estimation, the truncation side-
lobes may be suppressed by a suitable weight applied to the gather before
stack. The calculation of weights is complicated by the fact that a multiple
to be suppressed has a nonlinear moveout. The most effective weights are
likly proportional to a power of the local difference in dip between the
multiple and the primary. Of course, all this holds for any weak coherent
event to be stacked in the presence of a strong event of different dip.
Another way to reduce any truncation error present is to extrapolate, weight
and stack the data, which is analogous to the role of prediction error
filtering in spectral estimation. Problems with spatial aliasing on the
gather are not dealt with in this paper.
STANFORD