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The difference between stacking as defined by
`nmo0()` and by
`nmo1()`
is in the weighting function .Notice that can be factored into two weights, and *t*^{-3/2}.
One weight could be applied before NMO and the other after.
That would also be more efficient than weighting inside NMO,
as does `nmo1()`.
Additionally, it is likely that
these weighting functions should take into account
data truncation at the cable's end.
Stacking is the most important operator in seismology.
Perhaps some objective measure of quality can be defined
and arbitrary powers of *t*, *x*, and can be adjusted until the optimum stack is defined.
Likewise, we should consider weighting functions in the spectral domain.
As the weights and *t*^{-3/2}
tend to cancel one another,
perhaps we should filter with opposing filters
before and after NMO and stack.
The preconditioners used here are related to wave theory
in a constant velocity earth.
We can expect improvement if we redesign them for a stratified earth.
I expect the familiar velocity dependent divergence correction would appear.

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Stanford Exploration Project

11/16/1997