To take advantage of the efficiency of the nearest-neighbor triangle
interpolation in terms of minimizing indirect memory addressing, I use a
minimum triangle length such that .Above, I discussed the danger of over-smoothing resulting from this choice.
I also limit the maximum triangle length such that ,
where *f*_{min} is a user-specified parameter indicating the minimum frequency
at which real signal is present. This prevents the lowpass anti-aliasing
filters from enhancing low-frequency noise (and even d.c.) that may be
present in the data, and/or boosted by the double trace integration process.
Additionally,
to preserve the relative amplitude of a low-frequency anti-aliased
reflection compared to a fullband unaliased reflection, I scale the triangles
by inverse height instead of the usual inverse area factor. This boosts
the peak amplitudes of lowpassed steep dip events to compensate for their loss
of bandwidth due to the anti-aliasing process.
This inverse height triangle scaling is a first order amplitude effect on the
migration impulse responses, and warrants future study.
Finally, I weight the anti-aliased migration operator with the conventional
migration aperture and obliquity factors to suppress
post-vertical (evanescent) time-migration impulse response energy.

11/17/1997