When is anti-aliasing needed in Kirchhoff migration?

Anti-aliased migration

The diffractions from the salt flanks are obvious in the near-offset section (Figure 2a) and can be seen to be spatially aliased. The data exhibit some overall speckling because of temporal aliasing. This temporal aliasing is due to recording or processing which was performed on the original data before it arrived at SEP. The anti-aliased migration is displayed in Figure 2b. The salt flanks are nicely imaged and there is no evidence of operator aliasing. There are some artifacts due to the temporal aliasing: temporal aliasing is a different phenomena than operator aliasing and cannot be ameliorated by modifying the operator.

Gulfaa
Figure 2. (a) Near-offset section from the Gulf of Mexico. (b) Kirchhoff migration with triangle weighted anti-aliasing.

When is anti-aliasing needed in Kirchhoff migration?