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Aliased migration

In Figure 3a the data are migrated without triangular weighting. The effect of operator aliasing is most evident in the seafloor arrivals. We see precursors to the actual event. The top of the salt dome (earlier than $t = 0.6$ s) is poorly imaged and there is more overall speckling than in Figure 2b, suggesting that the effects of data aliasing are compounded by operator aliasing. Other prominent operator aliasing artifacts are seen at about midpoints 13000 to 14000 and time 0.6 s to 0.9 s as cross-cutting dipping events. Figure 4 is a comparison of the anti-aliased migration and the aliased migration (Figure 4a is a closeup of Figure 2b, and Figure 4b is a closeup of Figure 3a). The seafloor precursor artifacts before $t=0.18$ s and the cross-cutting dipping event artifacts are marked.

The operator aliasing has been somewhat contained by limiting the migration aperture to $45^\circ $ in Figure 3b; however, the seafloor event still has a precursor, the top of the salt dome is still poorly imaged, and there is more coherent noise than in Figure 2b.

Gulfaper
Gulfaper
Figure 3.
(a) Kirchhoff migration without any aperture limitation or anti-aliasing. The effect of operator aliasing is noticeable at the seafloor where migration velocity is slow and where there is significant operator dip. At later times, the migration velocity is fast and there is not much operator dip, so there is no operator aliasing. (b) Kirchhoff migration of Gulf of Mexico data with $45^\circ $ aperture limitation. Limiting the aperture reduces some, but not all, of the operator aliasing at the seafloor.
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Zoom2
Zoom2
Figure 4.
Close up of (a) the anti-aliased migration, and (b) the standard Kirchhoff migration without anti-aliasing. The seafloor operator aliasing artifacts and the dipping artifacts are marked.
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next up previous [pdf]

Next: Anti-aliasing is not needed Up: GULF OF MEXICO SALT Previous: Anti-aliased migration

2015-03-26