Page 238 - Acquisition and Processing of Marine Seismic Data

4.6 2D FOURIER TRANSFORM 229

FIG. 4.16 (A) A real shot gather consisting of 96 channels with 6.25 m group interval, and its decimated versions for
(B) 48 channels (12.5 m group interval), and (C) 32 channels (18.75 m group interval). The f-k spectra of each gather are illus-
trated in the lower panels. The aliasing frequency decreases with the increasing trace interval of the input.

shot with 18.75 m group interval in Fig. 4.16C the performance of some seismic processing
seem to be aliased twice approximately at applications, such as migration. Migration algo-
130 Hz in the f-k panel. The analysis suggests rithms recognize aliased energy incorrectly and
that the aliasing frequency significantly migrate it in the opposite updip direction. The-
decreases as the trace interval of the input data oretical approaches to avoid the spatial aliasing
increases. might be
The aliased energy is typically filtered out by
(i) decreasing the dips of the events in the
an f-k filter during the conventional seismic pro- input data
cessing. Spatial aliasing has negative effects on