Page 185 - Acquisition and Processing of Marine Seismic Data

176 3. NOISE IN MARINE SEISMICS

FIG. 3.4 (A) A filtered shot record with distinctive linear operational noise at near traces, and (B) same shot after appli-
cation of an f-k filter. Corresponding f-k domain representations are given in the lower panels.

sizes used for hydrocarbon exploration, are suit- be seen on the final stack sections when a single
ably tuned to suppress the bubble amplitude of air gun is used. In some cases, the amplitude of
the resultant seismic signal (Section 2.2.6). the first bubble is so strong that even its multiple
The bubble effect occurs as reversed polarity reflection can be visible on the stack data.
recurrent amplitudes on the seismic data Although bubble effect can be suppressed by air
(Fig. 3.5A). It appears a certain time later after gun arrays or by using a GI gun, it can also be
the seabed reflection, which mimics the seabed attenuated during the processing stage by a
with a good trace-by-trace consistency and gener- suitable deconvolution application (Fig. 3.6).
ally cross-cuts the primary reflections (Fig. 3.5B). Selection of suitable parameters for predictive de-
The first bubble with the largest amplitude can convolution is explained in detail in Section 6.4.