Page 180 - Acquisition and Processing of Marine Seismic Data

CHAPTER

3

Noise in Marine Seismics

OUTLINE

3.1 Operational Noise 174 3.7 Diffractions 193
3.2 Bubble Effect of the Air Gun 175 3.8 Guided Waves 193
3.3 Multiple Reflections 177 3.9 Seismic Interference 196

3.4 Swell Noise 180 3.10 Other Noise Types 200
3.10.1 Powerline Harmonic Noise 200
3.5 Bird Noise 183
3.10.2 Spikelike Noise 202
3.6 Inline Waves 185 3.10.3 Side-Sweep 204
3.6.1 Tail Buoy Noise 185 3.10.4 Noise From Other Marine
3.6.2 Mechanical Cable Noise 188 Vehicles 206
3.6.3 Direct Waves 190 3.10.5 Marine Mammals 208
3.6.4 Refracted Waves 191 3.10.6 Streamer Ballasts 208

Recorded traces during the seismic survey etc.). The first noise type is termed source-
consist of a linear summation of reflected signal generated noise whereas the second type is
and noise amplitudes. The “noise” can be known as ambient noise.
defined as all kind of events or amplitudes The noise in the seismic data is classified
appearing on the seismic data other than genu- either as coherent noise, which has trace-by-
ine reflections. Recorded noise is sometimes trace consistency and can be traced over several
generated by the seismic system components seismic traces, or random noise, which does not
themselves (e.g., air gun bubble, bird noise, have a systematic consistency from one trace to
etc.), and sometimes it arises because of the spec- another (Fig. 3.1). Coherent noise, such as multi-
ifications of the working environment (e.g., ple reflections or powerline harmonic noise, can
marine mammals, propellers, marine traffic, be modeled and subtracted from the data by a

Acquisition and Processing of Marine Seismic Data 171 # 2018 Elsevier Inc. All rights reserved.
https://doi.org/10.1016/B978-0-12-811490-2.00003-7