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GUIDED LOW‐FREQUENCY NOISE FROM AIRGUN SOURCES *
Author(s) -
KENNETT B. L. N.,
HARDING A. J.
Publication year - 1984
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/j.1365-2478.1984.tb01714.x
Subject(s) - geology , geophone , frequency domain , low frequency , seismology , waveguide , slowness , noise (video) , seabed , passive seismic , acoustics , geophysics , oceanography , optics , telecommunications , mathematical analysis , physics , artificial intelligence , computer science , image (mathematics) , mathematics
A bstract The presence of the water layer in marine seismic prospecting provides an effective waveguide for acoustic energy trapped between the sea‐bed and the sea‐surface. This energy persists to large ranges and can be the dominant early feature on far‐offset traces. On airgun records, there is commonly a lower frequency set of arrivals following the water‐trapped waves. These arrivals are not as obvious with higher frequency watergun sources. By using a combination of intercept‐time/slowness (τ— p ) mapping on observational data and theoretical modelling, we are able to identify the origin of the events. If a very rapid increase in a seismic wavespeed occurs beneath the sea‐bed sediments, a new waveguide is formed bounded by the sea surface and this transition zone. The low frequency waves are principally guided within this thicker waveguide. Numerical filtering in the τ— p domain followed by trace reconstruction is very effective in removing the low frequency noise.