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Coherent pressure fluctuations observed at two sites on the deep sea floor
Author(s) -
Webb Spahr C.
Publication year - 1986
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl013i002p00141
Subject(s) - physics , wavenumber , isotropy , wavelength , coherence (philosophical gambling strategy) , surface wave , surface gravity , bessel function , optics , dispersion (optics) , computational physics , geology , spectral line , quantum mechanics , astronomy
Pressure fluctuations from two sites on the deep sea floor separated by a distance of 32 km were found to be partially coherent at frequencies between .001 Hz and .015 Hz. The pressure fluctuations in this range are caused by surface gravity waves which are of sufficiently long wavelength that significant coherence exists. No coherence is detected at lower frequencies because temperature fluctuations disturb the reference in the pressure gauge, while at higher frequencies the surface gravity wave induced pressure fluctuations are sharply attenuated through the ocean. The real part of the coherency as a function of frequency resembles a J o Bessel function of argument kr (r is the distance between the sites and k is the magnitude of the wavenumber as determined by the surface gravity wave dispersion relation). The imaginary part of the complex coherency is smaller than the real part over most of the surface gravity wave band. The coherency is well modeled if the surface gravity wave field is assumed to be isotropic, but other models for the directional spectrum which require a very broad distribution in direction of propagation fit equally well. Narrow beam width models fit the data poorly.