COHERENCE LENGTHS OF SEA-FLOOR NOISE - EFFECT OF OCEAN BOTTOM STRUCTURE

Results are reported from an experiment, conducted in 1987, in which an ocean bottom seismograph array of 150-m aperture and minimally redundant design was used to record the ambient noise in deep water off the California coast. The minimum interelement spacing among the nine instruments was 8 m. The coherence lengths observed imply that the noise field in the 0.05-to 5-Hz band are fundamental and higher-mode Rayleigh/Stoneley/Scholte waves and the relative amplitudes of the modes imply that the excitation occurs within 20 km of the array. These observations imply that the noise energy is scattered into the seafloor waveguide at the boundaries of the sediment pond in which the array was sited. The implications for sub-bottom sensors are discussed. © 1990, Acoustical Society of America. All rights reserved.