Observations of deep‐ocean ambient noise using a seismometer array

An array of 12 ocean‐bottom seismometers (OBS) was deployed this past March in the deep ocean near San Diego. The array had a maximum extent of 150 m and a minimum interelement spacing of 8 m. The accuracy of the relative sensor positions was as good as 2 m in some cases. The seismometers were deployed in 3.8 km of water with a partially maneuverable vehicle at the end of a wire guided by a transponder net. The OBS capsules contained a vertical and two horizontal seismometers and a hydrophone. Three of the instruments had a low‐frequency hydrophone of the Cox design. Three‐min windows were recorded at intervals of 3 or 6 h for up to 30 days. Spectral levels have been calculated between 0.01 and 30 Hz. A power level drop of up to 40 dB below the microseism peak at frequencies below 0.1 Hz was observed. Similar spectra have been reported by Webb and Cox [J. Geophys. Res. 91, 7343–7358 (1986)]. At the time of the abstract deadline, correlation was being calculated as a function of sensor separation to determ...