EARS buoy applications by LADC: II. 3-D seismic airgun array characterization

In September 2007 the Littoral Acoustic Demonstration Center (LADC), a consortium of University and Navy scientists, conducted an experiment in the northwest Gulf of Mexico to measure the three-dimensional acoustic field of the primary arrival from a seismic airgun array. The water depth was approximately 1500 m. The acoustic measurements were made by Generation 2 4-channel EARS (Environmental Acoustic Recording System) buoys developed by the Naval Oceanographic Office (NAVOCEANO), with each channel capable of measuring to 25 kHz. A total of 48 hydrophones were deployed on 3 moorings at 20 different depths. At each depth there was a sensitive and desensitized phone, the latter used to prevent clipping. Eight hydrophones (four pairs) were ship-deployed near the surface. A dedicated source ship, the M/V Fairfield ENDEAVOR, supplied almost all the shots, although the M/V Veritas VANTAGE, which was conducting a survey in the area, provided a few lines of opportunity. The M/V CAPE HATTERAS was used to deploy, manage, and recover the receiving hydrophone arrays, as well as to conduct all environmental measurements. It also deployed and provided communication and control for the Ultra Short BaseLine Localization (USBL) system and a single Acoustic Doppler Current Profiler (ADCP), which were used to give accurate hydrophone positions during the experiment. About 3.5 TB of data were collected.