Geoacoustic inversion in the north-eastern Caribbean using a hydrographic survey vessel as a sound source of opportunity

Abstract

During the spring of 2006, hydrographic survey vessel HNLMS “Snellius” ran an extensive multibeam and sidescan survey of the Saba bank, a large submerged atoll located in the north-eastern Caribbean. The survey provided an excellent opportunity for a number of small-scale geoacoustic inversion experiments in a shallow water environment which attracts many divers for its unique tropical ecosystem and rich marine wildlife. The feasibility of a rapid deployment of ocean-acoustic sensors and equipment was demonstrated for the purpose of an environmental assessment of the area southwest of the small volcanic island of Saba. The environmental impact was kept to a minimum by exploiting the hydrographic ship as a sound source of opportunity that was moving along the survey lines and passing by a sparse vertical line array that was deployed from a rubber boat at anchor. Several low-frequency narrowband tones were identified for the inversion process that provided an accurate account of the experimental geometry in terms of moving source and receiving array positions, and detailed geoacoustic properties of the sea floor and sub-seafloor.