An environmental assessment in the Strait of Sicily: Measurement and analysis techniques for determining bottom and oceanographic properties

In October 1997 the EnVerse 97 shallow-water acoustic experiments were join tly conducted by SACLANT Centre, TNO-FEL, and DERA off the coast of Sicily, Italy. The primary goal of the experiments was to determine the sea-bed pr operties through inversion of acoustic data. Using a towed source, the inve rsion method is tested at different source/receiver separations in an area with a range-dependent bottom. The sources transmitted over a broad band of frequencies (90-600 Hz) and the signals were measured on a vertical array of hydrophones, The acoustic data were continuously collected as the range between the source and receiving array varied from 0.5 to 6 km, An extensiv e seismic survey was conducted along the track providing supporting informa tion about the Layered structure of the bottom as well as layer compression al sound speeds. The oceanic conditions were assessed using current meters, satellite remote sensing, wave height measurements, and casts for determin ing conductivity and temperature as a function of water depth. Geoacoustic inversion results taken at different source/receiver ranges show sea-bed pr operties consistent with the range-dependent features observed in the seism ic survey data. These results indicate that shallow-water bottom properties may be estimated over large areas using a towed source fixed receiver conf iguration.