ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

4aUW8. Shallow-water acoustic measurements in the southern Adriatic Sea.

J. M. Berkson

Naval Res. Lab., Washington, DC 20375

R. D. Hollett

M. Max

SACLANT Undersea Res. Ctr., 1-19138 La Spezia, Italy

Shallow-water acoustic and geoacoustic measurements were made in the southern Adriatic Sea in May--June 1995 in combination with detailed oceanographic, geological, and geophysical surveys. Seismic subbotom profiling, narrow-beam echosounding, and bottom coring results were used to select two shallow water sites with downward refracting conditions for acoustic experiments: (1) a flat seafloor at 90-m depth with about 1 m of rigid, nongaseous clay over a sequence of laminated clays and (2) a seafloor sloping from 49- to 37-m depth and consisting of soft gaseous mud over laminated clay. Broadband sparker and 180-g TNT explosive sources were used for propagation and reverberation to a vertical array receiver in addition to cw sources for propagation. Initial results for the deeper water site show frequency-independent propagation that is consistent with modeled results using geoacoustic parameters extrapolated from coring results. A modification of the Dix method to estimate sediment sound speed versus depth from wide-angle reflectivity experiments made at the deeper water site is described. [Work supported by ONR.]