ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pUW32. Measurement of upper-sediment geoacoustic properties in the Canadian high Arctic.

S. E. Dosso

Defence Res. Establishment Pacific, FMO Victoria, BC V0S 1B0, Canada

G. H. Brooke

Numerical Decisions Group, Victoria, BC V8Z 3K3, Canada

Geoacoustic properties of the ocean bottom can significantly affect acoustic propagation in shallow water. However, to date, few measurements of geoacoustic properties have been reported for the high Arctic. A seismoacoustic survey was carried out to determine a geoacoustic model for the upper sediments on the continental shelf of the Lincoln Sea, north of Ellesmere Island, Canada. The experiment involved deploying an ocean-bottom seismometer through 5 m of polar pack ice, and recording signals from seafloor sources at ranges of 35--900 m. Subsequently, a layered compressional-speed model of the upper sediments was determined from a travel-time analysis of refracted compressional waves (head waves), and a shear-speed model was determined by matching the observed dispersion characteristics of shear and seismic-interface (Scholte) waves. Frequency-dependent compressional and shear attenuation coefficients were estimated from an analysis of the decay of signal amplitude with range: An approximately linear dependence of attenuation on frequency was observed for both wave types. The sensitivity of acoustic propagation in the ocean to the various geoacoustic parameters was investigated using a numerical propagation model.