ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

4pUW10. Acoustic reverberation from a laboratory model of a shelf break.

Saimu Li

C. S. Clay

Geophys. and Polar Res. Ctr., Univ. of Wisconsin-Madison, 1215 W. Dayton St., Madison, WI 53706

The structure of continental boundaries such as the east coast of the United States has a shallow sloping bottom that changes to a steeper slope at the shelf break. Our laboratory acoustic model has exaggerated slopes. The ``shelf'' has a 10.8(degrees) slope; the bottom changes to a 50(degrees) slope at the shelf break. The surface and bottom of the acoustic model are drywall construction board. The source is a spark and the receiver is a small microphone (2 mmx2 mm). The Biot--Tolstoy exact time domain solution was used as a basis for numerical calculations [I. Tolstoy and C. S. Clay, Ocean Acoustics (American Institute of Physics, New York, 1987), Appendix 5]. Arrivals are reflected paths, diffractions from the shelf break, and reflected diffractions. The existence and amplitudes of arrivals depended on source and receiver locations. For example, a source location in the inner shelf gave reverberations that were mainly from the 10.8(degrees) wedge. A source position beyond the shelf break gave reverberations that were mainly from the 50(degrees) part of the model. Experimental signals matched the theory in amplitudes and arrival times.