ASA 126th Meeting Denver 1993 October 4-8

3aAO5. Determining elastic seafloor parameters in shallow water using ambient noise.

Grant B. Deane Nicholas M. Carbone Michael J. Buckingham

Marine Phys. Lab., Scripps Inst. of Oceanogr., 9500 Gilman Dr., La Jolla, CA 92093-0238

The ambient noise field in shallow water contains information about the seafloor. Measurements of the coherence of ambient noise have been used successfully [M. J. Buckingham and S. A. S. Jones, J. Acoust. Soc. Am. 81, 938--946 (1987)] to infer the critical angle of a variety of fluid basements. This technique has been extended to include the case of a shear-supporting bottom. A theoretical model of the ambient noise in an isovelocity, shallow water channel overlying an elastic basement with independent, randomly distributed surface sources will be presented. The model shows that elastic basements with shear speed greater than 650 m/s have sufficient effect on the noise field to enable the geoacoustic parameters of the bottom to be determined. The two main effects observed are an asymmetry in the vertical directionality and the arrival of energy at angles greater than the critical. [Work supported by ONR.]