ASA 126th Meeting Denver 1993 October 4-8

1pUW1. Scattering from under-ice features and estimation of ice roughness parameters.

Tarun K. Kapoor Henrik Schmidt

Dept. of Ocean Eng., MIT, Cambridge, MA 02139

Previous results by Kapoor and Schmidt [J. Acoust. Soc. Am. 93, 2419 (A) (1993)] have shown the possibility of isolating scattering hot spots under the ice sheet by matched-field processing of short-range returns assuming point scatterers. A natural extension of this approach is to model the scattered field, or replica field, assuming a more realistic model of the scatterers. Here, examination of the low-frequency scattering data from the CEAREX 89 field experiments conducted in the Central Arctic region with 1.8-lb SUS charges detonated at nominal depths of 800 ft is continued. The beamformer outputs from the crossed horizontal array and vertical line arrays are combined simulating a volumetric array, which provides much better resolution of the under-ice features. The scatterers are modeled as hemispherical and half-cylindrical protuberances. Importance of elastic properties of the ice and the protuberances will be addressed. Ice roughness parameters are estimated using the method of small perturbations. [Work supported by ONR.]