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

4pUW11. New multiple scatter model of the ocean sediment.

Dennis J. Yelton

Nicholas P. Chotiros

Appl. Res. Labs., Univ. of Texas, Austin, TX 78713-8029

Reflection, transmission, and scattering properties of an inhomogeneous Biot medium were studied via numerical simulation. The inhomogeneous medium was bounded by a semi-infinite water medium on the source side, and a semi-infinite Biot medium of equivalent average properties on the other side. The inhomogeneous medium was simulated as a randomly layered Biot material. Each layer represented a granular material of particular grain size. By setting the thickness of each layer equal to a random grain size, a randomly stratified granular medium was simulated. Lateral variations in grain size were simulated by performing a coherent ensemble average of results from several realizations of the randomly stratified medium. The free parameters were the grain size mean and standard deviation. Other parameters were chosen to represent water-saturated sand. Reflected and transmitted signals were computed for a 1-MHz normally incident plane wave. Coherent and random components of the reflected signal were calculated. The random component was related to the scattering strength of the medium. It was found to increase with both the mean and the standard deviation of the grain-size distribution. The results are consistent with previous experimental results [Nolle, 1394--1408 (1963)]. [Work supported by ONR code 1125OA.]