ASA 125th Meeting Ottawa 1993 May

4pUW9. Simulation of the transmitted pressure field inside a water-saturated porous (sand) sediment.

A. C. Kibblewhite

C. Y. Wu

Dept. of Phys., Univ. of Auckland, Auckland, New Zealand

As part of a study of the effects of porosity on reflectivity the influence of an underlying solid basement on the reflection from the interface between the water and a porous sedimentary structure has been examined analytically and numerical calculations made for various versions of this model. This paper presents the results of two applications of the codes developed. In the first the transmitted pressure field inside a sand sediment, resulting from a source above the water--sediment interface, is calculated and compared with that measured in a recent experiment which appears to demonstrate the Biot slow wave [Boyle and Chotiros, J. Acoust. Soc. Am. 91, 2615--2619 (1992)]. The simulation appears to confirm the demonstration of the slow wave in the tank experiment but suggests it is identified with a different feature in the experimental contour plot. In the second example signatures of the vertical component of the seabed displacement are calculated at various ranges from a very low pressure source, in a simulation of the potential use of both the shear and slow wave in the study of the geoacoustic properties of near-bottom sediments. [Work supplied by ONR.]