Accession Number : ADA335476

Title :   Multiple Scatter Theory of Ocean Sediments II

Descriptive Note : Final rept. 1 Mar 95-28 Feb 97

Corporate Author : TEXAS UNIV AT AUSTIN APPLIED RESEARCH LABS

Personal Author(s) : Chotiros, Nicholas P.

PDF Url : ADA335476

Report Date : 16 JAN 1998

Pagination or Media Count : 48

Abstract : It is postulated that a laminar sand bed may be modeled as an ensemble of randomly layered poroelastic material. The thickness of each layer was related to the associated grain size and porosity by a conservation of mass relationship. The effect of lateral variations in grain size were simulated by performing a coherent ensemble average of results from several realizations of the randomly stratified medium. Poroelastic medium parameters were chosen to represent water saturated sand. The mean and standard deviation of the grain size distribution were chosen to match existing experimental data. Specifically, the sand bed was modeled as bounded by a homogeneous water halfspace above, and a homogeneous poroelastic halfspace of equivalent average porosity below. Reflected and transmitted signals were computed. Coherent and random components of the reflected signal were calculated. The coherent parts were directly related to the reflected and the transmitted waves. Results show significant differences between the modeled sand bed and an equivalent uniform Biot medium. The fast wave attenuation shows strong anisotropy. The slow wave is only detectable in the sand bed at shallow grazing angles.

Descriptors :   *SAND, *ACOUSTIC ATTENUATION, *ACOUSTIC SCATTERING, *SEDIMENTS, ACOUSTIC WAVES, GRAIN SIZE, BACKSCATTERING, POROSITY, SATURATION, SEDIMENT TRANSPORT, ANISOTROPY, OCEAN BOTTOM, SHALLOW DEPTH, GRAZING ANGLES.

Subject Categories : Acoustics
      Geology, Geochemistry and Mineralogy

Distribution Statement : APPROVED FOR PUBLIC RELEASE