ASA 124th Meeting New Orleans 1992 October

1aUW9. Tomographic measurements of sediment inhomogeneities and determination of statistical parameters critical to sediment volume backscattering.

Altan Turgut

Div. of Appl. Marine Phys., Univ. of Miami/RSMAS, 4600 Rickenbacker Cswy., Miami, FL 33149

A tomographic method was used for measuring sound-speed fluctuations in the top 5 m of sediments in Biscayne Bay, Florida. Sub-bottom porosity and density fluctuations were estimated from measured sound-speed fluctuations by using Gassmann's [Geophysics 16, 673--685 (1951)] equations. Statistical parameters for volume backscattering calculations such as vertical correlation length, horizontal correlation length, and variance of acoustic impedance were obtained from tomographic measurements. Volume backscattering strengths for the experiment site were calculated using the theoretical results given by Crowther [Acoustics and the Seabed, edited by N. G. Pace (Bath University, Bath, 1983), pp. 147--155]. Measurements of acoustic backscattering strengths were also conducted at the same site. Comparisons between measured backscattering strengths and calculated volume backscattering strengths indicate that, for this particular location, scattering is mostly due to bottom roughness. [Work supported by ONR and UM-Research Program.]