Small scale volumetric inhomogeneities of shallow water sediments: measurements and discussion

Abstract

There is a consensus that high-frequency acoustic scattering by the ocean bottom is partly due to sediment volumetric inhomogeneities, r e., random fluctuations in sediment sound speed and density. Understanding the spatial distribution and tempoml variability of such inhomogeneities at the centimeter scale is of great importance to modeling and predicting sound interaction with shallow water sediments. Core data provide only sediment variability in depth, which is not sufficient for determining sound scattering, since fluctuations of sediment parameters versus horizontal dimensions are also needed. Efforts were made to measure sound speed and porosity variabilities of sediments using techniques based on acoustic tomography and microelectric conductivity. While the results are still preliminary, it is clear from the available data that sediment inhomogeneity is a general phenomenon, and measurements such as those reported here will make it possible to conduct unambiguous model-data comparisons in future high-frequency bottom-scattering experiments.