Measurement of In Situ Sediment Properties at the ONR/DRI Site

Abstract : My long goal with this project is to understand the chemical, geological and biological processes that control the physical properties of shallow water marine sediments. The physical properties of particular interest are those that are determined by grain-grain interactions, specifically including compressional wave velocity, attenuation and the permeability to fluid flow. In order to pursue the above goals, it became necessary to develop an instrument that can make accurate in situ measurements of the following parameters in the upper part of the sediment column; (1) compressional wave velocity at a variety of frequencies (velocity dispersion), (2) attenuation of acoustic waves, (3) in situ density, and (4) permeability to fluid flow. With the measurements of these critical in situ physical properties, it will then be possible to correlate this data with related parameters determined by other investigators over the same survey areas, including surface roughness, sediment grain petrology, porosity, total organic carbon content and bacterial cell counts and polymer density, and pore water content and chemistry. Observed correlations between these parameters within the two data sets can constrain any possible relationships between acoustic properties and the causative processes.