Statistical Correlation of Physical Properties and Sound Velocity in Sediments

Abstract

A systematic stepwise regression analysis is used to determine the statistical correlation between sound velocity and physical properties measured in the laboratory on sediments from 82 cores taken in the Atlantic, Pacific, and Indian Oceans, and the Mediterranean Sea. Carbonate content and shear strength show no significant correlation with sediment sound velocity. Mean grain size in phi units and porosity are the two parameters showing the highest significant correlation with sound velocity. The inclusion of void ratio, wet density, specific gravity, or the higher moments of the mean grain size statistics does not significantly improve the prediction equation for velocity. The data is grouped by different water depths, oceans, or physiographic provinces to determine the effect of these parameters on the velocity-porosity and velocity-grain size relationships. Results show that the prediction of velocity as a function of grain size is improved by using these groupings of data. In particular, for a given grain size, the velocity is higher in the Atlantic Ocean than in the Pacific Ocean. For a given porosity, the velocity is higher in the oceanic rise provinces than elsewhere. Overall, for all other provinces the data is well represented by one equation relating sound velocity V in meters per second to porosity P in percent. The equation is V = −22.9P + 0.1500P2 + 2367 with a standard error of 35 m/sec. One application is made using this equation and another equation which relates density to porosity. For each data point, a bottom loss is determined from the value of the sediment velocity and density predicted from a measured porosity, and then compared to a bottom loss determined from the actual measured velocity and density. The difference between these two determinations is less than 3 dB for each data point having a specific gravity within the broad range of 2.18 to 3.43 gm/cm3.