Attenuation in Water-Saturated Marine Sediments between 20 kcps and 40 kcps

Abstract

Sediment samples were placed in thin-walled cylindrical containers 2 in. in diameter and 5 in. long; these were driven as complaint-walled resonators at their lowest resonant modes. From measures of resonant frequency and mechanical Q, sound speed and attenuation were determined. A variety of natural sea-floor sediments, ranging from deep-sea clays to coarse sands from shallow water, have been studied. Lowest attenuations, 1 db/ft or less, were found in deep-sea clays and fine silts where porosity was greater than 0.75. Sediments of intermediate porosity, 0.75 to 0.45, had attenuations between 1 and about 7 db/ft. Sediments of porosity less than 0.45, which are sands, had attenuations between 2.5 and 4.5 db/ft. On a number of samples more than one resonant mode was obtained, and from these data there is an indication that attenuation increases as the first power of the frequency.