Experimental studies of attenuation in sediments

Recent theoretical work [R. D. Stoll, Geophysics 42 (4), 715–725 (1977)] indicates that attenuation in ocean sediments depends on two distinct types of energy loss; these losses result from inelasticity of the skeletal frame and motion of the pore‐water relative to the frame. In this paper, experimental evidence is presented which verifies the response predicted by the theoretical model. Torsional resonance and logarithmic decrement are measured over a wide frequency range in both water‐saturated and dry sediments. A change‐over from dominance by one type of loss to the other is clearly demonstrated by a change of response that is observed as the frequency is varied. Special equipment is used which allows the intergranular stress to be controlled to simulate various depths of embedment in the sea floor. Both the theory and the experiments suggest that for some sediments, the attenuation will vary in a manner quite different from the usual dependency on the first power of frequency that is often assumed. [Work supported by ONR.]