Shear wave velocity versus depth in marine sediments: A review : Hamilton, E L Log Analyst, V18, N1, Jan–Feb 1977, P33–40

Abstract

This paper reviews and studies measurements of the velocity of shear waves at various depths in some unlithified, water-saturated sediments, and discusses probable variations of shear velocity as a function of pressure and depth in the sea floor. Data from measurements on land were also used, and the study was confined to the two ''end-member'' sediment types (sand and silt-clays) and turbidites. The shear velocity data in sands included 29 selected in-situ measurements at depths to 12 m. The regression equation is: V/sub s/ = 128D/sup 0.28/, where V/sub s/ is shear-wave velocity in m/sec, and D is depth in meters. The data from field and laboratory studies indicate that shear-wave velocity is proportional to the 1/3 to 1/6 power of pressure or depth in sands; that the 1/6 power is not reached until very high pressures are applied; and that in most sand bodies the velocity of shear waves is proportional to the 3/10 to 1/4 power of depth or pressure. The use of a depth exponent of 0.25 is recommended for prediction of shear velocity versus depth in sands. The shear velocity data in silt-clays and turbidites include 47 selected in-situ measurements at depths to 650 m. Themore » equation for the 0 to 40 m interval (V/sub s/ = 116 + 4.65D) indicates the gradient (4.65 sec/sup -1/ to be 4 to 5 times greater than is the compressional velocity gradient in this interval in comparable sediments. At deeper depths, shear velocity gradients are 1.28 sec/sup -1/ from 40 to 120 m, and 0.58 sec/sup -1/ from 120 to 650 m. These deeper gradients are comparable to those of compressional wave velocities. These shear velocity gradients can be used as a basis for predicting shear velocity versus depth. (49 references.)« less