Influence of hydrostatic pressure on the sound speed of surficial seafloor sediments

Changes in seawater depth could cause variations of hydrostatic pressure and temperature conditions in surficial seafloor sediments. As a result, the sound speed of the sediments would change. Studies seldom have focused on the influence of hydrostatic pressure on such. According to calculations of the general model of sound speed (GMSS), the sound speed of sediment increased linearly when the hydrostatic pressure increased, the same trend as that of the seawater. Pressure-controlled experiments in the laboratory verified that the influence of hydrostatic pressure on the sediment sound speed was highly related to the pore water, which was consistent with the theoretical calculations from the GMSS. Hydrostatic pressure was found to have the same effect on sound speed for the three kinds of sediments: gravel-silty sand, clayey silt, and silty clay. For different hydrostatic pressures up to 40 MPa, the fluctuation of sound speed ratio calculated with the theoretical model was less than 1.96%, while that measured in the controlled experiment was less than 2.63%. This means that if the sound speed ratio is used as a constant to correct for the difference at different seawater depths of no more than 4000 m, the estimable error is about 2.63%