Sound velocity as a function of depth in marine sediments

• Published in: The Journal of the Acoustical Society of America
• Main Author: Hamilton, Edwin L.
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Institute of Physics 1985
• Subjects: Bering Sea
• Online Access: https://oceanrep.geomar.de/id/eprint/40037/; https://oceanrep.geomar.de/id/eprint/40037/1/Hamilton.pdf; https://doi.org/10.1121/1.392905

Additional data from sonobuoys and the Deep Sea Drilling Project (DSDP) justify separating sound‐velocity‐depth functions and velocity gradients (in the first layer of soft marine sediments) into some geographic areas and sediment types. Based on sonobuoy and core measurements (where V is sound velocity in km/s, and h is depth in sediments in km), the following data are obtained: continental shelf basins off Sumatra and Java—V=1.484+0.710h−0.085h2; U. S. Atlantic continental rise—V=1.513+0.828h−0.138h2; deep‐sea terrigenous sediments—V=1.519+1.227h−0.473h2; and siliceous sediments of the Bering Sea— V=1.509+0.869h−0.267h2. Selected DSDP data (through leg 74) in similar areas yield: continental terrace silt–clays—V=1.505+0.712h; deep‐sea terrigenous sediments—V=1.510+1.019h; and deep‐sea siliceous sediments—V=1.533+0.761h. Computed velocity gradients from sonobuoy measurements are generally supported by the DSDP gradients. Only DSDP data give the following: hemipelagic sediments—V=1.501+1.151h; deep‐sea calcareous sediments—V=1.541+0.928h; and deep‐sea pelagic clay—V=1.526+1.046h. Where fast sediment accumulation occurs, there has not been enough time to reduce sediment pore spaces under overburden pressure; areas of slow accumulation may have relatively high sediment structural strength. Both cases have lower velocity gradients because higher porosities and consequent lower velocities persist to deeper depths.