Sensing shallow seafloor and sediment properties, recent history

Near surface seafloor properties are needed for recreational, commercial, and military applications. Construction projects on the ocean seafloors often require extensive knowledge about strength, deformability, hydraulic, thermal, acoustic, and seismic characteristics for locating stable environments and ensuring proper functioning of structures, pipelines, and other installations on the surface of and buried into the marine sediments. The military is also interested in a variety of seafloor properties as they impact sound propagation, mine impact burial, trafficability, bearing capacity, time-dependent settlement, and stability of objects on the seafloor. Point measurements of sediment properties are done using core samplers and sediment grab devices (with subsequent lab analysis) and in-situ probes. These techniques are expensive in terms of ship time and provide limited area coverage. Sub-bottom acoustic and electromagnetic sensors can provide profiles of near surface sediment information with improved coverage rates. Fusion techniques are being developed to provide areal extent of sediment information from multiple sensors. This paper examines the recent history of techniques used to measure sediment properties in the upper portions of the seafloor and in shallow (< 100 m) water.