Using CSEM techniques to map the shallow section of seafloor: From the coastline to the edges of the continental slope

Many important processes occur within the shallow section of the seafloor on the continental shelf and slope, yet conventional geophysical constraints on the physical properties within this critical boundary layer are limited. Some of the key constraints involve quantification of fluids within the seafloor, which can be provided by electrical methods. This paper reviews the application of a towed EM system to map the uppermost 20 m of seafloor in a variety of settings ranging from nearshore regions in water depths of approximately 10 m on the continental shelf out to water depths of 1300 m. The system is a mapping tool that provides areal maps of seafloor resistivity and has been used for a variety of purposes, including sedimentary characterization and facies mapping, evaluation of groundwater discharge, and mapping seafloor mounds in the Gulf of Mexico, thought to contain massive deposits of gas hydrate.