This ocean sciences instrumentation development project will develop, construct, and test a transient electromagnetic sounding system to be deployed from the Scripps Deep Tow Vehicle or other remotely operated vehicles. The TDEM (time domain electromagnetic method) system is a deep-water adaptation of a similar instrument that was successfully tested in shallow water and one that has been employed in terrestrial studies. The system will be towed across the seafloor to continuously map the electrical conductivity of the underlying sediment and rock. A switched magnetic source generates a signal which diffuses through the seafloor rocks and is detected by magnetometers towed a fixed distances behind the source. Modifications in the detected signal from the source signal that are brought about by differing properties of underlying rocks, provides an estimate of electrical conductivity as a function of depth. Information may then be inferred about sub-seafloor hydrothermal circulation, sulfide ore deposits, sedimentation rates, and other geological features. Features may be measured as far as a few hundred meters beneath the seafloor and electromagnetic measurements are independent from those provided by seismic or sonar surveys.
