An Underwater Towed Electromagnetic Source for Geophysical Exploration

Low frequency electromagnetic methods are used in geophysical exploration by detecting the magnetic field distortion between a transmitter and receiver produced by locally conductive bodies. Both ground and airborne systems are in current use. One airborne multi-coil aerial electromagnetic prospecting system houses the transmitter and receiver in a 30 ft bird while another reduces the system to an impedance measurement using a single super-conducting coil. It is possible to extend low frequency airborne geologic prospecting techniques into the ocean environment by employing an underwater towed source of electromagnetic radiation and a receiving magnetic or electric field detector. The receiver can be simultaneously towed on an auxiliary cable, boom mounted on the towing platform (surface or subsurface), or land or underwater based.