HYDRA - A Bottom Towed Electric Multi Receiver System

HYDRA - A Bottom Towed Electric Multi-Receiver System Source: BGR

HYDRA is a seafloor-towed, electrical dipole –dipole system which consists of a 100 m long horizontal transmitting dipole and up to five electrical receiving dipoles connected along a data cable at offsets from 150 m to about 1000 m. The pig at the front end of the array is a heavy weight which also hosts the signal generator, the communication unit, a conductivity-temperature-pressure (CTD) - sensor, and an acoustic transponder to determine the position on the seafloor. The system is connected to the research vessel via the deep-tow cable and is towed along profiles in contact with the seafloor. HYDRA has been developed at BGR to derive the electrical resistivity of seafloor sediments down to a depth of about 400 m below the seafloor. Its main application is the exploration of submarine gas hydrates, but also the determination of sediment properties like porosity and nature of pore fluids.