Mapping of Seafloor Gravity Anomalies by Underwater Gravity Measurement System Using Autonomous Underwater Vehicle for Exploration of Seafloor Deposits

It is known that there are seafloor mineral deposits around Japan islands. Gravity survey is one of powerful methods to obtain density structure in crust, especially for exploration of underground deposits. We have developed an underwater gravity measurement system for exploration below a seafloor using an Autonomous Underwater Vehicle. In 2014 and 2015, mapping of seafloor gravity anomalies by the underwater gravity measurement system for actual seafloor hydrothermal deposits was performed using the Urashima in Izena Caldera, the middle Okinawa Trough, where seafloor deposits were found. We obtained Bouguer gravity anomalies and found two small high gravity areas. We interpreted that high gravity anomalies originate from hydrothermal deposits with high density. The gravity survey by using AUV is useful to estimate buried mineral deposits below seafloor.