Experiment and response analysis of marine monostatic EM instrument toward mapping seafloor sulfide massive deposit

摘要

We performed numerical and physical experiment with a marine monostatic electromagnetic (EM) survey system, which is developed primarily for exploration of seafloor mineral deposits. The system is a multi-frequency EM system housed to endure high pressure in deep sea up to 2000 m. To keep stable altitude of the system from the seafloor in rough seafloor topography condition, the system is connected rigidly to ROV (Remotely Operated Vehicle). We performed a test with the new loop EM system by keeping altitude of ROV 2 m above from the seafloor at a depth of 300 m sea water. Experimental results showed that electromagnetic anomaly was clearly identified at the location of metallic object, and the pattern of the EM responses matches well with the theoretical responses from a 3-D integral equation EM modeling code. With the off-shore test and the numerical analysis, we confirmed that the method of operation of the EM survey system by ROV is readily feasible, and the system are expected to detect actual seafloor sulfide massive deposits in the highly conductive seafloor environment.