Marine controlled-source electromagnetic sounding on submarine massive sulphides using 2.5-D simulation

Recently, controlled-source electromagnetic method is widely used for shallow sub-seafloor explorations. In this paper, we propose a new controlled-source electromagnetic method using two autonomous underwater vehicles (AUVs) for the exploration of submarine massive sulphides. A numerical simulation code for 2.5-D electromagnetic field in the frequency domain is developed in order to estimate electromagnetic responses on possible conductivity structures. As a result, we confirmed that the magnetic field on the seafloor is very sensitive to the horizontal distribution of buried conductive zone. We also confirmed that the intensity of received electric field decreases near the seafloor in an area wider than the horizontal extent of the buried conductive zone, when the current source dipole is located above the conductive zone. This is because electric field is attenuated due to the return current in the conductive zone. Based on our result, we think that the new controlled-source electromagnetic method is realizable.