Ishizu K.Siripunvaraporn W.Goto T.N.Koike K.Kasaya T.Iwamoto H.Mahidol University2023-06-182023-06-182022-03-29Geophysics Vol.87 No.4 (2022)00168033https://repository.li.mahidol.ac.th/handle/20.500.14594/84507Three-dimensional (3D) marine controlled-source electromagnetic (CSEM) surveys for mapping hydrocarbons use dozens of ocean-bottom electric (OBE) receivers deployed in a grid pattern and several transmitter towlines. This study considers seafloor massive sulfides (SMS) exploration and the horizontal survey scale of SMS is a few kilometers, which is small compared to hydrocarbon surveys of tens of kilometers. If we apply a 3D CSEM survey using a receiver deployment on grids to map SMS, high survey costs will be incurred despite the small survey size. We newly propose a cost-effective 3D marine CSEM survey that uses fewer receivers than the survey with a receiver deployment on grids to reduce survey costs for SMS. This proposed CSEM survey uses a line of OBE receivers in the center of the survey area and several transmitter towlines. Numerical tests demonstrate that the proposed survey (7 OBE receivers) using 80% fewer receivers than the survey with a receiver deployment on grids (35 OBE receivers) is able to accurately map SMS, obtaining a similar performance to that of the receiver deployment on grids. Then, we explored SMS in the Ieyama hydrothermal area off Okinawa, southwest Japan, using the proposed 3D CSEM survey with a line of six OBE receivers and three transmitter towlines. The resulting 3D resistivity distribution from the observed data highlights three potential SMS zones consisting of 0.2 ohm-m low resistivity embedded into 1 ohm-m sediment.Earth and Planetary SciencesArticleSCOPUS10.1190/geo2021-0328.12-s2.0-8512777047919422156