Multi-Stage Seismic Survey for Seafloor Massive Sulphide (SMS) Exploration

In SIP project “Next-generation technology for ocean resources exploration”, we have been developing “Integrated Survey System” for concealed SMS exploration. In this approach, seismic survey is one of key technologies to investigate subsurface structure with high resolution. The Multi-Stage Seismic Survey is our proposed reflection seismic methods for SMS deposits. This investigation method consists of VCS (Vertical Cable Seismic), ACS (Autonomous Cable Seismic) and ZVCS (Zero-offset Vertical Cable Seismic). VCS and ACS have already been published, but ZVCS is a newly developed system as an intermediate system between ACS and VCS. We can use it in semi-detailed and detailed surveys. In 2016, we carried out a multi-stage seismic survey in the Izena Hole, which is one of the most promising hydrothermal sulfide ore deposits areas around Japan. The purpose of this study is to understand the characteristic seismic facies of hydrothermal field and to show that the SMS deposit can be detected by this method. The results of these high-resolution surveys show the follows: First, the lower boundary of the massive sulfide beneath the sedimentary layer can be identified by negative-polarity reflections. Second, a strong hydrothermal alteration zone can be identified as a low amplitude area. Third, massive sulfide deposits in hydrothermal activity area can be identified by velocity model and characteristic seismic facies. These results provided valuable information to geologists. We conclude the multi-stage seismic survey is very effective in the “Integrate Survey System” for concealed SMS exploration.