Approach to Focusing the SMS Potential Area using High-Resolution Seismic Surveys

Multi-stage high-resolution seismic survey system has been developed to explore Seafloor Massive Sulfides (SMS) deposits. The authors demonstrated the feasibility of this system around offshore west Kume Island, Okinawa Trough. In the first stage, a deep-towed streamer (ACS; Autonomous Cable Seismic) was used at the survey area about tens of square kilometers. After the ACS, a ZVCS (Zero-offset Vertical Cable Seismic) survey was carried out in a more limited area within several square kilometers. A vertical hydrophone array is one of the key components of ZVCS in order to suppress noises caused by side reflections. The conventional VSP data processing techniques such as wave field separation and stacking can be applied to the data obtained by this system. Subsequently, 3DVCS (Three-Dimensional Vertical Cable Seismic) was deployed to obtain a 3D image of subsurface structures with high-resolution. Result of ACS survey gave us an opportunity to interpret characteristic seismic facies around the hydrothermally active area. High quality seismic sections acquired by ZVCS made it possible to image the complex shallow structures. The 3D seismic volume after pre-stack depth migration using 3DVCS data made us capable of interpreting three dimensional structures and tracking the key reflectors of SMS.t.