1Department of Geology and Geophysics, University of Hawaii, 1680 East-West Rd., Honolulu, HI 96822, USA
2Department of Earth Sciences, Chiba University, 1-33 Yayoi-cho, Inage-Ku, Chiba 263-8522, Japan
3Geological Institute, ETH Zürich, Sonneggstrasse 5, 8092 Zürich, Switzerland
4Department of Earth Sciences, Rice University, 6100 Main Street, MS-126, Houston, TX 77005, USA
5Center for Deep Earth Exploration, Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi, Kanazawa-ku, Yokohama 236-0001, Japan
Received: 21 Aug 2013 – Revised: 04 Nov 2013 – Accepted: 26 Nov 2013 – Published: 07 Jan 2014
Abstract. The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is designed to investigate fault mechanics and seismogenesis along a subduction megathrust, with objectives that include characterizing fault slip, strain accumulation, fault and wall rock composition, fault architecture, and state variables throughout an active plate boundary system. Integrated Ocean Drilling Program (IODP) Expedition 338 was planned to extend and case riser Hole C0002F from 856 to 3600 meters below the seafloor (m b.s.f.). Riser operations extended the hole to 2005.5 m b.s.f., collecting logging-while-drilling (LWD) and measurement-while-drilling, mud gas, and cuttings data. Results reveal two lithologic units within the inner wedge of the accretionary prism that are separated by a prominent fault zone at ~ 1640 m b.s.f. Due to damage to the riser during unfavorable winds and strong currents, riser operations were suspended, and Hole C0002F left for re-entry during future riser drilling operations.
Contingency riserless operations included coring at the forearc basin site (C0002) and at two slope basin sites (C0021 and C0022), and LWD at one input site (C0012) and at three slope basin sites (C0018, C0021 and C0022). Cores and logs from these sites comprehensively characterize the alteration stage of the oceanic basement input to the subduction zone, the early stage of Kumano Basin evolution, gas hydrates in the forearc basin, and recent activity of the shallow megasplay fault zone system and associated submarine landslides.
Moore, G. F., Kanagawa, K., Strasser, M., Dugan, B., Maeda, L., Toczko, S., and the IODP Expedition 338 Scientific Party: IODP Expedition 338: NanTroSEIZE Stage 3: NanTroSEIZE plate boundary deep riser 2, Sci. Dril., 17, 1-12, doi:10.5194/sd-17-1-2014, 2014.