International Ocean Discovery Program; Expedition 358 Scientific Prospectus; NanTroSEIZE plate boundary deep riser 4; Nankai seismogenic/slow slip megathrust

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doi: 10.14379/iodp.sp.358.2018
Author(s): Tobin, Harold; Kimura, Gaku; Kinoshita, Masataka; Toczko, Sean; Maeda, Lena
Author Affiliation(s): Primary:
University of Wisconsin at Madison, Department of Geoscience, Madison, WI, United States
Tokyo University of Marine Science and Technology, Japan
University of Tokyo, Japan
Japan Agency for Marine-Earth Science and Technology, Japan
Source: Scientific Prospectus (International Ocean Discovery Program), Vol.358, 8p. Publisher: International Ocean Discovery Program, College Station, TX, United States. ISSN: 2332-1385
Note: In English. 9 refs.
Summary: The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) program is a coordinated, multi-expedition drilling project designed to investigate fault mechanics and seismogenesis along subduction megathrusts through direct sampling, in situ measurements, and long-term monitoring in conjunction with allied laboratory and numerical modeling studies. The fundamental scientific objectives of the NanTroSEIZE project include characterizing the nature of fault slip and strain accumulation, fault and wall rock composition, fault architecture, and state variables throughout the active plate boundary system. Site C0002 is in the Kumano forearc basin above the seismogenic, and presumably locked, portion of the plate boundary thrust system. The Kumano Basin sedimentary sequence and uppermost part of the accretionary prism were drilled, logged, and sampled during Integrated Ocean Drilling Program Expeditions 314 (logging while drilling [LWD] to 1401.5 mbsf), 315 (coring to 1057 mbsf), 338 (LWD to 2005 mbsf and coring to 1120 mbsf), and 348 (LWD to 3058.5 mbsf, with limited coring from 2163-2218.5 mbsf). International Ocean Discovery Program (IODP) Expedition 358 aims to reach and sample the megasplay fault/plate boundary fault at Site C0002 by extending the riser borehole (Hole C0002P) established during previous Integrated Ocean Drilling Program NanTroSEIZE expeditions. Evidence suggests that the drilling target at the megasplay will reach a region where megathrust seismogenic processes are active. A new borehole will be "kicked off" from Hole C0002P and will be extended to ∼5000 meters below seafloor (mbsf) and then across the high-amplitude seismic reflector identified as the main plate boundary fault. Continuous LWD with drilling mud gas analysis and limited coring at the anticipated plate boundary fault depth, will leave the cased borehole completed at ∼5200 mbsf. A suite of analyses on cuttings, mud gases, and limited cores will address the four primary scientific objectives: (1) determine the composition, stratigraphy, and deformational history of the Miocene accretionary prism; (2) reconstruct its thermal, diagenetic, and metamorphic history; (3) determine horizontal stress orientations and magnitudes; and (4) investigate the mechanical and hydrological properties of the upper plate of the seismogenic plate boundary. The main scientific objective is to log and sample the hanging wall, the fault zone, and into the footwall. The main contingency plan is to leave a cased borehole in good condition for future installation of a long-term borehole monitoring system (LTBMS). These operations will extend drilling conducted during Integrated Ocean Drilling Program Expeditions 326, 338, and 348. The entire expedition will cover a period of 164 days, beginning on 7 October 2018 and ending on 21 March 2019.
Year of Publication: 2018
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 18 Geophysics, Solid-Earth; 19 Geophysics, Seismology; Asia; Boreholes; Continental margin; Crust; Earthquakes; Expedition 358; Far East; Fault planes; Fault zones; Faults; Honshu; IODP Site C0002; Integrated Ocean Drilling Program; International Ocean Discovery Program; Japan; Kii Peninsula; Kumano Basin; Measurement-while-drilling; Megathrust earthquakes; NanTroSEIZE; Nankai Trough; North Pacific; Northwest Pacific; Oceanic crust; Pacific Ocean; Plate boundaries; Plate tectonics; Seismic zoning; West Pacific
Coordinates: N331800 N331801 E1363801 E1363800
Record ID: 2018061380
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