Overview of NanTroSEIZE: The Nankai Trough Seismogenic Zone Experiment Harold Tobin University of Wisconsin – Madison Masataka Kinoshita JAMSTEC - IFREE Co-Chief Project Scientists & Expedition 314 co-Chiefs for NanTroSEIZE Proponents, Project Management Team, and Expedition 314 – 316 Scientists 1

NanTroSEIZE transect spans the up-dip limit of the M8+ seismogenic asperity 1944 1946 3D seismic & drilling transect

Inferred Asperity of 1944 Tonankai earthquake (Baba and Cummins, 2005) (Kikuchi and Yamanaka, 2001) (Ichinose et al., 2003) NanTroSEIZE targets an up-dip maximum of large slip in 1944 and the presumed locked portion of the plate interface today

NanTroSEIZE objectives: Building a distributed observatory spanning the up-dip end of the interplate seismogenic zone ~8 planned drilling sites, to depths from ~300 to ~6000+ m below the seafloor Core sampling, logging, downhole testing, and long-term monitoring – all to provide data on fault physics at several locations in P, T, and structural/diagenetic evolution

Objectives of NanTroSEIZE Document the material properties and state of the plate boundary fault system at several P-T and lithology conditions, testing hypotheses for stable vs. unstable frictional behavior. Investigate partitioning between seismic vs. aseismic processes on the main plate boundary, through monitoring of seismicity, borehole strain, pore fluid pressure, and temperature. Test whether there are interseismic temporal changes in state – including possible earthquake precursory signals. Calibrate observations in the broader geophysical volume (3D seismic) surrounding the boreholes to the rock properties and state. NanTroSEIZE is primarily about FAULT MECHANICS 5

NanTroSEIZE: Background on project organization Set of IODP Drilling Proposals submitted and reviewed from 2001 - 2004 IODP’s first “Complex Drilling Project” (CDP) designation and first “Project Management Team” (PMT) set up to implement 3D MCS survey funded as Site Survey by NSF-ODP (~25%) and MEXT (~75%), acquired in 2006 U.S. P.I.s: G. Moore, N. Bangs, H. Tobin, S. Gulick, D. Saffer) Drilling of Stage 1 from Sept 2007 - Feb 2008 6

3D seismic box 7

Nankai accretionary wedge 3D imaging by pre-stack depth migration Mega-Splay Fault Oceanic Crust Decollement

Stages Overview Stage 1 – 2007-2008 Stage 2 – Planned for 2009 Riserless drilling of 8 sites up to ~1400 m depth. Stage 2 – Planned for 2009 First riser-based deep site drilling at NT2-11 to ~3000 m. Additional riserless operations at Inputs sites and riserless observatories (“CORKs”) Stage 3 – Planned for 2011-2012 ?? ~6000 m riser site drilling C0002 (NT3-01) Observatory installation efforts at other sites. Stage 4 - Long-term monitoring system completion in 2 deep riser boreholes. 9

Chikyu gets underway September, 2007

NanTroSEIZE Stage 1: Expeditions 314, 315, and 316 First expeditions on Chikyu 71 scientists from 12 countries were onboard for 5 months of continuous operations (Sept 21, 2007 – Feb 5, 2008) Drilled 33 holes at 8 sites up to 1400 meters below the sea floor Obtained core samples from active faults and environment Found major variations in stress orientations, providing evidence for location of the up-dip limit of frictionally locked plate interface Future plan to drill up to 6000+ meters depth to sample and instrument in and around the seismogenic zone

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Stage 1 drilling on interpreted arbitrary line from 3D seismic Interp. by G. Moore, 2008

NanTroSEIZE Future Plans 2009: IODP Expeditions 319, 322, 323 Drill and prepare to install seismic / geodetic / hydrologic observatories at 3 sites above seismogenic zone Core the subduction inputs to basement

NanTroSEIZE Future Plans 2011 Install monitoring systems in cased boreholes: Seismometer array, Strainmeter, tiltmeter, pore pressure, and temperature 2012 until 20?? Drill with riser system to megasplay fault/plate boundary at C0002, or equivalent site.

Link to cabled observatory network for real-time monitoring Japanese seafloor cabled network DONET will be completed in 2010 NanTroSEIZE IODP borehole observatories will be connected

What has changed since project conception? Where does the plate boundary lie beneath the forearc basin and mega-splay?

What has changed since the project conception?

2009 Expeditions Call for Participants out now! www.iodp.org 2009 Expeditions Call for Participants out now!

NT2-11 Observatory option 1: TD=2500m bsf BBseismometer is installed at ~1600m to avoid high temperature 3 tiltmeters are installed within 9-5/8” section in the accretionary prism PP at the bottom, plus ~1600m (perforated and packer-sealed)