1. 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

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

3. 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

4. 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

5. 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

6. NanTroSEIZE: Background on project organization
Set of IODP Drilling Proposals submitted and reviewed from
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 Feb 2008 6

7. 3D seismic box 7

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

9. 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 ??
~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

10. Chikyu gets underway
September, 2007

11. 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 meters depth to sample and instrument in and around the seismogenic zone

12. 12 12

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

14. 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

15. 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.

16. 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

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

18. What has changed since the project conception?

19. 2009 Expeditions Call for Participants out now!
2009 Expeditions Call for Participants out now!

20. 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)