HR: 17:00h
AN: OS34A-04 [Abstracts]
TI: Long Term Borehole Monitoring System For NanTroSEIZE 3.5 km Riser Hole: Requirements And Specifications
AU: Kuramoto, S
EM: s.kuramoto@jamstec.go.jp
AF: Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi,
Kanazawa-ku, Yokohama, 236-0001, Japan
AU: * Kyo, M
EM: kyom@jamstec.go.jp
AF: Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi,
Kanazawa-ku, Yokohama, 236-0001, Japan
AU: Ito, H
EM: hisaoito@jamstec.go.jp
AF: Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi,
Kanazawa-ku, Yokohama, 236-0001, Japan
AU: Namba, Y
EM: nambay@jamstec.go.jp
AF: Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi,
Kanazawa-ku, Yokohama, 236-0001, Japan
AU: Kato, K
EM: katoka@jamstec.go.jp
AF: Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi,
Kanazawa-ku, Yokohama, 236-0001, Japan
AU: Higuchi, K
EM: higuchik@jamstec.go.jp
AF: Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi,
Kanazawa-ku, Yokohama, 236-0001, Japan
AU: Kinoshita, M
EM: masa@jamstec.go.jp
AF: Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi,
Kanazawa-ku, Yokohama, 236-0001, Japan
AU: Araki, E
EM: araki@jamstec.go.jp
AF: Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi,
Kanazawa-ku, Yokohama, 236-0001, Japan
AU: Suyehiro, K
EM: suyehiro@jamstec.go.jp
AF: Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi,
Kanazawa-ku, Yokohama, 236-0001, Japan
AB:
Most of the large earthquakes (magnitude greater than 8.0) observed in Japan fall into the subduction plate-
boundary category. Based on the results of previous Nankai Trough research efforts, further research
opportunities have been proposed under the umbrella of the IODP scientific drilling proposal 603 (NanTroSEIZE:
Nankai Trough Seismogenic Zone Experiment) ranked as the top level proposal in IODP. IODP proposal 603 not
only proposes drilling, coring and geological analysis, and geophysical logging, but also mandates that a long-
term borehole monitoring system be installed into two deep riser holes at about 3,500 m and about 6,000 m
below sea floor (mbsf), where we expect to encounter the mega-splay and the locked region of mega thrust fault,
respectively.
The first riser target (NT2-03 site) is expected to drill through five potential splay faults above 3,500 mbsf. We plan
to install sensors to monitor strain, tilt and optionally pore pressure for crustal deformation at and between splay
faults, to monitor seismometer array for micro and slow earthquakes detection and for seismic microstructures,
and to monitor pore pressure and temperature for hydrologic state change at the fault during interseismic period.
The major technical features to develop the deep ocean borehole observatory for NT2-03A are mainly as follows;
1) high temperature (125E#8249;C), 2) long life (5 years), 3) deployment (15,000 psi wellhead system, deep
well, retrieval, perforation, packer, mechanical shock), 4) coupling to formation (cement, clamp), 5) multi level
monitoring (against 5 spray faults), 6) multi purpose monitoring (seismic, geodetic, hydrogeologic), 7) low power
consumption, 8) real time monitoring (connecting to sea bed cable), 9) accurate synchronization, 10) wide
frequency range / high dynamic range ADC, 11) down sizing (installing into 9-5/8hcasing with tubing), 12)
system redundancy (fault tolerant).
We started to develop an experimental prototype (EXP) for field test using the borehole on land from 2007, and
plan to carry out the field test in 2009. The objectives of EXP are to collect real data to determine if the system
works as designed and to identify all unseen problems in the design. The implementation phase will be followed
to improve the system based on the field test results, upgrade the design, and produce the Engineering Prototype
(ENP) to be installed in NT2-03A in 2011.
DE: 0915 Downhole methods
DE: 0994 Instruments and techniques
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7294 Seismic instruments and networks (0935, 3025)
DE: 8010 Fractures and faults
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting