HR: 1340h
AN: T53A-1127    [Abstracts]
TI: First Results from NanTroSEIZE LWD, IODP Expedition 314: Physical and hydrologic properties
AU: * Kinoshita, M
EM: masa@jamstec.go.jp
AF: Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima, Yokosuka, 237- 0061, Japan
AU: Tobin, H
EM: htobin@wisc.edu
AF: Dept. of Geology and Geophysics University of Wisconsin - Madison, 1215 W. Dayton St., Madison, WI 53706, United States
AU: Scientific Party, I
EM: masa@jamstec.go.jp
AB: The IODP Expedition 314 will be carried out in September through November, 2007 off Kii Peninsula of Japan. It is the first leg of Nankai Trough Seismogenic Zone Experiments (NanTroSEIZE), a multi-year, multi-leg and multi- platform project to investigate fault mechanics and seismogenesis along a subduction megathrust through direct sampling, in situ measurements, and long-term monitoring. During Expedition 314, we plan to drill into 6 NanTroSEIZE sites down to ~1000m below sea floor (bsf). Using the LWD (Logging-While-Drilling) technique, we obtain continous vertical profiles of physical properties such as bulk density, resistivity, porosity, P-wave velocity, and borehole images at all six sites. These sites include the incoming plate trench sediments, the frontal thrust and toe of the accretionary prism, forearc basin deposits, a major out-of-sequence thrust system (the gmegasplayh fault), and highly-deformed rocks of the interior of the accretionary prism. We will show preliminary results of LWD physical properties obtained during Exp.314. One of the anticipated goals is to quantitatively describe the evolution of accretionary prism off Kumano, through porosity reduction with increasing depth and in the landward direction. Abrupt decrease in porosity or other properties is expected across the mega-splay, and its offset is estimated. The activity of mega-splay at shallow depth is inferred from this offset, as well as through analysis of slope failure deposits and young sediments in the forearc basin. Hydrological properties, such as permeability and storage coefficients are estimated as well as elastic properties, especially around fault intervals. They are essential to understand inter- and co-seismic behavior of the faults. Two of six sites will drill into the shallower part of two deep riser holes, targeting the mega-splay and mega-thrust faults. Results from these sites will make an important milestone toward understanding the state and interseismic behavior of the M8 seismogenic zone.
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 3036 Ocean drilling
DE: 3060 Subduction zone processes (1031, 3613, 8170, 8413)
DE: 5114 Permeability and porosity
DE: 8118 Dynamics and mechanics of faulting (8004)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting