Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Oral

S (Solid Earth Sciences) » S-CG Complex & General

[S-CG62] Crustal fluids and deformation

Wed. May 23, 2018 3:30 PM - 5:00 PM A03 (Tokyo Bay Makuhari Hall)

convener:Naoji Koizumi(School of Environmental Science,the University of Shiga Prefecture), Koji Umeda(Hirosaki University), Norio Matsumoto(産業技術総合研究所地質調査総合センター地震地下水研究グループ, 共同), Hidemi Tanaka(School of Science, The University of Tokyo), Chairperson:UMEDA KOJI, KOIZUMI NAOJI

4:30 PM - 4:45 PM

[SCG62-05] In-situ permeability of fault zones estimated by hydraulic tests and groundwater-pressure observations

★Invited Papers

*Norio Matsumoto1, Norio Shigematsu1 (1.Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST))

Keywords:permeability, fault zone, hydraulic test

In-situ permeability of the Median Tectonic Line (MTL) fault zone in Mie Prefecture, southwest Japan, was estimated using hydraulic tests and groundwater pressure observations in two boreholes. The screen depths in Holes 1 and 2 are located, respectively, in a major strand of the MTL fault zone within the Sambagawa metamorphic rocks and a branching fault developed in the hanging wall of the MTL within the Ryoke mylonite. The estimated permeability at Hole 1 ranges from 5.3 × 10−17 to 5.0 × 10−16 m2, and that at Hole 2 ranges from 4.4 × 10−16 to 1.5 × 10−15 m2. We also measured the permeability of the protolith close to the screened depth of Hole 1 (3.4 × 10−19 and 3.7 × 10−19 m2) and Hole 2 (3.1 × 10−19 and 6.2 × 10−19 m2). The permeability of the fault zone was found to be more than 100 and 700 times higher than the protolith permeability at Holes 1 and 2, respectively. The permeability data for Holes 1 and 2 are consistent with previously reported permeability data for samples from an MTL outcrop. The permeability observed in this study reflects the complex fault zone permeability structure of the MTL fault zone.