[S-CG62] 地殻流体と地殻変動

[SCG62-05] 水理試験と地下水圧観測から推定した原位置での断層帯の透水係数

★招待講演

*松本 則夫¹、重松 紀生¹ (1.産業技術総合研究所地質調査総合センター)

キーワード：透水係数、断層帯、水理試験

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.