Keywords:permeability, fault zone, hydraulic test, groundwater level
GSJ, AIST constructed an integrated groundwater observatory at Matsusaka-Iitaka as a part of the groundwater and crustal deformation observation network for the prediction research of the Nankai and Tonankai earthquakes (Shigematsu et al., 2012; Koizumi, 2013). Hole 1 (total depth 600m) was penetrated the Median Tectonic Line (MTL) at a depth of 473.9m. Total depth of Hole 2 is 208m. We obtained core samples and well logging data and conducted hydraulic tests in these wells. Screened depth of Hole 1 is 547.6 - 558.5 m and is located in the lower fracture zone of the MTL fault zone developed in the Sanbagawa metamorphic rocks. Screened depth of Hole 2 is 145.5-156.4 m and is located at a branch fault in the Ryoke Granitolds (Shigematsu et al., 2012).
The results of the hydraulic tests and continuous groundwater observation show 1.8 - 8.5 x 10 -16 and 1.8 x 10-15 m2 in Hole 1 and Hole 2, respectively. These permeabilities are consistent with laboratory permeability measurement of MTL fault rocks (Wibberley and Shimamoto, 2003).