Hydrological and geological characterization of deep subsurface structures in and around the main shaft fault at the Mizunami Underground Research Laboratory

Nohara, Tsuyoshi   ; Sakai, Toshihiro; Murakami, Hiroaki  ; Ishibashi, Masayuki

Existing data was analyzed in order to understand Hydrological and Geological Characterization of deep subsurface structures in and around the Main Shaft fault at the Mizunami Underground Research Laboratory. As a result, in response to the low permeability structure of the Main Shaft Fault, fault gouges and alteration parts are found to be continuously distributed in the wall of the Main Shaft. One of the most high-permeable structure was estimated to be constituted by low-angle fractures with a sheet-like calcite. Shear of low angle fractures showed relatively low permeability. It may be possible to understand the permeability structure of these features in a drilling survey of granitic rocks.