Study on influence of fault activity to geological environment; Case study at the Mizunami Underground Research Laboratory

Sasao, Eiji   ; Ishibashi, Masayuki; Kuboshima, Koji*; Murakami, Hiroaki  

Understanding of a range influenced by fault activity is quite important, because fault activity could lead to form and/or grow crushed zone and to increase water conductivity. We described fracture frequency, fracture filling and alteration along fracture, and then discuss relationship between those features and fault at the Mizunami Underground Research Laboratory. As a result of the study, those features are dominant around faults in the Laboratory. Alteration along fracture and some of the fracture filling suggest inflow of hydrothermal fluid. This implies opening of fracture or reopening of existed fracture. We try to find the evidence of shear fracture in the future study, because fault activity would form shear fracture.