@article{oai:nagoya.repo.nii.ac.jp:00022920,
 author = {Ishibashi, Masayuki and Yoshida, Hidekazu and Sasao, Eiji and Yuguchi, Takashi},
 journal = {Engineering Geology},
 month = {Jun},
 note = {Fracture zones around faults (damage zones) in crystalline rocks such as granite can act as significant transport pathways because the permeability of damage zones around active faults will likely be increased by the fracture network system. Understanding the characteristics and long-term behavior of damage zones along smaller scale faults is important for the safety assessment of deep underground facilities in the plutons of an orogenic belt; for example, facilities for the disposal of high-level radioactive waste. Therefore, this paper describes the features of a damage zone and the long-term behavior of its hydrogeological structures associated with faulting in an underground environment based on the results of geological and hydraulic investigations 300 and 500 m below ground level at the Mizunami Underground Research Laboratory, Central Japan. Detailed borehole and gallery wall investigations show the distributions of fractures, fracture fillings, predominant fracture orientations, groundwater inflow points, and hydraulic transmissivity in and around a damage zone. The results indicate that there are three stages in the development of hydrogeological structures. The first stage is the formation of background fractures that formed after the temperature of granitic plutons decreased through the ductile–brittle transition, forming fractures under brittle deformation conditions. The second stage is the formation of a damage zone and corresponding increase in hydraulic permeability as a result of the formation of relatively small fractures associated with faulting. The third stage is the formation of fracture fillings because of the infiltration of groundwater through the damage zone, decreasing the hydraulic permeability of the zone. In the late third stage, unconsolidated clayey fillings form in the large fractures associated with faulting resulting in decreased permeability of the fractures in the damage zone around the fault. These results underline the importance of understanding the development stages to evaluate the effect of faulting in orogenic belt plutons.},
 pages = {114--127},
 title = {Long term behavior of hydrogeological structures associated with faulting: An example from the deep crystalline rock in the Mizunami URL, Central Japan},
 volume = {208},
 year = {2016}
}