Abstract
Fault is inevitably associating the ‘damaged zone’ with fracturing along the fault plane. The distribution characteristics of fractures in the ‘damaged zone’ are considered to be reflecting the process of faulting and also to be used for understanding the influence of fault movement in the surrounding host rocks during the fault development. In order to understand such relation between fault movement and formation of ‘damaged zone’, the fracture density and its morphological feature along Atera fault distributed in Gifu prefecture, central Japan have been investigated. The result of detailed fracture mapping of the fractures in the ‘damaged zone’ shows that the fractures formed by faulting can be distinguished from those primarily developed in the host rock by its morphological features and the difference of fracture filling minerals. In particular, shortly transected network type fractures filled by iron-oxides have been preferentially formed in the ‘damaged zone’ along the Atera fault probably induced by fault movement. The density of fractures also suggests that the ‘damaged zone’ formed by fault movement is distributed up to ca. 200 meters from the fault plane. The results provide an idea that the detailed characterization of fractures and fracture fillings can be used to estimate the area of ‘damaged zone’developed along a fault, and the methodology is applicable to the site characterization and allocation of underground facilities such as a radioactive waste repository in crystalline rocks.
