Relationship between hydraulic conductivity and occurrence of fault rocks in Yangsan fault zone, Korea

Fault rocks that occur in the Yugye segment of the Yangsan fault zone, South Korea, are classified based on information from geological field and drilling surveys, including total core recovery, rock quality designation, particle size distribution analysis, characterization of fault rocks intersected in boreholes, and hydraulic conductivity values established from Lugeon tests. The classification assigns fault rocks to three categories, i.e., fault damage zone, fault breccia, or fault gouge, with average hydraulic conductivities of 1.22 × 10 −6 , 2.07 × 10 −4 , and 2.57 × 10 −5 cm/s, respectively. The hydraulic conductivity of the sedimentary host rock is 2.76 × 10 −6 cm/s, similar to that of the fault damage zones, which suggests that the multiple fractures in the fault damage zones are closed in situ. The hydraulic conductivity of the fault core (fault breccia and fault gouge) is greater than that of the fault damage zones and host rocks by one or two orders of magnitude. In addition, the permeability of the fault breccia is greater than that of the fault gouge, which contains more clay. The hydraulic conductivity of both the fault breccia and fault gouge show a positive correlation (R 2 ≥ 97%) with increasing fragment content.