Seismic and radar tomography of the SCV underground test area in Stripa, Sweden have detected two major sets of fracture zones. Slickenside striations in these zones indicate that they have undergone shear deformation. Utilizing a database consisting of 3100 logged fractures from borehole core and 900 fractures mapped on the walls of underground drifts, the character of these fracture zones have been analyzed. This data along with numerical modelling suggest that the higher fluid conductivities in the zones compared with the surrounding rock may be due to a combination of higher fracture densities, and stresses in the zones that promote dilatancy in fractures with certain orientations. This would also result in anisotropic flow in the zones, with the primary flow direction in the direction of the dilatant fractures.