Fig. 5

A Flow properties parallel to the pressure gradient as a function of P₁₀. As expected, the flows with the pressure gradient parallel the mean fracture direction are greater than those when the pressure gradient is across it. B Permeability anisotropy, defined as the ratio of the two flows illustrated in panel A. No meaningful error bars can be given for Model I (P₁₀ = 0.2 m⁻¹) because only 0.1% of networks have non-zero flows in both X and Y directions. C Mean flow perpendicular to the pressure gradient (in case where it is parallel to the MFD) is consistent with zero, as expected. D Schematic representation of pressure gradient, measured flow direction and mean fracture direction (MFD). Flows are ‘bulk’, i.e. the sum of many flows from individual fractures at each boundary. Flows in both directions are possible at each boundary but the arrows indicate the net effect. Error bars: 3 standard deviations