Fig. 4

Examples of backbone fracture networks. A Model A, P₁₀ = 0.6 m⁻¹ B–D: networks close to the percolation threshold (Model I, P₁₀ = 0.2 m⁻¹). B Network not connected across the model domain in either X or Y direction (approximately 65% models). C Strongly channelled network supporting flow only in the Y direction (approximately 35% of models). Each of the four channels is displayed in a different colour. D Network connected across the model in both directions (0.1% of models)