a) The change of fracture aperture of the fracture in Figure 1.a with effective normal stress (laboratory data) b) Calculated aspect ratio distribution of fracture voids with the following parameters: mean=0.045 and standard deviation=23.5 ) 15 b) 25 20 15 10 104 103 102 101 0.005 0.01 0.015 0.02 0.025 Aspect ratio of fracture voids,- Aperture change [mm] Effective normal stress [MPa] Frequency 5.