Table 1 Summary statistics from borehole images and input parameters for 2-D DFNs

Fracture centre location

All

No discerned clustering

Uniform distribution in each of X and Y directions

Orientation

All

Dominant population:

Dip magnitude: subvertical (82° ± 6°), dip direction to NW and SE

Strike: NE-SW

Minor population 1: dip magnitude 67° ± 12° and strike N-S

Minor population 2: dip magnitude between 30 and 70° and varied strike

Dominant population:

Dip magnitude: Normal distribution, mean = 90° (vertical) and standard deviation = 15°

Strike: models are orientated NW–SE, i.e., perpendicular to the measured dominant fracture strike

Minor populations: not modelled (see text for explanation)

Linear density (P₁₀, m⁻¹)

Sheet-like andesite

0.6 (n = 1405; Length of image = 2334 m)

0.6

Pyroclastic rocks/ignimbrite

0.8 (n = 648, Length of image = 807 m)

0.8

Rhyolite lava and breccia

1.7 (n = 826; Length of image = 496 m)

1.7

Length (L, m)

All

Unknown

Doubly-truncated power law PDF:

P(L) = A/L^λ

A = (1/a – 1/b)

with: a = 1, b = 100, λ = 2; a ≤ L ≤ b

Geometric aperture (a_g, m)

All

Power law PDF:

P(a_g) = A/a_g^α, α = 2.6

a_g = L/1000

Volume of fractures and veins per volume of rock (P₃₃, dimensionless)

All

0.01–0.1 at thin section, core and acoustic image scales

0.05 naturally results from choice of a_g

Hydraulic aperture (a_h, m)

All

Unknown

a_h = β L/1000

with: β = 0.002