Width of joint zones are not well known. The few sets of published data available show that joint width varies widely. For example, joint zones C and D in Figure 1 mapped by Laubach (1991) have width distributions plotted in Figure 2 which have maximum values of about 22-27 meters. According to Laubach, the widths in the area range from 7 to more than 50 meters. There is a certain degree of ambiguity in the dimensions of joint zones due to the difficulty of separating joint zones from fault zones. This issue will be revisited in 'Growth of Faults based on Sequential Shearing of Initial Discontinuities.'

Figure 1. Map of fractures and fracture zones (referred to as swarms by the original author) in the Pictured Cliffs Sandstone, New Mexico. From Laubach (1991).

Figure 2. Plots showing width distributions along two joint zones (C and D in Figure 1). Note that zone D has one termination point but the other end is uncertain. In both cases, the largest measured width is about 25 m with a possibility that one of them could be much wider. From Laubach (1992, unpublished).