Shear bands with associated splay shear bands are common in nature. For example, Figure 1 shows a shear band zone and a series of splay shear bands diverging from the zone at a small angle of about 30 degrees on a pavement of Entrada Sandstone exposed in the San Rafael Desert, Utah (Aydin et al. 2006). This mechanism is responsible for the formation of a network of multiple sets of shear bands. Also see the so-called Riedel shears (Figure 2) in which the splays (known as R' shears) are commonly confined between the initial overlapping shear bands (labelled as R shears). Please see Katz et al. (2004) and Mandl (1988) for additional examples.

Figure 1. (a) Splay shear bands with left-lateral sense of shearing associated with a shear band zone in Entrada Sandsone, San Rafael Desert, Utah. 20 cm ruler for scale. From Aydin et al. (2006). (b) Photograph showing shear bands and their splays in shearing modes on a pavement of Entrada Sandstone, San Rafael Desrt, Utah. Circles numbered 1 and 2 highlight left- and right-lateral shear offsets across two shear bands with a dihedral intersection angle and circles numbered 3 and 4 show divergent splay relationships.

Figure 2. Photograph and map of a Riedel shear zone with right-lateral overlapping R shears and the associated splay shear bands, the so-called R' shears with left-lateral sense of shear in the Navajo Sandstone exposed at the Capitol Reef National Park, Utah. The intersection angles are also marked. From Katz et al. (2004).