If movement occurs along a strike-slip fault in rugged country, the ridge crests are displaced in different directions on either side of the fault line. When movement brings ridge crests on one side
of the fault opposite valleys on the other side, the valleys are ‘shut off ‘. The ridges are therefore called shutter ridges (Figure 6.20). Where tensional stresses dominate strike-slip faults, subsidence occurs and long, shallow depres sions or sags may form. These are usually a few tens of metres wide and a few hundred metres long, and they may hold sag ponds. Where com pres sional stresses dominate a strike-slip fault, ridges and linear and en échelon scarplets may develop