The fault scarp is the commonest form to arise from faulting. Many fault scarps associated with faulting during earthquakes have been observed (Plate 6.7). The scarp is formed on the face of the upthrown block and overlooking the downthrown block. Erosion may remove all trace of a fault scarp but, providing that the rocks on either side of the fault line differ in hardness, the position of the fault is likely to be preserved by differential erosion. The erosion may produce a new scarp. Rather than being a fault scarp, this new landform is more correctly called a fault-line scarp. Once formed, faults are lines of weakness, and move ment along them often occurs again and again. Uplift along faults may produce prominent scarps that are dissected by streams. The ends of the
spurs are ‘sliced off’ along the fault line to produce triangular facets. If the fault moves repeatedly, the streams are rejuvenated to form wineglass or funnel valleys (Plate 6.8). Some fault scarps occur singly, but many occur in clusters. Individual members of fault-scarp clusters may run side by side for long distances, or they may run en échelon (offset but in parallel), or they may run in an intricate manner with no obvious pattern.