Like a pane of
glass dropped on the floor, some rocks are brittle: They break, or
fracture, in response to stress. Rocks tend to fracture when stress
is applied rapidly, at shallow depths, or at low temperatures. If rocks
on each side of a fracture are displaced, the fracture becomes a fault.
Earthquakes result from the brittle deformation that also creates
This road, which crosses a fault, moved
1.5 m during the 1992 Landers earthquake in southern California.