Fault

The majority of fault motion are slow and creeping movements, unlikely to be felt by humans at ground surface. Some movements occur as rapid spasms that happen in a few seconds and can cause ground displacements of inches or feet (centimeters or meters). These movements are resisted by friction along the two faces of the fault plane until the tensional, compressional or shear stress exceeds the frictional force. Earthquakes are caused by these sudden jumps or spasms. Severe shaking can result, and ground rupture can create fault scarps.