In geology, a fault is a planar fracture or discontinuity in a volume of
rock across which there has been significant displacement as a result of rock-
mass movements. Large faults within Earth's crust result from the action of
plate tectonic forces, with the largest forming the boundaries between the
plates, such as the megathrust faults of subduction zones or transform faults.
Energy release associated with rapid movement on active faults is the cause of
most earthquakes. Faults may also displace slowly, by aseismic creep.
A fault plane is the plane that represents the fracture surface of a fault.
A fault trace or fault line is a place where the fault can be seen or
mapped on the surface.