Fault:

In geology - fracture in the rocks of the Earth's crust, where compressional or tensional forces cause the rocks on the opposite sides of the fracture, or fault, to be displaced relative to each other.

Faults range in length from a few centimeters to many hundred kilometers, and displacement likewise may range from less than a centimeter to several hundred kilometers along the fracture surface.

Faults may be vertical, horizontal, or inclined at any angle.

Movement of rock along a fault may occur as a continuous creep or as a series of spasmodic jumps of a few meters during a few seconds.

Such jumps are separated by intervals during which stress builds up until it overcomes the frictional forces along the fault plane.

Most, if not all, earthquakes are caused by rapid movement along faults.