Three more user-level buttons should appear. A fault is a fracture surface within the earth on which slip or displacement has taken place. The total displacement on a fault may be less than a few centimeters or may be measured in hundreds of kilometers. Large displacements are commonly achieved by a series of sudden slips associated with earthquakes, but under some conditions involving slow slip, called creep. Normal faults involve a dipping fracture surface on which the block above the fault plane, the hanging-wall block, is downthrown with respect to the block below, called the footwall block.
Normal faults are common in regions of crustal extension.
In contrast, reverse fault displacements, which are common in regions of compression, are such that the block above the fracture surface is uplifted with respect to the block below. Strike-slip faults generally involve no vertical motion, but instead are produced by two blocks that are sliding laterally past one another. Imagine that you are standing on one side of the fault. If the other side has moved to the right, as may be indicated by offset streams, ridges, roads, fences, or other features that cross the fault, it is a right-lateral fault. If the other side has been offset to the left, the fault is left lateral.