Faults: A fault is a fracture across which two blocks have slipped; the displacement of adjacent blocks is parallel to the fault plane. Faulting corresponds to the brittle failure of an underformed rock formation or, alternatively, involves frictional sliding on a pre-existing fault plane. Faulting occurs when the maximum differential stress (maximum stress minus minimum stress:  ) exceeds the shear strength of an intact rock formation, or the frictional strength of a pre-existing fault.
Fault types: There are three types of faults.
Normal faults: the hanging wall moves down the dip of the fault relatively to the footwall => Tectonic regime in extension (the largest stress axis is vertical).
Reverse faults: the hanging wall moves up the dip of the fault relatively to the footwall => Tectonic regime in compression (the smallest stress axis is vertical).
Strike-slip faults: the blocks move horizontally past one another => Transcurrent Tectonic regime (the intermediate stress axis is vertical).
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