FAULT

(Geology) A fracture in rock along which movement can be demonstrated. A fracture in the earth's crust forming a boundary between rock masses that have shifted. Faults may be classified as follows: (1) Active Fault: A fault that has moved recently and which is likely to move again, usually defined as one that has shown movement within the last 11,000 years and can be expected to move again within the next 100 years; (2) Potentially Active Fault: A fault that moved within the Quaternary Period (i.e., within the last 2 million years) or a fault which, because it is judged to be capable of ground rupture or shaking, poses an unacceptable risk for a proposed project or structure; (3) Historically Active Fault: A fault active within the last 200 years; (4) Inactive Fault: A fault which has shown no evidence of movement in recent geologic time and no potential for movement in the relatively near future.