3.9.5 Fault Zone (Forkastningssone)
3.9.5.1 A fault zone is a structural unit consisting of many closely spaced faults. Neighbouring areas are distinguished from the zone by having a considerably lower frequency of faults. In many cases, individual faults in the fault zone will have been formed in close association with each other, but this is not a prerequisite (Fig. 17).
3.9.5.2 Fault zone ranks next above fault.
3.9.5.3 The outcrop of a fault zone will normally be confined to a long, narrow geographical area. The breadth of a fault zone is defined by the outermost faults in the zone. No other limitations are placed on its dimensions.
3.9.5.4 The structure is mappable with the help of geomorphological, geological and/or geophysical methods. The expression of a fault zone on a map will depend upon the scale of the map.
3.9.5.5 Individual faults in a fault zone may be characterized by having identical or different structural character (see Section 3.9.4.5).
3.9.5.6 A fault zone is given a formal or an informal name in accordance with the "general rules for naming and defining geological units" (Chap. 2) and the provisions of Section 3.9.1. The proper name (Section 2.2.2) is placed between the words "the ... Fault Zone" (formal) in the compound name.
3.9.5.7 A fault zone may be a fault set in which the individual faults are closely spaced. Fault zones may also define fault systems and fault complexes. Individual faults in fault zones are often en echelon oriented.
3.9.5.8 Example: The Møre--Trøndelag Fault Zone (Møre--Trøndelagsforkastningssonen) (Gabrielsen et al. 1984).
3.9.5.9 Key reference: Bates & Jackson (1980).
