Fault Plane

A fault plane is the surface of a fault between two rock blocks. A fault plane can have a quasi-planar or curved surface, and some have a listric surface or are part of a listric fault system. When a fault passes through different lithological strata, it can often be ‘refracted’ or join with a bedding fault to form a ‘step fault’. A fault plane can be a continuous or intermittent surface, and it can be a surface or a zone. A fault plane (or fault zone) can be brittle or ductile. A brittle fracture is characterised by a continuous fault surface, numerous scratches, and the formation of cataclastic tectonite. Ductile fractures are characterised by discontinuous fault planes, with both sides of the fault plane having a ‘pulled wire’ or ‘fitful’ appearance, and the formation of mylonitic tectonite. As a result of the abrasion of the blocks, the fault surface always has a mirror-like surface with many fault scratches as well as a thin layer of ‘dynamic encrustation’.