Fault: The fractures along which there has been relative movement of the blocks past each other. The entire process of development of fractures and displacement of the blocks against each other is termed as faulting.
Following factors are more considered important in classification of faults:
i) The apparent movement of the disrupted blocks along the fault plane.
ii) The direction of slip.
iii) The relation of fault attitude with the attitude of the attitude of the displaced beds.
iv) The amount of dip of the fault.
v) Mode of occurrence.
The apparent movement of the disrupted blocks along the fault plane in two types
i) Normal faults: Such a fault in which hanging wall has apparently moved down with respect to foot wall classified as a normal fault.
Normal faults are also often termed as gravity faults especially when it is established that the hanging wall has actually moved down with respect to the foot wall.
ii) Reversed faults: It is a type of fault in which the hanging wall appears to have moved up with respect to the foot wall. In reversed faults the fault plane is generally inclined between horizontal and 450 although reversed faults with steeply inclined fault surface have been also encountered by virtue of their inclination and direction of movement reverse faulting involves shortening of the earth.
iii) Strike- slip faults: This is the third major category of faults known to occur in nature and on a very large scale these may be defined as faults in which faulted blocks have been moved against each other in an essentially horizontal direction.
iv) Hinge faults: These are also called pivotal faults or rotational faults a hinge fault is characterized by a movement of the disrupted blocks along a medical poit called the hinge point.