Fault Fault A fracture or a zone of fractures along which there has been displacement of the sides relative to one another parallel to the fracture. Length and displacement of faults vary between a couple of centimeters to several meters.           Faults'elements   Strike: Strike and dip of faults have been measured, like strike and dip of layers. Therefore, the strike describes the orientation of a fault plane in terms of compass directions. Dip: the dip describes how steeply a fault plane dips into the ground. Dip varies between 0 for a horizontal fault and 90 for a vertical one. The variations of dip are in relation to inhomogenity of rock and their types. Flexibility of rocks will decrease the dip. The side overhanging the fault plane is called the hanging wall and the side underlying the fault plane is called the footwall. Different types of faults   Based on relative displacement and its type along with faults originating from their formation, different types of faults are available. *Reverse faults *Strike-slip faults *Normal faults Strike-slip faults When the net slip is entirely horizontal (with no vertical component), the fault is known as a strike-slip fault because the net displacement is parallel to the strike. Such faults are associated with crustal shearing. Based on the location of observer, these faults can be dextral (right-lateral) or sinistral (left-lateral). A fault on which the displacement is right-lateral separation is called dextral, and when displacement is left-lateral, it is called sinistral.       Reverse faults When the hanging wall has moved upward relative to the footwall the fault is called a reverse fault. This fault's dip is more than 45. Reverse fault is observed in form of a thrust or an overthrust. Thrust faults: A Reverse fault having a dip between 10 and 45 is called thrust fault. In this fault, footwall may move upwards, but hanging wall may remain static or vice versa. Thrust fault, Pennsylvanian Crab Orchard Mountain Group, near Ozone, Tennessee, Route 40/75 eastbound. Overthrust faults: It is a kind of reverse fault having a dip of less than 10. It has a lot of slides.   Normal faults When the hanging wall has moved downward relative to the footwall, the fault is known as a normal fault. The dip of normal faults varies between 40 to 70. Normal faults may have fault planes parallel to layers' dip, but sometimes fault dip is opposite to layers' dip. In normal faults, sometimes horst and graben phenomenon may occur. Graben: Graben An elongate, relatively depressed crustal unit or block that is bounded by faults on its long sides is called graben.   Horst: An elongate,relatively uplifted crustal unit or block that is bounded by faults on its long sides is called horst.