Faults, like joints, are the result of overstressing of the rock but are distinct from joints in that they exhibit measurable shear displacement. Faults are predominantly associated with mountain-building episodes and tectonic movements. They can occur as single features or more commonly as fault systems. Faults are often highly important to rock-engineering projects because they are often associated with large zones of weakened rock. They also act as barriers or passageways for fluids, cause general disruption to the geology, and are associated with sudden releases of energy (earthquakes). An example of a disruptive fault (inactive) is illustrated in figure below.
Evidence of a fault:
– Stretch marks
– Mountain mirror (smooth paraclase)
– Fault breccias
Types of faults
Tectonic Graben or trench – relatively lowered central part
Horst – relatively elevated central part