normalfault

A normal fault is a type of geologic fault where the hanging wall has moved downward relative to the footwall. This occurs in response to extensional forces, meaning the crust is being pulled apart. Imagine a block of rock being tilted. The upper block, which would overhang a miner if they were inside the fault, is called the hanging wall, and the lower block is the footwall. In a normal fault, the hanging wall moves down.

Normal faults are typically found in areas where tectonic plates are diverging, such as at mid-ocean ridges or in continental rift zones. The Great Rift Valley in East Africa is a prominent example of a region characterized by extensive normal faulting. The Basin and Range Province in the western United States also exhibits widespread normal fault systems, which have created the characteristic parallel mountain ranges and valleys of the region.

The movement along normal faults can vary greatly, from millimeters to several meters in a single event. Earthquakes are often associated with normal fault activity, as the sudden slip along the fault plane releases stored elastic energy. Understanding normal faults is crucial for seismic hazard assessment and for comprehending the processes that shape Earth's surface. The dip angle of a normal fault is typically greater than 45 degrees.