Fault (geology)

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  (Redirected from Fault line)

Part of a series on Earthquakes
Types
Foreshock • Aftershock • Blind thrust Doublet • Interplate • Intraplate Megathrust • Remotely triggered • Slow Submarine • Supershear Tsunami • Earthquake swarm
Causes
Fault movement • Volcanism  • Induced seismicity
Measurement
Epicenter • Mercalli scale • Richter scale Moment scale • Surface wave magnitude scale Body wave magnitude scale • Seismometer Earthquake duration magnitude
Prediction
Earthquake sensitive • Coordinating Committee for Earthquake Prediction
Other
Shear wave splitting • Earthquake engineering Flinn-Engdahl regions • Seismite
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"Fault line" redirects here. For other uses, see Fault line (disambiguation).

This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. Please help to improve this article by introducing more precise citations where appropriate. (March 2010)

Large normal fault in Triassic to Lower Jurassic Blue Anchor Formation sediments near Blue Anchor, Somerset, UK, with several smaller normal faults in its hanging wall

Ramon Fault on the southern side ofMakhtesh Ramon, Israel

Hanging wall and footwall

In geology, a fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement. Large faults within the Earth's crust result from the action of tectonic forces. Energy release associated with rapid movement on active faults is the cause of mostearthquakes, such as occurs on the San Andreas Fault,California.

A fault line is the surface trace of a fault, the line of intersection between the fault plane and the Earth's surface.^[1]

Since faults do not usually consist of a single, clean fracture, geologists use the term fault zone when referring to the zone of complex deformation associated with the fault plane.

The two sides of a non-vertical fault are known as the hanging wall andfootwall. By definition, the hanging wall occurs above the fault plane and the footwall all occurs below the fault.^[2] This terminology comes from mining: when working a tabular ore body, the miner stood with the footwall under his feet and with the hanging wall hanging above him.^[3]