User:Rockjockey222/New Sandbox

NEW HEADINGS
Main Fault header 'Fault (Geology)'

Fault architecture

Fault Types

Fault Rocks

Fault Mechanisms

Active Faults and Seismic Hazard

Economic Implications Oil traps (structural trap page,    Fluid transport and mineralization Brindlestick (talk) 15:47, 30 October 2019 (UTC)

Fault (Geology)
In geology, a fault can be thought of as a  planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movement. Large faults within the Earth's crust result from the motion of tectonic plates. The largest faults form at the boundaries between the plates, such as subduction zones or transform faults. The release of energy associated with rapid movement on active faults is the cause of earthquakes and most tsunamis.

The term fault refers to the discontinuities in the shallow part of the earth's crust that behave in a brittle manner. At lower depths of the crust, the physical characteristics of rocks change with increased pressure and temperature and deformation events occur differently. Deeper crustal deformation is described by shear zones and the transition is distinguished by the brittle-ductile transition zone.

Fault Architecture
A fault plane is the plane that represents the fracture surface that accommodated movement during the formation fault, also known as a deformation event. A fault trace or fault line is the two dimensional expression of a fault on the surface of the earth. A fault trace is also the line commonly plotted on geologic maps to represent a fault.

Because 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 tabular volume of rock affected by movement. A fault zone is made up of a fault core which

The two sides of a non-vertical fault are known as the hanging wall and footwall. The hanging wall describes the volume of rock above the fault plane and the footwall occurs below it. This terminology comes from historic mining: when working a tabular ore body, the miner stood with the footwall under their feet and would hang their lantern on the hanging wall.

Fault types
Based on direction of slip, faults can be categorized as:


 * strike-slip, where the offset is predominantly horizontal, parallel to the fault trace.
 * dip-slip, offset is predominantly vertical and/or perpendicular to the fault trace.
 * oblique-slip, combining strike and dip slip.

Strike-slip faults
Satellite image of the Piqiang Fault, a northwest trending left-lateral strike-slip fault in the Taklamakan Desert south of the Tien Shan Mountains, China (40.3°N, 77.7°E)

Schematic illustration of the two strike-slip fault types.

In a strike-slip fault (also known as a wrench fault, tear fault, or transcurrent fault), the fault surface (plane) is usually near vertical and the footwall moves laterally either left or right with very little vertical motion. Strike-slip faults with left-lateral motion are also known as sinistral faults, while those with right-lateral motion are known as dextral faults. Each is defined by the direction of movement of the ground as would be seen by an observer on the opposite side of the fault.

A special class of strike-slip fault is the transform fault, and can be found at plate boundaries. These faults are created from the offsets caused by spreading center s known as a mid-ocean ridge s, but can also be found within the continental lithosphere, such as the Dead Sea Transform in the Middle East or the Alpine Fault in New Zealand. Transform faults are also referred to as "conservative" plate boundaries, because lithosphere is neither created nor destroyed.**Reference

Dip-slip faults
Normal faults in Spain, between which rock layers have slipped downwards (at photo's centre)

Dip-slip faults can be either normal ("extensional ") or reverse (“compressiona l”).

The terminology of "normal" and "reverse" comes from coal-mining in England, where normal faults are the most common. In a normal fault, the hanging wall moves downward relative to the footwall**REFERENCE FIG. Normal faults typically occur in extensional environments, where the landmass on either side of a fault pulls apart. The dip of a normal fault is typically 60° in its preferred state, but this can vary**REF THIS. A reverse fault is the opposite of a normal fault, where the hanging wall moves upwards relative to the footwall. Reverse faults indicate compressive shortening of the crust, where two blocks are pushed towards one another, and typically have dip angles of 45°. A thrust fault has the same sense of motion as a reverse fault, but with the dip of the fault plane at less than 45°. Subduction zones are a special class of thrusts that form the largest faults on Earth and give rise to the largest earthquakes.**LINK THIS TO ANOTHER PAGE

A downthrown block between two normal faults dipping towards each other is a graben. **NEED A FIGUREAn upthrown block between two normal faults dipping away from each other is a horst. Low-angle normal faults with regional tectonic significance may be designated as detachment faults.**NEED FIGURE

Faults may be reactivated at a later time with the movement in the opposite direction to the original movement (fault inversion). A normal fault may therefore become a reverse fault and vice versa.**REFERENCE

Oblique-slip faults
Oblique-slip fault

A fault which has components of dip-slip and strike-slip is considered an oblique-slip fault. Nearly all faults will have some component of both dip-slip and strike-slip, so defining a fault as oblique requires both dip and strike components to be measurable and significant. Oblique faults can occur within transtensional or transpressional regimes, while others form when the direction of extension or shortening changes during deformation with pre-existing faults remaining active.

The hade angle is defined as the complement of the dip angle; it is the angle between the fault plane and a vertical plane that strikes parallel to the fault.

Listric fault
Listric fault (red line)

Listric faults are similar to normal faults but the fault plane curves, with the dip being steeper near the surface, then shallower with increasing depth. The dip may flatten into a nearly horizontal décollement, resulting in horizontal slip. The illustration shows slumping of the hanging wall along a listric fault.

Ring fault
Ring faults, also known as caldera faults, are faults that occur within collapsed volcanic calderas and the sites of bolide strikes, such as the Chesapeake Bay impact crater. Ring faults are the result of a series of overlapping normal faults, forming a circular outline. Fractures created by ring faults may be filled by ring dikes.

Synthetic and antithetic faults
Synthetic and antithetic faults are terms used to describe minor faults associated with a major fault.**NEEDS REFERENCE Synthetic faults dip in the same direction as the major fault while antithetic faults dip in the opposite direction. These faults may be accompanied by rollover anticlines (e.g. the Niger Delta Structural Style). Brindlestick (talk) 01:36, 28 October 2019 (UTC)

Fault Mechanisms
-BRIEFLY set up the fact that different mechanisms exist and then link to deformation mechanisms page

Active Faults and Seismic Hazard
Assessing the threat of potential earthquakes posed by active faults, and trying to mitigate the destruction or losses of life that they can impose, is the main driving force for seismologists in the study of faults.**NEEDS REF Active faults can be found across the world, but are most commonly found along plate boundaries. The size of an earthquake is directly linked to the area of a fault surface and the distance in which it slips during an event. Faults can vary from the microscopic scale to many hundreds of kilometres in length, with the largest event ever recorded occurring in Valdivia Chile in 1960 (REF**Barrientos, Ward 1990). The magnitude of this event was 9.5, and the length of the fault rupture was a staggering 800 km.

Seismic Hazard
Seismic hazard is a measure of the probability of a damaging earthquake occurring in an area over a given time length, typically on the scale of decades. Cities or important structures (such as pipelines, mines, or bridges) in areas with a significant risk of seismicity are often required to be built to a higher standard, in which they can withstand the maximum predicted shaking a region may experience. There is a large discrepancy in earthquake-related casualties based on the building quality and population density of any given country (REF** Holzer, Savage 2013). Earthquakes can also cause far more damage if located close to the surface, as the energy is less dissipated by the time it reaches a population center.

Associated Natural Disasters
Another side effect of large earthquakes is the potential for tsunamis, which can cause destruction rivaling or exceeding that of the earthquake itself. This was seen following the Tohoku earthquake in Japan in 2011 (Ref** Mori, Takashi, et al 2011). The intense shaking from large earthquakes can also trigger landslides. This occurred following the Denali fault rupture in 2002, which caused landslides at distances exceeding hundreds of kilometers from the earthquake source (REF** Jibson, Harp, et al 2004).

Brindlestick (talk) 20:33, 27 October 2019 (UTC) Brindlestick (talk) 01:36, 28 October 2019 (UTC) Brindlestick (talk) 02:20, 28 October 2019 (UTC)

Economic Implications
-briefly describe why oil and gas industry studies fault

-briefly describe how ore deposits favor faulted regions