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In
geology Geology () is a branch of natural science concerned with Earth and other Astronomical object, astronomical objects, the features or rock (geology), rocks of which it is composed, and the processes by which they change over time. Modern geology ...
, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large list of largest lakes and seas in the Solar System, volumes of water can be found throughout the Solar System, only water distributi ...
's crust result from the action of
plate tectonic Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...
forces, with the largest forming the boundaries between the plates, such as the megathrust faults of
subduction zones Subduction is a geological process in which the oceanic lithosphere is Geochemical cycle, recycled into the Earth's mantle at convergent boundary, convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less d ...
or
transform fault A transform fault or transform boundary, is a fault (geology), fault along a plate boundary where the motion (physics), motion is predominantly Horizontal plane, horizontal. It ends abruptly where it connects to another plate boundary, either an ...
s. Energy release associated with rapid movement on
active fault An active fault is a fault (geology), fault that is likely to become the source of another earthquake sometime in the future. Geologists commonly consider faults to be active if there has been movement observed or evidence of seismic activity duri ...
s is the cause of most
earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth Earth is the third planet from the Sun and the only astronomical object ...
s. Faults may also displace slowly, by aseismic creep. A ''fault plane'' is the
plane Plane(s) most often refers to: * Aero- or airplane An airplane or aeroplane (informally plane) is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, Propeller (aircraft), propeller, or rocket engine. Airplanes co ...
that represents the fracture surface of a fault. A ''
fault trace A fault trace describes the intersection of a Fault (geology), geological fault with the Earth's surface, which leaves a visible disturbance on the surface, usually looking like a crack in the surface with jagged rock structures protruding outwar ...
'' or ''fault line'' is a place where the fault can be seen or mapped on the surface. A fault trace is also the line commonly plotted on
geologic map A geologic map or geological map is a special-purpose map made to show various geological features. Rock (geology), Rock units or stratum, geologic strata are shown by color or symbols. Bed (geology), Bedding planes and structural features such ...
s to represent a fault. A ''fault zone'' is a cluster of parallel faults. However, the term is also used for the zone of crushed rock along a single fault. Prolonged motion along closely spaced faults can blur the distinction, as the rock between the faults is converted to fault-bound lenses of rock and then progressively crushed.


Mechanisms of faulting

Owing to
friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding (motion), sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative la ...
and the rigidity of the constituent rocks, the two sides of a fault cannot always glide or flow past each other easily, and so occasionally all movement stops. The regions of higher friction along a fault plane, where it becomes locked, are called '' asperities''. Stress builds up when a fault is locked, and when it reaches a level that exceeds the strength threshold, the fault ruptures and the accumulated
strain energy In physics, the elastic potential energy gained by a wire during elongation with a tensile (stretching) force is called strain energy. For Linear elasticity, linearly elastic materials, strain energy is: : U = \frac 1 2 V \sigma \epsilon = \frac ...
is released in part as
seismic wave A seismic wave is a wave of Sound, acoustic energy that travels through the Earth. It can result from an earthquake, types of volcanic eruptions, volcanic eruption, magma movement, a large landslide, and a large man-made explosion that produ ...
s, forming an
earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth Earth is the third planet from the Sun and the only astronomical object ...
. Strain occurs accumulatively or instantaneously, depending on the
liquid state A liquid is a nearly Compressibility, incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of State of matter#Four fundamental states, the four fund ...
of the rock; the
ductile Ductility is a List of materials properties, mechanical property commonly described as a material's amenability to Drawing (manufacturing), drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a materia ...
lower crust and mantle accumulate deformation gradually via
shearing Sheep shearing is the process by which the woollen fleece of a sheep is cut off. The person who removes the sheep's wool is called a '' shearer''. Typically each adult sheep is shorn once each year (a sheep may be said to have been "shorn" o ...
, whereas the brittle upper crust reacts by fracture – instantaneous stress release – resulting in motion along the fault. A fault in ductile rocks can also release instantaneously when the strain rate is too great.


Slip, heave, throw

''Slip'' is defined as the relative movement of geological features present on either side of a fault plane. A fault's ''sense of slip'' is defined as the relative motion of the rock on each side of the fault concerning the other side. In measuring the horizontal or vertical separation, the ''throw'' of the fault is the vertical component of the separation and the ''heave'' of the fault is the horizontal component, as in "Throw up and heave out". The vector of slip can be qualitatively assessed by studying any drag folding of strata, which may be visible on either side of the fault. Drag folding is a zone of folding close to a fault that likely arises from frictional resistance to movement on the fault. The direction and magnitude of heave and throw can be measured only by finding common intersection points on either side of the fault (called a
piercing point In geology, a piercing point is defined as a feature (usually a geologic feature, preferably a linear feature) that is cut by a fault (geology), fault, then moved apart. Reconfiguring the piercing point back in its original position is the primar ...
). In practice, it is usually only possible to find the slip direction of faults, and an approximation of the heave and throw vector.


Hanging wall and footwall

The two sides of a non-vertical fault are known as the ''hanging wall'' and ''footwall''. The hanging wall occurs above the fault plane and the footwall occurs below it. This terminology comes from mining: when working a tabular
ore Ore is natural Rock (geology), rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Ret ...
body, the miner stood with the footwall under his feet and with the hanging wall above him. These terms are important for distinguishing different dip-slip fault types: reverse faults and normal faults. In a reverse fault, the hanging wall displaces upward, while in a normal fault the hanging wall displaces downward. Distinguishing between these two fault types is important for determining the stress regime of the fault movement.


Fault types

Faults are mainly classified in terms of the angle that the fault plane makes with the earth's surface, known as the dip, and the direction of slip along the fault plane. Based on the 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; or * ''oblique-slip'', combining strike-slip and dip-slip.


Strike-slip faults

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 and those with right-lateral motion 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 A transform fault or transform boundary, is a fault (geology), fault along a plate boundary where the motion (physics), motion is predominantly Horizontal plane, horizontal. It ends abruptly where it connects to another plate boundary, either an ...
'' when it forms a plate boundary. This class is related to an offset in a
spreading center A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a Diverge ...
, such as a
mid-ocean ridge A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a Diverge ...
, or, less common, within continental
lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust (geology), crust and the portion of the upper mantle (geology), mantle that behaves elastically on time sca ...
, such as the
Dead Sea Transform The Dead Sea Transform (DST) fault system, also sometimes referred to as the Dead Sea Rift, is a series of faults that run from the Maras Triple Junction (a junction with the East Anatolian Fault in southeastern Turkey) to the northern end of the ...
in the
Middle East The Middle East ( ar, الشرق الأوسط, ISO 233: ) is a geopolitical region commonly encompassing Arabian Peninsula, Arabia (including the Arabian Peninsula and Bahrain), Anatolia, Asia Minor (Asian part of Turkey except Hatay Pro ...
or the
Alpine Fault The Alpine Fault is a geological fault that runs almost the entire length of New Zealand's South Island The South Island, also officially named , is the larger of the two major islands of New Zealand in surface area, the other being the smal ...
in New Zealand. Transform faults are also referred to as "conservative" plate boundaries since the lithosphere is neither created nor destroyed.


Dip-slip faults

Dip-slip faults can be either ''normal'' (" extensional") or ''reverse''. In a normal fault, the hanging wall moves downward, relative to the footwall. A downthrown block between two normal faults dipping towards each other is a
graben In geology, a graben () is a depression (geology), depressed block of the Crust (geology), crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German language, German, meaning 'ditch' or 't ...
. An upthrown block between two normal faults dipping away from each other is a horst. The dip of most normal faults is at least 60 degrees but some normal faults dip at less than 45 degrees. Low-angle normal faults with regional
tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of orogeny, mountain building, the growth and behavior of the strong, old cores of con ...
significance may be designated
detachment fault A detachment fault is a gently Strike and dip, dipping normal fault associated with large-scale extensional tectonics. Detachment Fault (geology), faults often have very large displacements (tens of km) and juxtapose unmetamorphosed hanging walls ...
s. A reverse fault is the opposite of a normal fault—the hanging wall moves up relative to the footwall. Reverse faults indicate compressive shortening of the crust. The terminology of "normal" and "reverse" comes from
coal mining Coal mining is the process of resource extraction, extracting coal from the ground. Coal is valued for its Energy value of coal, energy content and since the 1880s has been widely used to generate electricity. Steel and cement industries use c ...
in England, where normal faults are the most common. A ''
thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If ...
'' has the same sense of motion as a reverse fault, but with the dip of the fault plane at less than 45°. Thrust faults typically form ramps, flats and fault-bend (hanging wall and footwall) folds. Flat segments of thrust fault planes are known as ''flats'', and inclined sections of the thrust are known as ''ramps''. Typically, thrust faults move ''within'' formations by forming flats and climb up sections with ramps. Fault-bend folds are formed by the movement of the hanging wall over a non-planar fault surface and are found associated with both extensional and thrust faults. 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. Thrust faults form
nappe In geology, a nappe or thrust sheet is a large sheetlike body of rock (geology), rock that has been moved more than or above a thrust fault from its original position. Nappes form in compressional tectonic settings like continental collision z ...
s and klippen in the large thrust belts. Subduction zones are a special class of thrusts that form the largest faults on Earth and give rise to the largest earthquakes.


Oblique-slip faults

A fault which has a component of dip-slip and a component of strike-slip is termed an oblique-slip fault. Nearly all faults have some component of both dip-slip and strike-slip; hence, defining a fault as oblique requires both dip and strike components to be measurable and significant. Some oblique faults occur within transtensional and transpressional regimes, and others occur where the direction of extension or shortening changes during the deformation but the earlier formed faults remain active. The ''hade'' angle is defined as the
complement A complement is something that completes something else. Complement may refer specifically to: The arts * Complement (music), an interval that, when added to another, spans an octave ** Complement (music)#Aggregate complementation, Aggregate c ...
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 faults are similar to normal faults but the fault plane curves, the dip being steeper near the surface, then shallower with increased depth. The dip may flatten into a sub-horizontal décollement, resulting in a horizontal slip on a horizontal plane. The illustration shows slumping of the hanging wall along a listric fault. Where the hanging wall is absent (such as on a cliff) the footwall may slump in a manner that creates multiple listric faults.


Ring fault

Ring faults, also known as caldera faults, are faults that occur within collapsed volcanic
caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...
s and the sites of
bolide A bolide is normally taken to mean an exceptionally bright meteor, but the term is subject to more than one definition, according to context. It may refer to any large Impact crater, crater-forming body, or to one that explodes in the atmosphere ...
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 dike A ring dike or ring dyke is an Intrusive rock, intrusive igneous body that is circular, oval or arcuate in plan and has steep contacts. While the widths of ring dikes differ, they can be up to several thousand meters. The most commonly accepted met ...
s.


Synthetic and antithetic faults

''Synthetic'' and ''antithetic'' are terms used to describe minor faults associated with a major fault. Synthetic faults dip in the same direction as the major fault while the antithetic faults dip in the opposite direction. These faults may be accompanied by rollover anticlines (e.g. the
Niger Delta The Niger Delta is the River delta, delta of the Niger River sitting directly on the Gulf of Guinea on the Atlantic Ocean in Nigeria. It is located within nine coastal southern Nigerian states, which include: all six states from the South South ...
Structural Style).


Fault rock

All faults have a measurable thickness, made up of deformed rock characteristic of the level in the crust where the faulting happened, of the rock types affected by the fault and of the presence and nature of any mineralising fluids. Fault rocks are classified by their textures and the implied mechanism of deformation. A fault that passes through different levels of the
lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust (geology), crust and the portion of the upper mantle (geology), mantle that behaves elastically on time sca ...
will have many different types of fault rock developed along its surface. Continued dip-slip displacement tends to juxtapose fault rocks characteristic of different crustal levels, with varying degrees of overprinting. This effect is particularly clear in the case of
detachment fault A detachment fault is a gently Strike and dip, dipping normal fault associated with large-scale extensional tectonics. Detachment Fault (geology), faults often have very large displacements (tens of km) and juxtapose unmetamorphosed hanging walls ...
s and major
thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If ...
s. The main types of fault rock include: * Cataclasite – a fault rock which is cohesive with a poorly developed or absent planar
fabric Textile is an Hyponymy and hypernymy, umbrella term that includes various Fiber, fiber-based materials, including fibers, yarns, Staple (textiles)#Filament fiber, filaments, Thread (yarn), threads, different #Fabric, fabric types, etc. At f ...
, or which is incohesive, characterised by generally angular
clasts Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks ...
and rock fragments in a finer-grained matrix of similar composition. ** Tectonic or fault breccia – a medium- to coarse-grained cataclasite containing >30% visible fragments. ** Fault gouge – an incohesive,
clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4). Clays develop plasticity (physics), plasticity when wet, du ...
-rich fine- to ultrafine-grained cataclasite, which may possess a planar fabric and containing <30% visible fragments. Rock clasts may be present *** Clay smear - clay-rich fault gouge formed in
sedimentary Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentati ...
sequences containing clay-rich layers which are strongly deformed and sheared into the fault gouge. *
Mylonite Mylonite is a fine-grained, compact metamorphic rock produced by dynamic recrystallisation, dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. Mylonites can have many different mineralogy, ...
– a fault rock which is cohesive and characterized by a well-developed planar fabric resulting from tectonic reduction of grain size, and commonly containing rounded porphyroclasts and rock fragments of similar composition to
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
s in the matrix * Pseudotachylyte – ultrafine-grained glassy-looking material, usually black and
flint Flint, occasionally flintstone, is a sedimentary rock, sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Flint was widely used historically to make stone tool ...
y in appearance, occurring as thin planar
veins Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary vein, pulmonary and umbilical veins, both of which ca ...
, injection veins or as a matrix to pseudoconglomerates or
breccia Breccia () is a rock composed of large angular broken fragments of mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a speci ...
s, which infills dilation fractures in the host rock. Pseudotachylyte likely only forms as the result of seismic slip rates and can act as a fault rate indicator on inactive faults.


Impacts on structures and people

In
geotechnical engineering Geotechnical engineering is the branch of civil engineering concerned with the engineering behavior of earth materials. It uses the principles of soil mechanics and rock mechanics for the solution of its respective engineering problems. It als ...
, a fault often forms a discontinuity that may have a large influence on the mechanical behavior (strength, deformation, etc.) of
soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organism In biology, an organism () is any life, living system that functions as an individual entity. All organi ...
and rock masses in, for example,
tunnel A tunnel is an underground passageway, dug through surrounding soil, earth or rock, and enclosed except for the entrance and exit, commonly at each end. A Pipeline transport, pipeline is not a tunnel, though some recent tunnels have used ...
,
foundation Foundation may refer to: * Foundation (nonprofit), a type of charitable organization ** Foundation (United States law), a type of charitable organization in the U.S. ** Private foundation, a charitable organization that, while serving a good cause ...
, or
slope In mathematics, the slope or gradient of a line Line most often refers to: * Line (geometry) In geometry, a line is an infinitely long object with no width, depth, or curvature. Thus, lines are One-dimensional space, one-dimensional object ...
construction. The level of a fault's activity can be critical for (1) locating buildings, tanks, and pipelines and (2) assessing the
seismic Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "Earthquake, earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of Linear elasticity#Elastic wave, elast ...
shaking and
tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a tsunamis in lakes, large lake. Earthquakes, volcanic eruptions and othe ...
hazard to infrastructure and people in the vicinity. In California, for example, new building construction has been prohibited directly on or near faults that have moved within the
Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present Before Present (BP) years, or "years before present", is a geologic time scale, time scale used mainly in archaeology, geology and othe ...
Epoch (the last 11,700 years) of the Earth's geological history. Also, faults that have shown movement during the Holocene plus
Pleistocene The Pleistocene ( , often referred to as the '' Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed ...
Epochs (the last 2.6 million years) may receive consideration, especially for critical structures such as power plants, dams, hospitals, and schools. Geologists assess a fault's age by studying
soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organism In biology, an organism () is any life, living system that functions as an individual entity. All organi ...
features seen in shallow excavations and
geomorphology Geomorphology (from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following ...
seen in aerial photographs. Subsurface clues include shears and their relationships to
carbonate A carbonate is a salt (chemistry), salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containin ...
nodules,
eroded Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust, and then sediment transport, tra ...
clay, and
iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundance ...
oxide An oxide () is a chemical compound that contains at least one oxygen atom and one other chemical element, element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of ...
mineralization, in the case of older soil, and lack of such signs in the case of younger soil.
Radiocarbon dating Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon. The method was ...
of organic material buried next to or over a fault shear is often critical in distinguishing active from inactive faults. From such relationships, paleoseismologists can estimate the sizes of past
earthquakes An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...
over the past several hundred years, and develop rough projections of future fault activity.


Faults and ore deposits

Many ore deposits lie on or are associated with faults. This is because the fractured rock associated with fault zones allow for magma ascent or the circulation of mineral-bearing fluids. Intersections of near-vertical faults are often locations of significant ore deposits. An example of a fault hosting valuable
porphyry copper deposit Porphyry copper deposits are copper Copper is a chemical element with the Symbol (chemistry), symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductility, ductile metal with very high thermal conductivity, th ...
s is northern Chile's Domeyko Fault with deposits at
Chuquicamata Chuquicamata ( ; referred to as Chuqui for short) is the largest open pit Open-pit mining, also known as open-cast or open-cut mining and in larger contexts mega-mining, is a surface mining Surface mining, including strip mining, open-pi ...
, Collahuasi, El Abra,
El Salvador El Salvador (; , meaning "The Saviour"), officially the Republic of El Salvador ( es, República de El Salvador), is a country in Central America. It is bordered on the northeast by Honduras Honduras, officially the Republic of Honduras ...
, La Escondida and Potrerillos. Further south in Chile Los Bronces and El Teniente porphyry copper deposit lie each at the intersection of two fault systems. Faults may not always act as conduits to surface. It has been proposed that deep-seated "misoriented" faults may instead be zones where magmas forming porphyry copper stagnate achieving the right time for—and type of—
igneous differentiation In geology, igneous differentiation, or magmatic differentiation, is an umbrella term for the various processes by which magmas undergo bulk chemical change during the partial melting process, cooling, Intrusive rock, emplacement, or volcanic eru ...
. At a given time differentiated magmas would burst violently out of the fault-traps and head to shallower places in the crust where porphyry copper deposits would be formed.


See also

* Anderson's Theory of Faulting * Aseismic creep * * * * * * Paleostress inversion * * * Vertical displacement – Vertical movement of Earth's crust


References


Other reading

* * * * *


External links


Fault Motion Animations
at IRIS Consortium
Aerial view of the San Andreas fault in the Carrizo Plain, Central California, from "How Earthquakes Happen"
at
USGS The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States The United Stat ...

LANDSAT image of the San Andreas Fault in southern California, from "What is a Fault?"
at
USGS The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States The United Stat ...
{{DEFAULTSORT:Fault (Geology) Structural geology Stratigraphy Faults (geology) Tectonic landforms Earth's crust