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Asperity (faults)
An asperity is an area on an active fault where there is increased friction, such that the fault may become locked, rather than continuously slipping as in aseismic creep. Earthquake rupture generally begins with the failure of an asperity, allowing the fault to move. See also * Asperity (materials science) * Asperity (geotechnical engineering) * Earthquake * Fault friction * Fault mechanics Fault mechanics is a field of study that investigates the behavior of geologic faults. Behind every good earthquake is some weak rock. Whether the rock remains weak becomes an important point in determining the potential for bigger earthquakes. ... References External links IRIS page on fault asperities with simple cartoon video of an asperity on an active faultIRIS page on "Modeling Asperities on a Strike-Slip Fault with Spaghetti" {{geology-stub Seismology ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Fault
An active fault is a 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 during the last 10,000 years. * Active faulting is considered to be a geologic hazard - one related to earthquakes as a cause. Effects of movement on an active fault include strong ground motion, surface faulting, tectonic deformation, landslides and rockfalls, liquefaction, tsunamis, and seiches. Quaternary faults are those active faults that have been recognized at the surface and which have evidence of movement during the Quaternary Period. Related geological disciplines for ''active-fault'' studies include geomorphology, seismology, reflection seismology, plate tectonics, geodetics and remote sensing, risk analysis, and others. Location Active faults tend to occur in the vicinity of tectonic plate boundaries, and active fault research has foc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fault (geology)
In 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's crust result from the action of plate tectonic forces, with the largest forming the boundaries between the plates, such as the megathrust faults of subduction zones or transform faults. Energy release associated with rapid movement on active faults is the cause of most earthquakes. Faults may also displace slowly, by aseismic creep. A ''fault plane'' is the plane that represents the fracture surface of a fault. A '' fault trace'' 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 maps 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aseismic Creep
In geology, aseismic creep or fault creep is measurable surface displacement along a fault in the absence of notable earthquakes. Aseismic creep may also occur as "after-slip" days to years after an earthquake. Notable examples of aseismic slip include faults in California (e.g. Calaveras Fault, Hayward Fault, and San Andreas Fault). Causes Aseismic creep accommodates far-field motions on localized zones of deformation at tectonic plate boundaries. The underlying causes of aseismic creep are primarily attributed to poor frictional strength of the fault, low normal stress acting on the fault in the shallow crust, and excessive pore-fluid pressures, which limit the viable amount of normal stress on a fault. The frictional reaction of geologic materials can explain the transition from seismic to aseismic deformation with depth. Friction along faults can cause sudden slips with associated stress drops (earthquakes), along with phases of no motion as stress recharges. Measure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquake Rupture
In seismology, an earthquake rupture is the extent of slip that occurs during an earthquake in the Earth's crust. Earthquakes occur for many reasons that include: landslides, movement of magma in a volcano, the formation of a new fault, or, most commonly of all, a slip on an existing fault. Nucleation A tectonic earthquake begins by an initial rupture at a point on the fault surface, a process known as nucleation. The scale of the nucleation zone is uncertain, with some evidence, such as the rupture dimensions of the smallest earthquakes, suggesting that it is smaller than 100 m while other evidence, such as a slow component revealed by low-frequency spectra of some earthquakes, suggest that it is larger. The possibility that the nucleation involves some sort of preparation process is supported by the observation that about 40% of earthquakes are preceded by foreshocks. However, some large earthquakes, such as the M8.6 1950 India - China earthquake., have no foreshocks and it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asperity (materials Science)
In materials science, asperity, defined as "unevenness of surface, roughness, ruggedness" (from the Latin ''asper''—"rough"), has implications (for example) in physics and seismology. Smooth surfaces, even those polished to a mirror finish, are not truly smooth on a microscopic scale. They are rough, with sharp, rough or rugged projections, termed "asperities". Surface asperities exist across multiple scales, often in a self affine or fractal geometry. The fractal dimension of these structures has been correlated with the contact mechanics exhibited at an interface in terms of friction and contact stiffness. When two macroscopically smooth surfaces come into contact, initially they only touch at a few of these asperity points. These cover only a very small portion of the surface area. Friction and wear originate at these points, and thus understanding their behavior becomes important when studying materials in contact. When the surfaces are subjected to a compressive load, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asperity (geotechnical Engineering)
In geotechnical engineering and contact mechanics the term asperity is used to refer to individual features of unevenness (''roughness'') of the surface of a discontinuity, grain, or particle with heights in the range from approximately 0.1 mm to the order of metres. Below the asperity level, surface interactions are normally considered to be a ''material'' property, arising from mechanisms of adhesion and repulsion at the atomic scale (often accounted for by ''material friction'', ''atomic friction'' or ''molecular friction''). Dilation An often used definition for ''asperities'' in geotechnical engineering: Unevenness of a surface are ''asperities'' if these cause dilation if two blocks with in between a discontinuity with matching ''asperities'' on the two opposing surfaces (i.e. a ''fitting discontinuity'') move relative to each other, under low stress levels that do not cause breaking of the ''asperities''. Contrast with asperity in materials science Materials science ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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's lithosphere that creates seismic waves. Earthquakes can range in intensity, from those that are so weak that they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time period. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume. The word ''tremor'' is also used for non-earthquake seismic rumbling. At the Earth's surface, earthquakes manifest themselves by shaking and displacing or disrupting the ground. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fault Friction
Fault friction describes the relation of friction to fault mechanics. Rock failure and associated earthquakes are very much a fractal operation (see Characteristic earthquake). The process remains scale-invariant down to the smallest crystal. Thus, the behaviour of massive earthquakes is dependent on the properties of single molecular irregularities or asperities. If two clean nano-asperities are brought together in a vacuum, a cold weld will result. That is, the crystal tips will fuse as if one ( cohesion). In nature these tips are actually covered with a thin film of foreign material. By far, the most important component of this film, is water. If this water is removed, by extreme drying, the rock minerals do not behave at all as expected: they exhibit no ''fault healing'' or dynamic friction. The entire behaviour of earthquakes depends on very thin films. After a major earthquake, there starts a process known as ''fault healing''. This is a well-demonstrated phenomen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fault Mechanics
Fault mechanics is a field of study that investigates the behavior of geologic faults. Behind every good earthquake is some weak rock. Whether the rock remains weak becomes an important point in determining the potential for bigger earthquakes. On a small scale, fractured rock behaves essentially the same throughout the world, in that the angle of friction is more or less uniform (see Fault friction). A small element of rock in a larger mass responds to stress changes in a well defined manner: if it is squeezed by differential stresses greater than its strength, it is capable of large deformations. A band of weak, fractured rock in a competent mass can deform to resemble a classic geologic fault. Using seismometers and earthquake location, the requisite pattern of micro-earthquakes can be observed. For earthquakes, it all starts with an embedded penny-shaped crack as first envisioned by Brune. As illustrated, an earthquake zone may start as a single crack, growing to f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
