Earthquake
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This article is about the natural seismic phenomenon. For other uses, see Earthquake (disambiguation).
"Quake" redirects here. For other uses, see Quake (disambiguation).
An earthquake (also known as an earthquake, tremor or temblor) is the result of a sudden release of energy in the earth's crust, creating seismic waves. Earthquakes are recorded with a seismometer, also known as a seismograph. The moment magnitude (or the related and mostly obsolete Richter magnitude) of an earthquake is conventionally reported, with magnitude 3 or lower earthquakes mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale.
Earth's surface, earthquakes occur with agitation, and sometimes moving the ground. When a large earthquake epicenter is located offshore, the seabed sometimes suffers sufficient displacement to cause a tsunami. The shocks of earthquakes can cause landslides and volcanic activity from time to time.
In its most generic sense, the word earthquake is used to describe any seismic events - whether a natural phenomenon or an event caused by humans - that generates seismic waves. The earthquakes are caused mostly by rupture of geological faults, but also by volcanic activity, landslides, explosions of mines, and nuclear testing. Earthquake point of initial rupture is called its focus or Hypocenter. The epicenter term refers to the point at ground level, directly above the Hypocenter.
The global epicenter of the earthquake, 1963-1998
MovementContents global tectonic plate [hide]
1 Naturally occurring earthquakes
1.1 Earthquake fault types
1.2 earthquakes far from plate boundaries
1.3 Shallow-focus earthquakes and deep-focus
1.4 Earthquakes and volcanic activity
1.5 Earthquake clusters
1.5.1 Aftershocks
1.5.2 Earthquake swarms
1.5.3 Earthquake storms
2 Size and frequency of occurrence
3-induced seismicity
4 Measuring and locate earthquakes
5 Effect / effects of earthquakes
5.1 shaking and ground rupture
5.2 Landslides and avalanches
5.3 Fires
5.4 Soil liquefaction
5.5 Tsunami
5.6 Floods
5.7 Tidal forces
5.8 Human impacts
6 Major earthquakes
7 Preparation
8 History
8.1 Pre-Middle Ages
9 Earthquakes in culture
9.1 Mythology and religion
Popular Culture 9.2
10 See also
11 Notes
12 General references
13 External links
13.1 Educational
13.2 Seismological data centers
13.2.1 Europe
13.2.2 Japan
13.2.3 New Zealand
13.2.4 United States
13.3 Seismic scales
13.4 Scientific Information
13.5 Miscellaneous
Course earthquakes
Earthquake Fault typesTectonic occur anywhere in the world where there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane. In the case of processing or convergent type plate boundaries, which form the largest fault surface of the earth, moving past each other smoothly and aseismically only if there are no irregularities or asperities along the boundary that increase the frictional resistance. Most borders have such asperities and this leads to a form of stick-slip behavior. Once the boundary has locked, continued relative motion between the plates leads to increasing stress and, therefore, stored strain energy in the volume around the surface of failure. This continues until the voltage is increased sufficiently to break the asperity, suddenly allowing sliding along the closed part of the fault, releasing the stored energy. This energy is released as a combination of radiated elastic strain seismic waves, frictional heating of the surface of guilt and cracks in the rock, causing earthquakes. This process of gradual accumulation of strain and stress punctuated by some sudden earthquake failure is referred to as the Elastic-rebound theory. It is estimated that only 10 percent or less of total energy of an earthquake is radiated as seismic energy. Most of the energy of the earthquake is used to power the earthquake fracture growth or is converted into heat generated by friction. Therefore, earthquakes lowest available elastic potential energy of the earth and raise its temperature, although these changes are negligible compared to the flow of conductive and convective heat out of the deep interior of the Earth [1].
Earthquake failure modes
Main Fault (geology)
There are three main types of fault that could cause an earthquake: normal, reverse (thrust) and strike-slip. Normal and reverse faulting are examples of dip-slip, where the movement along the fault is in the direction of dip and movement on them leads to a vertical component. Normal faults mainly occur in the regions where the crust is extended as a boundary divergent. Reverse errors occur in areas where the crust has been reduced, as in a convergent boundary. Strike-slip faults are steep structures where the two sides of the fault slip horizontally past each other, transform boundaries are a special type of strike-slip fault. Most earthquakes are caused by movement on faults that are components of both dip-slip and strike-slip, this is known as oblique slip.
Earthquakes away from plate boundaries
Where plate boundaries occur within continental lithosphere, deformation is spread over an area much larger than the plate boundary itself. In the case of the San Andreas fault continental transform, many earthquakes occur away from the plate boundary and are related to strains developed within the larger zone of deformation caused by serious irregularities in the fault trace (eg, the "Big Bend" region ). The Northridge earthquake was associated with the movement on a blind thrust within such a zone. Another example is the border very oblique plate convergence between Arabs and Eurasian plates, where it crosses the north-west of the Zagros Mountains. The deformation associated with this plate boundary is divided into nearly pure sense of thrust movement perpendicular to the boundary over a large area to the southwest and nearly pure strike-slip motion along the Main Recent Fault is close to the actual plate boundary itself. This is demonstrated by earthquake focal mechanisms [2].
All tectonic plates have internal stress fields caused by their interactions with license plates from neighboring countries and sedimentary loading or unloading (eg deglaciation). These stresses may be sufficient to cause failure along existing fault planes, giving rise to interplacca earthquakes [3].
Shallow-focus earthquakes and deep-focus
The majority of tectonic earthquakes have the ring of fire in the depths of up to tens of kilometers. Earthquakes occurring at a depth of less than 70 km are classified as 'shallow-focus earthquakes', while those with focal depths between 70 and 300 km are commonly called 'mid-fire' or 'intermediate-depth' earthquakes. In subduction zones, where large and colder oceanic crust descends beneath another tectonic plate, deep-focus earthquakes may occur at depths much greater (from 300 up to 700 kilometers). [4] These seismically active areas of subduction are known as Wadati - Benioff zone. Deep-focus earthquakes occur at a depth at which the lithosphere subdotta should no longer be brittle, due to high temperature and pressure. A possible mechanism for the generation of deep focus earthquakes is faulting caused by olivine undergoing a phase transition into a spinel structure
From Wikipedia, the free encyclopedia
Jump to: navigation, search
This article is about the natural seismic phenomenon. For other uses, see Earthquake (disambiguation).
"Quake" redirects here. For other uses, see Quake (disambiguation).
An earthquake (also known as an earthquake, tremor or temblor) is the result of a sudden release of energy in the earth's crust, creating seismic waves. Earthquakes are recorded with a seismometer, also known as a seismograph. The moment magnitude (or the related and mostly obsolete Richter magnitude) of an earthquake is conventionally reported, with magnitude 3 or lower earthquakes mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale.
Earth's surface, earthquakes occur with agitation, and sometimes moving the ground. When a large earthquake epicenter is located offshore, the seabed sometimes suffers sufficient displacement to cause a tsunami. The shocks of earthquakes can cause landslides and volcanic activity from time to time.
In its most generic sense, the word earthquake is used to describe any seismic events - whether a natural phenomenon or an event caused by humans - that generates seismic waves. The earthquakes are caused mostly by rupture of geological faults, but also by volcanic activity, landslides, explosions of mines, and nuclear testing. Earthquake point of initial rupture is called its focus or Hypocenter. The epicenter term refers to the point at ground level, directly above the Hypocenter.
The global epicenter of the earthquake, 1963-1998
MovementContents global tectonic plate [hide]
1 Naturally occurring earthquakes
1.1 Earthquake fault types
1.2 earthquakes far from plate boundaries
1.3 Shallow-focus earthquakes and deep-focus
1.4 Earthquakes and volcanic activity
1.5 Earthquake clusters
1.5.1 Aftershocks
1.5.2 Earthquake swarms
1.5.3 Earthquake storms
2 Size and frequency of occurrence
3-induced seismicity
4 Measuring and locate earthquakes
5 Effect / effects of earthquakes
5.1 shaking and ground rupture
5.2 Landslides and avalanches
5.3 Fires
5.4 Soil liquefaction
5.5 Tsunami
5.6 Floods
5.7 Tidal forces
5.8 Human impacts
6 Major earthquakes
7 Preparation
8 History
8.1 Pre-Middle Ages
9 Earthquakes in culture
9.1 Mythology and religion
Popular Culture 9.2
10 See also
11 Notes
12 General references
13 External links
13.1 Educational
13.2 Seismological data centers
13.2.1 Europe
13.2.2 Japan
13.2.3 New Zealand
13.2.4 United States
13.3 Seismic scales
13.4 Scientific Information
13.5 Miscellaneous
Course earthquakes
Earthquake Fault typesTectonic occur anywhere in the world where there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane. In the case of processing or convergent type plate boundaries, which form the largest fault surface of the earth, moving past each other smoothly and aseismically only if there are no irregularities or asperities along the boundary that increase the frictional resistance. Most borders have such asperities and this leads to a form of stick-slip behavior. Once the boundary has locked, continued relative motion between the plates leads to increasing stress and, therefore, stored strain energy in the volume around the surface of failure. This continues until the voltage is increased sufficiently to break the asperity, suddenly allowing sliding along the closed part of the fault, releasing the stored energy. This energy is released as a combination of radiated elastic strain seismic waves, frictional heating of the surface of guilt and cracks in the rock, causing earthquakes. This process of gradual accumulation of strain and stress punctuated by some sudden earthquake failure is referred to as the Elastic-rebound theory. It is estimated that only 10 percent or less of total energy of an earthquake is radiated as seismic energy. Most of the energy of the earthquake is used to power the earthquake fracture growth or is converted into heat generated by friction. Therefore, earthquakes lowest available elastic potential energy of the earth and raise its temperature, although these changes are negligible compared to the flow of conductive and convective heat out of the deep interior of the Earth [1].
Earthquake failure modes
Main Fault (geology)
There are three main types of fault that could cause an earthquake: normal, reverse (thrust) and strike-slip. Normal and reverse faulting are examples of dip-slip, where the movement along the fault is in the direction of dip and movement on them leads to a vertical component. Normal faults mainly occur in the regions where the crust is extended as a boundary divergent. Reverse errors occur in areas where the crust has been reduced, as in a convergent boundary. Strike-slip faults are steep structures where the two sides of the fault slip horizontally past each other, transform boundaries are a special type of strike-slip fault. Most earthquakes are caused by movement on faults that are components of both dip-slip and strike-slip, this is known as oblique slip.
Earthquakes away from plate boundaries
Where plate boundaries occur within continental lithosphere, deformation is spread over an area much larger than the plate boundary itself. In the case of the San Andreas fault continental transform, many earthquakes occur away from the plate boundary and are related to strains developed within the larger zone of deformation caused by serious irregularities in the fault trace (eg, the "Big Bend" region ). The Northridge earthquake was associated with the movement on a blind thrust within such a zone. Another example is the border very oblique plate convergence between Arabs and Eurasian plates, where it crosses the north-west of the Zagros Mountains. The deformation associated with this plate boundary is divided into nearly pure sense of thrust movement perpendicular to the boundary over a large area to the southwest and nearly pure strike-slip motion along the Main Recent Fault is close to the actual plate boundary itself. This is demonstrated by earthquake focal mechanisms [2].
All tectonic plates have internal stress fields caused by their interactions with license plates from neighboring countries and sedimentary loading or unloading (eg deglaciation). These stresses may be sufficient to cause failure along existing fault planes, giving rise to interplacca earthquakes [3].
Shallow-focus earthquakes and deep-focus
The majority of tectonic earthquakes have the ring of fire in the depths of up to tens of kilometers. Earthquakes occurring at a depth of less than 70 km are classified as 'shallow-focus earthquakes', while those with focal depths between 70 and 300 km are commonly called 'mid-fire' or 'intermediate-depth' earthquakes. In subduction zones, where large and colder oceanic crust descends beneath another tectonic plate, deep-focus earthquakes may occur at depths much greater (from 300 up to 700 kilometers). [4] These seismically active areas of subduction are known as Wadati - Benioff zone. Deep-focus earthquakes occur at a depth at which the lithosphere subdotta should no longer be brittle, due to high temperature and pressure. A possible mechanism for the generation of deep focus earthquakes is faulting caused by olivine undergoing a phase transition into a spinel structure
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