An earthquake is the result from the sudden release of stored energy in the Earth's crust that
creates seismic waves. At the Earth's surface, earthquakes may manifest themselves by a
shaking or displacement of the ground and sometimes cause tsunamis, which may lead to loss of
life and destruction of property. An earthquake is caused by tectonic plates getting stuck and
putting a strain on the ground. The strain becomes so great that rocks give way by fault planes
breaking.
creates seismic waves. At the Earth's surface, earthquakes may manifest themselves by a
shaking or displacement of the ground and sometimes cause tsunamis, which may lead to loss of
life and destruction of property. An earthquake is caused by tectonic plates getting stuck and
putting a strain on the ground. The strain becomes so great that rocks give way by fault planes
breaking.
Naturally occurring earthquakes:
Most naturally occurring earthquakes are related to the tectonic nature of the Earth. Such
earthquakes are called tectonic earthquakes. The Earth's lithosphere is a patchwork of plates in
slow but constant motion caused by the heat in the Earth's mantle and planetary core. The heat
causes the rock under the earth to become liquid magma on geological timescales, on which the
plates are able to move, slowly but surely. Plate boundaries grind past each other, creating
frictional stress. When the frictional stress exceeds a critical value, called local strength, a
sudden failure occurs. The boundary of tectonic plates along which failure occurs is called the
fault plane. When the failure at the fault plane results in a violent displacement of the Earth's
crust, the elastic strain energy is released and seismic waves are radiated, thus causing an
earthquake. This process of strain, stress, and failure is referred to as the Elastic-rebound
theory. It is estimated that only 10 percent or less of an earthquake's total energy is radiated as
seismic energy. Most of the earthquake's energy is used to power the earthquake fracture
growth and is converted into heat. Therefore, earthquakes lower the Earth's available potential
energy, though these losses are negligible.
The majority of tectonic earthquakes originate at depths not exceeding tens of kilometers. In
subduction zones, where older and colder oceanic crust descends beneath another tectonic
plate, earthquakes may occur at much greater depths (up to seven hundred kilometers). These
seismically active areas of subduction are known as Wadati-Benioff zones. Deep focus
earthquakes are another phenomenon associated with a subducting slab. These are
earthquakes that occur at a depth at which the subducted lithosphere should no longer be brittle,
due to the 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.
Earthquakes may also occur in volcanic regions and are caused by the movement of magma in
volcanoes. Such quakes can be an early warning of volcanic eruptions.
A recently proposed theory suggests that some earthquakes may occur in a sort of earthquake
storm, where one earthquake will trigger a series of earthquakes each triggered by the previous
shifts on the fault lines, similar to aftershocks, but occurring years later, and with some of the
later earthquakes as damaging as the early ones. Such a pattern was observed in the sequence
of about a dozen earthquakes that struck the North Anatolian Fault in Turkey in the 20th
Century, the half dozen large earthquakes in New Madrid in 1811-1812, and has been inferred
for older anomalous clusters of large earthquakes in the Middle East and in the Mojave Desert.
Most naturally occurring earthquakes are related to the tectonic nature of the Earth. Such
earthquakes are called tectonic earthquakes. The Earth's lithosphere is a patchwork of plates in
slow but constant motion caused by the heat in the Earth's mantle and planetary core. The heat
causes the rock under the earth to become liquid magma on geological timescales, on which the
plates are able to move, slowly but surely. Plate boundaries grind past each other, creating
frictional stress. When the frictional stress exceeds a critical value, called local strength, a
sudden failure occurs. The boundary of tectonic plates along which failure occurs is called the
fault plane. When the failure at the fault plane results in a violent displacement of the Earth's
crust, the elastic strain energy is released and seismic waves are radiated, thus causing an
earthquake. This process of strain, stress, and failure is referred to as the Elastic-rebound
theory. It is estimated that only 10 percent or less of an earthquake's total energy is radiated as
seismic energy. Most of the earthquake's energy is used to power the earthquake fracture
growth and is converted into heat. Therefore, earthquakes lower the Earth's available potential
energy, though these losses are negligible.
The majority of tectonic earthquakes originate at depths not exceeding tens of kilometers. In
subduction zones, where older and colder oceanic crust descends beneath another tectonic
plate, earthquakes may occur at much greater depths (up to seven hundred kilometers). These
seismically active areas of subduction are known as Wadati-Benioff zones. Deep focus
earthquakes are another phenomenon associated with a subducting slab. These are
earthquakes that occur at a depth at which the subducted lithosphere should no longer be brittle,
due to the 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.
Earthquakes may also occur in volcanic regions and are caused by the movement of magma in
volcanoes. Such quakes can be an early warning of volcanic eruptions.
A recently proposed theory suggests that some earthquakes may occur in a sort of earthquake
storm, where one earthquake will trigger a series of earthquakes each triggered by the previous
shifts on the fault lines, similar to aftershocks, but occurring years later, and with some of the
later earthquakes as damaging as the early ones. Such a pattern was observed in the sequence
of about a dozen earthquakes that struck the North Anatolian Fault in Turkey in the 20th
Century, the half dozen large earthquakes in New Madrid in 1811-1812, and has been inferred
for older anomalous clusters of large earthquakes in the Middle East and in the Mojave Desert.
Human impacts:
Earthquakes may result in disease, lack of basic necessities such as food water and shelter, loss
of life, higher insurance premiums, general property damage, road and bridge damage, and
collapse of buildings or destabilization of the base of buildings which may lead to collapse in
future earthquakes.
Earthquakes may result in disease, lack of basic necessities such as food water and shelter, loss
of life, higher insurance premiums, general property damage, road and bridge damage, and
collapse of buildings or destabilization of the base of buildings which may lead to collapse in
future earthquakes.
Effects/impacts of earthquakes:
There are many effects of earthquakes including, but not limited to the following:
Shaking and ground rupture:
Shaking and ground rupture are the main effects created by earthquakes, principally resulting in
more or less severe damage to buildings or other rigid structures. The severity of the local
effects depends on the complex combination of the earthquake magnitude, the distance from
epicenter, and the local geological and geomorphological conditions, which may amplify or
reduce wave propagation. The ground-shaking is measured by ground acceleration.
Specific local geological, geomorphological, and geostructural features can induce high levels of
shaking on the ground surface even from low-intensity earthquakes. This effect is called site or
local amplification. It is principally due to the transfer of the seismic motion from hard deep soils
to soft superficial soils and to effects of seismic energy focalization owing to typical geometrical
setting of the deposits.
Landslides and avalanches:
Earthquakes can cause landslides and avalanches, which may cause damage in hilly and
mountainous areas.
Fires:
Following an earthquake, fires can be generated by break of the electrical power or gas lines.
Soil liquefaction:
Soil liquefaction occurs when, because of the shaking, water-saturated granular material
temporally loses their strength and transforms from a solid to a liquid. Soil liquefaction may cause
rigid structures, as buildings or bridges, to tilt or sink into the liquefied deposits.
There are many effects of earthquakes including, but not limited to the following:
Shaking and ground rupture:
Shaking and ground rupture are the main effects created by earthquakes, principally resulting in
more or less severe damage to buildings or other rigid structures. The severity of the local
effects depends on the complex combination of the earthquake magnitude, the distance from
epicenter, and the local geological and geomorphological conditions, which may amplify or
reduce wave propagation. The ground-shaking is measured by ground acceleration.
Specific local geological, geomorphological, and geostructural features can induce high levels of
shaking on the ground surface even from low-intensity earthquakes. This effect is called site or
local amplification. It is principally due to the transfer of the seismic motion from hard deep soils
to soft superficial soils and to effects of seismic energy focalization owing to typical geometrical
setting of the deposits.
Landslides and avalanches:
Earthquakes can cause landslides and avalanches, which may cause damage in hilly and
mountainous areas.
Fires:
Following an earthquake, fires can be generated by break of the electrical power or gas lines.
Soil liquefaction:
Soil liquefaction occurs when, because of the shaking, water-saturated granular material
temporally loses their strength and transforms from a solid to a liquid. Soil liquefaction may cause
rigid structures, as buildings or bridges, to tilt or sink into the liquefied deposits.
Earthquake
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