(also known as a quake
) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth
that creates seismic waves
. Earthquakes can range in size from those that are so weak that they cannot be felt to those violent enough to propel objects and people into the air, and wreak destruction across entire cities. The seismicity
, or seismic activity
, of an area is the frequency, type, and size of earthquakes experienced over a period of time. The word tremor
is also used for non-earthquake seismic rumbling
occur mostly along tectonic plate boundaries, and especially on the Pacific Ring of Fire
Global plate tectonic movement
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 can also trigger landslides
and occasionally, volcanic activity.
In its most general sense, the word earthquake
is used to describe any seismic event—whether natural or caused by humans—that generates seismic waves. Earthquakes are caused mostly by rupture of geological faults
but also by other events such as volcanic activity, landslides, mine blasts, and nuclear tests
. An earthquake's point of initial rupture is called its hypocenter
or focus. The epicenter
is the point at ground level directly above the hypocenter.
Naturally occurring earthquakes
Three types of faults:
Tectonic earthquakes occur anywhere in the earth where there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane
. The sides of a fault move past each other smoothly and aseismically
only if there are no irregularities or asperities
along the fault surface that increase the frictional resistance. Most fault surfaces do have such asperities, which leads to a form of stick-slip behavior
. Once the fault has locked, continued relative motion between the plates leads to increasing stress and therefore, stored strain energy in the volume around the fault surface. This continues until the stress has risen sufficiently to break through the asperity, suddenly allowing sliding over the locked portion of the fault, releasing the stored energy
This energy is released as a combination of radiated elastic strain seismic waves
frictional heating of the fault surface, and cracking of the rock, thus causing an earthquake. This process of gradual build-up of strain and stress punctuated by occasional sudden earthquake 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 or is converted into heat generated by friction. Therefore, earthquakes lower the Earth's available elastic potential energy
and raise its temperature, though these changes are negligible compared to the conductive and convective flow of heat out from the Earth's deep interior.
Earthquake fault types
There are three main types of fault, all of which may cause an interplate earthquake
: normal, reverse (thrust), and strike-slip. Normal and reverse faulting are examples of dip-slip, where the displacement along the fault is in the direction of dip
and where movement on them involves a vertical component. Normal faults occur mainly in areas where the crust is being extended
such as a divergent boundary
. Reverse faults occur in areas where the crust is being shortened
such as at 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 particular type of strike-slip fault. Many earthquakes are caused by movement on faults that have components of both dip-slip and strike-slip; this is known as oblique slip.
Reverse faults, particularly those along convergent plate boundaries
, are associated with the most powerful earthquakes, megathrust earthquakes
, including almost all of those of magnitude 8 or more. Megathrust earthquakes are responsible for about 90% of the total seismic moment released worldwide.
Strike-slip faults, particularly continental transforms
, can produce major earthquakes up to about magnitude 8. Earthquakes associated with normal faults are generally less than magnitude 7. For every unit increase in magnitude, there is a roughly thirtyfold increase in the energy released. For instance, an earthquake of magnitude 6.0 releases approximately 32 times more energy than a 5.0 magnitude earthquake and a 7.0 magnitude earthquake releases 1,000 times more energy than a 5.0 magnitude of earthquake. An 8.6 magnitude earthquake releases the same amount of energy as 10,000 atomic bombs like those used in World War II
This is so because the energy released in an earthquake, and thus its magnitude, is proportional to the area of the fault that ruptures
and the stress drop. Therefore, the longer the length and the wider the width of the faulted area, the larger the resulting magnitude. The topmost, brittle part of the Earth's crust, and the cool slabs of the tectonic plates that are descending down into the hot mantle, are the only parts of our planet that can store elastic energy and release it in fault ruptures. Rocks hotter than about 300 °C (572 °F) flow in response to stress; they do not rupture in earthquakes.
The maximum observed lengths of ruptures and mapped faults (which may break in a single rupture) are approximately 1,000 km (620 mi). Examples are the earthquakes in Alaska (1957)
, Chile (1960)
, and Sumatra (2004)
, all in subduction zones. The longest earthquake ruptures on strike-slip faults, like the San Andreas Fault
), the North Anatolian Fault
in Turkey (1939
), and the Denali Fault
in Alaska (2002
), are about half to one third as long as the lengths along subducting plate margins, and those along normal faults are even shorter.
Aerial photo of the San Andreas Fault in the Carrizo Plain
, northwest of Los Angeles
The most important parameter controlling the maximum earthquake magnitude on a fault, however, is not the maximum available length, but the available width because the latter varies by a factor of 20. Along converging plate margins, the dip angle of the rupture plane is very shallow, typically about 10 degrees.
Thus, the width of the plane within the top brittle crust of the Earth can become 50–100 km (31–62 mi) (Japan, 2011
; Alaska, 1964
), making the most powerful earthquakes possible.
Strike-slip faults tend to be oriented near vertically, resulting in an approximate width of 10 km (6.2 mi) within the brittle crust.
Thus, earthquakes with magnitudes much larger than 8 are not possible. Maximum magnitudes along many normal faults are even more limited because many of them are located along spreading centers, as in Iceland, where the thickness of the brittle layer is only about six kilometres (3.7 mi).
In addition, there exists a hierarchy of stress level in the three fault types. Thrust faults are generated by the highest, strike-slip by intermediate, and normal faults by the lowest stress levels.
This can easily be understood by considering the direction of the greatest principal stress, the direction of the force that "pushes" the rock mass during the faulting. In the case of normal faults, the rock mass is pushed down in a vertical direction, thus the pushing force (greatest
principal stress) equals the weight of the rock mass itself. In the case of thrusting, the rock mass "escapes" in the direction of the least principal stress, namely upward, lifting the rock mass up, and thus, the overburden equals the least
principal stress. Strike-slip faulting is intermediate between the other two types described above. This difference in stress regime in the three faulting environments can contribute to differences in stress drop during faulting, which contributes to differences in the radiated energy, regardless of fault dimensions.
Earthquakes away from plate boundaries
Comparison of the 1985
earthquakes on Mexico City, Puebla and Michoacán/Guerrero
Where plate boundaries occur within the continental lithosphere
, deformation is spread out over a much larger area 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 broader zone of deformation caused by major irregularities in the fault trace (e.g., the "Big bend" region). The Northridge earthquake
was associated with movement on a blind thrust within such a zone. Another example is the strongly oblique convergent plate boundary between the Arabian
and Eurasian plates
where it runs through the northwestern part of the Zagros Mountains
. The deformation associated with this plate boundary is partitioned into nearly pure thrust sense movements perpendicular to the boundary over a wide zone to the southwest and nearly pure strike-slip motion along the Main Recent Fault close to the actual plate boundary itself. This is demonstrated by earthquake focal mechanisms
All tectonic plates have internal stress fields caused by their interactions with neighboring plates and sedimentary loading or unloading (e.g., deglaciation).
These stresses may be sufficient to cause failure along existing fault planes, giving rise to intraplate earthquakes.
Shallow-focus and deep-focus earthquakes
The majority of tectonic earthquakes originate in the ring of fire at depths not exceeding tens of kilometers. Earthquakes occurring at a depth of less than 70 km (43 mi) are classified as "shallow-focus" earthquakes, while those with a focal-depth between 70 and 300 km (43 and 186 mi) are commonly termed "mid-focus" or "intermediate-depth" earthquakes. In subduction zones
, where older and colder oceanic crust
descends beneath another tectonic plate, deep-focus earthquakes
may occur at much greater depths (ranging from 300 to 700 km (190 to 430 mi)).
These seismically active areas of subduction are known as Wadati–Benioff zones
. Deep-focus earthquakes occur at a depth where 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
Earthquakes and volcanic activity
Earthquakes often occur in volcanic regions and are caused there, both by tectonic
faults and the movement of magma
. Such earthquakes can serve as an early warning of volcanic eruptions, as during the 1980 eruption of Mount St. Helens
Earthquake swarms can serve as markers for the location of the flowing magma throughout the volcanoes. These swarms can be recorded by seismometers
(a device that measures ground slope) and used as sensors to predict imminent or upcoming eruptions.
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 (330 ft) 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. Once the rupture has initiated, it begins to propagate along the fault surface. The mechanics of this process are poorly understood, partly because it is difficult to recreate the high sliding velocities in a laboratory. Also the effects of strong ground motion make it very difficult to record information close to a nucleation zone.
Rupture propagation is generally modeled using a fracture mechanics
approach, likening the rupture to a propagating mixed mode shear crack. The rupture velocity is a function of the fracture energy in the volume around the crack tip, increasing with decreasing fracture energy. The velocity of rupture propagation is orders of magnitude faster than the displacement velocity across the fault. Earthquake ruptures typically propagate at velocities that are in the range 70–90% of the S-wave velocity, which is independent of earthquake size. A small subset of earthquake ruptures appear to have propagated at speeds greater than the S-wave velocity. These supershear earthquakes
have all been observed during large strike-slip events. The unusually wide zone of coseismic damage caused by the 2001 Kunlun earthquake
has been attributed to the effects of the sonic boom
developed in such earthquakes. Some earthquake ruptures travel at unusually low velocities and are referred to as slow earthquakes
. A particularly dangerous form of slow earthquake is the tsunami earthquake
, observed where the relatively low felt intensities, caused by the slow propagation speed of some great earthquakes, fail to alert the population of the neighboring coast, as in the 1896 Sanriku earthquake
Co-seismic overpressuring and effect of pore pressure
During an earthquake, high temperatures can develop at the fault plane so increasing pore pressure consequently to vaporization of the ground water already contained within rock.
In the coseismic phase, such increase can significantly affect slip evolution and speed and, furthermore, in the post-seismic phase it can control the aftershock sequence
because, after the main event, pore pressure increase slowly propagates into the surrounding fracture network.
From the point of view of the Mohr-Coulomb strength theory
, an increase in fluid pressure reduces the normal stress acting on the fault plane that holds it in place, and fluids can exert a lubricating effect. As thermal overpressurisation may provide a positive feedback between slip and strength fall at the fault plane, a common opinion is that it may enhance the faulting process instability. After the main shock, the pressure gradient between the fault plane and the neighbouring rock causes a fluid flow which increases pore pressure in the surrounding fracture networks; such increase may trigger new faulting processes by reactivating adjacent faults, giving rise to aftershocks.
Analogously, artificial pore pressure increase, by fluid injection in Earth’s crust, may induce seismicity
Most earthquakes form part of a sequence, related to each other in terms of location and time.
Most earthquake clusters consist of small tremors that cause little to no damage, but there is a theory that earthquakes can recur in a regular pattern.
An aftershock is an earthquake that occurs after a previous earthquake, the mainshock. An aftershock is in the same region of the main shock but always of a smaller magnitude. If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a foreshock
. Aftershocks are formed as the crust around the displaced fault plane
adjusts to the effects of the main shock.
Earthquake swarms are sequences of earthquakes striking in a specific area within a short period of time. They are different from earthquakes followed by a series of aftershocks
by the fact that no single earthquake in the sequence is obviously the main shock, so none has a notable higher magnitude than another. An example of an earthquake swarm is the 2004 activity at Yellowstone National Park
In August 2012, a swarm of earthquakes shook Southern California
's Imperial Valley
, showing the most recorded activity in the area since the 1970s.
Sometimes a series of earthquakes occur in what has been called an earthquake storm
, where the earthquakes strike a fault in clusters, each triggered by the shaking or stress redistribution
of the previous earthquakes. Similar to aftershocks
but on adjacent segments of fault, these storms occur over the course of years, 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 and has been inferred for older anomalous clusters of large earthquakes in the Middle East.
Intensity of earth quaking and magnitude of earthquakes Quaking or shaking of the earth is a common phenomenon undoubtedly known to humans from earliest times. Prior to the development of strong-motion accelerometers
that can measure peak ground speed and acceleration directly, the intensity of the earth-shaking was estimated on the basis of the observed effects, as categorized on various seismic intensity scales
. Only in the last century has the source of such shaking been identified as ruptures in the Earth's crust, with the intensity of shaking at any locality dependent not only on the local ground conditions but also on the strength or magnitude
of the rupture, and on its distance.
Although the mass media commonly reports earthquake magnitudes as "Richter magnitude" or "Richter scale", standard practice by most seismological authorities is to express an earthquake's strength on the moment magnitude
scale, which is based on the actual energy released by an earthquake.
Frequency of occurrence
It is estimated that around 500,000 earthquakes occur each year, detectable with current instrumentation. About 100,000 of these can be felt.
Minor earthquakes occur nearly constantly around the world in places like California
in the U.S., as well as in El Salvador
, the Philippines
, the Azores
, New Zealand
Larger earthquakes occur less frequently, the relationship being exponential
; for example, roughly ten times as many earthquakes larger than magnitude 4 occur in a particular time period than earthquakes larger than magnitude 5.
In the (low seismicity) United Kingdom
, for example, it has been calculated that the average recurrences are: an earthquake of 3.7–4.6 every year, an earthquake of 4.7–5.5 every 10 years, and an earthquake of 5.6 or larger every 100 years.
This is an example of the Gutenberg–Richter law
The number of seismic stations has increased from about 350 in 1931 to many thousands today. As a result, many more earthquakes are reported than in the past, but this is because of the vast improvement in instrumentation, rather than an increase in the number of earthquakes. The United States Geological Survey
estimates that, since 1900, there have been an average of 18 major earthquakes (magnitude 7.0–7.9) and one great earthquake (magnitude 8.0 or greater) per year, and that this average has been relatively stable.
In recent years, the number of major earthquakes per year has decreased, though this is probably a statistical fluctuation rather than a systematic trend.
More detailed statistics on the size and frequency of earthquakes is available from the United States Geological Survey
A recent increase in the number of major earthquakes has been noted, which could be explained by a cyclical pattern of periods of intense tectonic activity, interspersed with longer periods of low intensity. However, accurate recordings of earthquakes only began in the early 1900s, so it is too early to categorically state that this is the case.
Most of the world's earthquakes (90%, and 81% of the largest) take place in the 40,000-kilometre-long (25,000 mi), horseshoe-shaped zone called the circum-Pacific seismic belt, known as the Pacific Ring of Fire
, which for the most part bounds the Pacific Plate
Massive earthquakes tend to occur along other plate boundaries too, such as along the Himalayan Mountains
While most earthquakes are caused by movement of the Earth's tectonic plates
, human activity can also produce earthquakes. Activities both above ground and below may change the stresses and strains on the crust, including building reservoirs
, extracting resources such as coal
, and injecting fluids underground for waste disposal or fracking
Most of these earthquakes have small magnitudes. The 5.7 magnitude 2011 Oklahoma earthquake
is thought to have been caused by disposing wastewater from oil production into injection wells
and studies point to the state's oil industry as the cause of other earthquakes in the past century.
A Columbia University
paper suggested that the 8.0 magnitude 2008 Sichuan earthquake
was induced by loading from the Zipingpu Dam
though the link has not been conclusively proved.
Measuring and locating earthquakes
Every tremor produces different types of seismic waves, which travel through rock with different velocities:
of the seismic waves through solid rock ranges from approx. 3 km/s (1.9 mi/s) up to 13 km/s (8.1 mi/s), depending on the density
of the medium. In the Earth's interior, the shock- or P-waves travel much faster than the S-waves (approx. relation 1.7:1). The differences in travel time from the epicenter
to the observatory are a measure of the distance and can be used to image both sources of quakes and structures within the Earth. Also, the depth of the hypocenter
can be computed roughly.
In the upper crust, P-waves travel in the range 2–3 km (1.2–1.9 mi) per second (or lower) in soils and unconsolidated sediments, increasing to 3–6 km (1.9–3.7 mi) per second in solid rock. In the lower crust, they travel at about 6–7 km (3.7–4.3 mi) per second; the velocity increases within the deep mantle to about 13 km (8.1 mi) per second. The velocity of S-waves ranges from 2–3 km (1.2–1.9 mi) per second in light sediments and 4–5 km (2.5–3.1 mi) per second in the Earth's crust up to 7 km (4.3 mi) per second in the deep mantle. As a consequence, the first waves of a distant earthquake arrive at an observatory via the Earth's mantle.
On average, the kilometer distance to the earthquake is the number of seconds between the P- and S-wave times 8
Slight deviations are caused by inhomogeneities of subsurface structure. By such analyses of seismograms the Earth's core was located in 1913 by Beno Gutenberg
S-waves and later arriving surface waves do most of the damage compared to P-waves. P-waves squeeze and expand material in the same direction they are traveling, whereas S-waves shake the ground up and down and back and forth.
Earthquakes are not only categorized by their magnitude but also by the place where they occur. The world is divided into 754 Flinn–Engdahl regions
(F-E regions), which are based on political and geographical boundaries as well as seismic activity. More active zones are divided into smaller F-E regions whereas less active zones belong to larger F-E regions.
Standard reporting of earthquakes includes its magnitude
, date and time of occurrence, geographic coordinates
of its epicenter
, depth of the epicenter, geographical region, distances to population centers, location uncertainty, a number of parameters that are included in USGS earthquake reports (number of stations reporting, number of observations, etc.), and a unique event ID.
Although relatively slow seismic waves have traditionally been used to detect earthquakes, scientists realized in 2016 that gravitational measurements could provide instantaneous detection of earthquakes, and confirmed this by analyzing gravitational records associated with the 2011 Tohoku-Oki
Effects of earthquakes
1755 copper engraving depicting Lisbon
in ruins and in flames after the 1755 Lisbon earthquake
, which killed an estimated 60,000 people. A tsunami
overwhelms the ships in the harbor.
The effects of earthquakes include, but are 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 and other rigid structures. The severity of the local effects depends on the complex combination of the earthquake magnitude
, the distance from the 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.
Ground rupture is a visible breaking and displacement of the Earth's surface along the trace of the fault, which may be of the order of several meters in the case of major earthquakes. Ground rupture is a major risk for large engineering structures such as dams
, bridges, and nuclear power stations
and requires careful mapping of existing faults to identify any that are likely to break the ground surface within the life of the structure.
Soil liquefaction occurs when, because of the shaking, water-saturated granular
material (such as sand) temporarily loses its strength and transforms from a solid
to a liquid
. Soil liquefaction may cause rigid structures, like buildings and bridges, to tilt or sink into the liquefied deposits. For example, in the 1964 Alaska earthquake
, soil liquefaction caused many buildings to sink into the ground, eventually collapsing upon themselves.
An earthquake may cause injury and loss of life, road and bridge damage, general property damage
, and collapse or destabilization (potentially leading to future collapse) of buildings. The aftermath may bring disease
, lack of basic necessities, mental consequences such as panic attacks, depression to survivors,
and higher insurance premiums.
Earthquakes can produce slope instability leading to landslides, a major geological hazard. Landslide danger may persist while emergency personnel are attempting rescue.
Earthquakes can cause fires
by damaging electrical power
or gas lines. In the event of water mains rupturing and a loss of pressure, it may also become difficult to stop the spread of a fire once it has started. For example, more deaths in the 1906 San Francisco earthquake
were caused by fire than by the earthquake itself.
Tsunamis are long-wavelength, long-period sea waves produced by the sudden or abrupt movement of large volumes of water—including when an earthquake occurs at sea
. In the open ocean the distance between wave crests can surpass 100 kilometers (62 mi), and the wave periods can vary from five minutes to one hour. Such tsunamis travel 600–800 kilometers per hour (373–497 miles per hour), depending on water depth. Large waves produced by an earthquake or a submarine landslide can overrun nearby coastal areas in a matter of minutes. Tsunamis can also travel thousands of kilometers across open ocean and wreak destruction on far shores hours after the earthquake that generated them.
Ordinarily, subduction earthquakes under magnitude 7.5 do not cause tsunamis, although some instances of this have been recorded. Most destructive tsunamis are caused by earthquakes of magnitude 7.5 or more.
Further information: Flood
Floods may be secondary effects of earthquakes, if dams are damaged. Earthquakes may cause landslips to dam rivers, which collapse and cause floods.
The terrain below the Sarez Lake
is in danger of catastrophic flooding if the landslide dam
formed by the earthquake, known as the Usoi Dam
, were to fail during a future earthquake. Impact projections suggest the flood could affect roughly 5 million people.
Earthquakes (M6.0+) since 1900 through 2017
Earthquakes of magnitude 8.0 and greater from 1900 to 2018. The apparent 3D volumes of the bubbles are linearly proportional to their respective fatalities.
One of the most devastating earthquakes in recorded history was the 1556 Shaanxi earthquake
, which occurred on 23 January 1556 in Shaanxi
province, China. More than 830,000 people died.
Most houses in the area were yaodongs
—dwellings carved out of loess
hillsides—and many victims were killed when these structures collapsed. The 1976 Tangshan earthquake
, which killed between 240,000 and 655,000 people, was the deadliest of the 20th century.
Earthquakes that caused the greatest loss of life, while powerful, were deadly because of their proximity to either heavily populated areas or the ocean, where earthquakes often create tsunamis
that can devastate communities thousands of kilometers away. Regions most at risk for great loss of life include those where earthquakes are relatively rare but powerful, and poor regions with lax, unenforced, or nonexistent seismic building codes.
is a branch of the science of seismology
concerned with the specification of the time, location, and magnitude
of future earthquakes within stated limits.
Many methods have been developed for predicting the time and place in which earthquakes will occur. Despite considerable research efforts by seismologists
, scientifically reproducible predictions cannot yet be made to a specific day or month.
is usually considered to be a type of prediction
, earthquake forecasting
is often differentiated from earthquake prediction
. Earthquake forecasting is concerned with the probabilistic assessment of general earthquake hazard, including the frequency and magnitude of damaging earthquakes in a given area over years or decades.
For well-understood faults the probability that a segment may rupture during the next few decades can be estimated.
Earthquake warning systems
have been developed that can provide regional notification of an earthquake in progress, but before the ground surface has begun to move, potentially allowing people within the system's range to seek shelter before the earthquake's impact is felt.
The objective of earthquake engineering
is to foresee the impact of earthquakes on buildings and other structures and to design such structures to minimize the risk of damage. Existing structures can be modified by seismic retrofitting
to improve their resistance to earthquakes. Earthquake insurance
can provide building owners with financial protection against losses resulting from earthquakes Emergency management
strategies can be employed by a government or organization to mitigate risks and prepare for consequences.
may help to assess buildings and plan precautionary operations: the Igor expert system
is part of a mobile laboratory that supports the procedures leading to the seismic assessment of masonry buildings and the planning of retrofitting operations on them. It has been successfully applied to assess buildings in Lisbon
Individuals can also take preparedness steps like securing water heaters
and heavy items that could injure someone, locating shutoffs for utilities, and being educated about what to do when shaking starts. For areas near large bodies of water, earthquake preparedness encompasses the possibility of a tsunami
caused by a large quake.
An image from a 1557 book depicting an earthquake in Italy in the 4th century BCE
From the lifetime of the Greek philosopher Anaxagoras
in the 5th century BCE to the 14th century CE, earthquakes were usually attributed to "air (vapors) in the cavities of the Earth."Thales
of Miletus (625–547 BCE) was the only documented person who believed that earthquakes were caused by tension between the earth and water.
Other theories existed, including the Greek philosopher Anaxamines' (585–526 BCE) beliefs that short incline episodes of dryness and wetness caused seismic activity. The Greek philosopher Democritus (460–371 BCE) blamed water in general for earthquakes. Pliny the Elder
called earthquakes "underground thunderstorms".
In recent studies, geologists claim that global warming
is one of the reasons for increased seismic activity. According to these studies, melting glaciers and rising sea levels disturb the balance of pressure on Earth's tectonic plates, thus causing an increase in the frequency and intensity of earthquakes.[better source needed]
In Norse mythology
, earthquakes were explained as the violent struggling of the god Loki
. When Loki, god
of mischief and strife, murdered Baldr
, god of beauty and light, he was punished by being bound in a cave with a poisonous serpent placed above his head dripping venom. Loki's wife Sigyn
stood by him with a bowl to catch the poison, but whenever she had to empty the bowl the poison dripped on Loki's face, forcing him to jerk his head away and thrash against his bonds, which caused the earth to tremble.
In Greek mythology
was the cause and god of earthquakes. When he was in a bad mood, he struck the ground with a trident
, causing earthquakes and other calamities. He also used earthquakes to punish and inflict fear upon people as revenge.
In Japanese mythology
(鯰) is a giant catfish
who causes earthquakes. Namazu lives in the mud beneath the earth, and is guarded by the god Kashima
who restrains the fish with a stone. When Kashima lets his guard fall, Namazu thrashes about, causing violent earthquakes.
In popular culture
The most popular single earthquake in fiction is the hypothetical "Big One" expected of California
's San Andreas Fault
someday, as depicted in the novels Richter 10
(1996), Goodbye California
(2009) and San Andreas
(2015) among other works.
Jacob M. Appel's widely anthologized short story, A Comparative Seismology
, features a con artist who convinces an elderly woman that an apocalyptic earthquake is imminent.
Contemporary depictions of earthquakes in film are variable in the manner in which they reflect human psychological reactions to the actual trauma that can be caused to directly afflicted families and their loved ones.
Disaster mental health response research emphasizes the need to be aware of the different roles of loss of family and key community members, loss of home and familiar surroundings, loss of essential supplies and services to maintain survival.
Particularly for children, the clear availability of caregiving adults who are able to protect, nourish, and clothe them in the aftermath of the earthquake, and to help them make sense of what has befallen them has been shown even more important to their emotional and physical health than the simple giving of provisions.
As was observed after other disasters involving destruction and loss of life and their media depictions, recently observed in the 2010 Haiti earthquake
, it is also important not to pathologize the reactions to loss and displacement or disruption of governmental administration and services, but rather to validate these reactions, to support constructive problem-solving and reflection as to how one might improve the conditions of those affected.
- ^ Ohnaka, M. (2013). The Physics of Rock Failure and Earthquakes. Cambridge University Press. p. 148. ISBN 978-1-107-35533-0.
- ^ Vassiliou, Marius; Kanamori, Hiroo (1982). "The Energy Release in Earthquakes". Bull. Seismol. Soc. Am. 72: 371–387.
- ^ Spence, William; S.A. Sipkin; G.L. Choy (1989). "Measuring the Size of an Earthquake". United States Geological Survey. Archived from the original on 2009-09-01. Retrieved 2006-11-03.
- ^ Stern, Robert J. (2002), "Subduction zones", Reviews of Geophysics, 40 (4): 17, Bibcode:2002RvGeo..40.1012S, doi:10.1029/2001RG000108
- ^ Geoscience Australia
- ^ Wyss, M. (1979). "Estimating expectable maximum magnitude of earthquakes from fault dimensions". Geology. 7 (7): 336–340. Bibcode:1979Geo.....7..336W. doi:10.1130/0091-7613(1979)7<336:EMEMOE>2.0.CO;2.
- ^ Sibson, R.H. (1982). "Fault Zone Models, Heat Flow, and the Depth Distribution of Earthquakes in the Continental Crust of the United States". Bulletin of the Seismological Society of America. 72 (1): 151–163.
- ^ Sibson, R.H. (2002) "Geology of the crustal earthquake source" International handbook of earthquake and engineering seismology, Volume 1, Part 1, p. 455, eds. W H K Lee, H Kanamori, P C Jennings, and C. Kisslinger, Academic Press, ISBN 978-0-12-440652-0
- ^ "Global Centroid Moment Tensor Catalog". Globalcmt.org. Retrieved 2011-07-24.
- ^ "Instrumental California Earthquake Catalog". WGCEP. Archived from the original on 2011-07-25. Retrieved 2011-07-24.
- ^ Hjaltadóttir S., 2010, "Use of relatively located microearthquakes to map fault patterns and estimate the thickness of the brittle crust in Southwest Iceland"
- ^ "Reports and publications | Seismicity | Icelandic Meteorological office". En.vedur.is. Retrieved 2011-07-24.
- ^ Schorlemmer, D.; Wiemer, S.; Wyss, M. (2005). "Variations in earthquake-size distribution across different stress regimes". Nature. 437 (7058): 539–542. Bibcode:2005Natur.437..539S. doi:10.1038/nature04094. PMID 16177788. S2CID 4327471.
- ^ Talebian, M; Jackson, J (2004). "A reappraisal of earthquake focal mechanisms and active shortening in the Zagros mountains of Iran". Geophysical Journal International. 156 (3): 506–526. Bibcode:2004GeoJI.156..506T. doi:10.1111/j.1365-246X.2004.02092.x.
- ^ Nettles, M.; Ekström, G. (May 2010). "Glacial Earthquakes in Greenland and Antarctica". Annual Review of Earth and Planetary Sciences. 38 (1): 467–491. Bibcode:2010AREPS..38..467N. doi:10.1146/annurev-earth-040809-152414.
- ^ Noson, Qamar, and Thorsen (1988). Washington State Earthquake Hazards: Washington State Department of Natural Resources. Washington Division of Geology and Earth Resources Information Circular 85.
- ^ "M7.5 Northern Peru Earthquake of 26 September 2005" (PDF). National Earthquake Information Center. 17 October 2005. Retrieved 2008-08-01.
- ^ Greene II, H.W.; Burnley, P.C. (October 26, 1989). "A new self-organizing mechanism for deep-focus earthquakes". Nature. 341 (6244): 733–737. Bibcode:1989Natur.341..733G. doi:10.1038/341733a0. S2CID 4287597.
- ^ Foxworthy and Hill (1982). Volcanic Eruptions of 1980 at Mount St. Helens, The First 100 Days: USGS Professional Paper 1249.
- ^ Watson, John; Watson, Kathie (January 7, 1998). "Volcanoes and Earthquakes". United States Geological Survey. Retrieved May 9, 2009.
- ^ a b National Research Council (U.S.). Committee on the Science of Earthquakes (2003). "5. Earthquake Physics and Fault-System Science". Living on an Active Earth: Perspectives on Earthquake Science. Washington, D.C.: National Academies Press. p. 418. ISBN 978-0-309-06562-7. Retrieved 8 July 2010.
- ^ Sibson, R.H. (1973). "Interactions between Temperature and Pore-Fluid Pressure during Earthquake Faulting and a Mechanism for Partial or Total Stress Relief". Nat. Phys. Sci. 243 (126): 66–68. doi:10.1038/physci243066a0.
- ^ Rudnicki, J.W.; Rice, J.R. (2006). "Effective normal stress alteration due to pore pressure changes induced by dynamic slip propagation on a plane between dissimilar materials" (PDF). J. Geophys. Res. 111, B10308. doi:10.1029/2006JB004396.
- ^ a b c Guerriero, V; Mazzoli, S. (2021). "Theory of Effective Stress in Soil and Rock and Implications for Fracturing Processes: A Review". Geosciences. 11 (3): 119. doi:10.3390/geosciences11030119.
- ^ a b Nur, A; Booker, J.R. (1972). "Aftershocks Caused by Pore Fluid Flow?". Science. 175 (4024): 885–887. doi:10.1126/science.175.4024.885. PMID 17781062. S2CID 19354081.
- ^ a b "What are Aftershocks, Foreshocks, and Earthquake Clusters?". Archived from the original on 2009-05-11.
- ^ "Repeating Earthquakes". United States Geological Survey. January 29, 2009. Retrieved May 11, 2009.
- ^ "Earthquake Swarms at Yellowstone". United States Geological Survey. Retrieved 2008-09-15.
- ^ Duke, Alan. "Quake 'swarm' shakes Southern California". CNN. Retrieved 27 August 2012.
- ^ Amos Nur; Cline, Eric H. (2000). "Poseidon's Horses: Plate Tectonics and Earthquake Storms in the Late Bronze Age Aegean and Eastern Mediterranean" (PDF). Journal of Archaeological Science. 27 (1): 43–63. doi:10.1006/jasc.1999.0431. ISSN 0305-4403. Archived from the original (PDF) on 2009-03-25.
- ^ "Earthquake Storms". Horizon. 1 April 2003. Retrieved 2007-05-02.
- ^ Bolt 1993.
- ^ Chung & Bernreuter 1980, p. 1.
- ^ The USGS policy for reporting magnitudes to the press was posted at USGS policyArchived 2016-05-04 at the Wayback Machine, but has been removed. A copy can be found at http://dapgeol.tripod.com/usgsearthquakemagnitudepolicy.htm.
- ^ a b "Cool Earthquake Facts". United States Geological Survey. Retrieved 2021-04-21.
- ^ a b Pressler, Margaret Webb (14 April 2010). "More earthquakes than usual? Not really". KidsPost. Washington Post: Washington Post. pp. C10.
- ^ "Earthquake Hazards Program". United States Geological Survey. Retrieved 2006-08-14.
- ^ USGS Earthquake statistics table based on data since 1900 Archived 2010-05-24 at the Wayback Machine
- ^ "Seismicity and earthquake hazard in the UK". Quakes.bgs.ac.uk. Retrieved 2010-08-23.
- ^ "Italy's earthquake history." BBC News. October 31, 2002.
- ^ "Common Myths about Earthquakes". United States Geological Survey. Archived from the original on 2006-09-25. Retrieved 2006-08-14.
- ^ Are Earthquakes Really on the Increase?Archived 2014-06-30 at the Wayback Machine, USGS Science of Changing World. Retrieved 30 May 2014.
- ^ "Earthquake Facts and Statistics: Are earthquakes increasing?". United States Geological Survey. Archived from the original on 2006-08-12. Retrieved 2006-08-14.
- ^ The 10 biggest earthquakes in historyArchived 2013-09-30 at the Wayback Machine, Australian Geographic, March 14, 2011.
- ^ "Historic Earthquakes and Earthquake Statistics: Where do earthquakes occur?". United States Geological Survey. Archived from the original on 2006-09-25. Retrieved 2006-08-14.
- ^ "Visual Glossary – Ring of Fire". United States Geological Survey. Archived from the original on 2006-08-28. Retrieved 2006-08-14.
- ^ Jackson, James (2006). "Fatal attraction: living with earthquakes, the growth of villages into megacities, and earthquake vulnerability in the modern world". Philosophical Transactions of the Royal Society. 364 (1845): 1911–1925. Bibcode:2006RSPTA.364.1911J. doi:10.1098/rsta.2006.1805. PMID 16844641. S2CID 40712253.
- ^ "Global urban seismic risk." Cooperative Institute for Research in Environmental Science.
- ^ Fougler, Gillian R.; Wilson, Miles; Gluyas, Jon G.; Julian, Bruce R.; Davies, Richard J. (2018). "Global review of human-induced earthquakes". Earth-Science Reviews. 178: 438–514. Bibcode:2018ESRv..178..438F. doi:10.1016/j.earscirev.2017.07.008. Retrieved July 23, 2020.
- ^ Fountain, Henry (March 28, 2013). "Study Links 2011 Quake to Technique at Oil Wells". The New York Times. Retrieved July 23, 2020.
- ^ Hough, Susan E.; Page, Morgan (2015). "A Century of Induced Earthquakes in Oklahoma?". Bulletin of the Seismological Society of America. 105 (6): 2863–2870. Bibcode:2015BuSSA.105.2863H. doi:10.1785/0120150109. Retrieved July 23, 2020.
- ^ Klose, Christian D. (July 2012). "Evidence for anthropogenic surface loading as trigger mechanism of the 2008 Wenchuan earthquake". Environmental Earth Sciences. 66 (5): 1439–1447. arXiv:1007.2155. doi:10.1007/s12665-011-1355-7. S2CID 118367859.
- ^ LaFraniere, Sharon (February 5, 2009). "Possible Link Between Dam and China Quake". The New York Times. Retrieved July 23, 2020.
- ^ "Speed of Sound through the Earth". Hypertextbook.com. Retrieved 2010-08-23.
- ^ "Newsela | The science of earthquakes". newsela.com. Retrieved 2017-02-28.
- ^ Geographic.org. "Magnitude 8.0 - SANTA CRUZ ISLANDS Earthquake Details". Global Earthquake Epicenters with Maps. Retrieved 2013-03-13.
- ^ "Earth's gravity offers earlier earthquake warnings". Retrieved 2016-11-22.
- ^ "Gravity shifts could sound early earthquake alarm". Retrieved 2016-11-23.
- ^ "On Shaky Ground, Association of Bay Area Governments, San Francisco, reports 1995,1998 (updated 2003)". Abag.ca.gov. Archived from the original on 2009-09-21. Retrieved 2010-08-23.
- ^ "Guidelines for evaluating the hazard of surface fault rupture, California Geological Survey"(PDF). California Department of Conservation. 2002. Archived from the original (PDF) on 2009-10-09.
- ^ "Historic Earthquakes – 1964 Anchorage Earthquake". United States Geological Survey. Archived from the original on 2011-06-23. Retrieved 2008-09-15.
- ^ "Earthquake Resources". Nctsn.org. Retrieved 2018-06-05.
- ^ "Natural Hazards – Landslides". United States Geological Survey. Retrieved 2008-09-15.
- ^ "The Great 1906 San Francisco earthquake of 1906". United States Geological Survey. Retrieved 2008-09-15.
- ^ a b Noson, Qamar, and Thorsen (1988). Washington Division of Geology and Earth Resources Information Circular 85 (PDF). Washington State Earthquake Hazards.
- ^ "Notes on Historical Earthquakes". British Geological Survey. Archived from the original on 2011-05-16. Retrieved 2008-09-15.
- ^ "Fresh alert over Tajik flood threat". BBC News. 2003-08-03. Retrieved 2008-09-15.
- ^ USGS: Magnitude 8 and Greater Earthquakes Since 1900 Archived 2016-04-14 at the Wayback Machine
- ^ "Earthquakes with 50,000 or More DeathsArchived November 1, 2009, at the Wayback Machine". U.S. Geological Survey
- ^ Spignesi, Stephen J. (2005). Catastrophe!: The 100 Greatest Disasters of All Time. ISBN 0-8065-2558-4
- ^ Kanamori Hiroo. "The Energy Release in Great Earthquakes" (PDF). Journal of Geophysical Research. Archived from the original (PDF) on 2010-07-23. Retrieved 2010-10-10.
- ^ USGS. "How Much Bigger?". United States Geological Survey. Retrieved 2010-10-10.
- ^ Geller et al. 1997, p. 1616, following Allen (1976, p. 2070), who in turn followed Wood & Gutenberg (1935)
- ^ Earthquake Prediction. Ruth Ludwin, U.S. Geological Survey.
- ^ Kanamori 2003, p. 1205. See also International Commission on Earthquake Forecasting for Civil Protection 2011, p. 327.
- ^ Working Group on California Earthquake Probabilities in the San Francisco Bay Region, 2003 to 2032, 2003, "Archived copy". Archived from the original on 2017-02-18. Retrieved 2017-08-28.
- ^ Pailoplee, Santi (2017-03-13). "Probabilities of Earthquake Occurrences along the Sumatra-Andaman Subduction Zone". Open Geosciences. 9 (1): 4. Bibcode:2017OGeo....9....4P. doi:10.1515/geo-2017-0004. ISSN 2391-5447. S2CID 132545870.
- ^ Salvaneschi, P.; Cadei, M.; Lazzari, M. (1996). "Applying AI to Structural Safety Monitoring and Evaluation". IEEE Expert. 11 (4): 24–34. doi:10.1109/64.511774.
- ^ a b c d "Earthquakes". Encyclopedia of World Environmental History. 1: A–G. Routledge. 2003. pp. 358–364.
- ^ "Fire and Ice: Melting Glaciers Trigger Earthquakes, Tsunamis and Volcanos". about News. Retrieved October 27, 2015.
- ^ Sturluson, Snorri (1220). Prose Edda. ISBN 978-1-156-78621-5.
- ^ George E. Dimock (1990). The Unity of the Odyssey. Univ of Massachusetts Press. pp. 179–. ISBN 978-0-87023-721-8.
- ^ "Namazu". World History Encyclopedia. Retrieved 2017-07-23.
- ^ a b c d Van Riper, A. Bowdoin (2002). Science in popular culture: a reference guide. Westport: Greenwood Press. p. 60. ISBN 978-0-313-31822-1.
- ^ JM Appel. A Comparative Seismology. Weber Studies (first publication), Volume 18, Number 2.
- ^ Goenjian, Najarian; Pynoos, Steinberg; Manoukian, Tavosian; Fairbanks, AM; Manoukian, G; Tavosian, A; Fairbanks, LA (1994). "Posttraumatic stress disorder in elderly and younger adults after the 1988 earthquake in Armenia". Am J Psychiatry. 151 (6): 895–901. doi:10.1176/ajp.151.6.895. PMID 8185000.
- ^ Wang, Gao; Shinfuku, Zhang; Zhao, Shen; Zhang, H; Zhao, C; Shen, Y (2000). "Longitudinal Study of Earthquake-Related PTSD in a Randomly Selected Community Sample in North China". Am J Psychiatry. 157 (8): 1260–1266. doi:10.1176/appi.ajp.157.8.1260. PMID 10910788.
- ^ Goenjian, Steinberg; Najarian, Fairbanks; Tashjian, Pynoos (2000). "Prospective Study of Posttraumatic Stress, Anxiety, and Depressive Reactions After Earthquake and Political Violence" (PDF). Am J Psychiatry. 157 (6): 911–916. doi:10.1176/appi.ajp.157.6.911. PMID 10831470. Archived from the original(PDF) on 2017-08-10.
- ^ Coates, SW; Schechter, D (2004). "Preschoolers' traumatic stress post-9/11: relational and developmental perspectives. Disaster Psychiatry Issue". Psychiatric Clinics of North America. 27 (3): 473–489. doi:10.1016/j.psc.2004.03.006. PMID 15325488.
- ^ Schechter, DS; Coates, SW; First, E (2002). "Observations of acute reactions of young children and their families to the World Trade Center attacks". Journal of ZERO-TO-THREE: National Center for Infants, Toddlers, and Families. 22 (3): 9–13.
- Allen, Clarence R. (December 1976), "Responsibilities in earthquake prediction", Bulletin of the Seismological Society of America, 66 (6): 2069–2074.
- Bolt, Bruce A. (1993), Earthquakes and geological discovery, Scientific American Library, ISBN 978-0-7167-5040-6.
- Chung, D.H.; Bernreuter, D.L. (1980), Regional Relationships Among Earthquake Magnitude Scales., NUREG/CR-1457.
- Deborah R. Coen. The Earthquake Observers: Disaster Science From Lisbon to Richter (University of Chicago Press; 2012) 348 pages; explores both scientific and popular coverage
- Geller, Robert J.; Jackson, David D.; Kagan, Yan Y.; Mulargia, Francesco (14 March 1997), "Earthquakes Cannot Be Predicted" (PDF), Science, 275 (5306): 1616, doi:10.1126/science.275.5306.1616, S2CID 123516228.
- Donald Hyndman; David Hyndman (2009). "Chapter 3: Earthquakes and their causes". Natural Hazards and Disasters (2nd ed.). Brooks/Cole: Cengage Learning. ISBN 978-0-495-31667-1.
- International Commission on Earthquake Forecasting for Civil Protection (30 May 2011), "Operational Earthquake Forecasting: State of Knowledge and Guidelines for Utilization", Annals of Geophysics, 54 (4): 315–391, doi:10.4401/ag-5350.
- Kanamori, Hiroo (2003), "Earthquake Prediction: An Overview", International Handbook of Earthquake and Engineering Seismology, International Geophysics, 616: 1205–1216, doi:10.1016/s0074-6142(03)80186-9, ISBN 978-0-12-440658-2.
- Wood, H.O.; Gutenberg, B. (6 September 1935), "Earthquake prediction", Science, 82 (2123): 219–320, Bibcode:1935Sci....82..219W, doi:10.1126/science.82.2123.219, PMID 17818812.
Wikimedia Commons has media related to Earthquake
Look up earthquake
in Wiktionary, the free dictionary.
Last edited on 24 June 2021, at 13:29
Content is available under CC BY-SA 3.0
unless otherwise noted.