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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 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 ...

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
tsunami
. Earthquakes can also trigger landslides. 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

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
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
dip
and where movement on them involves a vertical component. Many earthquakes are caused by movement on faults that have components of both dip-slip and strike-slip; this is known as oblique slip. The topmost, brittle part of the Earth's crust, and the cool slabs of the tectonic plates that are descending 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 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 . 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 ( 1857, 1906), the North Anatolian Fault in Turkey ( 1939), and the Denali Fault in Alaska (
2002
2002
), are about half to one third as long as the lengths along subducting plate margins, and those along normal faults are even shorter.


Normal faults

Normal faults occur mainly in areas where the crust is being extended such as a divergent boundary. Earthquakes associated with normal faults are generally less than magnitude 7. 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 .


Reverse faults

Reverse faults occur in areas where the crust is being shortened such as at a convergent boundary. 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

Strike-slip fault
Strike-slip fault
s 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. Strike-slip faults, particularly continental
transforms
transforms
, can produce major earthquakes up to about magnitude 8. Strike-slip faults tend to be oriented near vertically, resulting in an approximate width of within the brittle crust. Thus, earthquakes with magnitudes much larger than 8 are not possible. In addition, there exists a hierarchy of stress levels 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, 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.


Energy released

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 earthquake. An 8.6 magnitude earthquake releases the same amount of energy as 10,000 atomic bombs of the size 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 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 ( Japan, 2011; Alaska, 1964), making the most powerful earthquakes possible.


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 are classified as "shallow-focus" earthquakes, while those with a focal-depth between are commonly termed "mid-focus" or "intermediate-depth" earthquakes. In
subduction
subduction
zones, where older and colder oceanic crust descends beneath another tectonic plate, deep-focus earthquakes may occur at much greater depths (ranging from ). These seismically active areas of subduction are known as
Wadati–Benioff zone A Wadati–Benioff zone (also Benioff–Wadati zone or Benioff zone or Benioff seismic zone) is a planar zone of seismicity corresponding with the down-going slab in a subduction Subduction is a geological process in which the oceanic litho ...
s. 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 The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...

olivine
undergoing a
phase transition In chemistry, thermodynamics, and other related fields, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic State of ...
into a
spinel Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , which means ''spine'' in reference to its pointed crystals. Properties Sp ...

spinel
structure.


Earthquakes and volcanic activity

Earthquakes often occur in volcanic regions and are caused there, both by
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 ...

tectonic
faults and the movement of
magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

magma
in
volcano A volcano is a rupture in the Crust (geology), crust of a Planet#Planetary-mass objects, planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and volcanic gas, gases to escape from a magma chamber below the surface. On Ear ...

volcano
es. 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 seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, Types of volcanic eruptions, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to f ...
and
tiltmeter A tiltmeter is a sensitive inclinometer An inclinometer or clinometer is an measuring instrument, instrument used for measuring angles of slope, elevation, or depression (geology), depression of an object with respect to gravity's direction. ...
s (a device that measures ground slope) and used as sensors to predict imminent or upcoming eruptions.


Rupture dynamics

A tectonic earthquake begins as an area of initial slip on the fault surface that forms the focus. Once the rupture has initiated, it begins to propagate away from the focus, spreading out along the fault surface. Lateral propagation will continue until either the rupture reaches a barrier, such as the end of a fault segment, or a region on the fault where there is insufficient stress to allow continued rupture. For larger earthquakes, the depth extent of rupture will be constrained downwards by the brittle-ductile transition zone and upwards by the ground surface. The mechanics of this process are poorly understood, because it is difficult either to recreate such rapid movements in a laboratory or to record seismic waves close to a nucleation zone due to strong ground motion. In most cases the rupture speed approaches, but does not exceed, the
shear wave __NOTOC__ In seismology and other areas involving elastic waves, S waves, secondary waves, or shear waves (sometimes called elastic S waves) are a type of elastic wave and are one of the two main types of elastic body waves, so named because ...
(S-wave) velocity of the surrounding rock. There are a few exceptions to this:


Supershear earthquakes

Supershear earthquake In seismology, a supershear earthquake is an earthquake in which the propagation of the Earthquake rupture, rupture along the Fault (geology), fault surface occurs at speeds in excess of the seismic S-wave, shear wave (S-wave) velocity. This caus ...
ruptures are known to have propagated at speeds greater than the S-wave velocity. These have so far all been observed during large strike-slip events. The unusually wide zone of damage caused by the 2001 Kunlun earthquake has been attributed to the effects of the
sonic boom A sonic boom is a sound associated with shock waves created when an object travels through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding similar to an explosion or a thunderclap to t ...

sonic boom
developed in such earthquakes.


Slow earthquakes

Slow earthquake A slow earthquake is a discontinuous, 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 p ...
ruptures travel at unusually low velocities. 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 In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in Epicenter, the same area of the main shock, caused as the displaced Crust (geology), crust adjusts to the effects of the main shock. Large earthquakes can ...
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 overpressurization may provide 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 mainshock, the pressure gradient between the fault plane and the neighboring 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.


Tidal forces

Tides Tides are the rise and fall of sea levels caused by the combined effects of the gravity, gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide t ...

Tides
may induce some seismicity.


Earthquake clusters

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. Earthquake clustering has been observed, for example, in Parkfield, California where a long term research study is being conducted around the
Parkfield earthquake Parkfield earthquake is a name given to various large earthquakes that occurred in the vicinity of the town of Parkfield, California, United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. ...
cluster.


Aftershocks

An aftershock is an earthquake that occurs after a previous earthquake, the mainshock. Rapid changes of stress between rocks, and the stress from the original earthquake are the main causes of these aftershocks, along with the crust around the ruptured fault plane as it adjusts to the effects of the mainshock. An aftershock is in the same region of the main shock but always of a smaller magnitude, however they can still be powerful enough to cause even more damage to buildings that were already previously damaged from the mainshock. If an aftershock is larger than the mainshock, the aftershock is redesignated as the mainshock and the originalmain shock is redesignated as a
foreshock A foreshock is an earthquake that occurs before a larger seismic event (the mainshock) and is related to it in both time and space. The designation of an earthquake as ''foreshock'', ''mainshock'' or aftershock is only possible after the full sequ ...
. Aftershocks are formed as the crust around the displaced fault plane adjusts to the effects of the mainshock.


Earthquake swarms

Earthquake swarms are sequences of earthquakes striking in a specific area within a short period. They are different from earthquakes followed by a series of
aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in Epicenter, the same area of the main shock, caused as the displaced Crust (geology), crust adjusts to the effects of the main shock. Large earthquakes can ...
s 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 Yellowstone National Park is an American national park located in the western United States, largely in the northwest corner of Wyoming and extending into Montana and Idaho. It was established by the 42nd U.S. Congress with the Yellowsto ...
. In August 2012, a swarm of earthquakes shook
Southern California Southern California (commonly shortened to SoCal) is a geographic and cultural region that generally comprises the southern portion of the U.S. state of California California is a U.S. state, state in the Western United States, located ...
's
Imperial Valley The Imperial Valley ( es, Valle de Imperial or ''Valle Imperial'') of Southern California lies in Imperial County, California, Imperial and Riverside County, California, Riverside counties, with an urban area centered on the city of El Centro. The ...
, 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
aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in Epicenter, the same area of the main shock, caused as the displaced Crust (geology), crust adjusts to the effects of the main shock. Large earthquakes can ...
s 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 and magnitude of earthquakes

Shaking of the earth is a common phenomenon that has been experienced by humans from the earliest of times. Before the development of strong-motion accelerometers, the intensity of a seismic event was estimated based on the observed effects. Magnitude and intensity are not directly related and calculated using different methods. The magnitude of an earthquake is a single value that describes the size of the earthquake at its source. Intensity is the measure of shaking at different locations around the earthquake. Intensity values vary from place to place, depending on distance from the earthquake and underlying rock or soil makeup. The first scale for measuring earthquake magnitudes was developed by Charles F. Richter in 1935. Subsequent scales (see
seismic magnitude scales Seismic magnitude scales are used to describe the overall strength or "size" of 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 energ ...
) have retained a key feature, where each unit represents a ten-fold difference in the amplitude of the ground shaking and a 32-fold difference in energy. Subsequent scales are also adjusted to have approximately the same numeric value within the limits of the scale. 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 and Alaska in the U.S., as well as in El Salvador, Mexico, Guatemala, Chile, Peru, Indonesia, the Philippines, Iran, Pakistan, the
Azores ) , motto =( en, "Rather die free than subjected in peace") , anthem= ( en, "Anthem of the Azores") , image_map=Locator_map_of_Azores_in_EU.svg , map_alt=Location of the Azores within the European Union , map_caption=Location of the Azores wi ...
in Portugal, Turkey, New Zealand, Greece, Italy, India, Nepal and Japan. Larger earthquakes occur less frequently, the relationship being
exponential Exponential may refer to any of several mathematical topics related to exponentiation, including: *Exponential function, also: **Matrix exponential, the matrix analogue to the above *Exponential decay, decrease at a rate proportional to value *Expo ...
; 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 The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific government agency, agency of the Federal government of the United States, United States government. The scientists of the USGS study th ...
(USGS) 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 , horseshoe-shaped zone called the circum-Pacific seismic belt, known as the
Pacific Ring of Fire The Ring of Fire (also known as the Pacific Ring of Fire, the Rim of Fire, the Girdle of Fire or the Circum-Pacific belt) is a region around much of the rim of the Pacific Ocean where many Types of volcanic eruptions, volcanic eruptions and ...
, which for the most part bounds the
Pacific Plate The Pacific Plate is an oceanic Plate tectonics, tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon Pl ...
. Massive earthquakes tend to occur along other plate boundaries too, such as along the
Himalayan Mountains The Himalayas, or Himalaya (; ; ), is a mountain range A mountain range or hill range is a series of mountains or hills arranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges wi ...
. With the rapid growth of
mega-cities A megacity is a very large city, typically with a population of more than 10 million people. Precise definitions vary: the United Nations Department of Economic and Social Affairs in its 2018 "World Urbanization Prospects" report counted urban ...
such as Mexico City, Tokyo and Tehran in areas of high
seismic risk Seismic risk refers to the risk of damage from earthquake to a building, system, or other entity. Seismic risk has been defined, for most management purposes, as the potential economic, social and environmental consequences of hazardous events th ...
, some seismologists are warning that a single earthquake may claim the lives of up to three million people.


Induced seismicity

While most earthquakes are caused by movement of the Earth's
tectonic plate 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 ...
s, 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 or oil, and injecting fluids underground for waste disposal or
fracking Fracking (also known as hydraulic fracturing, hydrofracturing, or hydrofracking) is a well stimulation technique involving the fracturing of bedrock Formation (geology), formations by a pressurized liquid. The process involves the high-pressure ...
. 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 Columbia University (also known as Columbia, and officially as Columbia University in the City of New York) is a Private university, private research university in New York City. Established in 1754 as King's College on the grounds of Trinity ...
paper suggested that the 8.0 magnitude
2008 Sichuan earthquake The 2008 Sichuan earthquakeSome early Western reports used the term Chengdu quake; e.g., , , etc. This term never picked up widely in media reports, but was reportedly used by BBC America in a follow-up report on preparations for winter an ...
was induced by loading from the Zipingpu Dam, though the link has not been conclusively proved.


Measuring and locating earthquakes

The instrumental scales used to describe the size of an earthquake began with the
Richter magnitude scale The Richter scale —also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale—is a measure of the strength of earthquakes, developed by Charles Francis Richter and presented in his landmark 1935 p ...
in the 1930s. It is a relatively simple measurement of an event's amplitude, and its use has become minimal in the 21st century.
Seismic waves 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 ...
travel through the
Earth's interior The internal structure of Earth is the solid portion of the Earth, excluding its Earth's atmosphere, atmosphere and hydrosphere. The structure consists of an outer silicate mineral, silicate solid crust (geology), crust, a highly viscosity, v ...
and can be recorded by
seismometer A seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, Types of volcanic eruptions, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to f ...
s at great distances. The
surface wave magnitude The surface wave magnitude (M_s) scale is one of the magnitude scales used in seismology Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "Earthquake, earthquake" and -λογία (''-logía'') meaning "study of") is t ...
was developed in the 1950s as a means to measure remote earthquakes and to improve the accuracy for larger events. The
moment magnitude scale The moment magnitude scale (MMS; denoted explicitly with or Mw, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. It was defined in a 1979 pape ...
not only measures the amplitude of the shock but also takes into account the
seismic moment Seismic moment is a quantity used by seismologists to measure the size of an earthquake. The scalar seismic moment M_0 is defined by the equation M_0=\mu AD, where *\mu is the shear modulus of the rocks involved in the earthquake (in pascal (unit), ...
(total rupture area, average slip of the fault, and rigidity of the rock). The
Japan Meteorological Agency seismic intensity scale The Japan Meteorological Agency (JMA) Seismic Intensity Scale (known in Japan as the Shindo seismic scale) is a seismic intensity scale used in Japan to categorize the intensity of local ground shaking caused by earthquakes. The Japan Meteoro ...
, the
Medvedev–Sponheuer–Karnik scale The Medvedev–Sponheuer–Karnik scale, also known as the MSK or MSK-64, is a macroseismic intensity scale used to evaluate the severity of ground shaking on the basis of observed effects in an area where an earthquake An earthquake (a ...
, and the
Mercalli intensity scale The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scales, seismic intensity scale used for measuring the intensity of shaking produced by an earthq ...
are based on the observed effects and are related to the intensity of shaking.


Seismic waves

Every earthquake produces different types of seismic waves, which travel through rock with different velocities: * Longitudinal
P-waves A P wave (primary wave or pressure wave) is one of the two main types of elastic Body wave (seismology), body waves, called seismic waves in seismology. P waves travel faster than other seismic waves and hence are the first signal from an eart ...
(shock- or pressure waves) * Transverse
S-waves __NOTOC__ In seismology and other areas involving elastic waves, S waves, secondary waves, or shear waves (sometimes called elastic S waves) are a type of Linear elasticity#Elastic wave, elastic wave and are one of the two main types of elastic ...
(both body waves) *
Surface wave In physics, a surface wave is a mechanical wave that propagates along the Interface (chemistry), interface between differing media. A common example is gravity waves along the surface of liquids, such as ocean waves. Gravity waves can also occu ...
s – ( Rayleigh and
Love Love encompasses a range of strong and positive emotional and mental states, from the most sublime virtue or good habit, the deepest Interpersonal relationship, interpersonal affection, to the simplest pleasure. An example of this range of ...
waves)


Speed of seismic waves

Propagation velocity of the seismic waves through solid rock ranges from approx. up to , depending on the
density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek language, Greek letter Rho (letter), rho), although the Latin letter ''D'' ca ...
and elasticity 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 The epicenter, epicentre () or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter, hypocenter or focus, the point where an earthquake or an underground explosion originates. Surface damage Before the inst ...
to the observatory are a measure of the distance and can be used to image both sources of earthquakes and structures within the Earth. Also, the depth of the hypocenter can be computed roughly.


P-wave speed

Upper crust soils and unconsolidated sediments: per second Upper crust solid rock: per second Lower crust: per second Deep mantle: per second.


S-waves speed

Light sediments: per second in Earths crust: per second Deep mantle: per second


Seismic wave arrival

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 analysis of seismograms, the Earth's core was located in 1913 by
Beno Gutenberg Beno Gutenberg (; June 4, 1889 – January 25, 1960) was a German-American seismologist who made several important contributions to the science. He was a colleague and mentor of Charles Francis Richter at the California Institute of Technolog ...
. S-waves and later arriving surface waves do most of the damage compared to P-waves. P-waves squeeze and expand the material in the same direction they are traveling, whereas S-waves shake the ground up and down and back and forth.


Earthquake location and reporting

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 The geographic coordinate system (GCS) is a spherical coordinate system, spherical or ellipsoidal coordinates (geodesy), ellipsoidal coordinate system for measuring and communicating position (geometry), positions directly on the Earth as lati ...
of its epicenter, depth of the epicenter, geographical region, distances to population centers, location uncertainty, several 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 ("Fukushima") earthquake.


Effects of earthquakes

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 Wave propagation is any of the ways in which wave (physics), waves travel. Single wave propagation can be calculated by 2nd order wave equation (standing wavefield) or 1st order one-way wave equation. With respect to the direction of the oscillat ...
. 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 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 ...
motion from hard deep soils to soft superficial soils and the effects of seismic energy focalization owing to the typical geometrical setting of such 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 A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, tap water, human consumption, Industri ...
, bridges, and
nuclear power stations A nuclear power plant (NPP) is a thermal power station in which the heat source is a nuclear reactor. As is typical of thermal power stations, heat is used to generate steam that drives a steam turbine connected to a electric generator, generato ...
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

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 The 1964 Alaskan earthquake, also known as the Great Alaskan earthquake and Good Friday earthquake, occurred at 5:36 PM AKST on Good Friday Good Friday is a Christian holiday commemorating the crucifixion of Jesus and his death at Calvary. ...
, soil liquefaction caused many buildings to sink into the ground, eventually collapsing upon themselves.


Human impacts

Physical damage from an earthquake will vary depending on the intensity of shaking in a given area and they type of population. Undeserved and developing communities frequently experience more severe impacts (and longer lasting) from a seismic event compared to well developed communities. Impacts may include: * Injuries and loss of life * Damage to critical infrastructure (short and long term) ** Roads, bridges and public transportation networks ** Water, power, swear and gas interruption ** Communication systems * Loss of critical community services including hospitals, police and fire * General
property damage Property damage (or cf. criminal damage in England and Wales) is damage or destruction of Real property, real or tangible Personal property, personal property, caused by negligence, Willful violation, willful destruction, or Act of God, act of na ...
* Collapse or destabilization (potentially leading to future collapse) of buildings With these impacts and others, the aftermath may bring disease, lack of basic necessities, mental consequences such as panic attacks, depression to survivors, and higher insurance premiums. Recovery times will vary based off the level of damage along with the socioeconomic status of the impacted community.


Landslides

Earthquakes can produce slope instability leading to landslides, a major geological hazard. Landslide danger may persist while emergency personnel are attempting rescue work.


Fires

Earthquakes can cause fires by damaging
electrical power Electric power is the rate at which electrical energy is transferred by an electric circuit. The SI unit of Power (physics), power is the watt, one joule per second. Standard prefixes apply to watts as with other SI units: thousands, millions ...
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 At 05:12 Pacific Standard Time on Wednesday, April 18, 1906, the coast of Northern California was struck by a major earthquake with an estimated Moment magnitude scale, moment magnitude of 7.9 and a maximum Mercalli intensity scale, Mercalli ...
were caused by fire than by the earthquake itself.


Tsunami

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 , 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.


Floods

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 Sarez Lake (russian: Сарезское озеро; tg, Сарез кӯл, Sarez Kūl) is a lake in Rushon District of Gorno-Badakhshan province, Tajikistan. Length about , depth few hundred meters, water surface elevation about above sea l ...
in Tajikistan is in danger of catastrophic flooding if the
landslide dam A landslide dam or barrier lake is the natural dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such a ...
formed by the earthquake, known as the
Usoi Dam The Usoi Dam is a natural landslide dam along the Murghab River in Tajikistan Tajikistan (, ; tg, Тоҷикистон, Tojikiston; russian: Таджикистан, Tadzhikistan), officially the Republic of Tajikistan ( tg, Ҷумҳур ...
, were to fail during a future earthquake. Impact projections suggest the flood could affect roughly 5 million people.


Major earthquakes

One of the most devastating earthquakes in recorded history was the
1556 Shaanxi earthquake The 1556 Shaanxi earthquake (formerly romanized ''Shensi''), known in Chinese colloquially by its regnal year A regnal year is a year of the reign of a sovereign ''Sovereign'' is a title which can be applied to the highest leader in variou ...
, which occurred on 23 January 1556 in
Shaanxi Shaanxi (alternatively Shensi, see #Name, § Name) is a landlocked Provinces of China, province of China. Officially part of Northwest China, it borders the province-level divisions of Shanxi (NE, E), Henan (E), Hubei (SE), Chongqing (S), Sichu ...
, China. More than 830,000 people died. Most houses in the area were
yaodong A yaodong () or "house cave" is a particular form of earth shelter An earth shelter, also called an earth house, earth bermed house, or underground house, is a structure (usually a house) with earth (soil) against the walls, on the roof, or th ...
s—dwellings carved out of
loess Loess (, ; from german: Löss ) is a clastic rock, clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of Earth's land area is covered by loess or similar deposition (geology), deposits. ...
hillsides—and many victims were killed when these structures collapsed. The
1976 Tangshan earthquake The 1976 Tangshan earthquake () was a 7.6 earthquake that hit the region around Tangshan, Hebei, China, at 3:42 a.m. on 28 July 1976. The maximum intensity of the earthquake was XI (''Extreme'') on the Mercalli intensity scale, Mercalli sca ...
, which killed between 240,000 and 655,000 people, was the deadliest of the 20th century. The 1960 Chilean earthquake is the largest earthquake that has been measured on a seismograph, reaching 9.5 magnitude on 22 May 1960. Its epicenter was near Cañete, Chile. The energy released was approximately twice that of the next most powerful earthquake, the
Good Friday earthquake The 1964 Alaskan earthquake, also known as the Great Alaskan earthquake and Good Friday earthquake, occurred at 5:36 PM AKST on Good Friday Good Friday is a Christian holiday commemorating the crucifixion of Jesus and his death at Calvary. ...
(27 March 1964), which was centered in
Prince William Sound Prince William Sound (Sugpiaq language, Sugpiaq: ''Suungaaciq'') is a Sound (geography), sound of the Gulf of Alaska on the south coast of the U.S. state of Alaska. It is located on the east side of the Kenai Peninsula. Its largest port is Valdez ...
, Alaska. The ten largest recorded earthquakes have all been megathrust earthquakes; however, of these ten, only the
2004 Indian Ocean earthquake An earthquake and a tsunami, known as the Boxing Day Tsunami and, by the scientific community, the Sumatra–Andaman earthquake, occurred at 07:58:53 local time (UTC+07:00, UTC+7) on 26 December 2004, with an epicentre off the west coast of no ...
is simultaneously one of the deadliest earthquakes in history. 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 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 ...
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.


Prediction

Earthquake prediction Earthquake prediction is a branch of the science of seismology Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "Earthquake, earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earth ...
is a branch of the science of
seismology 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 ...
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
seismologist Seismology (; 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 per ...
s, scientifically reproducible predictions cannot yet be made to a specific day or month.Earthquake Prediction
Ruth Ludwin, U.S. Geological Survey.


Forecasting

While
forecasting Forecasting is the process of making predictions based on past and present data. Later these can be compared (resolved) against what happens. For example, a company might Estimation, estimate their revenue in the next year, then compare it against ...
is usually considered to be a type of
prediction A prediction (Latin ''præ-'', "before," and ''dicere'', "to say"), or forecasting, forecast, is a statement about a future event (probability theory), event or data. They are often, but not always, based upon experience or knowledge. There i ...
, earthquake forecasting is often differentiated from
earthquake prediction Earthquake prediction is a branch of the science of seismology Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "Earthquake, earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earth ...
. 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.


Preparedness

The objective of
earthquake engineering Earthquake engineering is an Interdisciplinarity, interdisciplinary branch of engineering that designs and analyzes structures, such as buildings and bridges, with earthquakes in mind. Its overall goal is to make such structures more resistant to ...
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 Earthquake insurance is a form of property insurance that pays the policyholder in the event of an earthquake that causes damage to the property. Most ordinary homeowners insurance policies do not cover earthquake damage. Most earthquake insuranc ...
can provide building owners with financial protection against losses resulting from earthquakes.
Emergency management Emergency management or disaster management is the managerial function charged with creating the framework within which communities reduce vulnerability to hazards and cope with disasters. Emergency management, despite its name, does not actuall ...
strategies can be employed by a government or organization to mitigate risks and prepare for consequences.
Artificial intelligence Artificial intelligence (AI) is intelligence—perceiving, synthesizing, and inferring information—demonstrated by machines, as opposed to intelligence displayed by animal cognition, animals and human intelligence, humans. Example tasks in ...
may help to assess buildings and plan precautionary operations: the Igor
expert system In artificial intelligence, an expert system is a computer system emulating the decision-making ability of a human expert. Expert systems are designed to solve complex problems by automated reasoning, reasoning through bodies of knowledge, repres ...
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 Lisbon (; pt, Lisboa ) is the capital and largest city of Portugal, with an estimated population of 544,851 within its administrative limits in an area of 100.05 km2. Grande Lisboa, Lisbon's urban area extends beyond the city's administr ...
,
Rhodes Rhodes (; el, Ρόδος , translit=Ródos ) is the largest and the historical capital of the Dodecanese islands of Greece. Administratively, the island forms a separate municipality within the Rhodes (regional unit), Rhodes regional unit, w ...
,
Naples Naples (; it, Napoli ; nap, Napule ), from grc, Νεάπολις, Neápolis, lit=new city. is the regional capital of Campania and the third-largest city of Italy, after Rome and Milan, with a population of 909,048 within the city's adminis ...
. 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 the shaking starts. For areas near large bodies of water, earthquake preparedness encompasses the possibility of a caused by a large earthquake.


Historical views

From the lifetime of the Greek philosopher
Anaxagoras Anaxagoras (; grc-gre, Ἀναξαγόρας, ''Anaxagóras'', "lord of the assembly";  500 –  428 BC) was a Pre-Socratic philosophy, Pre-Socratic Greek philosophy, Greek philosopher. Born in Clazomenae at a time when Anatolia, Asia ...
in the 5th century BCE to the 14th century CE, earthquakes were usually attributed to "air (vapors) in the cavities of the Earth."
Thales Thales of Miletus ( ; grc-gre, wikt:Θαλῆς, Θαλῆς; ) was a Greeks, Greek Greek Mathematics, mathematician, astronomer, statesman, and Pre-Socratic philosophy, pre-Socratic philosopher from Miletus in Ionia, Asia Minor. He was one of ...
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 Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman Empire, Roman author, Natural history, naturalist and Natural philosophy, natural philosopher, and naval and army commander of the early Roman Empire, and a friend of t ...
called earthquakes "underground thunderstorms".


In culture


Mythology and religion

In
Norse mythology Norse, Nordic, or Scandinavian mythology is the body of myths belonging to the North Germanic peoples, stemming from Old Norse religion and continuing after the Christianization of Scandinavia, and into the Nordic folklore of the modern period. ...
, earthquakes were explained as the violent struggling of the god
Loki Loki is a Æsir, god in Norse mythology. According to some sources, Loki is the son of Fárbauti (a jötunn) and Laufey (mentioned as a goddess), and the brother of Helblindi and Býleistr. Loki is married to Sigyn and they have two sons, Narfi ...
. When Loki,
god In monotheistic thought, God is usually viewed as the supreme being, creator, and principal object of faith. Swinburne, R.G. "God" in Honderich, Ted. (ed)''The Oxford Companion to Philosophy'', Oxford University Press, 1995. God is typicall ...
of mischief and strife, murdered
Baldr Baldr (also Balder, Baldur) is a æsir, god in Germanic mythology. In Norse mythology, Baldr (Old Norse: ) is a son of the god Odin and the goddess Frigg, and has Sons of Odin, numerous brothers, such as Thor and Váli. In wider Germanic mythol ...
, 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 A major branch of classical mythology, Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the Cosmogony, origin and Cosmology#Metaphysical co ...
,
Poseidon Poseidon (; grc-gre, wikt:Ποσειδῶν, Ποσειδῶν) was one of the Twelve Olympians in Religion in ancient Greece, ancient Greek religion and Greek mythology, myth, god of the sea, storms, earthquakes and horses.Burkert 1985pp. 1 ...
was the cause and god of earthquakes. When he was in a bad mood, he struck the ground with a
trident A trident is a three-tine (structural), pronged spear. It is used for spear fishing and historically as a polearm. The trident is the weapon of Poseidon, or Neptune (mythology), Neptune, the God of the Sea in classical mythology. The trident ma ...
, causing earthquakes and other calamities. He also used earthquakes to punish and inflict fear upon people as revenge. In
Japanese mythology Japanese mythology is a collection of traditional stories, folktales, and beliefs that emerged in the islands of the Japanese archipelago. Shinto and Buddhism, Buddhist traditions are the cornerstones of Japanese mythology. The history of thousan ...
, Namazu (鯰) is a giant
catfish Catfish (or catfishes; order (biology), order Siluriformes or Nematognathi) are a diverse group of Actinopterygii, ray-finned fish. Named for their prominent barbel (anatomy), barbels, which resemble a cat's whiskers, catfish range in size a ...
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

In modern popular culture, the portrayal of earthquakes is shaped by the memory of great cities laid waste, such as Kobe in 1995 or San Francisco in 1906. Fictional earthquakes tend to strike suddenly and without warning. For this reason, stories about earthquakes generally begin with the disaster and focus on its immediate aftermath, as in ''Short Walk to Daylight'' (1972), '' The Ragged Edge'' (1968) or '' Aftershock: Earthquake in New York'' (1999). A notable example is Heinrich von Kleist's classic novella, '' The Earthquake in Chile'', which describes the destruction of Santiago in 1647.
Haruki Murakami is a Japanese writer. His novels, essays, and short stories have been bestsellers in Japan and internationally, with his work translated into 50 languages and having sold millions of copies outside Japan. He has received numerous awards for his ...
's short fiction collection '' After the Quake'' depicts the consequences of the Kobe earthquake of 1995. 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'' (1977), ''
2012 File:2012 Events Collage V3.png, From left, clockwise: The passenger cruise ship Costa Concordia lies capsized after the Costa Concordia disaster; Damage to Casino Pier in Seaside Heights, New Jersey as a result of Hurricane Sandy; People gather ...
'' (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.


See also

* *
United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific government agency, agency of the Federal government of the United States, United States government. The scientists of the USGS study th ...
* * * * * * *
Marsquake A marsquake is a quake which, much like 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 t ...
* * * * * * Vertical displacement


References


Sources

* . * . * , NUREG/CR-1457. * Deborah R. Coen. ''The Earthquake Observers: Disaster Science From Lisbon to Richter'' (
University of Chicago Press The University of Chicago Press is the largest and one of the oldest university presses in the United States. It is operated by the University of Chicago and publishes a wide variety of academic titles, including ''The Chicago Manual of Style'', ...
; 2012) 348 pages; explores both scientific and popular coverage * . * . * . * .


Further reading

* *


External links


Earthquake Hazards Program
of the U.S. Geological Survey

– IRIS Consortium {{Authority control Geological hazards Seismology Natural disasters Lithosphere