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Earthquake

Global earthquake epicenters, 1963–1998

An earthquake is a sudden and sometimes catastrophic movement of a part of the Earth's surface. Earthquakes result from the dynamic release of elastic strain energy that radiates seismic waves. Earthquakes typically result from the movement of faults, planar zones of deformation within the Earth's upper crust. The word earthquake is also widely used to indicate the source region itself. The Earth's lithosphere is a patch work of plates in slow but constant motion (see plate tectonics). Earthquakes occur where the stress resulting from the differential motion of these plates exceeds the strength of the crust. The highest stress (and possible weakest zones) are most often found at the boundaries of the tectonic plates and hence these locations are where the majority of earthquakes occur. Events located at plate boundaries are called interplate earthquakes; the less frequent events that occur in the interior of the lithospheric plates are called intraplate earthquakes (see, for example, New Madrid Seismic Zone). Earthquakes related to plate tectonics are called tectonic earthquakes. Most earthquakes are tectonic, but they also occur in volcanic regions and as the result of a number of anthropogenic sources, such as reservoir induced seismicity, mining and the removal or injection of fluids into the crust. Seismic waves including some strong enough to be felt by humans can also be caused by explosions (chemical or nuclear), landslides, and collapse of old mine shafts, though these sources are not strictly earthquakes.

Characteristics

Large numbers of earthquakes occur on a daily basis on Earth, but the majority of them are detected only by seismometers and cause no damage .

Most earthquakes occur in narrow regions around plate boundaries down to depths of a few tens of kilometres where the crust is rigid enough to support the elastic strain. Where the crust is thicker and colder they will occur at greater depths and the opposite in areas that are hot. At subduction zones where plates descend into the mantle, earthquakes have been recorded to a depth of 600 km, although these deep earthquakes are caused by different mechanisms than the more common shallow events. Some deep earthquakes may be due to the transition of olivine to spinel, which is more stable in the deep mantle.

Large earthquakes can cause serious destruction and massive loss of life through a variety of agents of damage, including fault rupture, vibratory ground motion (i.e., shaking), inundation (e.g., tsunami, seiche, dam failure), various kinds of permanent ground failure (e.g. liquefaction, landslide), and fire or a release of hazardous materials. In a particular earthquake, any of these agents of damage can dominate, and historically each has caused major damage and great loss of life, but for most of the earthquakes shaking is the dominant and most widespread cause of damage. There are four types of seismic waves that are all generated simultaneously and can be felt on the ground. S-waves (secondary or shear waves) and the two types of surfaces waves (Love waves and Rayleigh waves) are responsible for the shaking hazard.

Damage from the 1906 San Francisco earthquake. Section of collapsed freeway after the 1989 Loma Prieta earthquake.

Most large earthquakes are accompanied by other, smaller ones, that can occur either before or after the principal quake — these are known as foreshocks or aftershocks, respectively. While almost all earthquakes have aftershocks, foreshocks are far less common occurring in only about 10% of events. The power of an earthquake is distributed over a significant area, but in the case of large earthquakes, it can spread over the entire planet. Ground motions caused by very distant earthquakes are called teleseisms. The Rayleigh waves from the Sumatra-Andaman Earthquake of 2004 caused ground motion of over 1 cm even at the seismometers that were located far from it, although this displacement was abnormally large. Using such ground motion records from around the world it is possible to identify a point from which the earthquake's seismic waves appear to originate. That point is called its "focus" or "hypocenter" and usually proves to be the point at which the fault slip was initiated. The location on the surface directly above the hypocenter is known as the "epicenter". The total size of the fault that slips, the rupture zone, can be as large as 1000 km, for the biggest earthquakes. Just as a large loudspeaker can produce a greater volume of sound than a smaller one, large faults are capable of higher magnitude earthquakes than smaller faults are.

Earthquakes that occur below sea level and have large vertical displacements can give rise to tsunamis, either as a direct result of the deformation of the sea bed due to the earthquake or as a result of submarine landslips or "slides" directly or indirectly triggered by it.

Earthquake Size

The first method of quantifying earthquakes was intensity scales. In the United States the Mercalli (or Modified Mercalli, MM) scale is commonly used, while Japan (shindo) and the EU (European Macroseismic Scale) each have their own scales. These assign a numeric value (different for each scale) to a location based on the size of the shaking experienced there. The value 6 (normally denoted "VI") in the MM scale for example is:

Everyone feels movement. People have trouble walking. Objects fall from shelves. Pictures fall off walls. Furniture moves. Plaster in walls might crack. Trees and bushes shake. Damage is slight in poorly built buildings. No structural damage.

A Shakemap recorded by the Pacific Northwest Seismograph Network that shows the instrument recorded intensity of the shaking of the Nisqually earthquake on February 28, 2001. A Community Internet Intensity Map generated by the USGS that shows the intensity felt by humans by ZIP Code of the shaking of the Nisqually earthquake on February 28, 2001.

The problem with these scales is the measurement is subjective, often based on the worst damage in an area and influenced by local effects like site conditions that make it a poor measure for the relative size of different events in different places. For some tasks related to engineering and local planning it is still useful for the very same reasons and thus still collected. If you feel an earthquake in the US you can report the effects to the USGS.

The first attempt to qualitatively define one value to describe the size of earthquakes was the magnitude scale (the name being taking from similar formed scales used on the brightness of stars). In the 1930s, a California seismologist named Charles F. Richter devised a simple numerical scale (which he called the magnitude) to describe the relative sizes of earthquakes in Southern California. This is known as the “Richter scale”, “Richter Magnitude” or “Local Magnitude” (ML). It is obtained by measuring the maximum amplitude of a recording on a Wood-Anderson torsion seismometer (or one calibrated to it) at a distance of 600km from the earthquake. Other more recent Magnitude measurements include: body wave magnitude (mb), surface wave magnitude (Ms) and duration magnitude (MD). Each of these is scaled to gives values similar to the values given by the Richter scale. However as each is also based on the measurement of one part of the seismogram they do not measure the overall power of the source and can suffer from saturation at higher magnitude values (larger events fail to produce higher magnitude values).These scales are also empirical and as such there is no physical meaning to the values. They are still useful however as they can be rapidly calculated, there are catalogues of them dating back many years and are they are familiar to the public. Seismologists now favor a measure called the seismic moment, related to the concept of moment in physics, to measure the size of a seismic source. The seismic moment is calculated from seismograms but can also by obtained from geologic estimates of the size of the fault rupture and the displacement. The values of moments for different earthquakes ranges over several order of magnitude. As a result the moment magnitude (MW) scale was introduced by Hiroo Kanamori, which is comparable to the other magnitude scales but will not saturate at higher values.

Larger earthquakes occur less frequently than smaller earthquakes, the relationship being exponential, ie roughly ten times as many earthquakes larger than 4 occur in a particular time period than earthquakes larger than magnitude 5. For example it has been calculated that the average recurrence for the United Kingdom can be described as follows:

  • an earthquake of 3.7 or larger every 1 year
  • an earthquake of 4.7 or larger every 10 years
  • an earthquake of 5.6 or larger every 100 years.

Causes

Most earthquakes are powered by the release of the elastic strain that accumulate over time, typically, at the boundaries of the plates that make up the Earth's lithosphere via a process called Elastic-rebound theory. The Earth is made up of tectonic plates driven by the heat in the Earth's mantle and core. Where these plates meet stress accumulates. Eventually when enough stress accumulates, the plates move, causing an earthquake. Deep focus earthquakes, at depths of 100's km, are possibly generated as subducted lithospheric material catastrophically undergoes a phase transition since at the pressures and temperatures present at such depth elastic strain cannot be supported. Some earthquakes are also caused by the movement of magma in volcanoes, and such quakes can be an early warning of volcanic eruptions. A rare few earthquakes have been associated with the build-up of large masses of water behind dams, such as the Kariba Dam in Zambia, Africa, and with the injection or extraction of fluids into the Earth's crust (e.g. at certain geothermal power plants and at the Rocky Mountain Arsenal). Such earthquakes occur because the strength of the Earth's crust can be modified by fluid pressure. Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Netherlands. Finally, ground shaking can also result from the detonation of explosives. Thus scientists have been able to monitor, using the tools of seismology, nuclear weapons tests performed by governments that were not disclosing information about these tests along normal channels. Earthquakes such as these, that are caused by human activity, are referred to by the term induced seismicity.

Another type of movement of the Earth is observed by terrestrial spectroscopy. These oscillations of the earth are either due to the deformation of the Earth by tide caused by the Moon or the Sun, or other phenomena.

A recently proposed theory suggests that some earthquakes may occur in a sort of earthquake storm, where one earthquake will trigger a series of earthquakes each triggered by the previous shifts on the fault lines, similar to aftershocks, but occurring years later.

Preparation for earthquakes

  • Emergency preparedness
  • Household seismic safety
  • Seismic retrofit
  • Earthquake prediction

Specific fault articles

  • Alpine Fault
  • Calaveras Fault
  • Hayward Fault Zone
  • North Anatolian Fault Zone
  • New Madrid Fault Zone
  • San Andreas Fault

Specific earthquake articles

  • Shaanxi Earthquake (1556). Deadliest known earthquake in history, estimated to have killed 830,000 in China.
  • Cascadia Earthquake (1700).
  • Kamchatka earthquakes (1737 and 1952).
  • Lisbon earthquake (1755).
  • New Madrid Earthquake (1811).
  • Fort Tejon Earthquake (1857).
  • Charleston earthquake (1886). Largest earthquake in the Southeast and killed 100.
  • San Francisco Earthquake (1906).
  • Great Kanto earthquake (1923). On the Japanese island of Honshu, killing over 140,000 in Tokyo and environs.
  • Kamchatka earthquakes (1952 and 1737).
  • Great Chilean Earthquake (1960). Biggest earthquake ever recorded, 9.5 on Moment magnitude scale.
  • Good Friday Earthquake (1964) Alaskan earthquake.
  • Ancash earthquake (1970). Caused a landslide that buried the town of Yungay, Peru; killed over 40,000 people.
  • Sylmar earthquake (1971). Caused great and unexpected destruction of freeway bridges and flyways in the San Fernando Valley, leading to the first major seismic retrofits of these types of structures, but not at a sufficient pace to avoid the next California freeway collapse in 1989.
  • Tangshan earthquake (1976). The most destructive earthquake of modern times. The official death toll was 255,000, but many experts believe that two or three times that number died.
  • Great Mexican Earthquake (1985). 8.1 on the Richter Scale, killed over 6,500 people (though it is believed as many as 30,000 may have died, due to missing people never reappearing.)
  • Whittier Narrows earthquake (1987).
  • Armenian earthquake (1988). Killed over 25,000.
  • Loma Prieta earthquake (1989). Severely affecting Santa Cruz, San Francisco and Oakland in California. Revealed necessity of accelerated seismic retrofit of road and bridge structures.
  • Northridge, California earthquake (1994). Damage showed seismic resistance deficiencies in modern low-rise apartment construction.
  • Great Hanshin earthquake (1995). Killed over 6,400 people in and around Kobe, Japan.
  • İzmit earthquake (1999) Killed over 17,000 in northwestern Turkey.
  • Düzce earthquake (1999)
  • Chi-Chi earthquake (1999).
  • Nisqually Earthquake (2001).
  • Gujarat Earthquake (2001).
  • Dudley Earthquake (2002).
  • Bam Earthquake (2003).
  • Parkfield, California earthquake (2004). Not large (6.0), but the most anticipated and intensely instrumented earthquake ever recorded and likely to offer insights into predicting future earthquakes elsewhere on similar slip-strike fault structures.
  • Chuetsu Earthquake (2004).
  • Indian Ocean Earthquake (2004). One of the largest earthquakes ever recorded at 9.0. Epicenter off the coast of the Indonesian island Sumatra. Triggered a tsunami which caused nearly 300,000 deaths spanning several countries.
  • Sumatran Earthquake (2005).
  • Fukuoka earthquake (2005).
  • Kashmir earthquake (2005). Killed over 79,000 people. Many more at risk from the Kashmiri winter.
  • Lake Tanganyika earthquake (2005).

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A recently proposed theory suggests that some earthquakes may occur in a sort of earthquake storm, where one earthquake will trigger a series of earthquakes each triggered by the previous shifts on the fault lines, similar to aftershocks, but occurring years later.
. These oscillations of the earth are either due to the deformation of the Earth by tide caused by the Moon or the Sun, or other phenomena. During the 19th century Chinese and Italian inmigrants came to the country to work on the construction of the railroad system as well. Another type of movement of the Earth is observed by terrestrial spectroscopy. The Atlantic coast, meanwhile, was populated with African slaves in the 17th and 18th centuries, altough most Caribbean Costa Ricans of African ascent descend from Jamaican workers brought in during the 19th century to work in the construction of railways connecting the urban populations of the Central Plateau to the port of Limon on the Caribbean coast. Earthquakes such as these, that are caused by human activity, are referred to by the term induced seismicity. However, the indigenous people have influenced modern Costa Rican culture to a relatively small degree, as most of the Indians died from disease and mistreatment by the Spaniards.

Thus scientists have been able to monitor, using the tools of seismology, nuclear weapons tests performed by governments that were not disclosing information about these tests along normal channels. The center and southern portions of the country had Chibcha influences. Finally, ground shaking can also result from the detonation of explosives. The northwest of the country, Nicoya, was the southernmost point of Nahuatl cultural influence when the Spanish conquerors (conquistadores) came in the 16th century. Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Netherlands. Costa Rica was the point where the Mesoamerican and South American native cultures met. Such earthquakes occur because the strength of the Earth's crust can be modified by fluid pressure. Costa Rica boasts a varied history.

at certain geothermal power plants and at the Rocky Mountain Arsenal). Their spoken accent is rather closer to certain areas of Colombia than its Central American counterparts. A rare few earthquakes have been associated with the build-up of large masses of water behind dams, such as the Kariba Dam in Zambia, Africa, and with the injection or extraction of fluids into the Earth's crust (e.g. Costa Rican traditions and culture tend to retain a strong degree of Spanish influence. Some earthquakes are also caused by the movement of magma in volcanoes, and such quakes can be an early warning of volcanic eruptions. It encapsulates the pervading ideology of living in peace in a calm, unflustered manner, appreciating a life surrounded by nature and family and friends. Deep focus earthquakes, at depths of 100's km, are possibly generated as subducted lithospheric material catastrophically undergoes a phase transition since at the pressures and temperatures present at such depth elastic strain cannot be supported. The phrase "Pura Vida" (literally pure life) is a motto ubiquitous in Costa Rica.

Eventually when enough stress accumulates, the plates move, causing an earthquake. Visitors from the United States are often referred to as gringos, which is virtually always congenial in nature. Where these plates meet stress accumulates. The tico ideal is that of a very friendly, helpful, laid back, unhurried, educated and environmentally aware people, with little worry for deadlines or the "normal" stresses of United States life. The Earth is made up of tectonic plates driven by the heat in the Earth's mantle and core. 'momentico' instead of 'momentito'). Most earthquakes are powered by the release of the elastic strain that accumulate over time, typically, at the boundaries of the plates that make up the Earth's lithosphere via a process called Elastic-rebound theory. "Tico" comes from the locally popular usage of "tico" diminutive suffixes (eg.

For example it has been calculated that the average recurrence for the United Kingdom can be described as follows:. The locals refer to themselves as tico, maje or mae (sort of "man", actually maje means "dumb") idiom in a very popular and "only with close friends" way, or tica (female). Larger earthquakes occur less frequently than smaller earthquakes, the relationship being exponential, ie roughly ten times as many earthquakes larger than 4 occur in a particular time period than earthquakes larger than magnitude 5.
. As a result the moment magnitude (MW) scale was introduced by Hiroo Kanamori, which is comparable to the other magnitude scales but will not saturate at higher values. [4] In addition there are many Americans who either come to retire or move to the country to live. The values of moments for different earthquakes ranges over several order of magnitude. Another one percent is ethnically Chinese.

The seismic moment is calculated from seismograms but can also by obtained from geologic estimates of the size of the fault rupture and the displacement. Altogether, Costa Ricans of mestizo and European descent account for a combined 94 percent (the vast majority being of Spanish decent). Seismologists now favor a measure called the seismic moment, related to the concept of moment in physics, to measure the size of a seismic source. Descendants of black 19th-century Jamaican immigrant workers constitute an English-speaking minority and at three percent of the population number about 96,000. They are still useful however as they can be rapidly calculated, there are catalogues of them dating back many years and are they are familiar to the public. In Guanacaste Province, most of the population descends from a mix of the Chorotega Indians, Bantu Africans and Spaniards. However as each is also based on the measurement of one part of the seismogram they do not measure the overall power of the source and can suffer from saturation at higher magnitude values (larger events fail to produce higher magnitude values).These scales are also empirical and as such there is no physical meaning to the values. The pure indigenous population today numbers about 29,000, less than one percent of the population.

Each of these is scaled to gives values similar to the values given by the Richter scale. Costa Rica has a population of 4,016,173 persons (July 2005 est.) In the central part of the country, most people are of European descent but some are also mestizos (to varying degrees).[3] Because of little intermarriage, most of the population today retain European complexions. Other more recent Magnitude measurements include: body wave magnitude (mb), surface wave magnitude (Ms) and duration magnitude (MD).
. It is obtained by measuring the maximum amplitude of a recording on a Wood-Anderson torsion seismometer (or one calibrated to it) at a distance of 600km from the earthquake.
. This is known as the “Richter scale”, “Richter Magnitude” or “Local Magnitude” (ML). Also see:.

Richter devised a simple numerical scale (which he called the magnitude) to describe the relative sizes of earthquakes in Southern California. The entity entrusted to do genetic and biochemical prospection on Costa Rica's biological wealth is the INBIO (Instituto Nacional de Biodiversidad), and it is allowed to collect royalties on any biological discoveries of medical importance. In the 1930s, a California seismologist named Charles F. Costa Rica as a whole has about 850 species of birds. The first attempt to qualitatively define one value to describe the size of earthquakes was the magnitude scale (the name being taking from similar formed scales used on the brightness of stars). Over 400 types of bird can be found here, as well as over 100 species of mammal. If you feel an earthquake in the US you can report the effects to the USGS. The Monteverde Cloud Forest Reserve hosts 2,000 plant species including numerous orchids.

For some tasks related to engineering and local planning it is still useful for the very same reasons and thus still collected. Giant leatherback, hawksbill, and loggerhead turtles also nest here. The problem with these scales is the measurement is subjective, often based on the worst damage in an area and influenced by local effects like site conditions that make it a poor measure for the relative size of different events in different places. is considered the most important nesting site for this specie. No structural damage. Tortuguero National Park (the name Tortuguero can be translated as turtle catcher or turtle hunter) is home to spider, howler and White-throated Capuchin monkeys, the Three-toed sloth, 320 species of birds (including eight species of parrots), a variety of reptiles, but is mostly recognized for the annual nesting of the endangered green turtle. Damage is slight in poorly built buildings. One national park that is internationally renowned among ecologists for its biodiversity (including big cats and tapirs) and where visitors can expect to see an abundance of wildlife is the Corcovado National Park.

Trees and bushes shake. Over 25% of Costa Rica is composed of protected forests and reserves. Plaster in walls might crack. Costa Rica has no military or navy, but an abundance of wildlife; it has been said that the soldiers are the leaf cutter ants, the pilots are the macaws and the navy ships are the whales. Furniture moves. While the country has only about 0.1% of the world's land mass, it contains 5% of the world's biodiversity. Pictures fall off walls. Costa Rica is home to a rich variety of plants and animals.

Objects fall from shelves. For instance, during the Cold War Costa Rica was the first Central American country to have diplomatic ties with the Soviet Union as a way to boost its coffee exports, to the dismay of the Nixon administration. People have trouble walking. Nevertheless, economic pragmatism may prevail over ideology. Everyone feels movement. Costa Rica's main foreign policy objective is to foster human rights and sustainable development as a way to secure stability and growth. The value 6 (normally denoted "VI") in the MM scale for example is:. Costa Rica is currently a member of the Cairns Group, an alliance of countries opposed to agricultural subsidies in the first world.

These assign a numeric value (different for each scale) to a location based on the size of the shaking experienced there. Costa Rica has no embassy in Cuba, but does have an embassy in Israel, and has diplomatic relations with the Republic of China in Taiwan, not the People's Republic of China. In the United States the Mercalli (or Modified Mercalli, MM) scale is commonly used, while Japan (shindo) and the EU (European Macroseismic Scale) each have their own scales. instead set up such a center in El Salvador, a country alleged to have a tradition of human rights equivocacy. The first method of quantifying earthquakes was intensity scales. The U.S. Earthquakes that occur below sea level and have large vertical displacements can give rise to tsunamis, either as a direct result of the deformation of the sea bed due to the earthquake or as a result of submarine landslips or "slides" directly or indirectly triggered by it. offers to set up a security training center in the country on the grounds that a country with no army could not harbor a center with possible military purposes.

Just as a large loudspeaker can produce a greater volume of sound than a smaller one, large faults are capable of higher magnitude earthquakes than smaller faults are. Costa Rica is a member of the International Criminal Court and rejected U.S. The total size of the fault that slips, the rupture zone, can be as large as 1000 km, for the biggest earthquakes. While Costa Rica is not expected to join the tide of new left-leaning governments in Latin America its foreign policy does not always line up with the interests of the USA. The location on the surface directly above the hypocenter is known as the "epicenter". dollar; currently about 600 to the euro. That point is called its "focus" or "hypocenter" and usually proves to be the point at which the fault slip was initiated. The unit of currency is the colón (CRC), which trades around 500 to the U.S.

Using such ground motion records from around the world it is possible to identify a point from which the earthquake's seismic waves appear to originate. Economic growth stood at 4.2%, nevertheless the country faced high inflation (14%) and a trade deficit of 5.2%. The Rayleigh waves from the Sumatra-Andaman Earthquake of 2004 caused ground motion of over 1 cm even at the seismometers that were located far from it, although this displacement was abnormally large. For the fiscal year 2005 the country showed a government deficit of 2.1%, internal revenue increased an 18%, exports increased a 12.8% and the number of visiting tourists increased a 19%, reaching 1.5 million people. Ground motions caused by very distant earthquakes are called teleseisms. Trade with South East Asia and Russia has boomed during 2004 and 2005, and the country is expected to obtain full Asia-Pacific Economic Cooperation Forum (APEC) membership by 2007 (the country became an observer in 2004). The power of an earthquake is distributed over a significant area, but in the case of large earthquakes, it can spread over the entire planet. Several global high tech corporations have already started developing in the area exporting goods including chip manufacturer Intel and pharmaceutical companies such as Procter & Gamble and Glaxo Smith Kline.

While almost all earthquakes have aftershocks, foreshocks are far less common occurring in only about 10% of events. Relatively high levels of education among its residents make the country an attractive investing location. Most large earthquakes are accompanied by other, smaller ones, that can occur either before or after the principal quake — these are known as foreshocks or aftershocks, respectively. The central government offers tax exemptions for those who are willing to invest in the country. S-waves (secondary or shear waves) and the two types of surfaces waves (Love waves and Rayleigh waves) are responsible for the shaking hazard. The economy has been expanding for Costa Rica in part because the Government had implemented a seven year plan of expansion in the high tech industry. There are four types of seismic waves that are all generated simultaneously and can be felt on the ground. Costa Rica's location in the Central American isthmus provides easy access to American markets as it has the same time zone as the central part of the United States and direct ocean access to Europe and Asia.

In a particular earthquake, any of these agents of damage can dominate, and historically each has caused major damage and great loss of life, but for most of the earthquakes shaking is the dominant and most widespread cause of damage. Costa Rica's economy is mostly based on agriculture (coffee, bananas, pineapples, ornamentals), but in recent times ecotourism, electronics, financial outsourcing and software develoment are rapidly expanding sources of business. liquefaction, landslide), and fire or a release of hazardous materials. Costa Rica consists of seven provinces:. Large earthquakes can cause serious destruction and massive loss of life through a variety of agents of damage, including fault rupture, vibratory ground motion (i.e., shaking), inundation (e.g., tsunami, seiche, dam failure), various kinds of permanent ground failure (e.g. See also: Military of Costa Rica. Some deep earthquakes may be due to the transition of olivine to spinel, which is more stable in the deep mantle. Costa Rica has no military by constitution but maintains domestic Police and armed National Guard forces for internal security.

At subduction zones where plates descend into the mantle, earthquakes have been recorded to a depth of 600 km, although these deep earthquakes are caused by different mechanisms than the more common shallow events. Autonomous state agencies enjoy considerable operational independence; they include the telecommunications and electrical power monopoly, the nationalized commercial banks, the state insurance monopoly, and the social security agency. Where the crust is thicker and colder they will occur at greater depths and the opposite in areas that are hot. There are no provincial legislatures. Most earthquakes occur in narrow regions around plate boundaries down to depths of a few tens of kilometres where the crust is rigid enough to support the elastic strain. Governors appointed by the president head the country's seven provinces, but they exercise little power. Large numbers of earthquakes occur on a daily basis on Earth, but the majority of them are detected only by seismometers and cause no damage . Costa Rica uses a form of proportional representation to elect its national legislative body.

. Arias is promoter of free trade and supports the free trade agreement with the United States which is the source of a great controversy that might develop in protests around the country in the upcoming months. Seismic waves including some strong enough to be felt by humans can also be caused by explosions (chemical or nuclear), landslides, and collapse of old mine shafts, though these sources are not strictly earthquakes. In April 2003 the prohibition was officially recognized, in a highly polemic resolution, as anti-constitutional allowing Óscar Arias (Nobel Peace Prize, 1987) to run for President a second time in the upcoming 2006 elections. Most earthquakes are tectonic, but they also occur in volcanic regions and as the result of a number of anthropogenic sources, such as reservoir induced seismicity, mining and the removal or injection of fluids into the crust. An amendment to the constitution to allow second presidential terms was proposed and also the constitutionality of the prohibition against a second presidential term has been challenged in the courts. Earthquakes related to plate tectonics are called tectonic earthquakes. A constitutional amendment approved in 1969 limited presidents and deputies to one term, although a deputy may run again for an Assembly seat after sitting out a term.

Events located at plate boundaries are called interplate earthquakes; the less frequent events that occur in the interior of the lithospheric plates are called intraplate earthquakes (see, for example, New Madrid Seismic Zone). The president and 57 Legislative Assembly deputies are elected for 4-year terms. The highest stress (and possible weakest zones) are most often found at the boundaries of the tectonic plates and hence these locations are where the majority of earthquakes occur. There also are two vice presidents and a 15-member cabinet that includes one of the vice presidents. Earthquakes occur where the stress resulting from the differential motion of these plates exceeds the strength of the crust. Executive responsibilities are vested in a president, who is the country's center of power. The Earth's lithosphere is a patch work of plates in slow but constant motion (see plate tectonics). It is seen as one of the most stable countries in Latin America.

The word earthquake is also widely used to indicate the source region itself. Costa Rica is a democratic republic with a strong constitution. Earthquakes typically result from the movement of faults, planar zones of deformation within the Earth's upper crust. Costa Rica protects over 25% of its national territory within national parks. Earthquakes result from the dynamic release of elastic strain energy that radiates seismic waves. The country is highly recognized and praised for its national park system: a developed and progressive system which stresses ecotourism. An earthquake is a sudden and sometimes catastrophic movement of a part of the Earth's surface. The largest lake in Costa Rica is Lake Arenal.

Lake Tanganyika earthquake (2005). Cocos Island stands out because of its distance from continental landmass (24 km² [9.25 mi²], 500 km [310 mi] from Puntarenas coast), but Calero Island is the biggest island of the country (151.6 km² [58.5 mi²]). Many more at risk from the Kashmiri winter. Costa Rica also comprises several islands. Killed over 79,000 people. The highest volcano in the country is the Irazú Volcano (3,431 m or 11,257 feet). Kashmir earthquake (2005). The highest point in the country is Cerro Chirripo, with 3,810 metres (12,500 ft), the second highest peak in Central America, after Volcan Tajumulco in Guatemala.

Fukuoka earthquake (2005). state of West Virginia and about half the size of Ireland. Sumatran Earthquake (2005). In total, Costa Rica comprises 51,100 km² (19,730 mi²), of which 50,610 km² (19,540 mi²) is land and 440 km² (170 mi²) is water, making it slightly smaller than the U.S. Triggered a tsunami which caused nearly 300,000 deaths spanning several countries. Costa Rica also borders Nicaragua to the north (309 km [192 mi] of border) and Panama to the south-southeast (639 km [397 mi] of border). Epicenter off the coast of the Indonesian island Sumatra. It borders both the Caribbean Sea (to the east) and the North Pacific Ocean (to the west), with a total of 1,290 km (802 mi) of coastline (212km [132 mi] on the Caribbean coast and 1,016 km [631 mi] on the Pacific).

One of the largest earthquakes ever recorded at 9.0. Costa Rica is located on the Central American isthmus, 10° North of the equator and 84° West of the Prime Meridian. Indian Ocean Earthquake (2004). Land ownership is widespread and Electronics is a rapidly expanding industry. Chuetsu Earthquake (2004). Costa Rica (Spanish for "Rich Coast"), although still a largely agricultural country, has achieved a relatively high standard of living. Not large (6.0), but the most anticipated and intensely instrumented earthquake ever recorded and likely to offer insights into predicting future earthquakes elsewhere on similar slip-strike fault structures. In 1949, José Figueres Ferrer abolished the army; and since then Costa Rica has been one of the few countries to operate within the democratic system without the assistance of a military.

Parkfield, California earthquake (2004). Since the late 19th century only two brief periods of violence have marred its democratic development. Bam Earthquake (2003). Costa Rica has avoided the violence that has plagued Central America; it is seen as an example of political stability in the region, and is referred to as the "Switzerland of the Americas". Dudley Earthquake (2002). From the 1840s on, Costa Rica was an independent nation. Gujarat Earthquake (2001). In 1824, the capital moved to San José.

Nisqually Earthquake (2001). After briefly joining the Mexican Empire of Agustín de Iturbide (see: History of Mexico and Mexican Empire), Costa Rica became a state in the United Provinces of Central America (see: History of Central America) from 1823 to 1839. Chi-Chi earthquake (1999). The provincial capital was in Cartago. Düzce earthquake (1999). Costa Rica was then the southernmost province in the Spanish territory of New Spain. İzmit earthquake (1999) Killed over 17,000 in northwestern Turkey. The native people of the Mayans and Aztecs were conquered by Spain in the 16th century.

Killed over 6,400 people in and around Kobe, Japan. These groups are also believed to have created the Stone spheres of Costa Rica, between 200 BC and AD 1600. Great Hanshin earthquake (1995). This has recently been redefined to include the Isthmo-Colombian area, defined by the presence of groups that spoke Chibchan languages. Damage showed seismic resistance deficiencies in modern low-rise apartment construction. In Pre-Columbian times the Native Americans in what is now Costa Rica were part of the Intermediate Area located between the Mesoamerican and Andean cultural regions. Northridge, California earthquake (1994). .

Revealed necessity of accelerated seismic retrofit of road and bridge structures. Costa Rica was the first country in the world to constitutionally abolish its army. Severely affecting Santa Cruz, San Francisco and Oakland in California. The Republic of Costa Rica is a country in Central America, bordered by Nicaragua to the north, Panama to the south-southeast, the Pacific Ocean to the west and south, and the Caribbean Sea to the east. Loma Prieta earthquake (1989).
September 15, 1821. Killed over 25,000.
 - Date.

Armenian earthquake (1988). Debi Nova, singer. Whittier Narrows earthquake (1987). Maribel Guardia, singer, actress, model. 8.1 on the Richter Scale, killed over 6,500 people (though it is believed as many as 30,000 may have died, due to missing people never reappearing.). Chavela Vargas, singer. Great Mexican Earthquake (1985). National hero.

The official death toll was 255,000, but many experts believe that two or three times that number died. Juan Santamaría. The most destructive earthquake of modern times. Olympic gold medallist. Tangshan earthquake (1976). Claudia Poll. Caused great and unexpected destruction of freeway bridges and flyways in the San Fernando Valley, leading to the first major seismic retrofits of these types of structures, but not at a sufficient pace to avoid the next California freeway collapse in 1989. Clodomiro Picado Twight, Toxicologist.

Sylmar earthquake (1971). Franklin Chang Díaz, Astronaut. Caused a landslide that buried the town of Yungay, Peru; killed over 40,000 people. José Figueres Ferrer, National caudillo and President of the Republic (1948–1949, 1953–1958, and 1970–1974. Ancash earthquake (1970). Óscar Arias Sánchez, Nobel Peace Prize winner (1987) and President of the Republic (1986–1990). Good Friday Earthquake (1964) Alaskan earthquake. Instituto Nacional de Biodiversidad [2].

Biggest earthquake ever recorded, 9.5 on Moment magnitude scale. List of birds of Costa Rica. Great Chilean Earthquake (1960). Wildlife of Costa Rica. Kamchatka earthquakes (1952 and 1737). San José (Capital)(political and economical center of Costa Rica, see image below). On the Japanese island of Honshu, killing over 140,000 in Tokyo and environs. Puntarenas (along most of the Pacific coast, with a large bulge in the south-west and a smaller one at the northern end at both sides of the Golfo de Nicoya, where the homonymous capital is located).

Great Kanto earthquake (1923). Limón (caribbean coast, agricultural and eco-tourism area). San Francisco Earthquake (1906). Heredia (central; north of capital, manufacturing and core of Costa Rica's IT industry). Largest earthquake in the Southeast and killed 100. Guanacaste (north-west, important touristic and agricultural area). Charleston earthquake (1886). Cartago (former Costa Rican Provicial capital during colonial times).

Fort Tejon Earthquake (1857). Alajuela (central; north of capital San José, agriculture and industrial manufacturing). New Madrid Earthquake (1811). Lisbon earthquake (1755). Kamchatka earthquakes (1737 and 1952).

Cascadia Earthquake (1700). Deadliest known earthquake in history, estimated to have killed 830,000 in China. Shaanxi Earthquake (1556). San Andreas Fault.

New Madrid Fault Zone. North Anatolian Fault Zone. Hayward Fault Zone. Calaveras Fault.

Alpine Fault. Earthquake prediction. Seismic retrofit. Household seismic safety.

Emergency preparedness. an earthquake of 5.6 or larger every 100 years. an earthquake of 4.7 or larger every 10 years. an earthquake of 3.7 or larger every 1 year.

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