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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).

This page about Earthquakes includes information from a Wikipedia article.
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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. They are also issued to inform repair shops how to repair paint damaged by acid rain, etc. 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. The Ford GT TSBs show that some cars may need hose clamps adjusted or replaced, and a few other tiny problems. Another type of movement of the Earth is observed by terrestrial spectroscopy. TSBs are Technical Service Bulletins that help eliminate problems that some cars may have. Earthquakes such as these, that are caused by human activity, are referred to by the term induced seismicity. There are a few other TSBs for the car.

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. Some journalists felt that this was an improper fix for an expensive supercar and criticized Ford for not either replacing the defective crankshaft or replacing the entire engine. Finally, ground shaking can also result from the detonation of explosives. Ford dealers stopped the leak with a new main seal and a "Speedi-Sleeve" around the crankshaft, a device commonly used to repair worn engines in older cars. Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Netherlands. The finish of some crankshafts was flawed, causing an oil leak. Such earthquakes occur because the strength of the Earth's crust can be modified by fluid pressure. There was also a TSB (Technical Service Bulletin) to inspect the engine on early cars built in 2004 for an oil leak at the main seal.

at certain geothermal power plants and at the Rocky Mountain Arsenal). A similar problem was found in 1990 on the Ferrari F40.[3]. 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. But after Ford discovered a crack in one of the high-mileage development cars, the company decided to replace the parts on all the production cars. Some earthquakes are also caused by the movement of magma in volcanoes, and such quakes can be an early warning of volcanic eruptions. They had been "squash cast" for added strength, a new process also used by Porsche and Alfa Romeo. 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. In December of 2004, Ford recalled all Ford GTs that had been built up to that point (448 units were built, but only 283 had been shipped to dealers, and only 106 had been delivered to retail customers) because of concerns regarding the strength of the suspension control arms.

Eventually when enough stress accumulates, the plates move, causing an earthquake. Early production Ford GT experienced a few minor problems (including glitches with the electrical and climate control systems, leaking power steering and engine coolant hoses, and a steering column rattle on some cars), and two bigger problems. Where these plates meet stress accumulates. The production run of the GT will end with the 2006 model year in September, and the Wixom Assembly plant, where the GT is assembled, is scheduled for closing in 2007 [2]. The Earth is made up of tectonic plates driven by the heat in the Earth's mantle and core. Recognizing the ongoing demand for the car, Ford raised the base sticker by $10,000 to $149,995 in late 2005. 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. By June 2005 prices had dropped to $10,000 to $20,000 over MSRP, and in August 2005 several new GTs had sold on eBay for MSRP.

For example it has been calculated that the average recurrence for the United Kingdom can be described as follows:. Independent sources [1] then began gathering and analysing public information on production, sales, and selling prices, and posted that information as a resource for buyers and sellers. 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 with many highly desirable new vehicles, when the Ford GT was first released demand outpaced supply, and the cars initially sold for premium prices, with the first selling for over $500,000 to a retired Microsoft executive at a charity auction and later cars selling for up to $100,000 or more over the suggested retail price ($140,000 - $157,000 depending on options). 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. With production ending, it is unlikely that the full 4500 will be produced. The values of moments for different earthquakes ranges over several order of magnitude. Of the 4,500 GTs produced, only 101 will be exported to Europe, starting in late 2005, and 200 are destined for Canada.

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. Installation of the engine, transmission, and interior is handled by Ford's Wixom, Michigan plant.
. 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 GT is built and painted by Saleen in a small, 180,000 ft² (17,000 m²) factory in Troy, Michigan. 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. The first customers took delivery in September 2004. 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. Full production began in spring 2004, with a projected annual volume of 1500 cars for three years.

Each of these is scaled to gives values similar to the values given by the Richter scale. . Other more recent Magnitude measurements include: body wave magnitude (mb), surface wave magnitude (Ms) and duration magnitude (MD). Top speed is over 200 mph (322 km/h). 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. The powerplant is a mid-mounted supercharged 5.4 liter V8, producing 550 horsepower (410 kW) and 500 foot-pounds (678 Nm) of torque. This is known as the “Richter scale”, “Richter Magnitude” or “Local Magnitude” (ML). It is a very high-performance, two-seater vehicle with a strong styling resemblance to its racing ancestor and performance to match.

Richter devised a simple numerical scale (which he called the magnitude) to describe the relative sizes of earthquakes in Southern California. Positive response on the auto show circuit in 2002 helped persuade the company to produce the car in limited quantities, and the first production versions appeared in 2003. In the 1930s, a California seismologist named Charles F. The designers drew inspiration from Ford's classic GT40 race cars of the 1960s. 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). Camillo Pardo the head of Ford's "Living Legends" studio is credited as the chief designer of the GT and worked under the guidance of Jay Mays. If you feel an earthquake in the US you can report the effects to the USGS. The Ford GT began as a concept car designed in anticipation of Ford's centennial year and as part of its drive to showcase and revive its "heritage" names such as Mustang and Thunderbird.

For some tasks related to engineering and local planning it is still useful for the very same reasons and thus still collected. URL accessed on February 9, 2006.. 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. FordGTPrices.com. No structural damage. Unofficial Ford GT selling prices. Damage is slight in poorly built buildings. This will mark the first time that an American car has been sponsored in the JGTC (First time that a Ford GT is used in a racing format?).

Trees and bushes shake. A Ford GT will participate in the GT300 class of the JGTC in 2006. Plaster in walls might crack. Rumor has it that one of those nine has been sold to a local dealer and subsequently sold to a private party. Furniture moves. The first nine GT's were reserved for internal use and appear to be owned by the Ford family. Pictures fall off walls. Jay Leno purchased the second publicly available Ford GT (chassis number 12, red with white stripes) for exactly list price.

Objects fall from shelves. Jon Shirley, a retired executive from Microsoft, purchased the first publicly available Ford GT (chassis number 11, white with black stripes) in 2003 for $557,500 in a charity auction hosted by Jay Leno. People have trouble walking. Also in Season 7, the Top Gear Awards awarded it the "Gas Guzzler" award, beating out the Range Rover (8MPG), the Bugatti Veyron (4MPG), and the Hemel Hempstead Hertfordshire Oil Storage Terminal fire (60 Million gallons and never moved an inch). Everyone feels movement. The car was then involved in a Season 7 episode of Top Gear where it (plus a Pagani Zonda and a Ferrari F430) caused a major traffic jam in Paris as it tried to get out of a parking garage but ended up barely scraping the pavement due to height issues. The value 6 (normally denoted "VI") in the MM scale for example is:. When reviewing the GT, Clarkson compared it to the Ford GT40: he barely fit into the GT, while a portion of his head laid outside of the GT40 when the doors closed.

    .

    These assign a numeric value (different for each scale) to a location based on the size of the shaking experienced there. Twice. 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. However, he subsequently bought the car back. The first method of quantifying earthquakes was intensity scales. However, as documented on Top Gear, his GT was delivered late, and ongoing problems with its anti-theft alarm led him to return it to Ford in June 2005. 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. Jeremy Clarkson was one of the first 28 GT owners in the UK.

    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. An obvious clone of the GT also appears in GTA: San Andreas, under the name "Bullet". The total size of the fault that slips, the rupture zone, can be as large as 1000 km, for the biggest earthquakes. A heavily modified racing version appears both on the cover, and the FMV Intro. The location on the surface directly above the hypocenter is known as the "epicenter". Gran Turismo 4 uses a GT as its display car for the game. That point is called its "focus" or "hypocenter" and usually proves to be the point at which the fault slip was initiated.

    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. 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. Ground motions caused by very distant earthquakes are called teleseisms. 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.

    While almost all earthquakes have aftershocks, foreshocks are far less common occurring in only about 10% of events. 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. S-waves (secondary or shear waves) and the two types of surfaces waves (Love waves and Rayleigh waves) are responsible for the shaking hazard. There are four types of seismic waves that are all generated simultaneously and can be felt on the ground.

    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. liquefaction, landslide), and fire or a release of hazardous materials. 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. Some deep earthquakes may be due to the transition of olivine to spinel, which is more stable in the deep mantle.

    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. Where the crust is thicker and colder they will occur at greater depths and the opposite in areas that are hot. 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. 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 .

    . 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. 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. Earthquakes related to plate tectonics are called tectonic earthquakes.

    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 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. Earthquakes occur where the stress resulting from the differential motion of these plates exceeds the strength of the crust. The Earth's lithosphere is a patch work of plates in slow but constant motion (see plate tectonics).

    The word earthquake is also widely used to indicate the source region itself. Earthquakes typically result from the movement of faults, planar zones of deformation within the Earth's upper crust. Earthquakes result from the dynamic release of elastic strain energy that radiates seismic waves. An earthquake is a sudden and sometimes catastrophic movement of a part of the Earth's surface.

    Lake Tanganyika earthquake (2005). Many more at risk from the Kashmiri winter. Killed over 79,000 people. Kashmir earthquake (2005).

    Fukuoka earthquake (2005). Sumatran Earthquake (2005). Triggered a tsunami which caused nearly 300,000 deaths spanning several countries. Epicenter off the coast of the Indonesian island Sumatra.

    One of the largest earthquakes ever recorded at 9.0. Indian Ocean Earthquake (2004). Chuetsu 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.

    Parkfield, California earthquake (2004). Bam Earthquake (2003). Dudley Earthquake (2002). Gujarat Earthquake (2001).

    Nisqually Earthquake (2001). Chi-Chi earthquake (1999). Düzce earthquake (1999). İzmit earthquake (1999) Killed over 17,000 in northwestern Turkey.

    Killed over 6,400 people in and around Kobe, Japan. Great Hanshin earthquake (1995). Damage showed seismic resistance deficiencies in modern low-rise apartment construction. Northridge, California earthquake (1994).

    Revealed necessity of accelerated seismic retrofit of road and bridge structures. Severely affecting Santa Cruz, San Francisco and Oakland in California. Loma Prieta earthquake (1989). Killed over 25,000.

    Armenian earthquake (1988). Whittier Narrows earthquake (1987). 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.). Great Mexican Earthquake (1985).

    The official death toll was 255,000, but many experts believe that two or three times that number died. The most destructive earthquake of modern times. Tangshan earthquake (1976). 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.

    Sylmar earthquake (1971). Caused a landslide that buried the town of Yungay, Peru; killed over 40,000 people. Ancash earthquake (1970). Good Friday Earthquake (1964) Alaskan earthquake.

    Biggest earthquake ever recorded, 9.5 on Moment magnitude scale. Great Chilean Earthquake (1960). Kamchatka earthquakes (1952 and 1737). On the Japanese island of Honshu, killing over 140,000 in Tokyo and environs.

    Great Kanto earthquake (1923). San Francisco Earthquake (1906). Largest earthquake in the Southeast and killed 100. Charleston earthquake (1886).

    Fort Tejon Earthquake (1857). 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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