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 earthquake includes information from a Wikipedia article.
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. This has led to a number of allegations:. 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. It is worth noting that the USDA is responsible for promoting agricultural commerce, rather than the health of American citizens. 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. It is alleged that the research leading to the construction of the food guide pyramid was partially funded by the meat, dairy, sugar and grain industries, or that the pyramid reflects lobbying by these industries.
Another type of movement of the Earth is observed by terrestrial spectroscopy. Therefore it is thought that there might be a fundamental flaw in the guidance as implemented by public agencies such as schools, etc.

Earthquakes such as these, that are caused by human activity, are referred to by the term induced seismicity. The worldwide problem of obesity is increasing in the developed world as well as in developing countries. 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. In general terms the food guide pyramid recommends the following intake of different food groups each day, although exact amounts of calorie intake depends on sex, age, and lifestyle:. Finally, ground shaking can also result from the detonation of explosives. On April 19, 2005, the USDA released the food guide pyramid's successor, MyPyramid. Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Netherlands. The food guide pyramid replaced the four food groups.

Such earthquakes occur because the strength of the Earth's crust can be modified by fluid pressure. Released in 1992, it suggested how much of each food category one should eat each day. at certain geothermal power plants and at the Rocky Mountain Arsenal). One issue that this pyramid had was that it was seen as too rigid; the new pyramid relects the idea that a diet should be shaped according to an individual's needs, and the old pyramid did not do this. 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. This initial pyramid became famous throughout the world, and was, in some way, an American icon. Some earthquakes are also caused by the movement of magma in volcanoes, and such quakes can be an early warning of volcanic eruptions. The original food guiding pyramid, informally known as the food pyramid, was a nutrition guide created by the USDA.

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. HSPH. Eventually when enough stress accumulates, the plates move, causing an earthquake. They include calcium and multi-vitamin supplements as well as moderate amounts of alcohol. Where these plates meet stress accumulates. Harvard claims to have a more neutral view and provides some dry-to-read information about a more sensible pyramid. The Earth is made up of tectonic plates driven by the heat in the Earth's mantle and core.
Newest Innovations.

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. These websites are mainly: MyPyramid.gov and MyPyramid Tracker. For example it has been calculated that the average recurrence for the United Kingdom can be described as follows:. In 2005, the United States Department of Agriculture (USDA) released a completely new pyramid on its websites, featuring the newest technology, like individualized plans and statistical tools on their interactive system. 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. At that same time, some oils are now seen as essential parts of the diet, but the difference is not reflected in the pyramid (see essential fatty acid).

The values of moments for different earthquakes ranges over several order of magnitude. Many people claim that sweets and most oils and fats are entirely unnecessary and have no place in the pyramid. 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. These foods are placed in the largest box in the pyramid. 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. Others feel that high-glycemic carbohydrate foods such as potatoes, pasta and grains receive too much emphasis. 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. This has caused some nutritionists to suggest following a vegan diet, or at least a diet with reduced quantities of meat and dairy produce.

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. Some feel that this biased the research towards including higher amounts of meat and dairy produce in the food pyramid than are actually healthy, and that modern nutritional research suggests that the amounts of meat and dairy produce suggested is too high. Each of these is scaled to gives values similar to the values given by the Richter scale. This foods needs to be eaten once or twice, or as said—sparingly. Other more recent Magnitude measurements include: body wave magnitude (mb), surface wave magnitude (Ms) and duration magnitude (MD). The top of the pyramid (sweets, fats, and oils, to be used sparingly) contains foods that are very high in energy (fats and oils) or release their energy very quickly (sweets). 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. Nuts and beans are high in fiber, but nuts also have a high fat content.

This is known as the “Richter scale”, “Richter Magnitude” or “Local Magnitude” (ML). Dairy products are high in calcium. Richter devised a simple numerical scale (which he called the magnitude) to describe the relative sizes of earthquakes in Southern California. They also provide energy and some vitamins. In the 1930s, a California seismologist named Charles F. The third layer (animal products, nuts, and beans) contains high-protein foods. 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). The second layer (fruit and vegetables) contains food that are high in vitamins and fiber, also providing some energy.

If you feel an earthquake in the US you can report the effects to the USGS. It may also contribute significant quantities of vitamins and fiber, especially if whole grains are used. For some tasks related to engineering and local planning it is still useful for the very same reasons and thus still collected. The largest, bottom layer (grains) provides mainly energy (calories or joules) in the form of complex carbohydrates. 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. sparing use of fats, oils, and sweets; or can be 2-4 times in two months. No structural damage. 2-3 servings of dairy products including cheese and yogurt every other day;.

Damage is slight in poorly built buildings. 2-3 servings of meat, fish, eggs, nuts, or beans a day;. Trees and bushes shake. 2-4 servings of fruits a day;. Plaster in walls might crack. 3-5 servings a day of vegetables, especially green, leafy vegetables;. Furniture moves. 6-11 servings a day of grain foods including rice, bread, cereals, and pasta;.

Pictures fall off walls. Introductory Video. Objects fall from shelves. See graphical statistics over time and improve your nutrition. People have trouble walking. mypyramidtracker.gov tracker: Track what you eat. Everyone feels movement. The extensive Literature.

The value 6 (normally denoted "VI") in the MM scale for example is:. It includes a new symbol: "Physical Activity" (The person on the stairs). These assign a numeric value (different for each scale) to a location based on the size of the shaking experienced there. Measuring quantities in cups instead of serving size. 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. The first method of quantifying earthquakes was intensity scales.

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. 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. The total size of the fault that slips, the rupture zone, can be as large as 1000 km, for the biggest earthquakes. The location on the surface directly above the hypocenter is known as the "epicenter".

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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