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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. The number of contiguous configurations for one through seven blocks, counting reflections but not counting rotations is in this table:. Another type of movement of the Earth is observed by terrestrial spectroscopy. Lego itself sells a line of sets named "Lego Studios," which contains a Lego web cam (repackaged Logitech USB Quickcam), software to record video on a computer, clear plastic rods which can be used to manipulate minifigures from off-camera, and a minifigure resembling Steven Spielberg. Earthquakes such as these, that are caused by human activity, are referred to by the term induced seismicity. Several webcomics are illustrated with Lego, notably Irregular Webcomic!.

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. Director Michel Gondry filmed a live version of the video, digitized the result, and then recreated it entirely with Lego bricks. Finally, ground shaking can also result from the detonation of explosives. Another notable example is the award-winning music video for the song "Fell in Love with a Girl" by the White Stripes. Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Netherlands. [2]. Such earthquakes occur because the strength of the Earth's crust can be modified by fluid pressure. 'Art Craziest Nation' was shown at the Walker Art Gallery in Liverpool, UK.

at certain geothermal power plants and at the Rocky Mountain Arsenal). The Little Artists have created an entire Modern Art collection in a Lego Gallery. 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. Artists have also used Lego sets with one of the more notorious examples being Polish artist Zbigniew Libera's "Lego Concentration Camp," a collection of mocked-up concentration camp-themed Lego sets.[1]. Some earthquakes are also caused by the movement of magma in volcanoes, and such quakes can be an early warning of volcanic eruptions. For example, the Monty Python and the Holy Grail Special Edition DVD contained a version of the "Camelot" musical sequence redone with Lego minifigures and accessories. 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. They usually use stop-motion animation.

Eventually when enough stress accumulates, the plates move, causing an earthquake. Such movies are called "Lego movies", "Brickfilms", or "cinema Lego". Where these plates meet stress accumulates. One hobby among enthusiasts is to re-create popular scenes from famous movies, using Lego bricks for the scenery and Lego play sets as characters. The Earth is made up of tectonic plates driven by the heat in the Earth's mantle and core. Another novel application of Lego bricks is the combination of bricks and electronic components to obtain a Lego Electronic Lab Kit. 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. Because of the high degree of uniformity in Lego bricks, they have also been used in fields such as computer vision, in which knowing the exact dimensions and relative positions of objects is useful for creating test data.

For example it has been calculated that the average recurrence for the United Kingdom can be described as follows:. A set of software tools called LDraw or Lego Digital Designer can be used to model possible Lego creations in 3D. 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. The website theory.org.uk (by academic David Gauntlett) features Lego versions of social theorists. 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. Legowars, the generic term for a number of wargames (most notably Brikwars) involving Lego bricks enjoys a cult-like popularity. The values of moments for different earthquakes ranges over several order of magnitude. The site features over 2,000 photographs of Biblical scenes.

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. For example, at The Brick Testament "The Reverend" Brendan Powell Smith has built the Bible in Lego pieces. 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. Lego toys have been used in a number of unexpected ways. 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. A group which calls itself "AFOLs" (for "Adult Fans of Lego") is an important demographic for The Lego Group, which has recently begun reintroducing popular sets from previous years to appeal to this group. 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. Photos of many fan creations like these can be seen at Brickshelf and at MOCpages.

Each of these is scaled to gives values similar to the values given by the Richter scale. One such masterpiece solves a Rubik's Cube through the use of Lego motors and cameras, a task that many humans cannot accomplish. Other more recent Magnitude measurements include: body wave magnitude (mb), surface wave magnitude (Ms) and duration magnitude (MD). Large mosaics, fully functional padlocks and pendulum clocks, a harpsichord and an inkjet printer (built by Google co-founder Larry Page while at the University of Michigan) have been constructed from Lego pieces. 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. Some sculptures use hundreds of thousands of pieces and weigh tens of kilograms. This is known as the “Richter scale”, “Richter Magnitude” or “Local Magnitude” (ML). A cult following of people who have used Lego pieces to make sculptures, very large mosaics and complex machines has developed.

Richter devised a simple numerical scale (which he called the magnitude) to describe the relative sizes of earthquakes in Southern California. The Lego Group itself has developed a form of business consultancy fostering creative thinking, called Lego Serious Play, in which team members build metaphors of their organisational experiences using Lego bricks, and work through imaginary scenarios using the visual device of the Lego constructions and by exploring possibilities in a 'serious' form of 'play'. In the 1930s, a California seismologist named Charles F. Lego bricks today are used for purposes beyond children's play. 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). As of year end 2005, there are 25 LEGO Brand Retail stores in the USA, a number of stores in Europe, and a franchised LEGO store in Abu Dhabi. If you feel an earthquake in the US you can report the effects to the USGS. There are also several Lego retail stores, including at Downtown Disney in both the Disneyland and Walt Disney World Resorts and in the Mall of America in Bloomington, Minnesota.

For some tasks related to engineering and local planning it is still useful for the very same reasons and thus still collected. Lego Group operates several Legoland amusement parks in Europe and California. 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. It also allows advanced participants an opportunity to modify the Lego Mindstorms platform, adding their own sensors and actuators, as well as other mechanical, electrical, electronic and software related systems. No structural damage. Lego Mindstorms provides primary and secondary school aged participants of RoboCup Junior an easy and intuitive introduction to robotics. Damage is slight in poorly built buildings. The international RoboCup Junior autonomous soccer competition involves extensive use of Lego Mindstorms equipment which is often pushed to its limits.

Trees and bushes shake. A related competition is FIRST Lego League for elementary and middle schools. Plaster in walls might crack. The earliest, and likely the largest, is Botball, a national US middle- and high-school competition stemming from the MIT 6270 lego robotics tournament. Furniture moves. There are several competitions which use Lego bricks and the RCX, among other microcontrollers, for robotics. Pictures fall off walls. These programmable bricks are sold under the name Lego Mindstorms.

Objects fall from shelves. There are even special bricks, like the LEGO RCX that can be programmed with a PC to perform very complicated and useful tasks. People have trouble walking. There are also motors, gears, lights, sensors, and cameras available to be used with Lego components. Everyone feels movement. LEGO recently announced the procurement of worldwide toy rights with the cable TV channel Nickelodeon for building sets with themes from two hit TV shows such as SpongeBob SquarePants and Avatar: The Last Airbender which will be available Summer of 2006. The value 6 (normally denoted "VI") in the MM scale for example is:. Sets containing new pieces are released frequently.

These assign a numeric value (different for each scale) to a location based on the size of the shaking experienced there. Since it began producing plastic bricks, the Lego Group has released thousands of play sets themed around space, robots, pirates, vikings, medieval castles, dinosaurs, cities, suburbia, holiday locations, wild west, the Arctic, boats, racing cars, trains, Spider-Man, Star Wars, Harry Potter, Bionicle, and more. 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. Annual production of Lego bricks averages approximately 20 billion (2 × 1010) per year, or about 600 pieces per second. The first method of quantifying earthquakes was intensity scales. Brick decorations and packaging is done at plants in Denmark, Switzerland, United States, South Korea and the Czech Republic. 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. Moulding is done at one of two plants in Denmark and Switzerland.

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. Manufacturing of Lego bricks occurs at a number of locations around the world. The total size of the fault that slips, the rupture zone, can be as large as 1000 km, for the biggest earthquakes. It is thanks to this care in manufacturing that the Lego Group has maintained such a high degree of quality over the decades; this is one of the main reasons that pieces manufactured over 40 years ago still interlock neatly with pieces manufactured today. The location on the surface directly above the hypocenter is known as the "epicenter". According to the Lego Group, its moulding processes are so accurate that only 18 bricks out of every million fail to meet its stringent standards. That point is called its "focus" or "hypocenter" and usually proves to be the point at which the fault slip was initiated. Worn-out moulds are encased in the foundations of buildings to prevent their falling into competitors' hands.

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. Precision-machined, small-capacity moulds are used, and human inspectors meticulously check the output of the moulds, to eliminate significant variations in colour or thickness. 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. Since 1963, Lego pieces are manufactured from a strong, resilient plastic known as acrylonitrile butadiene styrene, or ABS. Ground motions caused by very distant earthquakes are called teleseisms. In order for pieces to have just the right "clutch power", Lego elements are manufactured within a tolerance of 2 micrometres (0.00008 in). 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. They cannot be too easy to pull apart, or the result will be Lego creations that are unstable; they cannot be too difficult to pull apart, since the disassembly of one creation in order to build another is part of the Lego appeal.

While almost all earthquakes have aftershocks, foreshocks are far less common occurring in only about 10% of events. When snapped together, pieces must have just the right amount of "clutch power"; they must stay together until pulled apart. 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. Bricks, beams, axles, minifigures, and all other elements in the Lego system are manufactured to an exacting degree of tolerance. S-waves (secondary or shear waves) and the two types of surfaces waves (Love waves and Rayleigh waves) are responsible for the shaking hazard. Retail Lego sets for young children are compatible with those made for teenagers. There are four types of seismic waves that are all generated simultaneously and can be felt on the ground. Lego pieces from 1963 still interlock with pieces made in 2006, despite radical changes in shape and design over the years.

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. Since their introduction in 1949, Lego pieces of all varieties have been, first and foremost, part of a system. liquefaction, landslide), and fire or a release of hazardous materials. Nevertheless, such corporate admonitions are frequently ignored as corporate intervention in the use of language, and the word lego is commonly used not only as a noun to refer to Lego bricks but also as a generic term referring to any kind of interlocking toy brick. 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. The company asserts that to protect its brand name, the word Lego must always be used as an adjective, as in "LEGO set," "LEGO products," "LEGO universe," and so forth. Some deep earthquakes may be due to the transition of olivine to spinel, which is more stable in the deep mantle. "Lego" is officially written in all uppercase letters.

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. Thank you! Susan Williams, Consumer Services. Where the crust is thicker and colder they will occur at greater depths and the opposite in areas that are hot. Please always refer to our bricks as 'LEGO Bricks or Toys' and not 'LEGOS.' By doing so, you will be helping to protect and preserve a brand of which we are very proud and that stands for quality the world over. 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. We would sincerely like your help in keeping it special. 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 . The word LEGO® is a brand name and is very special to all of us in the LEGO Group Companies.

. Lego catalogues in the 1970s and 1980s contained a note that read:. 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. The Lego Group's name has become so synonymous with its flagship toy that many use the words "Lego" (collectively) or "Legos" to refer to the bricks themselves, and even to any plastic bricks resembling Lego bricks, although the Lego Group discourages this as dilution of their trademark. 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. Over the years many more Lego sets, series, and pieces were created, with many innovative improvements and additions, culminating in the colourful versatile building toys that we know today. Earthquakes related to plate tectonics are called tectonic earthquakes. It wasn't until 1958 that the modern-day brick design was developed, and it took another five years to find exactly the right material for it.

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). Godtfred saw the immense potential in Lego bricks to become a system for creative play, but the bricks still had some problems from a technical standpoint: their "locking" ability was limited, and they were not very versatile. 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. It was his conversation with an overseas buyer that struck the idea of a toy system. Earthquakes occur where the stress resulting from the differential motion of these plates exceeds the strength of the crust. By 1954, Christiansen's son, Godtfred, had become the junior managing director of the Lego Group. The Earth's lithosphere is a patch work of plates in slow but constant motion (see plate tectonics). Many of the Lego Group's shipments were returned, following poor sales; it was thought that plastic toys could never replace wooden ones.

The word earthquake is also widely used to indicate the source region itself. The use of plastic for toy manufacture was not highly regarded by retailers and consumers of the time. Earthquakes typically result from the movement of faults, planar zones of deformation within the Earth's upper crust. The blocks snapped together, but not so tightly that they couldn't be pulled apart. Earthquakes result from the dynamic release of elastic strain energy that radiates seismic waves. They had several round "studs" on top, and a hollow rectangular bottom. An earthquake is a sudden and sometimes catastrophic movement of a part of the Earth's surface. A few years later, in 1949, Lego began producing similar bricks, calling them "Automatic Binding Bricks." These bricks, manufactured from cellulose acetate, were developed in the spirit of traditional wooden blocks that could be stacked upon one another; however, these plastic bricks could be "locked" together.

Lake Tanganyika earthquake (2005). Hilary Harry Fisher Page, a child psychologist. Many more at risk from the Kashmiri winter. These "Kiddicraft Self-Locking Building Bricks" were designed and patented in the UK by Mr. Killed over 79,000 people. In 1947, Ole Kirk and his son Godtfred obtained samples of interlocking plastic bricks produced by the company Kiddicraft. Kashmir earthquake (2005). It should be noted, however, that the original, Greek verb "legein" actually has the meaning "put together".

Fukuoka earthquake (2005). The Lego Group claims that "Lego" means "I put together" or "I assemble" in Latin, though this is a rather liberal translation; the more accepted and widely used application of the word is "I read". Sumatran Earthquake (2005). The company name Lego was coined by Christiansen from the Danish phrase leg godt, meaning "play well". Triggered a tsunami which caused nearly 300,000 deaths spanning several countries. Ole Kirk started creating wooden toys in 1932, but it wasn't until 1949 that the famous plastic Lego brick was created. Epicenter off the coast of the Indonesian island Sumatra. The Lego Group had humble beginnings in the workshop of Ole Kirk Christiansen, a poor carpenter from Billund, Denmark.

One of the largest earthquakes ever recorded at 9.0. . Indian Ocean Earthquake (2004). The sets are produced by the Lego Group, a privately-held company based in Denmark. Chuetsu Earthquake (2004). High production quality and careful attention to detail ensures that Lego pieces can fit together in myriad ways, which is one of the main reasons for the toy's success. 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. Cars, planes, trains, buildings, castles, sculptures, ships, spaceships, and even working robots are just a few of the many things that can be made with Lego bricks.

Parkfield, California earthquake (2004). Lego is a line of toys featuring colourful plastic bricks, gears, minifigures (also called minifigs or mini-figs), and other pieces which can be assembled to create models of almost anything imaginable. Bam Earthquake (2003). The number 102,981,504 (four more than that figure) is the number of six-piece towers (of a height of six). Dudley Earthquake (2002). The figure of 102,981,500 is often given for six pieces, but it is incorrect. Gujarat Earthquake (2001). Six eight-stud Lego bricks of the same colour can be put together in 915,103,765 ways, and just three bricks of the same colour offer 1,560 combinations.

Nisqually Earthquake (2001). "Legot" (or "leegot"), plural form of "lego" (or "leego") is also used as a Finnish slang term for human teeth, because of the rectangular shape of the teeth. 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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