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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. None of the three "non-major" groups listed above could make that claim. 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. The Union's chief claim to major status would rest on having had some direct impact on the other majors, due to roster-raiding. 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. Louis) and its membership was a revolving door.
Another type of movement of the Earth is observed by terrestrial spectroscopy. Conversely, some historians question whether the Union Association really qualifies as "major", because it really only had one major-league caliber team (St.

Earthquakes such as these, that are caused by human activity, are referred to by the term induced seismicity. Specifically, the following can be said of these leagues:. 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, the official stance is that game and statistical records for these particular leagues were not kept in a consistent manner and/or those leagues did not have a significant direct impact on the major leagues. Finally, ground shaking can also result from the detonation of explosives. Some researchers contend that the following leagues deserve consideration as major leagues due to the caliber of player and the level of play exhibited:. Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Netherlands. The MLB list included the following:.

Such earthquakes occur because the strength of the Earth's crust can be modified by fluid pressure. The list is sometimes disputed by baseball researchers. at certain geothermal power plants and at the Rocky Mountain Arsenal). In 1969, the centennial of professional baseball, a commission chartered by Major League Baseball identified the following leagues as "major leagues". 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. MLB's reluctance to take a hard line on drugs (as many other sports feature far more strict testing and penalties) is widely seen as one of the main reasons why baseball has been dropped from the Olympics with effect from 2012. Some earthquakes are also caused by the movement of magma in volcanoes, and such quakes can be an early warning of volcanic eruptions. These new proposed penalties are much harsher, however they must be accepted by MLB players and owners before any changes can be made.

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. Finally, the 3rd positive test would result in a lifetime suspension from MLB. Eventually when enough stress accumulates, the plates move, causing an earthquake. The 2nd positive test would result in a 100 game suspension. Where these plates meet stress accumulates. The 1st positive test would result in a 50 game suspension. The Earth is made up of tectonic plates driven by the heat in the Earth's mantle and core. The new penalties that Bud Selig has proposed are a “three strikes and you’re out approach” and go as follows:.

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. In recent news, Bud Selig, the Commissioner of MLB, has proposed even tougher penalties for positive tests than the ones in place today. For example it has been calculated that the average recurrence for the United Kingdom can be described as follows:. The new agreement makes sure that first time offenders are rightfully suspended. 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. Under the old policy, which was established in 2002, a first time offense would only result in treatment for the player. 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. This program would replaces the previous steroid testing program under which, for example, no player was even suspended in 2004.

The values of moments for different earthquakes ranges over several order of magnitude. (See: List of Major League Baseball players suspended for steroids). 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. Players will be tested at least once per year, with the chance that several players can be tested a numerous amount of times per year. 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. Finally, the 5th positive test will result in a penalty at the commissioner’s discretion. 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 4th positive test will result in a suspension of one full year.

However as each is also based on the measurement of one part of the seismogram they do not measure the overall power of the source and can suffer from saturation at higher magnitude values (larger events fail to produce higher magnitude values).These scales are also empirical and as such there is no physical meaning to the values. The 3rd positive test will result in a suspension of 60 days. Each of these is scaled to gives values similar to the values given by the Richter scale. The 2nd positive test will result in a suspension of 30 days. Other more recent Magnitude measurements include: body wave magnitude (mb), surface wave magnitude (Ms) and duration magnitude (MD). The 1st positive test will result in a suspension of up to 10 days. 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 new policy, which was accepted by Major League Baseball players and owners, was issued at the start of the 2005 season and goes as follows:.

This is known as the “Richter scale”, “Richter Magnitude” or “Local Magnitude” (ML). However, after the BALCO steroid scandal, which involved allegations that top baseball players had used illegal performance enhancing drugs, Major League Baseball has finally decided to issue harsher penalties for steroid users. Richter devised a simple numerical scale (which he called the magnitude) to describe the relative sizes of earthquakes in Southern California. Over most of the course of Major League Baseball, steroid testing was never a major issue. In the 1930s, a California seismologist named Charles F. The team belonging to the league that won the mid-season All-Star game receives home-field advantage in the World Series. 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 first and second round of the playoffs, the better seeded team has home-field advantage.

If you feel an earthquake in the US you can report the effects to the USGS. 4 seed. For some tasks related to engineering and local planning it is still useful for the very same reasons and thus still collected. 3 seed and 2 seed vs. 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. 3 seed, unless this would result in a matchup of two teams from the same division, in which case the matchup is 1 seed vs. No structural damage. 4 seed, and 2 seed vs.

Damage is slight in poorly built buildings. The matchup for the first round of the playoffs is usually 1 seed vs. Trees and bushes shake. Three rounds of series of games are played to determine the champion:. Plaster in walls might crack. The remaining two "wild-card" spots are filled by each league's team that has the best regular season record and is not a division champion. Furniture moves. The first six teams are each league's three division champions.

Pictures fall off walls. When the regular season ends after the first Sunday in October, eight teams enter the post-season playoffs. Objects fall from shelves. This rule exists so that fans of every team have a player to watch for in the All Star Game. People have trouble walking. By MLB regulation, every team in the majors must have at least one designated all-star player, regardless of voting. Everyone feels movement. In 2004, however, MLB instituted a system where some reserves and pitchers were selected by a vote of MLB players, and some were selected by the manager after consulting with the Commissioner's Office.

The value 6 (normally denoted "VI") in the MM scale for example is:. The remaining position players and all of the pitchers on each league's roster were, for a long number of years, solely at the discretion of that team's manager. These assign a numeric value (different for each scale) to a location based on the size of the shaking experienced there. Since the 1970s, the eight position players for each team who take the field initially have been voted into the game by fans. 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 Boston Red Sox and Chicago White Sox took full advantage of the rule, with both teams winning the World Series in a 4-0 sweep in 2004 and 2005, respectively. The first method of quantifying earthquakes was intensity scales. Through the 2005 season, the AL has won all three contests with this rule.

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. The 2005 contest, played in Detroit, followed this format, and it is expected that it will remain that way until the MLB says otherwise, since it has become popular with fans but has upset purists over the previous format of the two leagues alternating home-field advantage every other year. 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. As a result, for a two-year trial in 2003 and 2004, the league which won the game received the benefit of home-field advantage (four of the seven games of that year's World Series taking place at their home park). The total size of the fault that slips, the rupture zone, can be as large as 1000 km, for the biggest earthquakes. The 2002 contest ended in an 11-inning tie because both teams were out of pitchers, a ridiculous result which proved highly unpopular with the fans. The location on the surface directly above the hypocenter is known as the "epicenter". The All-Star game pits players from the NL, headed up by the manager of the previous NL World Series team, against players from the AL, similarly managed, in an exhibition game.

That point is called its "focus" or "hypocenter" and usually proves to be the point at which the fault slip was initiated. Early July marks the midway point of the season, during which a three day break is taken when the Major League Baseball All-Star Game is staged. 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. For a detailed history of the length of the regular season, see Major League Baseball season. 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. The MLB Draft is among the least followed of the professional sports drafts in the United States. Ground motions caused by very distant earthquakes are called teleseisms. Each year in June, Major League Baseball conducts a draft for first year players who have never signed a Major or Minor League contract.

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. Typically many intra-division games are scheduled toward the end of the season, anticipating the possibility of close divisional races and heightened fan interest. While almost all earthquakes have aftershocks, foreshocks are far less common occurring in only about 10% of events. The interleague games are confined to the mid-summer months. 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. In 1997 Major League Baseball introduced interleague play, which was criticized by the sport's purists but has since proven very popular with most fans. S-waves (secondary or shear waves) and the two types of surfaces waves (Love waves and Rayleigh waves) are responsible for the shaking hazard. Games are played predominantly against teams within each league through an unbalanced schedule which heavily favors intra-divisional play.

There are four types of seismic waves that are all generated simultaneously and can be felt on the ground. A 140 game schedule (7 X 20) was played in 1919, and the schedule before 1904 varied from year to year. 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. Unplanned shortened seasons were played in 1918 due to the outbreak of World War I, and in 1972, 1981, 1994 and 1995 due to player strikes and lockouts. liquefaction, landslide), and fire or a release of hazardous materials. The number of games per opponent now varies depending on various factors, but the total number of games has been kept at 162. 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. Expansion from 8 to 10 teams in each league in the early 1960s resulted in a revised schedule of 162 games (9 opponents X 18 games apiece, initially) in their expansion years, for the American in 1961 and the National in 1962.

Some deep earthquakes may be due to the transition of olivine to spinel, which is more stable in the deep mantle. From 1904 into the early 1960s, except for 1919, a 154-game schedule was played in both leagues (7 opponents X 22 games apiece). 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. Each team's regular season consists of 162 games, a duration established in 1961 in the American League and 1962 in the National League. Where the crust is thicker and colder they will occur at greater depths and the opposite in areas that are hot. They are (number of teams in each division in parenthesis): NL East (5), NL Central (6), NL West (5), AL East (5), AL Central (5) and AL West (4). 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. Each has its teams split into three divisions grouped generally by geography.

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 . In all there are 30 teams in the two leagues: 16 in the older National League ("NL") and 14 in the American League ("AL"). .
. 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. At the moment, however, the major leagues are each split into three divisions, and structured as listed in the table below. 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. At the time of writing the Commissioner of Baseball, Bud Selig, has often floated the idea of international expansion and realignment of the major leagues.

Earthquakes related to plate tectonics are called tectonic earthquakes. Three rounds of playoffs follow the regular season, culminating in the World Series in late October or early November. 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). Players and teams prepare for the season in spring training, primarily in Florida and Arizona, during February and March. 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. The Major League regular season runs from late March or early April to late September or early October. 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). MLB Productions is a similarly-structured wing of the league, focusing on video and traditional broadcast media. The word earthquake is also widely used to indicate the source region itself. Its charter states that MLB Advanced Media holds editorial independence from the League itself, but it is indeed under the same ownership group and revenue-sharing plan. Earthquakes typically result from the movement of faults, planar zones of deformation within the Earth's upper crust. The production/multimedia wing of MLB is New York-based MLB Advanced Media, which oversees MLB.com and all 30 of the individual teams' websites. Earthquakes result from the dynamic release of elastic strain energy that radiates seismic waves. National League which declared baseball is not considered interstate commerce (and therefore not subject to federal antitrust law), despite baseball's own references to itself as an "industry" rather than a "sport.".

An earthquake is a sudden and sometimes catastrophic movement of a part of the Earth's surface. Supreme Court ruling in Federal Baseball Club v. Lake Tanganyika earthquake (2005). This is due in large part to a 1922 U.S. Many more at risk from the Kashmiri winter. MLB also maintains a unique, controlling relationship over the sport, including most aspects of minor league baseball. Killed over 79,000 people. As is the case for most North American sports leagues, the 'closed shop' aspect of MLB effectively prevents the yearly promotion and demotion of teams into the Major League by virtue of their performance.

Kashmir earthquake (2005). Major League Baseball, under the direction of its Commissioner, Bud Selig, hires and maintains the sport's umpiring crews, and negotiates marketing, labor, and television contracts. Fukuoka earthquake (2005). Major League Baseball is governed by the Major League Baseball Constitution, an agreement that has undergone several incarnations since 1876 then called the NL Constitution, with the most recent revisions being made in 2005. Sumatran Earthquake (2005). On an organizational level, MLB effectively operates as a single "league", and as such it constitutes one of the major professional sports leagues of North America. Triggered a tsunami which caused nearly 300,000 deaths spanning several countries. More specifically, Major League Baseball ("MLB") refers to the entity that operates North America's two major leagues, the National League and the American League, by means of a joint organizational structure which has existed between them since 1903.

Epicenter off the coast of the Indonesian island Sumatra. Major League Baseball (MLB) is the highest level of play in professional baseball in the world. One of the largest earthquakes ever recorded at 9.0. It is a debate that has no clear resolution, which is why most historians are content to simply regard them as a category unto themselves. Indian Ocean Earthquake (2004). It could also be argued that the Negro Leagues were more properly equated to the highest levels of minor league ball, such as the Pacific Coast League. Chuetsu Earthquake (2004). The fact that many young players were able to come into the majors in the late 1940s and early 1950s, and have immediate impact, possibly argues for major status.

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. Some historians have labeled their time the era of "shadow ball", a segregated parallel to the (all-white) major leagues. Parkfield, California earthquake (2004). The Negro Leagues are the toughest call. Bam Earthquake (2003). That changed in 1901. Dudley Earthquake (2002). However, in 1900 it operated independently and did not conduct raids on major league rosters.

Gujarat Earthquake (2001). The AL itself asserted that it was a minor league in 1900, although it was already located in most of the cities it would be operating in the following year. Nisqually Earthquake (2001). The NL was a wholly new entity that took the best remnants of the NA and imposed a discipline that was lacking in the failed NA. Chi-Chi earthquake (1999). The standard position is that the NA was a "transitional" league that was not quite up to major league standards. Düzce earthquake (1999). The NA is unquestionably recognized as the first professional league, and is the direct precursor to the NL, most of whose original eight teams came from the NA.

İzmit earthquake (1999) Killed over 17,000 in northwestern Turkey. The Negro Leagues (primarily during the years from 1921-1946). Killed over 6,400 people in and around Kobe, Japan. The first year of the American League (1900). Great Hanshin earthquake (1995). The National Association (1871-1875). Damage showed seismic resistance deficiencies in modern low-rise apartment construction. 1914-1915: Federal League.

Northridge, California earthquake (1994). 1901-present: American League. Revealed necessity of accelerated seismic retrofit of road and bridge structures. 1890: Players League. Severely affecting Santa Cruz, San Francisco and Oakland in California. 1884: Union Association. Loma Prieta earthquake (1989). 1882-1891: American Association.

Killed over 25,000. 1876-present: National League of Professional Baseball Clubs. Armenian earthquake (1988). http://www.wnbc.com/mikedup/4077510/detail.html. Whittier Narrows earthquake (1987). World Series, a best-of-seven game series played between the champions of each league. 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.). American League Championship Series and National League Championship Series, each a best-of-seven game series played between the surviving teams from the ALDS and NLDS; and.

Great Mexican Earthquake (1985). American League Division Series and National League Division Series, each a best-of-five game series;. 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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