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Encyclopedia > Richter magnitude scale

The Richter magnitude scale, or more correctly local magnitude ML scale, assigns a single number to quantify the amount of seismic energy released by an earthquake. It is a base-10 logarithmic scale obtained by calculating the logarithm of the combined horizontal amplitude of the largest displacement from zero on a Wood-Anderson torsion seismometer output. The effective limit of measurement for local magnitude is about ML=6.8. The energy release of an earthquake scales with the 3/2 power of the shaking amplitude, and thus a difference in magnitude of 1.0 is equivalent to a factor of 31.6 in the energy released; a difference of magnitude of 2.0 is equivalent to a factor of 1000 in the energy released. This article is about the natural seismic phenomenon. ... A logarithmic scale is a scale of measurement that uses the logarithm of a physical quantity instead of the quantity itself. ... It has been suggested that pulse amplitude be merged into this article or section. ... Seismometers is of Greek origin and comes from Seism - the shakes and Meteo - I measure are instruments that measure and record motions of the ground, including those of seismic waves generated by earthquakes, nuclear explosions, and other seismic sources. ...

Contents

Development

Developed in 1935 by Charles Richter in partnership with Beno Gutenberg, both of the California Institute of Technology, the scale was originally intended to be used only in a particular study area in California, and on seismograms recorded on a particular instrument, the Wood-Anderson torsion seismometer. (Many[attribution needed] scientists and historians feel it should be known as the Richter-Gutenberg scale.) Richter originally reported values to the nearest quarter of a unit, but decimal numbers were used later. His motivation for creating the local magnitude scale was to separate the vastly larger number of smaller earthquakes from the few larger earthquakes observed in California at the time. 1935 (MCMXXXV) was a common year starting on Tuesday (link will display full calendar). ... Charles Francis Richter (April 26, 1900 – April 20, 1985), was an American seismologist, born in Hamilton, Ohio. ... Beno Gutenberg (June 4, 1889 – January 25, 1960) was a German-born seismologist who made several important contributions to the science. ... The California Institute of Technology (commonly referred to as Caltech)[1] is a private, coeducational research university located in Pasadena, California, in the United States. ... This article is about the U.S. state. ... Seismometers is of Greek origin and comes from Seism - the shakes and Meteo - I measure are instruments that measure and record motions of the ground, including those of seismic waves generated by earthquakes, nuclear explosions, and other seismic sources. ...


His inspiration was the apparent magnitude scale used in astronomy to describe the brightness of stars and other celestial objects. Richter arbitrarily chose a magnitude 0 event to be an earthquake that would show a maximum combined horizontal displacement of 1 micrometre on a seismograph recorded using a Wood-Anderson torsion seismometer 100 km from the earthquake epicenter. This choice was intended to prevent negative magnitudes from being assigned. However, the Richter scale has no upper or lower limit, and sensitive modern seismographs now routinely record quakes with negative magnitudes. The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ...


Because of the limitations of the Wood-Anderson torsion seismometer used to develop the scale, the original ML cannot be calculated for events larger than about 6.8. Investigators have proposed extensions to the local magnitude scale, the most popular being the surface wave magnitude mS and the body wave magnitude mb. These traditional magnitude scales have largely been superseded by the implementation of methods for estimating the seismic moment and its associated moment magnitude scale. Body waves and surface waves Earthquake wave paths p-wave and s-wave from seismograph A seismic wave is a wave that travels through the Earth, most often as the result of a tectonic earthquake, sometimes from an explosion. ... The moment magnitude scale was introduced in 1979 by Tom Hanks and Hiroo Kanamori as a successor to the Richter scale and is used by seismologists to compare the energy released by earthquakes. ...


Richter magnitudes

The Richter magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs (adjustments are included to compensate for the variation in the distance between the various seismographs and the epicenter of the earthquake). Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; in terms of energy, each whole number increase corresponds to an increase of about 31.6 times the amount of energy released. Look up logarithm in Wiktionary, the free dictionary. ... It has been suggested that pulse amplitude be merged into this article or section. ...


Events with magnitudes of about 4.6 or greater are strong enough to be recorded by any of the seismographs in the world.


The following describes the typical effects of earthquakes of various magnitudes near the epicenter. This table should be taken with extreme caution, since intensity and thus ground effects depend not only on the magnitude, but also on the distance to the epicenter, the depth of the earthquake's focus beneath the epicenter, and geological conditions (certain terrains can amplify seismic signals).

Richter Magnitudes Description Earthquake Effects Frequency of Occurrence
Less than 2.0 Micro Microearthquakes, not felt. About 8,000 per day
2.0-2.9 Minor Generally not felt, but recorded. About 1,000 per day
3.0-3.9 Minor Often felt, but rarely causes damage. 49,000 per year (est.)
4.0-4.9 Light Noticeable shaking of indoor items, rattling noises. Significant damage unlikely. 6,200 per year (est.)
5.0-5.9 Moderate Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings. 800 per year
6.0-6.9 Strong Can be destructive in areas up to about 100 miles across in populated areas. 120 per year
7.0-7.9 Major Can cause serious damage over larger areas. 18 per year
8.0-8.9 Great Can cause serious damage in areas several hundred miles across. 1 per year
9.0-9.9 Great Devastating in areas several thousand miles across. 1 per 20 years
10.0+ Great Never recorded; see below for equivalent seismic energy yield. Extremely rare (Unknown)

(Based on U.S. Geological Survey documents.)[1]


Great earthquakes occur once a year, on average. The largest recorded earthquake was the Great Chilean Earthquake of May 22, 1960 which had a magnitude (MW) of 9.5.[2] Map showing the areas affected by the tsunami The Great Chilean Earthquake or Valdivian Earthquake (Terremoto de Valdivia in Spanish) of 22 May 1960 is the most intense earthquake ever recorded, rating a 9. ... is the 142nd day of the year (143rd in leap years) in the Gregorian calendar. ... Year 1960 (MCMLX) was a leap year starting on Friday (link will display full calendar) of the Gregorian calendar. ...


The following table lists the approximate energy equivalents in terms of TNT explosive force[3] - though note that the energy here is that of the underground energy release (ie a small atomic bomb blast will not simply cause light shaking of indoor items) rather than the overground energy release; the majority of energy transmission of an earthquake is not transmitted to and through the surface, but is instead dissipated into the crust and other subsurface structures. Unit of energy commonly used to quantify laerge amounts of energy. ...

Richter
Approximate Magnitude
Approximate TNT for
Seismic Energy Yield
Joule equivalent Example
0.5 5.6 kg (12.4 lb) 23.5 MJ large Hand grenade
1.0 32 kg (70 lb) 134.4 MJ Construction site blast
1.5 178 kg (392 lb) 747.6 MJ WWII conventional bombs
2.0 1 metric ton 4.2 GJ late WWII conventional bombs
2.5 5.6 metric tons 23.5 GJ WWII blockbuster bomb
3.0 32 metric tons 134.4 GJ Massive Ordnance Air Blast bomb
3.5 178 metric tons 747.6 GJ Chernobyl nuclear disaster, 1986
4.0 1 kiloton 4.2 TJ Small atomic bomb
5.0 32 kiloton 134.4 TJ Nagasaki atomic bomb (actual seismic yield was negligible since it detonated in the atmosphere)
2008 Lincolnshire earthquake
5.5 178 kilotons 747.6 TJ Little Skull Mtn., NV earthquake, 1992, Alum Rock, San Jose CA 2007
6.0 1 megaton 4.2 PJ Double Spring Flat, NV earthquake, 1994
6.7 5.6 megatons 23.5 PJ Northridge earthquake, 1994
7.1 50 megatons 210 PJ Tsar Bomba, largest thermonuclear weapon ever tested (magnitude seen on seismographs reduced because it detonated 4 km in the atmosphere.)
7.5 178 megatons 747.6 PJ 1976 Tangshan earthquake
2005 Kashmir earthquake
2007 Antofagasta earthquake
8.0 1 gigaton 4.2 EJ Toba eruption 75,000 years ago; and the Toba catastrophe theory, according to which modern human evolution was affected by this event
San Francisco, CA earthquake, 1906
Gujarat earthquake, 2001
Earthquake near Chincha Alta, Peru, August 2007
Earthquake near Indonesia September 12th 2007
9.0 31.6 gigatons 134.4 EJ 1964 Anchorage, AK earthquake
9.3 114 ?? gigatons ?? EJ 2004 Indian Ocean earthquake
9.5 178 gigatons 747.6 EJ 1960 Chile Earthquake
10.0 1 teraton 4.2 ZJ estimate for a 2 km rocky meteorite impacting at 25 km/s
12.0 160 teratons 672 ZJ Earth’s daily receipt of solar energy[3]

Kg redirects here. ... Look up pound in Wiktionary, the free dictionary. ... To help compare different orders of magnitude we list here energies between 107 joules and 108 joules. ... Grenade redirects here. ... To help compare different orders of magnitude we list here energies between 108 joules and 109 joules. ... To help compare different orders of magnitude we list here energies between 108 joules and 109 joules. ... Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... A tonne (also called metric ton) is a non-SI unit of mass, accepted for use with SI, defined as: 1 tonne = 103 kg (= 106 g). ... To help compare different orders of magnitude we list here energies between 109 joules (a gigajoule, symbol GJ) and 1010 joules. ... To help compare different orders of magnitude we list here energies between 1010 joules and 1011 joules. ... A Lancaster drops bundles of incendiary bombs (left), incendiary bombs and a “cookie” (right) on Duisburg on 15 October 1944 Blockbuster or Cookie was the name given to several of the largest conventional bombs used in World War II by the Royal Air Force (RAF). ... To help compare different orders of magnitude we list here energies between 1011 joules and 1012 joules. ... The Massive Ordnance Air Blast bomb (MOAB) (also known as the Mother Of All Bombs) is a large-yield conventional bomb developed by the United States military by Albert L. Weimorts Jr. ... To help compare different orders of magnitude we list here energies between 1011 joules and 1012 joules. ... The nuclear power plant at Chernobyl prior to the completion of the sarcophagus. ... A megaton or megatonne is a unit of mass equal to 1,000,000 metric tons, i. ... To help compare different orders of magnitude we list here energies between 1012 joules (a terajoule, symbol TJ) and 1013 joules. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 km (11 mi) above the epicenter. ... To help compare different orders of magnitude we list here energies between 1014 joules and 1015 joules. ... This article is about the nuclear weapon used in World War II. For other uses, see Fat Man (disambiguation). ... To help compare different orders of magnitude we list here energies between 1014 joules and 1015 joules. ... A megaton or megatonne is a unit of mass equal to 1,000,000 metric tons, i. ... To help compare different orders of magnitude we list here energies between 1015 joules (a petajoule, symbol PJ) and 1016 joules. ... To help compare different orders of magnitude we list here energies between 1016 joules and 1017 joules. ... The Northridge earthquake occurred on January 17, 1994 at 4:31 AM Pacific Standard Time in Reseda, a neighborhood in the city of Los Angeles, California. ... To help compare different orders of magnitude we list here energies between 1017 joules and 1018 joules. ... Tsar Bomba (, literally King Bomb) is the Western name for the RDS-220 hydrogen bomb (codenamed Иван (Ivan) by its developers) — the largest, most powerful nuclear weapon ever detonated. ... To help compare different orders of magnitude we list here energies between 1017 joules and 1018 joules. ... Many buildings were flattened into rubble when the earthquake hit. ... The Kashmir earthquake (also known as the South Asian earthquake or the Great Pakistan earthquake) of 2005, was a major earthquake, of which the epicentre was the Pakistan-administered Kashmir. ... The 2007 Antofagasta earthquake was an earthquake registered on November 14, 2007 at 15:40:53 UTC (12:40:53 local time). ... A gigaton (or gigatonne) is a metric unit of mass, equal to 1,000,000,000 (1 billion) metric tons, 1,000,000,000,000 (1 trillion) kilograms, or 1 quadrillion grams. ... To help compare different orders of magnitude we list here energies between 1018 joules (an exajoule, symbol EJ) and 1019 joules. ... The Toba eruption (the Toba event) was the largest volcanic eruption on Earth in the last 28 million years. ... Eruption column rising, Mount Redoubt, Alaska According to the Toba catastrophe theory, modern human evolution was affected by a recent, large volcanic event. ... For the history of humans on Earth, see History of the world. ... San Francisco Earthquake redirects here. ... The 2001 Gujarat earthquake was reportedly the most devastating earthquake in India in recent history. ... The 2007 Peru earthquake was an earthquake measuring 8. ... The September 2007 Sumatra earthquakes were a series of earthquakes that struck the Java Trench off the coast of Sumatra, Indonesia, three greater than magnitude 7. ... To help compare different orders of magnitude we list here energies between 1019 joules and 1020 joules. ... Earthquake Damage, Anchorage The Good Friday Earthquake (also called the Great Alaska Earthquake) of Friday, March 27, 1964 (Good Friday, a Christian holy day associated with a historical earthquake[1]), 5:36 P.M. AST (03:36 3/27 UTC) had a magnitude of 9. ... To help compare different orders of magnitude we list here energies between 1020 joules and 1021 joules. ... The 2004 Indian Ocean earthquake, known by the scientific community as the Sumatra-Andaman earthquake,[1] was a great undersea earthquake that occurred at 00:58:53 UTC (07:58:53 local time) December 26, 2004 with an epicentre off the west coast of Sumatra, Indonesia. ... Map showing the areas affected by the tsunami The Great Chilean Earthquake or Valdivian Earthquake (Terremoto de Valdivia in Spanish) of 22 May 1960 is the most intense earthquake ever recorded, rating a 9. ... A teraton is equal to 1,000 gigatons. ... To help compare different orders of magnitude we list here energies between 1021 joules (a zettajoule, symbol ZJ) and 1022 joules. ... Willamette Meteorite A meteorite is a natural object originating in outer space that survives an impact with the Earths surface without being destroyed. ... To help compare different orders of magnitude we list here energies between 1023 joules and 1024 joules. ...

References

  1. ^ USGS: FAQ- Measuring Earthquakes
  2. ^ USGS: List of World's Largest Earthquakes
  3. ^ a b What is Richter Magnitude?, with mathematic equations

See also

A seismic scale is used to measure and compare the relative severity of earthquakes. ... The moment magnitude scale was introduced in 1979 by Tom Hanks and Hiroo Kanamori as a successor to the Richter scale and is used by seismologists to compare the energy released by earthquakes. ... The Japan Meteorological Agency seismic intensity scale (震度 shindo) is a measure used in Japan to indicate the strength of earthquakes. ... An order of magnitude is the class of scale or magnitude of any amount, where each class contains values of a fixed ratio to the class preceding it. ...

External links

Seismic scales
view  talk  edit
Modern scales
Intensity scales
European Macroseismic Scale (EMS) | INQUA | Medvedev-Sponheuer-Karnik (MSK) | Modified Mercalli (MM) | Shindo
Magnitude scales
Local magnitude (Richter scale) | Moment magnitude
Historical scales
Mercalli-Cancani-Sieberg (MCS) | Mercalli-Wood-Neuman (MWN) | Omori | Rossi-Forel
The European Macroseismic Scale (EMS) is the basis for evaluation of seismic intensity in European countries. ... The Medvedev-Sponheuer-Karnik scale (MSK-64) is a macroseismic intensity scale used to measure the effects of earthquakes on humans, objects of nature, and structures. ... The Mercalli intensity scale is a scale used for measuring the intensity of an earthquake. ... The Japan Meteorological Agency seismic intensity scale (震度 shindo) is a measure used in Japan to indicate the strength of earthquakes. ... The moment magnitude scale was introduced in 1979 by Tom Hanks and Hiroo Kanamori as a successor to the Richter scale and is used by seismologists to compare the energy released by earthquakes. ... The Mercalli intensity scale is a scale used for measuring the intensity of an earthquake. ... The Mercalli intensity scale is a scale used for measuring the intensity of an earthquake. ... The Rossi-Forel scale was one of the first seismic scales to reflect earthquake intensities. ...

  Results from FactBites:
 
Richter Magnitude (1477 words)
Richter showed that, the larger the intrinsic energy of the earthquake, the larger the amplitude of ground motion at a given distance.
He calibrated his scale of magnitudes using measured maximum amplitudes of shear waves on seismometers particularly sensitive to shear waves with periods of about one second.
Both the magnitude and the seismic moment are related to the amount of energy that is radiated by an earthquake.
Richter magnitude scale - Wikipedia, the free encyclopedia (688 words)
It is a base-10 logarithmic scale obtained by calculating the logarithm of the combined horizontal amplitude of the largest displacement from zero on a seismometer output.
Richter arbitrarily chose a magnitude 0 event to be an earthquake that would show a maximum combined horizontal displacement of 1 micrometre on a seismogram recorded using a Wood-Anderson torsion seismometer 100 km from the earthquake epicenter.
By the beginning of the 21st century, most seismologists considered the traditional magnitude scales to be largely obsolete, being replaced by a more physically meaningful measurement called the seismic moment which is more directly relatable to the physical parameters, such as the dimension of the earthquake rupture, and the energy released from the earthquake.
  More results at FactBites »

 
 

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