Richter magnitude scale 1

Richter magnitude scaleThe expression Richter Magnitude Scale refers to a number of ways to assign a single number to quantify theenergy contained in an earthquake.In all cases, the magnitude is a base-10 logarithmic scale obtained by calculating the logarithm of the amplitude ofwaves measured by a seismograph. An earthquake that measures 5.0 on the Richter scale has a shaking amplitude 10times larger and corresponds to an energy release of √1000 ≈ 31.6 times greater than one that measures 4.0.[1]

Since the 1970s the use of the Richter Magnitude Scale has largely been supplanted by the moment magnitude scale.

Development

Charles Richter, c. 1970

Developed in 1935 by Charles Richter in partnership with BenoGutenberg, both from the California Institute of Technology, thescale was firstly intended to be used only in a particular study areain California, and on seismograms recorded on a particularinstrument, the Wood-Anderson torsion seismograph. Richteroriginally reported values to the nearest quarter of a unit, butvalues were later reported with one decimal place. His motivationfor creating the local magnitude scale was to compare the size ofdifferent earthquakes.[1] His inspiration was the apparentmagnitude scale used in astronomy to describe the brightness ofstars and other celestial objects.[2] Richter arbitrarily chose amagnitude 0 event to be an earthquake that would show amaximum combined horizontal displacement of 1 µm (0.00004 in)on a seismogram recorded using a Wood-Anderson torsionseismograph 100 km (unknown operator: u'strong' mi) from theearthquake epicenter. This choice was intended to prevent negativemagnitudes from being assigned. The smallest earthquakes thatcould be recorded and located at the time were of magnitude 3,approximately. However, the Richter scale has no lower limit, andsensitive modern seismographs now routinely record quakes withnegative magnitudes.

ML (local magnitude) was not designed to be applied to data with distances to the hypocenter of the earthquakegreater than 600 km[3] (373 mi). For national and local seismological observatories the standard magnitude scale istoday still ML. Unfortunately this scale saturates at M6.5, approximately, because the high frequency waves recordedlocally have wavelengths shorter than the rupture lengths of large earthquakes.

To be able to measure the size of earthquakes around the globe, Gutenberg and Richter later developed a magnitudescale based on surface waves, surface wave magnitude MS; and another based on body waves, body wavemagnitude mb.[4] These are types of waves that are recorded at teleseismic distances. The two scales were adjustedsuch that they were consistent with the ML scale. This succeeded better with the Ms scale than with the mb scale.Both of these scales saturate when the earthquake is bigger than magnitude 8 and therefore the moment magnitudescale, Mw, was invented.[5]

These older magnitude scales have been superseded by the implementation of methods for estimating the seismicmoment, creating the moment magnitude scale, although the former are still widely used because they can becalculated quickly.

Richter magnitude scale 2

DetailsThe Richter scale proper was defined in 1935 for particular circumstances and instruments; the instrument usedsaturated for strong earthquakes. The scale was replaced by the moment magnitude scale (MMS); for earthquakesadequately measured by the Richter scale, numerical values are approximately the same. Although values measuredfor earthquakes now are actually (MMS), they are frequently reported as Richter values, even for earthquakesof magnitude over 8, where the Richter scale becomes meaningless. Anything above 5 is classed as a risk.The Richter and MMS scales measure the energy released by an earthquake; another scale, the Mercalli intensityscale, classifies earthquakes by their effects, from detectable by instruments but not noticeable to catastrophic. Theenergy and effects are not necessarily strongly correlated; a shallow earthquake in a populated area with soil ofcertain types can be far more intense than a much more energetic deep earthquake in an isolated area.There are several scales which have historically been described as the "Richter scale," especially the localmagnitude and the surface wave scale. In addition, the body wave magnitude, , and the momentmagnitude, , abbreviated MMS, have been widely used for decades, and a couple of new techniques to measuremagnitude are in the development stage.All magnitude scales have been designed to give numerically similar results. This goal has been achieved well for

, , and .[6][7] The scale gives somewhat different values than the other scales. The reason for somany different ways to measure the same thing is that at different distances, for different hypocentral depths, and fordifferent earthquake sizes, the amplitudes of different types of elastic waves must be measured.

is the scale used for the majority of earthquakes reported (tens of thousands) by local and regionalseismological observatories. For large earthquakes worldwide, the moment magnitude scale is most common,although is also reported frequently.The seismic moment, , is proportional to the area of the rupture times the average slip that took place in theearthquake, thus it measures the physical size of the event. is derived from it empirically as a quantity withoutunits, just a number designed to conform to the scale.[8] A spectral analysis is required to obtain , whereasthe other magnitudes are derived from a simple measurement of the amplitude of a specifically defined wave.All scales, except , saturate for large earthquakes, meaning they are based on the amplitudes of waves whichhave a wavelength shorter than the rupture length of the earthquakes. These short waves (high frequency waves) aretoo short a yardstick to measure the extent of the event. The resulting effective upper limit of measurement for is about 6.5 and about 8 for .[9]

New techniques to avoid the saturation problem and to measure magnitudes rapidly for very large earthquakes arebeing developed. One of these is based on the long period P-wave,[10] the other is based on a recently discoveredchannel wave.[11]

The energy release of an earthquake, which closely correlates to its destructive power, scales with the 3⁄2 power ofthe shaking amplitude. Thus, a difference in magnitude of 1.0 is equivalent to a factor of 31.6 ( ) inthe energy released; a difference in magnitude of 2.0 is equivalent to a factor of 1000 ( ) in theenergy released.[12] The elastic energy radiated is best derived from an integration of the radiated spectrum, but onecan base an estimate on because most energy is carried by the high frequency waves.

Richter magnitude scale 3

Richter magnitudesThe Richter magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded byseismographs (adjustments are included to compensate for the variation in the distance between the variousseismographs and the epicenter of the earthquake). The original formula is:[13]

where A is the maximum excursion of the Wood-Anderson seismograph, the empirical function A0 depends only onthe epicentral distance of the station, . In practice, readings from all observing stations are averaged afteradjustment with station-specific corrections to obtain the ML value.Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increasein measured amplitude; in terms of energy, each whole number increase corresponds to an increase of about 31.6times the amount of energy released, and each increase of 0.2 corresponds to a doubling of the energy released.Events with magnitudes greater than about 4.6 are strong enough to be recorded by a seismograph anywhere in theworld, so long as its sensors are not located in the earthquake's shadow.The following describes the typical effects of earthquakes of various magnitudes near the epicenter. The values aretypical only and should be taken with extreme caution, since intensity and thus ground effects depend not only on themagnitude, but also on the distance to the epicenter, the depth of the earthquake's focus beneath the epicenter, andgeological conditions (certain terrains can amplify seismic signals).

Magnitude Description Earthquake effects Frequency of occurrence

Less than2.0

Micro Micro earthquakes, not felt.[14] Continual

2.0–2.9 Minor Generally not felt, but recorded. 1,300,000 per year (est.)

3.0–3.9 Often felt, but rarely causes damage. 130,000 per year (est.)

4.0–4.9 Light Noticeable shaking of indoor items, rattling noises. Significant damage unlikely. 13,000 per year (est.)

5.0–5.9 Moderate Can cause major damage to poorly constructed buildings over small regions. Atmost slight damage to well-designed buildings.

1,319 per year

6.0–6.9 Strong Can be destructive in areas up to about 160 kilometres (unknown operator:u'strong' mi) across in populated areas.

134 per year

7.0–7.9 Major Can cause serious damage over larger areas. 15 per year

8.0–8.9 Great Can cause serious damage in areas several hundred kilometres across. 1 per year

9.0–9.9 Devastating in areas several thousand kilometres across. 1 per 10 years (est.)

10.0+ Massive Never recorded, widespread devastation across very large areas; see below forequivalent seismic energy yield.

Extremely rare (Unknown/May notbe possible)

(Based on U.S. Geological Survey documents.)[15]

Great earthquakes occur once a year, on average. The largest recorded earthquake was the Great Chilean Earthquakeof May 22, 1960, which had a magnitude of 9.5 on the moment magnitude scale.[16]

ExamplesThe following table lists the approximate energy equivalents in terms of TNT explosive force – though note that theearthquake energy is released underground rather than overground.[17] Most energy from an earthquake is nottransmitted to and through the surface; instead, it dissipates into the crust and other subsurface structures. In contrast,a small atomic bomb blast (see nuclear weapon yield) will not simply cause light shaking of indoor items, since itsenergy is released above ground.

Richter magnitude scale 4

Following, 31.623 to the power of 0 equals 1, 31.623 to the power of 1 equals 31.623 and 31.623 to the power of 2equals 1000. Therefore, an 8.0 on the Richter scale releases 31.623 times more energy than a 7.0 and a 9.0 on theRichter scale releases 1000 times more energy than a 7.0.

ApproximateMagnitude

ApproximateTNT for

Seismic EnergyYield

Jouleequivalent

Example

0.0 15 g 63 kJ

0.2 30 g 130 kJ Large hand grenade

0.5 85 g 360 kJ

1.0 480 g 2.0 MJ

1.2 1.1 kg 4.9 MJ Single stick of dynamite [DynoMax Pro]

1.4 2.2 kg 9.8 MJ Seismic impact of typical small construction blast

1.5 2.7 kg 11 MJ

2.0 15 kg 63 MJ

2.5 85 kg 360 MJ

3.0 480 kg 2.0 GJ

3.5 2.7 metric tons 11 GJ PEPCON fuel plant explosion, 1988

3.87 9.5 metric tons 40 GJ Explosion at Chernobyl nuclear power plant, 1986

3.91 11 metric tons 46 GJ Massive Ordnance Air Blast bomb

4.0 15 metric tons 63 GJ El Cerrito (California, USA) earthquake, 2012

4.3 43 metric tons 180 GJ Kent Earthquake (Britain), 2007

4.5 85 metric tons 360 GJ Tajikistan earthquake, 2006

5.0 480 metric tons 2.0 TJ Lincolnshire earthquake (UK), 2008Ontario-Quebec earthquake (Canada), 2010[18][19]

5.5 2.7 kilotons 11 TJ Little Skull Mtn. earthquake (Nevada, USA), 1992Alum Rock earthquake (California, USA), 2007Chino Hills earthquake (Los Angeles, USA), 2008

5.6 3.8 kilotons 16 TJ Newcastle Earthquake Australia, 1989Sparks Earthquake (Oklahoma, USA), 2011

6.0 15 kilotons 63 TJ Double Spring Flat earthquake (Nevada, USA), 1994

6.3 43 kilotons 180 TJ Rhodes earthquake (Greece), 2008Christchurch earthquake (New Zealand), 2011

6.4 60 kilotons 250 TJ Kaohsiung earthquake (Taiwan), 2010 Vancouver earthquake (Canada), 2011

6.5 85 kilotons 360 TJ Caracas earthquake (Venezuela), 1967Eureka earthquake (California, USA), 2010

Zumpango del Rio earthquake (Guerrero, Mexico), 2011[20]

6.6 120 kilotons 500 TJ San Fernando earthquake (California, USA), 1971

6.7 170 kilotons 710 TJ Northridge earthquake (California, USA), 1994

6.8 240 kilotons 1.0 PJ Nisqually earthquake (Anderson Island, WA), 2001Gisborne earthquake (Gisborne, NZ), 2007

Richter magnitude scale 5

6.9 340 kilotons 1.4 PJ San Francisco Bay Area earthquake (California, USA), 1989Pichilemu earthquake (Chile), 2010Sikkim earthquake (Nepal-India Border), 2011

7.0 480 kilotons 2.0 PJ Java earthquake (Indonesia), 2009Haiti earthquake, 2010

7.1 680 kilotons 2.8 PJ Messina earthquake (Italy), 1908San Juan earthquake (Argentina), 1944Canterbury earthquake (New Zealand), 2010

7.2 950 kilotons 4.0 PJ Vrancea earthquake (Romania), 1977Baja California earthquake (Mexico), 2010

7.5 2.7 megatons 11 PJ Kashmir earthquake (Pakistan), 2005Antofagasta earthquake (Chile), 2007

7.6 3.8 megatons 16 PJ Oaxaca earthquake (Mexico), 2012 Gujarat earthquake (India), 2001İzmit earthquake (Turkey), 1999

7.7 5.4 megatons 22 PJ Sumatra earthquake (Indonesia), 2010

7.8 7.6 megatons 32 PJ Tangshan earthquake (China), 1976Hawke's Bay earthquake (New Zealand), 1931Luzon earthquake (Philippines), 1990

7.9 10-15 megatons 42-63 PJ Tunguska event

8.0 15 megatons 63 PJ Mino-Owari earthquake (Japan), 1891San Juan earthquake (Argentina), 1894San Francisco earthquake (California, USA), 1906

Queen Charlotte Islands earthquake (B.C., Canada), 1949Chincha Alta earthquake (Peru), 2007Sichuan earthquake (China), 2008

Kangra earthquake, 1905

8.1 21 megatons 89 PJ México City earthquake (Mexico), 1985Guam earthquake, August 8, 1993[21]

8.35 50 megatons 210 PJ Tsar Bomba - Largest thermonuclear weapon ever tested

8.5 85 megatons 360 PJ Sumatra earthquake (Indonesia), 2007

8.6 - - Sumatra earthquake (Indonesia), 2012

8.7 170 megatons 710 PJ Sumatra earthquake (Indonesia), 2005

8.75 200 megatons 840 PJ Krakatoa 1883

8.8 240 megatons. 1.0 EJ Chile earthquake, 2010,

9.0 480 megatons 2.0 EJ Lisbon earthquake (Portugal), All Saints Day, 1755Great East Japan Earthquake, March 2011

9.15 800 megatons 3.3 EJ Toba eruption 75,000 years ago; among the largest known volcanic events.[22]

9.2 950 megatons 4.0 EJ Anchorage earthquake (Alaska, USA), 1964Sumatra-Andaman earthquake and tsunami (Indonesia), 2004

9.5 2.7 gigatons 11 EJ Valdivia earthquake (Chile), 1960

10.0 15 gigatons 63 EJ Never recorded

12.55 100 teratons 420 ZJ Yucatán Peninsula impact (creating Chicxulub crater) 65 Ma ago (108 megatons; over4x1030 ergs = 400 ZJ).[23][24][25][26][27]

32.0 1.5×1043 tons 6.3×1052 J Approximate magnitude of the starquake on the magnetar SGR 1806-20, registered onDecember 27, 2004.[28]

Richter magnitude scale 6

• Quakes using the more modern magnitude scales will denote their abbreviations: and . Those thathave no denoted prefix are . Please be advised that the magnitude "number" (example 7.0) displayed forthose quakes on this table may represent a significantly greater or lesser release in energy than by the correctlygiven magnitude (example ).

Magnitude empirical formulaeThese formulae are an alternative method to calculate Richter magnitude instead of using Richter correlation tablesbased on Richter standard seismic event ( =0, A=0.001mm, D=100km).The Lillie empirical formula:

Where:•• A is the amplitude (maximum ground displacement) of the P-wave, in micrometers, measured at 0.8 Hz.• is the epicentral distance, in km.For distance less than 200km:

For distance between 200km and 600km:

where A is seismograph signal amplitude in mm, D distance in km.The Bisztricsany (1958) empirical formula for epicentral distances between 4˚ to 160˚:

Where:• is magnitude (mainly in the range of 5 to 8)• is the duration of the surface wave in seconds• is the epicentral distance in degrees.The Tsumura empirical formula:

Where:• is the magnitude (mainly in the range of 3 to 5).• is the total duration of oscillation in seconds.• is the epicentral distance in kilometers.The Tsuboi, University of Tokio, empirical formula:

Where:• is the magnitude.• is the amplitude in um.• is the epicentral distance in kilometers.

Richter magnitude scale 7

References[1] The Richter Magnitude Scale (http:/ / earthquake. usgs. gov/ learn/ topics/ richter. php)[2] Hough, S.E. (2007). Richter's scale: measure of an earthquake, measure of a man (http:/ / books. google. co. uk/

books?id=rvmDeAxEiO8C& pg=PA121& dq=richter+ scale+ star+ brightness& hl=en& ei=bA7jToe6M4Wc8gOPgJH5Aw& sa=X&oi=book_result& ct=result& resnum=1& sqi=2& ved=0CDQQ6AEwAA#v=onepage& q=richter scale star brightness& f=false). PrincetonUniversity Press. p. 121. ISBN 9780691128078. . Retrieved 10 December 2011.

[3] "USGS Earthquake Magnitude Policy" (http:/ / earthquake. usgs. gov/ aboutus/ docs/ 020204mag_policy. php). USGS. March 29, 2010. .[4] William L. Ellsworth (1991). SURFACE-WAVE MAGNITUDE (Ms) AND BODY-WAVE MAGNITUDE (mb) (http:/ / www. johnmartin. com/

earthquakes/ eqsafs/ safs_694. htm). USGS. . Retrieved 2008-09-14.[5][5] Kanamori[6][6] Richter, C.F., 1936. "An instrumental earthquake magnitude scale", Bulletin of the Seismological Society of America 25, no., 1-32.[7][7] Richter, C.F., "Elementary Seismology", edn, Vol., W. H. Freeman and Co., San Francisco, 1956.[8][8] Hanks, T. C. and H. Kanamori, 1979, "Moment magnitude scale", Journal of Geophysical Research, 84, B5, 2348.[9] "Richter scale" (http:/ / earthquake. usgs. gov/ hazards/ qfaults/ glossary. php). Glossary. USGS. March 31, 2010. .[10] Di Giacomo, D., Parolai, S., Saul, J., Grosser, H., Bormann, P., Wang, R. & Zschau, J., 2008. Rapid determination of the enrgy magnitude

Me, in European Seismological Commission 31st General Assembly, Hersonissos.[11] Rivera, L. & Kanamori, H., 2008. Rapid source inversion of W phase for tsunami warning, in European Geophysical Union General

Assembly, pp. A-06228, Vienna.[12] USGS: Measuring the Size of an Earthquake, Section 'Energy, E' (http:/ / earthquake. usgs. gov/ learn/ topics/ measure. php)[13] Ellsworth, William L. (1991). The Richter Scale ML, from The San Andreas Fault System, California (Professional Paper 1515) (http:/ /

www. johnmartin. com/ earthquakes/ eqsafs/ safs_693. htm). USGS. pp. c6, p177. . Retrieved 2008-09-14.[14] This is what Richter wrote in his Elementary Seismology (1958), an opinion copiously reproduced afterwards in Earth's science primers.

Recent evidence shows that earthquakes with negative magnitudes (down to −0.7) can also be felt in exceptional cases, especially when thefocus is very shallow (a few hundred metres). See: Thouvenot, F.; Bouchon, M. (2008). What is the lowest magnitude threshold at which anearthquake can be felt or heard, or objects thrown into the air?, in Fréchet, J., Meghraoui, M. & Stucchi, M. (eds), Modern Approaches inSolid Earth Sciences (vol. 2), Historical Seismology: Interdisciplinary Studies of Past and Recent Earthquakes, Springer, Dordrecht, 313–326.

[15] (http:/ / earthquake. usgs. gov/ earthquakes/ eqarchives/ year/ eqstats. php)[16] USGS: List of World's Largest Earthquakes (http:/ / earthquake. usgs. gov/ regional/ world/ 10_largest_world. php)[17] FAQs – Measuring Earthquakes (http:/ / earthquake. usgs. gov/ learn/ faq/ ?faqID=33)[18] "Magnitude 5.0 – Ontario-Quebec border region, Canada" (http:/ / earthquake. usgs. gov/ earthquakes/ recenteqsww/ Quakes/ us2010xwa7.

php#details). earthquake.usgs.gov. . Retrieved 2010-06-23.[19] "Moderate 5.0 earthquake shakes Toronto, Eastern Canada and U.S." (http:/ / news. nationalpost. com/ 2010/ 06/ 23/

tremors-felt-in-toronto-ottawa-reports/ ). nationalpost.com. . Retrieved 2010-06-23.[20] km al NOROESTE de ZUMPANGO DEL RIO, GRO &regresar=catalogo1 "Zumpango Del Rio Earthquake" (http:/ / www. ssn. unam. mx/

website/ jsp/ localizacion. jsp?& archivo=111210_194725. gif& evento=1& fecha=2011-12-10& hora=19:47:25& latitud=17. 84&longitud=-99. 98& profundidad=58& magnitud=6. 5& epicentro=53) (in Mexican). Servicio Sismologico Nacional. km al NOROESTE deZUMPANGO DEL RIO, GRO &regresar=catalogo1. Retrieved 28 December 2011.

[21] "M8.1 South End of Island August 8, 1993." (http:/ / www. eeri. org/ site/ reconnaissance-activities/ 64-guam/ 182-m81southendofisland).eeri.org. . Retrieved 2011-03-11..

[22] Petraglia, M.; R. Korisettar, N. Boivin, C. Clarkson,4 P. Ditchfield,5 S. Jones,6 J. Koshy,7 M.M. Lahr,8 C. Oppenheimer,9 D. Pyle,10 R.Roberts,11 J.-C. Schwenninger,12 L. Arnold,13 K. White. (6 July 2007). "Middle Paleolithic Assemblages from the Indian SubcontinentBefore and After the Toba Super-eruption" (http:/ / toba. arch. ox. ac. uk/ pub_files/ Petraglia2007Science. pdf). Science 317 (5834): 114–116.doi:10.1126/science.1141564. PMID 17615356.

[23] Bralower, Timothy J.; Charles K. Paull; R. Mark Leckie (1998). "The Cretaceous-Tertiary boundary cocktail: Chicxulub impact triggersmargin collapse and extensive sediment gravity flows" (http:/ / www. geosc. psu. edu/ people/ faculty/ personalpages/ tbralower/Braloweretal1998. pdf). Geology 26: 331–334. Bibcode 1998Geo....26..331B. doi:10.1130/0091-7613(1998)026<0331:TCTBCC>2.3.CO;2.ISSN 0091-7613. . Retrieved 2009-09-03.

[24] Klaus, Adam; Norris, Richard D.; Kroon, Dick; Smit, Jan (2000). "Impact-induced mass wasting at the K-T boundary: Blake Nose, westernNorth Atlantic". Geology 28: 319–322. Bibcode 2000Geo....28..319K. doi:10.1130/0091-7613(2000)28<319:IMWATK>2.0.CO;2.ISSN 0091-7613.

[25] Busby, Cathy J.; Grant Yip; Lars Blikra; Paul Renne (2002). "Coastal landsliding and catastrophic sedimentation triggered byCretaceous-Tertiary bolide impact: A Pacific margin example?". Geology 30: 687–690. Bibcode 2002Geo....30..687B.doi:10.1130/0091-7613(2002)030<0687:CLACST>2.0.CO;2. ISSN 0091-7613.

[26] Simms, Michael J. (2003). "Uniquely extensive seismite from the latest Triassic of the United Kingdom: Evidence for bolide impact?".Geology 31: 557–560. Bibcode 2003Geo....31..557S. doi:10.1130/0091-7613(2003)031<0557:UESFTL>2.0.CO;2. ISSN 0091-7613.

[27] Simkin, Tom; Robert I. Tilling; Peter R. Vogt; Stephen H. Kirby; Paul Kimberly; David B. Stewart (2006). "This dynamic planet. Worldmap of volcanoes, earthquakes, impact craters, and plate tectonics. Inset VI. Impacting extraterrestrials scar planetary surfaces" (http:/ /mineralsciences. si. edu/ tdpmap/ pdfs/ impact. pdf). U.S. Geological Survey. . Retrieved 2009-09-03.

Richter magnitude scale 8

[28] Phil Plait (2009). "Anniversary of a cosmic blast" (http:/ / blogs. discovermagazine. com/ badastronomy/ 2009/ 12/ 27/anniversary-of-a-cosmic-blast/ ). discovermagazine.com. . Retrieved 2010-11-26.

External links• IRIS Real-time Seismic Monitor of the Earth (http:/ / www. iris. edu/ seismon/ )• USGS: magnitude and intensity comparison (http:/ / earthquake. usgs. gov/ learning/ topics/ mag_vs_int. php)• USGS: Earthquake Magnitude Policy (http:/ / earthquake. usgs. gov/ aboutus/ docs/ 020204mag_policy. php)• USGS: 2000–2006 Earthquakes worldwide (http:/ / neic. usgs. gov/ neis/ eqlists/ eqstats. html)• USGS: 1990–1999 Earthquakes worldwide (http:/ / neic. usgs. gov/ neis/ eqlists/ info_1990s. html)• Alaska Railroad Earthquake (http:/ / www. alaskarails. org/ historical/ earthquake/ earthquake-richter. html) with

a table of yield-to-magnitude relations.

Article Sources and Contributors 9

Article Sources and ContributorsRichter magnitude scale  Source: http://en.wikipedia.org/w/index.php?oldid=489796213  Contributors: 21655, 62.253.64.xxx, A p3rson, A.Ou, A3RO, Aagneyaatreya, Abdullais4u, Acebero,Achowat, Acroterion, Adacus12, Adbento, Aeon1006, Ahoerstemeier, Airodyssey, Aitias, Alemand, Alex.muller, Alfio, Altenmann, Amalthea, AmiDaniel, Andre Engels, Andrew Gray,AngryParsley, Animum, Anon 5584, Aoi, Arcturus, Argyriou, Arjun01, Armandeh, Armando, Ashanda, Ashill, Asknine, Atchom, Atif.t2, Auntof6, Austria156, AvicAWB, Avicennasis,AxelBoldt, Babylon pride, Banaticus, Baodo, Bbatsell, Beach drifter, Ben-Zin, BenFrantzDale, Bender235, Bento00, Berland, Beru7, Bgautrea, Bjornkri, Bjquinn, Blackfyr, Blanchardb,Blrt1016, Bluemoose, Bmicomp, Bobblewik, Bobo192, Boffman, Bongwarrior, Borat fan, Borbrav, Brandon5485, Brianhill, Bruce1ee, CWenger, CWii, Camden7, Can't sleep, clown will eat me,CanadianLinuxUser, Cedric Tsui, Cekli829, Charles Nielsen, Cherkash, ChessA4, Chessmanlau, Chris 73, Christian List, Cmdrbond, ColdCase, Colinmotox11, Collegebookworm, Conversionscript, Cubs Fan, Curps, Cynix, Cyoney, D4g0thur, DJ Clayworth, DasallmächtigeJ, David.Monniaux, Davidwj, Dawright12, De728631, Delirium, Deltabeignet, Denisarona, DerHexer, Deus exmachina, Diagonalfish, Diego Grez, Diemunkiesdie, Discospinster, Dkf11, Doctorwho123456, Dod1, DopefishJustin, Dpmwuzzlefuzzle, Dragslice, Drfunko, Drpixie, Duncan.france, E23,ESkog, Earl Andrew, Edinburgh Wanderer, Ehinson56, Electron9, Elipongo, Eliz81, Elizium23, Emx, Endersdouble, Epbr123, Ercolev, Ericorbit, Erlenmayr, Eshafto, Esp666, Euclidcrescent,Ewa5050, Eyreland, Fatalvampire420, Ferkelparade, Finlay McWalter, Firien, Flubeca, Fly by Night, Fragilewindows, Francesco Betti Sorbelli, Frap, Fritsebits, Fullyaddicted, Funky Monkey,Fæ, GDonato, GManNickG, GTamber, Gabriel, Gareth E Kegg, Gblandst, Gene Nygaard, Geographical, Georgexx316, Gfoley4, Gianfranco, Giftlite, Gilliam, Gilo1969, Gimmetoo, Gioto,Glane23, Glenn L, GorillaSalsa, Graham87, GrahamN, GreaterWikiholic, Greg Glover, GregorB, Griffin4prez, GromXXVII, Grymwulf, Gurch, Gwernol, HYC, Habbit, Hackersr4us, Hadal,Halette, HalfShadow, Hankwang, Havocrazy, Hertz1888, Himanlol123, Historynut101, Hmains, Hoary, Hockachu, Hqb, Huangcjz, Huji, Hullcannons, Hyacinth, Hydrargyrum, Illuminatedwax,Im.a.lumberjack, Impossiblepolis, Insanity Incarnate, Intovert2438, Inversionbursatil, Iridescent, Island Monkey, Ixfd64, J.delanoy, JM5349, JPG-GR, Jagged 85, Jay Gatsby, Jayjg, Jcarkeys,Jeandré du Toit, Jeepday, Jernejovc, Jerry Zhang, Jimp, Jkominek, Jkwchui, Jlgnlkdf, Joeinwap, Joemc72, Johann Wolfgang, John, John.St, JohnBlackburne, JohnCD, Joowwww, JosephSpadaro, Josh Parris, Joshuavandyk, Jossi, Juan A. 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Image Sources, Licenses and ContributorsImage:CharlesRichter.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:CharlesRichter.jpg  License: Public Domain  Contributors: Infrogmation, Kyro, 1 anonymous edits

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