Richter scale

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The Richter magnitude scale is a scale of numbers used to tell the size of earthquakes. Charles Richter developed the Richter Scale in 1935. His scale was based on the seismogram measured by a particular type of seismometer at a distance of 100 kilometres (62 mi) from the earthquake.

Earthquakes 4.5 or higher on the Richter scale can be measured by tools all over the world.

The scale is logarithmic, with a base of 10. The amplitude of an earthquake that scores 3.0 is about 10 times the amplitude of one that scores 2.0. The energy that is released increases by a factor of about 32.

Descriptor Richter Magnitude number Damage caused by the earthquake Frequency of occurrence
Micro Less than 2.0 Micro (very small) earthquakes, people cannot feel these. About 8,000 each day
Very minor 2.0-2.9 People do not feel these, but seismographs are able to detect them. About 1,000 per day
Minor 3.0-3.9 People often feel these, but they rarely cause damage. About 49,000 each year
Light 4.0-4.9

Objects inside houses are disturbed, causing noise. Nothing is damaged.

About 6,200 each year
Moderate 5.0-5.9

Buildings that are not built well may be damaged. Light objects inside a house may be moved.

About 800 per year
Strong 6.0-6.9

Moderately powerful. May cause a lot of damage in a larger area.

About 120 per year
Major 7.0-7.9 Can damage things seriously over larger areas. About 18 per year
Great 8.0-9.9 Massive damage is caused. Heavy objects are thrown into the air and cracks appear on the ground, as well as visible shockwaves. Overhead highways may be destroyed, and buildings are toppled. About 1 per 20 years
Meteoric 10.0+ There are no records of anything of this size. The vibration is about the same as that of a 15 mi meteor. Unknown

(Adapted from U.S. Geological Survey documents)

The earthquake with the biggest recorded magnitude was the Great Chilean Earthquake. It had a magnitude of 9.5 (approximately 9.5 on the Richter scale) and occurred in 1960. About 6,000 people died because of the earthquake.

More examples[change | edit source]

Approximate Richter Magnitude number Seismic energy equivalent: Amount of TNT Example event
0.5 5.6kg Large hand grenade
1.5 178kg Bomb used in WWII
2 1 metric ton Large Bomb used in WWII
2.5 5.6 metric tons Blockbuster bomb (dropped from airplanes) in WWII
3.5 178 metric tons Chernobyl accident, 1986
4 1 kiloton Small atomic bomb
5 32 kilotons Nagasaki atomic bomb
Lincolnshire earthquake (UK), 2008
5.4 150 kilotons 2008 Chino Hills earthquake (Los Angeles, United States)
5.5 178 kilotons Little Skull Mtn. earthquake (NV, USA), 1992
Alum Rock earthquake (CA, USA), 2007
6.0 1 megaton Double Spring Flat earthquake (NV, USA), 1994
6.5 5.6 megatons Caracas (Venezuela), 1967
Rhodes (Greece), 2008
Eureka Earthquake (Humboldt County CA, USA), 2010
6.7 16.2 megatons Northridge earthquake (CA, USA), 1994
6.9 26.8 megatons San Francisco Bay Area earthquake (CA, USA), 1989
7.0 32 megatons Java earthquake (Indonesia), 2009, 2010 Haiti Earthquake
7.1 50 megatons Energy released is equivalent to that of Tsar Bomba, the largest thermonuclear weapon ever tested
1944 San Juan earthquake
7.5 178 megatons Kashmir earthquake (Pakistan), 2005
Antofagasta earthquake (Chile), 2007
7.8 600 megatons Tangshan earthquake (China), 1976
8.0 1 gigaton San Francisco earthquake (CA, USA), 1906
Queen Charlotte earthquake (BC, Canada), 1949
México City earthquake (Mexico), 1985
Gujarat earthquake (India), 2001
Chincha Alta earthquake (Peru), 2007
Sichuan earthquake (China), 2008 (initial estimate: 7.8)
1894 San Juan earthquake
8.5 5.6 gigatons Toba eruption 75,000 years ago; the largest known volcanic event.[1]
Sumatra earthquake (Indonesia), 2007
9.0 32 gigatons 2011 Sendai, Japan Earthquake and Tsunami, Lisbon Earthquake (Lisbon, Portugal), All Saints Day, 1755
9.1 67 gigatons Indian Ocean earthquake, 2004 (40 ZJ in this case)
9.2 90.7 gigatons Anchorage earthquake (AK, USA), 1964
9.5 178 gigatons Valdivia earthquake (Chile), 1960
13.0 108 megatons = 100 teratons Yucatán Peninsula impact (causing Chicxulub crater) 65 Ma ago.[2][3][4][5][6]

References[change | edit source]

  1. 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 Subcontinent Before and After the Toba Super-eruption". Science 317 (5834): 114–116. doi:10.1126/science.1141564. PMID 17615356.
  2. Bralower, Timothy J.; Charles K. Paull; R. Mark Leckie (1998). "The Cretaceous-Tertiary boundary cocktail: Chicxulub impact triggers margin collapse and extensive sediment gravity flows". Geology 26: 331–334. doi:10.1130/0091-7613(1998)026<0331:TCTBCC>2.3.CO;2. ISSN 0091-7613. http://www.geosc.psu.edu/people/faculty/personalpages/tbralower/Braloweretal1998.pdf. Retrieved 2009-09-03.
  3. Klaus, Adam (2000). "Impact-induced mass wasting at the K-T boundary: Blake Nose, western North Atlantic". Geology 28: 319–322. doi:10.1130/0091-7613(2000)28<319:IMWATK>2.0.CO;2. ISSN 0091-7613.
  4. Busby, Cathy J.; Grant Yip; Lars Blikra; Paul Renne (2002). "Coastal landsliding and catastrophic sedimentation triggered by Cretaceous-Tertiary bolide impact: A Pacific margin example?". Geology 30: 687–690. doi:10.1130/0091-7613(2002)030<0687:CLACST>2.0.CO;2. ISSN 0091-7613.
  5. Simms, Michael J. (2003). "Uniquely extensive seismite from the latest Triassic of the United Kingdom: Evidence for bolide impact?". Geology 31: 557–560. doi:10.1130/0091-7613(2003)031<0557:UESFTL>2.0.CO;2. ISSN 0091-7613.
  6. Simkin, Tom; Robert I. Tilling; Peter R. Vogt; Stephen H. Kirby; Paul Kimberly; David B. Stewart (2006). "This dynamic planet. World map of volcanoes, earthquakes, impact craters, and plate tectonics. Inset VI. Impacting extraterrestrials scar planetary surfaces". U.S. Geological Survey. http://mineralsciences.si.edu/tdpmap/pdfs/impact.pdf. Retrieved 2009-09-03.

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