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Richter scale

Updated: 12/11/2025, 2:11:53 PM Wikipedia source

The Richter scale (), also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale, is a measure of the strength of earthquakes, developed by Charles Richter in collaboration with Beno Gutenberg, and presented in Richter's landmark 1935 paper, where he called it the "magnitude scale". This was later revised and renamed the local magnitude scale, denoted as ML or ML . Because of various shortcomings of the original ML  scale, most seismological authorities now use other similar scales such as the moment magnitude scale (Mw ) to report earthquake magnitudes, but much of the news media still erroneously refers to these as "Richter" magnitudes. All magnitude scales retain the logarithmic character of the original and are scaled to have roughly comparable numeric values (typically in the middle of the scale). Due to the variance in earthquakes, it is essential to understand the Richter scale uses common logarithms simply to make the measurements manageable (i.e., a magnitude 3 quake factors 10³ while a magnitude 5 quake factors 105 and has seismometer readings 100 times larger).

Tables

· Richter magnitudes
1.0–1.9
1.0–1.9
Magnitude
1.0–1.9
Description
Micro
Typical maximum modified Mercalli intensity
MMI I (Not felt)
Average earthquake effects
Microearthquakes, not felt. Recorded by seismographs.
Average frequency of occurrence globally (estimated)
Continual/several million per year
2.0–2.9
2.0–2.9
Magnitude
2.0–2.9
Description
Minor
Typical maximum modified Mercalli intensity
MMI I (Not felt)
Average earthquake effects
Felt slightly by some people. No damage to buildings.
Average frequency of occurrence globally (estimated)
Over one million per year
3.0–3.9
3.0–3.9
Magnitude
3.0–3.9
Description
Slight
Typical maximum modified Mercalli intensity
MMI II (Weak)toMMI III (Weak)
Average earthquake effects
Often felt by people, but very rarely causes damage. Shaking of indoor objects can be noticeable.
Average frequency of occurrence globally (estimated)
Over 100,000 per year
4.0–4.9
4.0–4.9
Magnitude
4.0–4.9
Description
Light
Typical maximum modified Mercalli intensity
MMI IV (Light)toMMI V (Moderate)
Average earthquake effects
Noticeable shaking of indoor objects and rattling noises. Felt by most people in the affected area. Slightly felt outside. Generally causes zero to minimal damage. Moderate to significant damage is very unlikely. Some objects may fall off shelves or be knocked over.
Average frequency of occurrence globally (estimated)
10,000 to 15,000 per year
5.0–5.9
5.0–5.9
Magnitude
5.0–5.9
Description
Moderate
Typical maximum modified Mercalli intensity
MMI V (Moderate)toMMI VI (Strong)
Average earthquake effects
Can cause damage of varying severity to poorly constructed buildings. Zero to slight damage to all other buildings. Felt by everyone.
Average frequency of occurrence globally (estimated)
1,000 to 1,500 per year
6.0–6.9
6.0–6.9
Magnitude
6.0–6.9
Description
Strong
Typical maximum modified Mercalli intensity
MMI VI (Strong)toMMI IX (Violent)
Average earthquake effects
Damage to a moderate number of well-built structures in populated areas. Earthquake-resistant structures survive with slight to moderate damage. Poorly designed structures receive moderate to severe damage. Felt in wider areas; up to hundreds of kilometers from the epicenter. Strong to violent shaking in the epicentral area.
Average frequency of occurrence globally (estimated)
100 to 150 per year.
7.0–7.9
7.0–7.9
Magnitude
7.0–7.9
Description
Major
Typical maximum modified Mercalli intensity
MMI VIII (Severe)or higher
Average earthquake effects
Causes damage to most buildings, some to partially or completely collapse or receive severe damage. Well-designed structures are likely to receive damage. Felt across great distances with major damage mostly limited to 250 km from the epicenter. A magnitude 7.0 or greater will result in a tsunami alert being issued to certain regions.
Average frequency of occurrence globally (estimated)
10 to 20 per year
8.0–8.9
8.0–8.9
Magnitude
8.0–8.9
Description
Great
Typical maximum modified Mercalli intensity
Major damage to buildings, and structures likely to be destroyed. Will cause moderate to heavy damage to sturdy or earthquake-resistant buildings. Damaging in large areas. Felt in extremely large regions.
Average earthquake effects
One per year
9.0–9.9
9.0–9.9
Magnitude
9.0–9.9
Description
Extreme
Typical maximum modified Mercalli intensity
Near total destruction – severe damage or collapse to all buildings. Heavy damage and shaking extend to distant locations. Permanent changes in ground topography.
Average earthquake effects
One to three per century
Magnitude
Description
Typical maximum modified Mercalli intensity
Average earthquake effects
Average frequency of occurrence globally (estimated)
1.0–1.9
Micro
MMI I (Not felt)
Microearthquakes, not felt. Recorded by seismographs.
Continual/several million per year
2.0–2.9
Minor
MMI I (Not felt)
Felt slightly by some people. No damage to buildings.
Over one million per year
3.0–3.9
Slight
MMI II (Weak)toMMI III (Weak)
Often felt by people, but very rarely causes damage. Shaking of indoor objects can be noticeable.
Over 100,000 per year
4.0–4.9
Light
MMI IV (Light)toMMI V (Moderate)
Noticeable shaking of indoor objects and rattling noises. Felt by most people in the affected area. Slightly felt outside. Generally causes zero to minimal damage. Moderate to significant damage is very unlikely. Some objects may fall off shelves or be knocked over.
10,000 to 15,000 per year
5.0–5.9
Moderate
MMI V (Moderate)toMMI VI (Strong)
Can cause damage of varying severity to poorly constructed buildings. Zero to slight damage to all other buildings. Felt by everyone.
1,000 to 1,500 per year
6.0–6.9
Strong
MMI VI (Strong)toMMI IX (Violent)
Damage to a moderate number of well-built structures in populated areas. Earthquake-resistant structures survive with slight to moderate damage. Poorly designed structures receive moderate to severe damage. Felt in wider areas; up to hundreds of kilometers from the epicenter. Strong to violent shaking in the epicentral area.
100 to 150 per year.
7.0–7.9
Major
MMI VIII (Severe)or higher
Causes damage to most buildings, some to partially or completely collapse or receive severe damage. Well-designed structures are likely to receive damage. Felt across great distances with major damage mostly limited to 250 km from the epicenter. A magnitude 7.0 or greater will result in a tsunami alert being issued to certain regions.
10 to 20 per year
8.0–8.9
Great
Major damage to buildings, and structures likely to be destroyed. Will cause moderate to heavy damage to sturdy or earthquake-resistant buildings. Damaging in large areas. Felt in extremely large regions.
One per year
9.0–9.9
Extreme
Near total destruction – severe damage or collapse to all buildings. Heavy damage and shaking extend to distant locations. Permanent changes in ground topography.
One to three per century

References

  1. Kanamori 1978, p. 411. Hough (2007, pp. 122–126) discusses the name at some length.
  2. Annals of the Former World
  3. Kanamori 1978, p. 411; Richter 1935.
  4. Gutenberg & Richter 1956b, p. 30.
  5. stewartmath.com
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  6. The San Andreas Fault System, California
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  7. American Journal of Physics
    http://aapt.scitation.org/doi/10.1119/1.12026
  8. A dictionary of earth sciences
    https://search.worldcat.org/oclc/177509121
  9. Bulletin Volcanologique
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  10. "What is the Richter Magnitude Scale?"
    https://web.archive.org/web/20210803200647/https://www.gns.cri.nz/Home/Learning/Science-Topics/Earthquakes/Monitoring-Earthquakes/Other-earthquake-questions/What-is-the-Richter-Magnitude-Scale
  11. "Magnitude / Intensity Comparison"
    https://web.archive.org/web/20110623113247/http://earthquake.usgs.gov/learn/topics/mag_vs_int.php
  12. This is what Richter wrote in his Elementary Seismology (1958), an opinion copiously reproduced afterward in Earth's sci
  13. Geology
    https://doi.org/10.1130%2FG24402A.1
  14. "Earthquake Facts and Statistics"
    https://web.archive.org/web/20100524161817/http://earthquake.usgs.gov/earthquakes/eqarchives/year/eqstats.php
  15. "How Often Do Earthquakes Occur"
    https://web.archive.org/web/20161221093605/http://www.mgs.md.gov/seismic/education/no3.pdf
  16. "Largest Earthquakes in the World Since 1900"
    https://web.archive.org/web/20091007163455/http://earthquake.usgs.gov/regional/world/10_largest_world.php
  17. The signal and the noise : the art and science of prediction
  18. The Japan Times
    https://www.japantimes.co.jp/news/2012/12/15/national/magnitude-10-temblor-could-happen-study/
  19. Bolt 1993, p. 47.
  20. Hough 2007;
  21. Hough 2007, p. 57.
  22. Hough 2007, pp. 57, 116.
  23. Richter 1935, p. 2.
  24. Richter 1935, pp. 1–5.
  25. Richter 1935, pp. 2–3.
  26. [pending]
  27. Richter 1935, p. 14: Gutenberg & Richter 1936, p. 183.
  28. Richter 1935, p. 5. See also Hutton & Boore 1987, p. 1; Chung & Bernreuter 1980, p. 10.
  29. Richter 1935, p. 6, Table I.
  30. Richter 1935, p. 32.
  31. Chung & Bernreuter 1980, p. 5.
  32. Richter 1935, p. 1. His article is titled: "An Instrumental Earthquake Magnitude Scale".
  33. Hough 2007, pp. 123–124.
  34. "Explanation of Bulletin Listings, USGS"
    https://earthquake.usgs.gov/earthquakes/eqarchives/mineblast/definitions.php
  35. Richter 1935.
  36. Richter, C.F., "Elementary Seismology", ed, Vol., W. H. Freeman and Co., San Francisco, 1956.
  37. Journal of Geophysical Research
    https://ui.adsabs.harvard.edu/abs/1979JGR....84.2348H
  38. "On Earthquake Magnitudes"
    https://web.archive.org/web/20170524163729/http://www.weather.gov.hk/education/edu02rga/article/ele-EarthquakeMagnetude_e.htm
  39. Glossary
    https://earthquake.usgs.gov/hazards/qfaults/glossary.php
  40. Di Giacomo, D., Parolai, S., Saul, J., Grosser, H., Bormann, P., Wang, R. & Zschau, J., 2008. "Rapid determination of th
  41. Rivera, L. & Kanamori, H., 2008. "Rapid source inversion of W phase for tsunami warning," in European Geophysical Union
  42. Bull. Seismol. Soc. Am
  43. Earthquakes and Volcanoes
    https://earthquake.usgs.gov/learn/topics/measure.php
  44. US Geological Survey open-file report
  45. Journal of King Saud University – Science
    https://doi.org/10.1016%2Fj.jksus.2011.04.001
  46. Journal of King Saud University – Science
    https://doi.org/10.1016%2Fj.jksus.2011.04.001
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