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Earthquake Magnitude

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Encyclopedia of Engineering Geology

Part of the book series: Encyclopedia of Earth Sciences Series ((EESS))

Definition

Earthquake magnitude (M) describes the energy release (or size) of an earthquake.

There are many types of earthquake magnitude scales, with the vast majority based on recorded seismic waveforms (Bormann 2002). Magnitude scales are logarithmic, correct for distance from the earthquake, and are unbounded (the smallest earthquakes are less than zero, and the largest recorded event to date is the 1960 M9.5, Chile earthquake).

Some magnitude scales are based on measurements of shorter-period body waves (primary (P) or secondary (S)-waves), and some are based on longer-period surface waves. The original (and most famous) magnitude scale, the “Richter scale” was developed in the 1930s for California earthquakes (Richter 1935). The modern and most commonly used magnitude scale is moment magnitude , Mw (Hanks and Kanamori 1979). It is based on seismic moment (Mo) release, which directly relates to the fault rupture area and amount of slip.

It is important to note that each unit...

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References

  • Bormann P (2002) Chapter 3: Magnitude of seismic events (Section 3.2). In: Bormann P (ed) New manual of seismological observatory practice (NMSOP), vol 1. GeoForschungs Zentrum, Potsdam, pp 16–49

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  • Hanks TC, Kanamori H (1979) A moment magnitude scale. J Geophys Res 84(B5):2348–2350. https://doi.org/10.1029/JB084iB05p02348

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  • Keefer DK (2002) Investigating landslides caused by earthquakes – a historical review. Surv Geophys 23(6):473–510

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  • Richter CF (1935) An instrumental earthquake magnitude scale. Bull Seismol Soc Am. Seismological Society of America 25(1–2):1–32

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  • Wang C, Wong A, Dreger DS, Manga M (2006) Liquefaction limit during earthquakes and underground explosions – implications on ground-motion attenuation. Bull Seismol Soc Am 96(1):355–363

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Author information

Authors and Affiliations

  1. Geological Survey of Canada, Natural Resources Canada, Sidney, BC, Canada

    John F. Cassidy

Authors
  1. John F. Cassidy
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Correspondence to John F. Cassidy .

Editor information

Editors and Affiliations

  1. Natural Resources Canada, Geological Survey of Canada Natural Resources Canada, Sidney, Ontario, Canada

    Peter Bobrowsky

  2. London, United Kingdom

    Brian Marker

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Cassidy, J.F. (2018). Earthquake Magnitude. In: Bobrowsky, P., Marker, B. (eds) Encyclopedia of Engineering Geology. Encyclopedia of Earth Sciences Series. Springer, Cham. https://doi.org/10.1007/978-3-319-12127-7_102-1

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  • DOI: https://doi.org/10.1007/978-3-319-12127-7_102-1

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  • Publisher Name: Springer, Cham

  • Print ISBN: 978-3-319-12127-7

  • Online ISBN: 978-3-319-12127-7

  • eBook Packages: Springer Reference Earth and Environm. ScienceReference Module Physical and Materials ScienceReference Module Earth and Environmental Sciences

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