Concepts

Moment Magnitude Scale

Also Known As Mw scale

Citation Formats

General Reference

Earth and Environment Atlas. "Moment Magnitude Scale." Accessed August 29, 2026. https://dev-earth.interactiveatlas.org/concepts/moment-magnitude-scale.

APA Style

Earth and Environment Atlas. (n.d.). Moment Magnitude Scale. Retrieved August 29, 2026, from https://dev-earth.interactiveatlas.org/concepts/moment-magnitude-scale

BibTeX

@misc{earthandenvironmentatlas-moment-magnitude-scale,
  author = {Earth and Environment Atlas},
  title = {Moment Magnitude Scale},
  year = {2026},
  url = {https://dev-earth.interactiveatlas.org/concepts/moment-magnitude-scale},
  note = {Accessed August 29, 2026}
}

The standard modern measure of earthquake size, computed from seismic moment, the product of fault area, slip and rock rigidity, rather than from the amplitude a particular instrument records. Unlike the Richter scale it does not saturate for great earthquakes, which is why the largest events, like the magnitude 9 class megathrusts of 2004 and 2011, are stated in moment magnitude.

Facts

Origin Year

1979 1

Introduced by Thomas Hanks and Hiroo Kanamori in 1979, building on Kanamori's 1977 work on seismic moment.

Cross-Tradition Connections

Anticipated By

Richter Magnitude Scale

Richter's local magnitude is the scale moment magnitude was designed to be consistent with while fixing its saturation for great earthquakes.

Source Moment Magnitude Scale (Wikipedia)

Associated With

Modified Mercalli Intensity Scale

Modern seismology pairs Mercalli intensity readings with moment magnitude for the same reason it once paired them with Richter: intensity is local and felt, magnitude is a single value for the whole earthquake.

Source Modified Mercalli Intensity Scale (Wikipedia)