Editing Earthquake (section)

=== {{anchor|Magnitude}}Intensity and magnitude ===
The shaking of the earth is a common phenomenon that has been experienced by humans from the earliest of times. Before the development of strong-motion accelerometers, the intensity of a seismic event was estimated based on the observed effects. Magnitude and intensity are not directly related and calculated using different methods. The magnitude of an earthquake is a single value that describes the size of the earthquake at its source. Intensity is the measure of shaking at different locations around the earthquake. Intensity values vary from place to place, depending on the distance from the earthquake and the underlying rock or soil makeup.<ref>{{Cite book |last1=Earle |first1=Steven |date=September 2015 |title=Physical Geology |edition=2nd |chapter=11.3 Measuring Earthquakes |chapter-url=https://opentextbc.ca/geology/chapter/11-3-measuring-earthquakes/|access-date=2022-10-22 |archive-date=2022-10-21 |archive-url=https://web.archive.org/web/20221021040843/https://opentextbc.ca/geology/chapter/11-3-measuring-earthquakes/ |url-status=live }}</ref>

The [[Seismic magnitude scales#Richter|first scale for measuring earthquake magnitudes]] was developed by [[Charles Francis Richter]] in 1935. Subsequent scales ([[seismic magnitude scales]]) have retained a key feature, where each unit represents a ten-fold difference in the amplitude of the ground shaking and a 32-fold difference in energy. Subsequent scales are also adjusted to have approximately the same numeric value within the limits of the scale.<ref>{{Harvnb|Chung|Bernreuter|1980|p=1}}.</ref>

Although the mass media commonly reports earthquake magnitudes as "Richter magnitude" or "Richter scale", standard practice by most seismological authorities is to express an earthquake's strength on the [[seismic scale#Mw|moment magnitude]] scale, which is based on the actual energy released by an earthquake, the static seismic moment.<ref>{{cite web |title=USGS Earthquake Magnitude Policy (implemented on January 18, 2002) |url=https://earthquake.usgs.gov/aboutus/docs/020204mag_policy.php |publisher=United States Geological Survey |url-status=dead |archive-url=https://web.archive.org/web/20160504144754/http://earthquake.usgs.gov/aboutus/docs/020204mag_policy.php |archive-date=2016-05-04 }} A copy can be found at {{cite web |title=USGS Earthquake Magnitude Policy |url=http://dapgeol.tripod.com/usgsearthquakemagnitudepolicy.htm |access-date=2017-07-25 |archive-date=2017-07-31 |archive-url=https://web.archive.org/web/20170731230704/http://dapgeol.tripod.com/usgsearthquakemagnitudepolicy.htm |url-status=live }}</ref><ref>{{Cite journal |last1=Bormann |first1=P |last2=Di Giacomo |first2=D |date=2011 |title=The moment magnitude Mw and the energy magnitude Me: common roots and differences |url=https://doi.org/10.1007/s10950-010-9219-2 |journal=Journal of Seismology |volume=15 |issue=2 |pages=411–427 |doi=10.1007/s10950-010-9219-2 |via=Springer Link}}</ref>