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|[[Microearthquake|Micro]]
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|Microearthquakes, not felt, or felt rarely. Recorded by seismographs.<ref>This is what Richter wrote in his ''Elementary Seismology'' (1958), an opinion copiously reproduced afterwardsafterward in Earth's science primers. Recent evidence shows that earthquakes with negative magnitudes (down to −0.7) can also be felt in exceptional cases, especially when the focus is very shallow (a few hundred metresmeters). See: Thouvenot, F.; Bouchon, M. (2008). "What is the lowest magnitude threshold at which an earthquake can be felt or heard, or objects thrown into the air?," in Fréchet, J., Meghraoui, M. & Stucchi, M. (eds), ''Modern Approaches in Solid Earth Sciences'' (vol. 2), ''Historical Seismology: Interdisciplinary Studies of Past and Recent Earthquakes,'' Springer, Dordrecht, 313–326.</ref>
|Continual/several million per year
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Millions of minor earthquakes occur every year worldwide, equating to hundreds every hour every day.<ref name="IRIS">{{cite web|title=How Often Do Earthquakes Occur|url=http://www.mgs.md.gov/seismic/education/no3.pdf}}</ref> On the other hand, earthquakes of magnitude ≥8.0 occur about once a year, on average.<ref name="IRIS" /> The largest recorded earthquake was the [[1960 Valdivia earthquake|Great Chilean earthquake]] of May 22, 1960, which had a magnitude of 9.5 on the [[moment magnitude scale]].<ref>{{cite web |url=https://earthquake.usgs.gov/regional/world/10_largest_world.php |title=Largest Earthquakes in the World Since 1900 |date=30 November 2012 |access-date=18 December 2013 |url-status=dead |archive-url=https://web.archive.org/web/20091007163455/http://earthquake.usgs.gov/regional/world/10_largest_world.php |archive-date=October 7, 2009 |df=mdy-all }}</ref>
Seismologist Susan Hough has suggested that a magnitude 10 quake may represent a very approximate upper limit for what the Earth's tectonic zones are capable of, which would be the result of the largest known continuous belt of faults rupturing together (along the Pacific coast of the Americas).<ref>{{cite book|last1=Silver|first1=Nate|title=The signal and the noise : the art and science of prediction|date=2013|publisher=Penguin|location=London|isbn=9780141975658}}</ref> A research at the [[Tohoku University]] in Japan found that a magnitude 10 earthquake was theoretically possible if a combined {{convert|3,000|km|mi}} of faults from the [[Japan Trench]] to the [[Kuril–Kamchatka Trench]] ruptured together and moved by {{convert|60|m|ft}} (or if a similar large-scale rupture occurred elsewhere). Such an earthquake would cause ground motions for up to an hour, with tsunamis hitting shores while the ground is still shaking, and if this kind of earthquake occurred, it would probably be a 1-in-10,000 -year event.<ref name="Magnitude 10 tremblor">{{citesite web|url=https://www.japantimes.co.jp/news/2012/12/15/national/magnitude-10-temblor-could-happen-study/|title=Magnitude 10 temblor could happen: study|author=Kyodo|publisher=The Japan Times|date=15 December 2012|access-date=15 September 2020}}</ref>
== Development ==
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