Editing Earthquake (section)

===Tsunami===
[[File:2004-tsunami.jpg|thumb|The tsunami of the [[2004 Indian Ocean earthquake]]]]
{{main|Tsunami}}

Tsunamis are long-wavelength, long-period sea waves produced by the sudden or abrupt movement of large volumes of water—including when an earthquake [[Submarine earthquake|occurs at sea]]. In the open ocean, the distance between wave crests can surpass {{convert|100|km|mi}}, and the wave periods can vary from five minutes to one hour. Such tsunamis travel 600–800&nbsp;kilometers per hour (373–497 miles per hour), depending on water depth. Large waves produced by an earthquake or a submarine landslide can overrun nearby coastal areas in a matter of minutes. Tsunamis can also travel thousands of kilometers across open ocean and wreak destruction on far shores hours after the earthquake that generated them.<ref name=Noson>{{Cite book|last1=Noson|first1=L.L.|last2=Qamar|first2=A.|last3=Thorsen|first3=G.W.|publisher=Washington State Earthquake Hazards|year=1988|title=Washington Division of Geology and Earth Resources Information Circular 85|url=http://file.dnr.wa.gov/publications/ger_ic85_earthquake_hazards_wa.pdf|access-date=2019-12-01|archive-date=2020-02-04|archive-url=https://web.archive.org/web/20200204162651/https://file.dnr.wa.gov/publications/ger_ic85_earthquake_hazards_wa.pdf|url-status=live}}</ref>

Ordinarily, subduction earthquakes under magnitude 7.5 do not cause tsunamis, although some instances of this have been recorded. Most destructive tsunamis are caused by earthquakes of magnitude 7.5 or more.<ref name=Noson/>