Depth km (43 mi) and 300 km (190

Depth of focus (tectonics)From Wikipedia, the free encyclopediaIn seismology, the depth of focus or focal depth refers to the depth at which an earthquake occurs. Earthquakes occurring at a depth of less than 70 km (43 mi) are classified as shallow-focus earthquakes, while those with a focal depth between 70 km (43 mi) and 300 km (190 mi) are commonly termed mid-focus or intermediate-depth earthquakes.1 In subduction zones, where older and colder oceanic crust descends beneath another tectonic plate, deep-focus earthquakes may occur at much greater depths in the mantle, ranging from 300 km (190 mi) up to 700 km (430 mi).23The cause of deep-focus earthquakes is still not entirely understood since subducted lithosphere at that pressure and temperature regime should not exhibit brittle behavior. A possible mechanism for the generation of deep-focus earthquakes is faulting caused by olivine undergoing a phase transition into a spinel structure,4 with which they are believed to be associated. Earthquakes at this depth of focus typically occur at oceanic-continental convergent boundaries, along Wadati–Benioff zones.5DiscoveryeditThe evidence for deep-focus earthquakes was discovered in 1922 by H.H. Turner of Oxford, England. Previously, all earthquakes were considered to have shallow focal depths. The existence of deep-focus earthquakes was confirmed in 1931 from studies of the seismograms of several earthquakes, which in turn led to the construction of travel-time curves for intermediate and deep earthquakes.1See alsoeditAsthenosphereLithosphereReferencesedit^ Jump up to:a b Spence, William, Stuart A. Sipkin, and George L. Choy (1989). “Measuring the Size of an Earthquake.” Earthquake Information Bulletin (USGS). 21 (1), 58–63.Jump up^ “M7.5 Northern Peru Earthquake of 26 September 2005” (PDF). National Earthquake Information Center. 17 October 2005. Retrieved 2008-08-01.Jump up^ USGS. “M7.5 Northern Peru Earthquake of 26 September 2005” (PDF). Retrieved 2008-08-01.Jump up^ Greene II, H. W.; Burnley, P. C. (October 26, 1989). “A new self-organizing mechanism for deep-focus earthquakes”. Nature. 341 (6244): 733–737. Bibcode:1989Natur.341..733G. doi:10.1038/341733a0.Jump up^ Marius Vassiliou, Bradford Hager, and Arthur Raefsky (1984): “The Distribution of Earthquakes with Depth and Stresses in Subducting Slabs”, Journal of Geodynamics 1, 11–28. This article incorporates public domain material from the United States Geological Survey document: William Spence. “Measuring the Size of an Earthquake”.This tectonics article is a stub. You can help Wikipedia by expanding it.Categories: Plate tectonicsTypes of earthquakeTectonics stubsNavigation menuNot logged inTalkContributionsCreate accountLog inArticleTalkReadEditView historySearchMain pageContentsFeatured contentCurrent eventsRandom articleDonate to WikipediaWikipedia storeInteractionHelpAbout WikipediaCommunity portalRecent changesContact pageToolsWhat links hereRelated changesUpload fileSpecial pagesPermanent linkPage informationWikidata itemCite this pagePrint/exportCreate a bookDownload as PDFPrintable versionLanguages???????Deutsch?????????Edit linksThis page was last edited on 29 November 2017, at 02:16.Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.

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