| Revision as of 17:25, 4 February 2012 editAstronaut (talk | contribs)Extended confirmed users, Pending changes reviewers19,192 edits Is that a better layout?← Previous edit | Revision as of 17:56, 4 February 2012 edit undoPrimeHunter (talk | contribs)Administrators79,207 edits move image to left in response to help desk postNext edit → | ||
| Line 1: | Line 1: | ||
| ⚫ | ]'s focus (]).]] | ||
| {{Otheruses}} | {{Otheruses}} | ||
| {{stack begin}} | |||
| {{Earthquakes}} | {{Earthquakes}} | ||
| {{Wiktionary}} | {{Wiktionary}} | ||
| {{stack end}} | |||
| The '''epicenter''' or '''epicentre''' ({{IPA-en|ˈɛpɪsɛntər|pron}}) is the point on the ]'s surface that is directly above the ] or focus, the point where an ] or underground explosion originates. The word derives from the ] noun ''epicentrum'',<ref>{{Cite book | title = Merriam-Webster Online Dictionary | chapter = epicenter | year = 2009 | url = http://www.merriam-webster.com/dictionary/epicenter | accessdate = 2009-10-19}}</ref> the ] of the ] adjective ἐπίκεντρος (''epikentros''), "occupying a cardinal point, situated on a centre",<ref>, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus</ref> from ἐπί (''epi'') "on, upon, at"<ref>, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus</ref> and κέντρον (''kentron'') "]".<ref>, on Oxford Dictionaries</ref> | The '''epicenter''' or '''epicentre''' ({{IPA-en|ˈɛpɪsɛntər|pron}}) is the point on the ]'s surface that is directly above the ] or focus, the point where an ] or underground explosion originates. The word derives from the ] noun ''epicentrum'',<ref>{{Cite book | title = Merriam-Webster Online Dictionary | chapter = epicenter | year = 2009 | url = http://www.merriam-webster.com/dictionary/epicenter | accessdate = 2009-10-19}}</ref> the ] of the ] adjective ἐπίκεντρος (''epikentros''), "occupying a cardinal point, situated on a centre",<ref>, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus</ref> from ἐπί (''epi'') "on, upon, at"<ref>, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus</ref> and κέντρον (''kentron'') "]".<ref>, on Oxford Dictionaries</ref> | ||
| ⚫ | ]'s focus (]).]] | ||
| In the case of earthquakes, the epicenter is directly above the point where the ] begins to rupture, and in most cases, it is the area of greatest damage. However, in larger events, the length of the fault rupture is much longer, and damage can be spread across the rupture zone. For example, in the magnitude 7.9, ] in ], the epicenter was at the western end of the rupture, but the greatest damage occurred about 330 km away at the eastern end of the rupture zone.<ref>{{cite web|url=http://pubs.usgs.gov/fs/2003/fs014-03/|title=Rupture in South-Central Alaska—The Denali Fault Earthquake of 2002|publisher=USGS|first=Gary|last=Fuis|coauthors=Wald, Lisa|accessdate=2008-04-20}}</ref> | In the case of earthquakes, the epicenter is directly above the point where the ] begins to rupture, and in most cases, it is the area of greatest damage. However, in larger events, the length of the fault rupture is much longer, and damage can be spread across the rupture zone. For example, in the magnitude 7.9, ] in ], the epicenter was at the western end of the rupture, but the greatest damage occurred about 330 km away at the eastern end of the rupture zone.<ref>{{cite web|url=http://pubs.usgs.gov/fs/2003/fs014-03/|title=Rupture in South-Central Alaska—The Denali Fault Earthquake of 2002|publisher=USGS|first=Gary|last=Fuis|coauthors=Wald, Lisa|accessdate=2008-04-20}}</ref> | ||
Revision as of 17:56, 4 February 2012
For other uses, see Epicenter (disambiguation).| Part of a series on |
| Earthquakes |
|---|
 |
| Types |
| Causes |
| Characteristics |
| Measurement |
| Prediction |
| Other topics |
The epicenter or epicentre (pronounced /ˈɛpɪsɛntər/) is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates. The word derives from the New Latin noun epicentrum, the latinisation of the ancient Greek adjective ἐπίκεντρος (epikentros), "occupying a cardinal point, situated on a centre", from ἐπί (epi) "on, upon, at" and κέντρον (kentron) "centre".
In the case of earthquakes, the epicenter is directly above the point where the fault begins to rupture, and in most cases, it is the area of greatest damage. However, in larger events, the length of the fault rupture is much longer, and damage can be spread across the rupture zone. For example, in the magnitude 7.9, 2002 Denali earthquake in Alaska, the epicenter was at the western end of the rupture, but the greatest damage occurred about 330 km away at the eastern end of the rupture zone.
Epicentral distance
During an earthquake seismic waves propagate spherically out from the hypocenter. Seismic shadowing occurs on the opposite side of the Earth from the earthquake epicenter because the liquid outer core refracts the longitudinal or compressional (P-waves) while it absorbs the transverse or shear waves (S-waves). Outside of the seismic shadow zone both types of wave can be detected but, due to their different velocities and paths through the Earth, they arrive at different times. By measuring the time difference on any seismograph as well as the distance on a travel-time graph at which the P-wave and S-wave have the same separation, geologists can calculate the distance to the earthquake's epicenter. This distance is called the epicentral distance, commonly measured in ° (degrees) and denoted as Δ (delta) in seismology.
Once epicentral distances have been calculated from at least three seismographic measuring stations, it is a simple matter to find out where the epicenter was located using trilateration.
Epicentral distance is also used in calculating seismic magnitudes developed by Richter and Gutenberg.
References
- "epicenter". Merriam-Webster Online Dictionary. 2009. Retrieved 2009-10-19.
- ἐπίκεντρος, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
- ἐπί, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
- epicentre, on Oxford Dictionaries
- Fuis, Gary. "Rupture in South-Central Alaska—The Denali Fault Earthquake of 2002". USGS. Retrieved 2008-04-20.
{{cite web}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - Tyler M. Schau (1991). "The Richter Scale (ML)". USGS. Retrieved 2008-09-14.
{{cite journal}}: Cite journal requires|journal=(help) - William L. Ellsworth (1991). "SURFACE-WAVE MAGNITUDE (Ms) AND BODY-WAVE MAGNITUDE (mb)". USGS. Retrieved 2008-09-14.
{{cite journal}}: Cite journal requires|journal=(help)