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Tuesday, May 05, 06:38:51pm [ Login ] [ Contact Forum Admin ] [ Main index ] [ Post a new message ] [ Search | Check update time | Archives: 1, 2, 3, 4, 5, 6, 7, [8], 9, 10 ]

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Date Posted: Monday, November 07, 10:17:24pm
Author: tg
Author Host/IP: pool-98-119-57-72.lsanca.fios.verizon.net / 98.119.57.72
Subject: ok lij...your take on the oklahoma earthquakes?

is it the new madrid?

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[> No... it's a completely different fault system running westward through Arkansas and into Oklahoma.... -- Lij, Tuesday, November 08, 02:46:45am (adsl-108-67-95-223.dsl.bltnin.sbcglobal.net/108.67.95.223)

From the USGS:

The location of the earthquake and the focal mechanism it is possible that this earthquake occurred on the Wilzetta fault. The Wilzetta fault is one of a series of small faults formed in the Pennsylvanian Epoch (approx. 300 million year ago) during the intraplate deformation known as the Ancestral Rocky Mountains mountain-building episode (orogeny). The relationship between the recent earthquakes and this older structure is still unknown and requires further investigation.

I find it odd that it happened on a thrust fault but if the focal mechanism agrees with that type of fault then so be it. A thrust fault is caused by crustal compression. The area is not generally considered to be under compression anymore.

This is well east of the New Madrid fault system. In between you have the thrust faulted Ouachita Mtns and the normal faulting north of there of the Arkoma Basin (area of the Arkansas River through Arkansas. Westward you run into sometime funky faulting which is associated with the same mountain building as the Ancestral Rockies (ca360mya) and that is also associated with the development of the Anadarko basin in SW Oklahoma (and some really old fault lines associated with the Nemaha Ridge which goes back as much as a billion years ago or more).


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