Scientists studying extraordinary earthquakes in the central U.S. in 1811-12 along the New Madrid seismic zone have revealed a possible new driving mechanism for intraplate seismicity.
The earthquakes were unprecedented in the historical record within stable continental plate interiors.
Forte et al. analyze viscous flow models of the mantle based on high-resolution seismic tomography. They find that remnants of the ancient Farallon plate, a slab of crust swallowed beneath the western North American continental margin nearly 70 million years ago, continue to descend into the deep mantle under central North America.
The descent induces mantle flow towards the Earth’s deep interior directly below the New Madrid seismic zone. That flow, in turn, may strain the overlying crust, causing seismic ruptures, the authors hypothesize. Their results may shed light on present-day seismic hazards in the central Mississippi River Valley.
Title: Descent of the ancient Farallon slab drives localized mantle flow below the New Madrid seismic zone
Authors: A. M. Forte and R. Moucha: Départment des Sciences de la Terre et de l’Atmosphère, Centre de Recherche en Géochimie et en Géodynamique, Université du Québec à Montréal, Montréal, Quebec, Canada; J. X. Mitrovica: Department of Physics, University of Toronto, Toronto, Ontario, Canada; N. A. Simmons and S. P. Grand: Jackson School of Geological Sciences, University of Texas at Austin, Austin, Texas, U.S.A.
Source: Geophysical Research Letters (GRL) paper 10.1029/2006GL027895, 2007
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