HR: 16:30h
AN: T54C-03 INVITED    [Abstracts]
TI: Intraplate Seismicity Within "Stable" North America
AU: * Mooney, W D
EM: mooney@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd. MS 977, Menlo Park, CA 94025, United States
AU: van lanen, X
EM: lanx@geo.vu.nl
AF: US Geological Survey, 345 Middlefield Rd. MS 977, Menlo Park, CA 94025, United States
AB: The origin of earthquakes within stable continental regions (SCR"s) has been the subject of debate over the past thirty years. Here we examine the correlation of North American SCR earthquakes with four geologic and geophysical data. We find that: (1) Archean age (3.8-2.5 Ga.) North American crust is essentially aseismic, whereas post-Archean (less than 2.5 Ga.) crust shows no clear correlation of crustal age and earthquake frequency or moment release; (2) seismicity is correlated with continental paleo-rifts, and (3) seismicity is correlated with the NE-SW structural grain of the crust of eastern North America, which in turn reflects the opening and closing of the proto- and modern Atlantic oceans. Seismicity levels are very low to the west of the Grenville Front (i.e., in the Archean Superior craton). The correlation of seismicity with NE-SW oriented lineaments implies that some SCR seismicity is related to the accretionary and rifting processes that have formed the North American continental crust during the past 2 Gy. We further evaluate this hypothesis by correlating SCR seismicity with recently-obtained deep seismic reflection images of the Appalachian and Grenville crust of southern Canada. These images show numerous faults that penetrate deeply (40 km) into the crust. We conclude that the deep structure of the crust, in particular the existence of deeply penetrating faults, is the controlling parameter, rather than lateral variations in temperature, rheology, or high pore pressure. The distribution of SCR earthquakes in eastern North America is consistent with the existence of deeply penetrating crustal faults that have been reactivated in the present stress field. This implies that seismic hazard is more widespread in central and eastern North America than indicated by the limited known historical distribution of seismicity.
DE: 7209 Earthquake dynamics (1242)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8110 Continental tectonics: general (0905)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting