Old wounds: The impact of inherited density anomalies on the stress field and modern seismicity in the central and eastern United States
William Levandowski
USGS National Earthquake Information Center
- Date & Time
- Location
- Building 3, Room 3240 (main USGS conference room)
- Summary
Lateral variations in lithospheric density can, themselves, be a source of stress. Therefore, features left behind by ancient tectonism in the central and eastern United States thickened or thinned crust, metasomatized mantle, or mafic intrusions continue to produce fault zone-scale heterogeneity in the direction and magnitude of deviatoric stress, variably encouraging and discouraging slip on inherited faults. In fact, I argue that the magnitude of deviatoric stress due to density variations alone is equal to or greater than that transmitted inward from the boundaries of North America, so estimating lithospheric density and quantifying its effects is of paramount importance in understanding seismic hazard. Examples from New Madrid, the western Great Plains, and Oklahoma illustrate the profound heterogeneity extant within the stable North American lithosphere and illuminate the link between gravitational stress and both natural and induced seismicity.
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