HR: 17:00h
AN: S32F-05    [PDF]
TI: Stress Evolution and Intraplate Seismicity in the Central-Eastern North America
AU: * Li, Q
EM: qlpkd@mizzou.edu
AF: University of Missouri-Columbia, 101 Geological Sciences Building, MU, Columbia, MO 65211
AU: Liu, M
EM: lium@missouri.edu
AF: University of Missouri-Columbia, 101 Geological Sciences Building, MU, Columbia, MO 65211
AU: Sandvol, E
EM: sandvole@missouri.edu
AF: University of Missouri-Columbia, 101 Geological Sciences Building, MU, Columbia, MO 65211
AB: Intraplate earthquakes within the stable interior of the North America plate are surprisingly common, large, and poorly understood. The New Madrid Seismic Zone (NMSZ), with three large events (M=7.0-7.5) in 1811-1812, is the most prominent intraplate seismic zone within the stable North American plate. However, most of the post 1811-1812 events (M$>$5) occurred not within the NMSZ but in the surrounding regions. We have simulated the stress evolution in the NMSZ and surrounding regions following the 1811-1812 events in a visco-elastic finite element model. Our results show that re-accumulation of stress within the NMSZ following the 1811-1812 events is slow and lags behind that in the surrounding regions, because the released stress may be supported by the relatively strong surrounding crust. The regions with the predicted highest deviatoric stress are found in southern Illinois and eastern Arkansas, consistent with the distribution of moderately sized (M$>$5) earthquakes following the 1811-1812 NMSZ events. To better understand the stress evolution and intraplate seismicity in the rest of the stable North American plate, we have developed a regional visco-elastic geodynamic model and systematically investigated the impact of major lithospheric rheological changes, such as ancient rifts and lithospheric thickness variation, on the crustal stress field. Our model predicts higher deviatoric stress in the edge surrounding the North America craton than within the craton. This is consistent with the observation of most seismicity being concentrated around and not within the North America craton.
DE: 1734 Seismology
DE: 4255 Numerical modeling
DE: 8164 Stresses--crust and lithosphere
SC: Seismology [S]
MN: 2003 Fall Meeting