Abstract
Earthquakes far from tectonic plate boundaries generally exploit ancient faults, but not all intraplate faults are equally active. The North American Great Plains exemplify such intraplate earthquake localization, with both natural and induced seismicity generally clustered in discrete zones. Here we use seismic velocity, gravity and topography to generate a 3D lithospheric density model of the region; subsequent finite-element modelling shows that seismicity focuses in regions of high-gravity-derived deviatoric stress. Furthermore, predicted principal stress directions generally align with those observed independently in earthquake moment tensors and borehole breakouts. Body forces therefore appear to control the state of stress and thus the location and style of intraplate earthquakes in the central United States with no influence from mantle convection or crustal weakness necessary. These results show that mapping where gravitational body forces encourage seismicity is crucial to understanding and appraising intraplate seismic hazard.
Highlights
Earthquakes far from tectonic plate boundaries generally exploit ancient faults, but not all intraplate faults are active
Earthquake moment tensors and borehole breakouts[21] reveal that the principal stress directions are different along the Yavapai–Mazatzal suture zone (YMS) and Cheyenne Belt (CB) than in their surroundings
Greater magnitudes and other orientations of regional stress worsen the fit substantially (Supplementary Fig. 12a,c–g,i). This finding suggests that the relative contribution of density variations to long-term fault loading matches or exceeds that of edge-stress or basal shear. Earthquakes, both natural and induced, on the Great Plains of intraplate North America occur in discrete zones
Summary
Earthquakes far from tectonic plate boundaries generally exploit ancient faults, but not all intraplate faults are active. The North American Great Plains exemplify such intraplate earthquake localization, with both natural and induced seismicity generally clustered in discrete zones. Body forces appear to control the state of stress and the location and style of intraplate earthquakes in the central United States with no influence from mantle convection or crustal weakness necessary. Tectonic processes may contribute to post-Miocene rock uplift on the YMS and CB Both Proterozoic boundaries are foci of modern seismicity (Fig. 1). The NW–SE extension on the Cheraw and Wheatland/Whalen faults represents 45–90° rotations of the regional stress field Because seismicity occurs both near and at great distance from the Arkansas and North Platte thalwegs, focused erosion due to post-Miocene climatic changes cannot explain these patterns. Uniform erosion would very slightly increase the Coulomb stress on buried faults, bringing them closer to failure, it cannot account for anomalous principal stress directions
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call