Yet many ancient fault zones remain seismically quiet, and even high-rate wastewater injection does not everywhere induce seismicity 1. If the interaction between plates at their distant boundary were the only source of deviatoric stress in continental interiors, then the intraplate stress field would be broadly uniform, and all suitably oriented faults would have equal chance of experiencing an earthquake. These results show that mapping where gravitational body forces encourage seismicity is crucial to understanding and appraising intraplate seismic hazard. 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. Furthermore, predicted principal stress directions generally align with those observed independently in earthquake moment tensors and borehole breakouts.

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. The North American Great Plains exemplify such intraplate earthquake localization, with both natural and induced seismicity generally clustered in discrete zones. Earthquakes far from tectonic plate boundaries generally exploit ancient faults, but not all intraplate faults are equally active.

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