Geodynamic modeling of the Southeastern United States: Associations
between gravitational potential energy, modern tectonism, and inherited
structures
Abstract
Regional geodynamics studies of the eastern United States (e.g., Ghosh
et al., 2019) have shed light on the force balance controlling
intraplate, passive margin seismicity. Recent observations of crustal
structure in the Southeastern United States (Chen et al., 2018; Hopper
et al., 2016; Parker et al., 2016; Savage et al., 2017; Wagner et al.,
2018) now allow us to examine the gravitational component of force
balance in more detail. Here, we examine the role of gravitational
potential energy (GPE) within the crust and upper mantle in ongoing
stress, strain, and tectonism in the Southeastern United States. We
first calculate GPE differences using density and crustal thickness data
from Crust 1.0 (Laske et al., 2013) which are integrated over the
thickness of the lithosphere on a 0.5 by 0.5 degree grid (e.g., Flesch
et al., 2001). In further models we modify crustal densities using
recent seismic observations (e.g., Parker et al., 2016; Wagner et al.,
2018). We compare model results to earthquake epicenters and locations
of inherited structures within our study area, including the Reelfoot
Rift; New Madrid Seismic Zone; Illinois Basin; New York-Alabama
Lineament; sutures between sections of accreted terrane; and a region of
high seismic velocity beneath central West Virginia interpreted as
delaminated, eclogitized crust (Biryol et al., 2016). Whereas in most
locations seismicity is associated with higher magnitudes of GPE,
inherited structures may explain regions in which earthquakes occur in
areas with lower magnitudes of GPE.