Crustal and Upper Mantle Structure Beneath the Southeastern United States From Joint Inversion of Receiver Functions and Rayleigh Wave Dispersion

Using data from 186 stations belonging to the USArray Transportable Array, a three-dimensional shear wave velocity model for the southeastern United States is constructed for the top 180 km by a joint inversion of receiver functions and Rayleigh wave phase velocity dispersion computed from ambient noise and teleseismic earthquake data. The resulting shear wave velocity model and the crustal thickness and Vp/Vs (kappa) measurements show a clear spatial correspondence with major surficial geological features. The distinct low velocities observed in the depth range of 0-25 km beneath the eastern Gulf Coastal Plain reflect the thick layer of unconsolidated or poorly consolidated sediments atop the crystalline crust. The low kappa (1.70-1.74) and slow lowermost crustal velocities observed beneath the eastern Southern Appalachian Mountains (including the Carolina Terrane and Inner Piedmont) relative to the adjacent Blue Ridge Mountains and Valley and Ridge can be interpreted by lower crustal delamination followed by relamination. The Osceola intrusive complex in the central Suwannee Terrane has similar crustal characteristics as the eastern Southern Appalachian Mountains and thus can similarly be attributed to crustal delamination/relamination processes. The Grenville Province and adjacent areas possess relatively high kappa values which can be attributed to mafic intrusion associated with crustal extension in a recently recognized segments of the eastern arm of the Proterozoic Midcontinent Rift.

Automated summary

A three-dimensional shear wave velocity model for the southeastern United States was constructed by jointly inverting receiver functions and Rayleigh wave phase velocity dispersion data. The resulting model shows clear spatial correspondence with major surficial geological features.