Lithospheric structure beneath the southeastern United States: Constraints from joint inversion of receiver functions and Rayleigh wave dispersion

Abstract:

To provide new constraints on crustal structure and evolution models beneath a collage of tectonic provinces in the southeastern United States, we conduct a joint inversion of receiver functions and Rayleigh wave phase velocity dispersion using 186 USArray broadband seismic stations. H-k stacking receiver function analysis is applied to provide reliable crustal thickness and Vp/Vs measurements for generating the inversion models. Phase velocity at short periods (6 – 24 s) and long periods (28 – 120 s) are obtained from ambient noise and teleseismic earthquake data, respectively. By jointly inverting the receiver functions and phase velocities, we construct a 3-D shear wave velocity model from the surface to the depth of 180 km. Our resulting crustal thickness distributions from both H-k and joint inversion analyses are generally consistent with each other and show good correspondence with surficial geological features with thicker crust measured in the southern Appalachian Mountains and thinner crust in the Atlantic Coastal Plain. Comparing with the southern Appalachian Mountains, the relatively thinner crust (32.9 ± 2.0 km) and lower Vp/Vs (1.79 ± 0.05) in the Carolina Terrane could be best explained by the delamination and relamination of the lower crust. Due to the thick sediments along the Atlantic Coastal Plain, the lowest velocities in the shallow crust are observed in that region, and the effects caused by the loose sediments even extend into the lowermost crust. High crustal velocities observed in the southern Appalachian Mountains are consistent with the isostacy theory.