UPPER MANTLE SHEAR WAVE STRUCTURE IN THE SOUTHEASTERN UNITED STATES FROM RAYLEIGH WAVE TOMOGRAPHY

In this study, we model the shear wave velocity structure beneath the southeastern United States using Rayleigh Wave tomography in order to image the mantle lithosphere below the proposed Suwannee suture in southern Georgia. Data used for this analysis were recorded by the SESAME (the Southeastern Suture of the Appalachian Margin Experiment) seismic network, comprising 85 broadband Earthscope Flexible Array stations. We also include data from nearby Transportable Array stations and permanent stations.

Rayleigh waves were analyzed for events recorded between May 2012 and May 2013 using the two plane wave method developed by Forsyth and Li (2004) and the finite frequency kernels of Yang and Forsyth (2006). Azimuthal coverage for the study area was relatively well distributed except from back-azimuths ranging from ~45°-160°. Preliminary results for shear wave velocities indicate a distinct difference in the depth to the lithosphere-asthenosphere boundary (LAB) between northern and southern Georgia. The LAB is significantly deeper north of the Suwannee suture than to the south, consistent with preliminary results from S-p receiver functions (Hopper et al., 2013). Further refinement of our model will provide higher resolution images of structures in the mantle lithosphere across the southeastern United States. These constraints will help us better understand the accretion of the Suwannee terrane and the subsequent effects of rift processes during the breakup of Pangea.