CRUSTAL THICKNESS AND VP/VS ESTIMATES ACROSS THE SOUTHERN APPALACHIANS USING RECEIVER FUNCTIONS FROM THE SESAME ARRAY

The Southeastern Suture of the Appalachian Margin Experiment (SESAME) is designed to investigate lithospheric dynamics associated with Paleozoic terrane accretion, continental collision, and Mesozoic rifting. So far, we have deployed 63 broadband instruments along two N-S trending profiles across Georgia and northern Florida. A third NW-trending profile consisting of 19 stations extends from Augusta, GA to eastern TN. Preliminary H-k stacking using 8 teleseismic receiver functions (RF) from station D05 on the NW-trending profile near the Inner Piedmont-Carolina terrane boundary yields estimates of crustal thickness (H) of 36-37 km and Vp/Vs (k) of 1.64-1.69. The estimate for H is comparable to previous wide-angle reflection profiling estimates of 37-38 km in the vicinity of D05, while k is lower than previous estimates of 1.73 and 1.75 for the Inner Piedmont and Carolina terrane, respectively. The discrepancy in Vp/Vs values may be related to limited RF data, but the results suggest that the average crustal composition is relatively felsic, possibly caused by unrecognized deep crustal imbrication during collision. At station D17, located southeast of the Blue Ridge foothills near the Brevard zone, H-k stacking using 10 RF’s yields estimates for H and k of 43-44 km and 1.73-1.78, respectively. These results are also in close agreement with a crustal thickness estimate of 45-km from a nearby wide-angle mid-point and average crustal Vp/Vs of 1.75 throughout the Blue Ridge province. At station W33 on the southeast flank of the Blue Ridge (on the western N-S profile), H-k stacking using 15 RF’s provides estimates for H of 54-56 km and k of 1.68-1.74. Although the results are preliminary, this observation suggests that the crustal root beneath western North Carolina evident from regional wide-angle profiling and previous RF analysis (USNSN station MYNC) may extend further south into northeast Georgia. In general, the RF results are consistent with wide-angle reflection profiling results showing gradual crustal thickening from the Coastal Plain to the Blue Ridge province and a slight increase in Vp/Vs values toward the orogen. Forthcoming results from other stations will complement existing wide-angle coverage and provide valuable constraints on crustal structure where gaps are present.