Crustal Thickness and Vp/Vs Beneath the Florida to Edmonton Broadband Seismometer Array

Ps receiver functions were used to constrain crustal thickness (H) and Vp/Vs beneath the 28 stations of the Florida to Edmonton Broadband Seismometer Array and 6 nearby permanent stations (IRIS/GSN, USNSN, CNSN, and NMSN). The stacking algorithm of Zhu and Kanamori (2000) was applied to receiver functions for the 9 stations exhibiting clear Pms, PmpPms, and PmpSms/PmsPms converted phases, thus constraining both H and Vp/Vs. For the remaining stations where only high quality Pms phases were evident, Vp/Vs was prescribed based on interpolation of well-constrained neighboring values, and the receiver functions were stacked to constrain H. Because a number of FLED stations overlie significant sedimentary layers, potential bias in H and Vp/Vs estimates from intracrustal phase interference was assessed via deconvolution and stacking of synthetic waveforms. Even for models where sediment layers have a high Vp/Vs and intracrustal phases are strong, accurate estimates of H and average crustal Vp/Vs can be retrieved from receiver function stacking. Along the FLED array, roots of thickened crust were observed beneath the Paleozoic Appalachian and Proterozoic Trans-Hudson orogens. In both cases, the ratio of surface elevation to root thickness and crustal root buoyancy inferred from gravity data decrease with orogenic age, thus fitting global trends. Crustal thickening was also observed beneath the Proterozoic Mid-Continent Rift in Iowa, consistent with compressional inversion of the rift during the Grenville orogeny. Crustal thickness decreases beneath the highest elevations at the NW end of the array. Because Vp/Vs also decreases at these stations, the increase in elevation could be compensated by a reduction in average crustal density, although contributions from mantle buoyancy cannot be ruled out.