P-Wave Reflectivity of the Crust and Upper Mantle Beneath the Southern Appalachians and Atlantic Coastal Plain Using Global Phases

Reflection profiles generated using PKPdf as a virtual source show laterally continuous reflections from structures at depths less than 1 km to roughly 200 km beneath the southern Appalachian orogen and Atlantic coastal plain. Arrivals interpreted as reflections from the Moho increase in time from similar to 10 s beneath the coastal plain to 17.4 s (similar to 57 km) beneath the Blue Ridge Mountains, providing additional evidence that the southern Appalachians are in rough isostatic equilibrium. Reflections at 32-36 s (120-135 km) are consistent with the depth to the base of the lithosphere found in recent inversions of Ps arrivals and surface waves. Alternatively, these and later reflections at times up to 58 s (similar to 224 km) may be due to layering associated with drag-induced flow in the asthenosphere, suggesting largely horizontal rather than vertical flow for depths less than 225 km beneath the Georgia coastal plain.