P-wave Reflectivity of the Crust and Upper Mantle Beneath the Southern
Appalachians and Atlantic Coastal Plain using Global Phases
Abstract
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 ~10 s beneath the Coastal
Plain to 17.4 s (~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 (~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.