Data and code from: Using contrasts in horizontal P-wave reflectivity to map the base of the continental lithosphere: Results for the central and eastern U.S.

We used seismic P-waves generated by earthquakes in the western Pacific to
conduct “echo soundings” of geologic structure beneath the United
States.  Our goals were to investigate the deep structure of the
Appalachian Mountains, determine the thickness of the underlying North
American tectonic plate ("lithosphere"), and investigate the
nature of flow within the asthenosphere, the layer of less rigid material
beneath the plate.  After traveling through the Earth’s core,
these waves are reflected at Earth’s surface and travel back into the
interior, where they are reflected back to the surface by major
compositional boundaries.  The echoes were recorded by the
“Transportable Array” of seismograph stations that moved across the United
States from 2004 to 2014.   We used a subset of stations
from 15 east-west profiles to construct cross sections across the Atlantic
Coastal Plain, Appalachian Mountains, and more ancient crust of the
continental interior.  Our soundings are consistent with results
of earlier studies that suggest that the lithosphere gets thicker as it
gets older.   The lower lithosphere is marked by a
significant increase in the number and continuity of reflections,
supporting the interpretation of elevated strain in the lowermost
lithosphere as well as drag-induced flow in the asthenosphere produced by
westward motion of the overlying plate.