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. 

Methods
The original data set was recorded by broadband seismograph stations along Lines L through Z of the Transportable Array as part of the EarthScope project.  Waveforms downloaded from the IRIS Data Management Center can be found in "part3" of the archive.      Processing of the data is explained in detail in directory "part2".   "part4", "part 5", "part 6", and "part7" of the archive contain input files, shell scripts, and output files.  The directory "part1" contains all software developed by Hawman for analysis of the seismic waveform data.  Three subdirectories contain the source code, make files, and executable files (compiled on macOS version 10.8.4; tested on macOS versions through 10.12.6).