Seismic refraction interferometry with a semblance analysis on the crosscorrelation gather

Crosscorrelating wavefields recorded at two receivers to produce data as if one receiver was a source is commonly referred to as seismic interferometry, or the virtual source method. An artifact in seismic interferometry related to critically refracted waves allowed us to estimate the velocity in the refracting layer. In addition, we devised a new semblance analysis on the crosscorrelation of reflection and refraction energy to robustly estimate the depth and velocity of the slow layer, tested with a numerical example and field data from the Boise Hydrogeophysical Research Site.