This geophysical method is based on the measurement of the arrival times of the seismic waves (P waves and S waves) refracted by the interfaces between soil stratifications, characterized by different propagation speeds.
The energy source is represented by an impact on the surface. The energy radiates from the "shot point", traveling both directly in the uppermost layer (direct arrivals) and traveling deep down and laterally along layers at a higher velocity (refracted arrivals), and then returning to the surface, where it is measured through the spreading of geophones (10Hz frequency). Energizing in different positions on the surface it will be possible to deduce information about the geometry of the deep refractor layer, in many cases coinciding with the bedrock.
Starting from the values of Vp and Vs of the seismic-stratigraphic model obtained, it will also be possible to estimate the elastic modulus of the various horizons identified.


This method is suited to refraction profiles where source/receiver spacings are denser than for conventional profiles. The inversion method is based on an iterative solution of the linearized problem, and allows a high resolution determination of continuous velocity variations as well as geometry of sismo-stratigraphic interfaces.