Seismic Refraction Tomography (SRT) uses P- or S-wave travel times to map vertical and lateral changes in the subsurface. A hammer blow (the shot) generates a seismic wave that travels through the subsurface. The seismic-refraction method measures the time a seismic-energy pulse takes to travel from a source point to several receivers after being redirected by one or more subsurface interfaces.

The method is economical in cost, time and area of coverage. It poses no danger to the environment to which the work is done, or neither personal nor damage to instruments used.