1. n. [Geophysics]

A seismic aquisition method in which the incident and reflected angles are critical. These refraction surveys can be useful for evaluating increasing velocity gradients and locating features that have anomalously high velocities, such as a salt dome within surrounding rocks of lower velocities.

See: angle of incidence,  critical angle,  Fermat's principle,  reflection,  refraction,  Snell's law