Editing Seismic refraction (section)

{{Short description|Geophysical principle}}
[[File:Refracted wave.png|thumb|Propagating seismic waves (bottom) and related travel time diagram (top) of the direct (blue) and the first refracted phase (green)]]
'''Seismic refraction''' is a geophysical principle governed by [[Snell's Law]] of [[refraction]]. The seismic refraction method utilizes the refraction of seismic waves by rock or soil layers to characterize the subsurface geologic conditions and [[Structural geology|geologic structure]].

Seismic refraction is exploited in [[engineering geology]], [[geotechnical engineering]] and [[exploration geophysics]]. [[Seismic refraction traverse]]s ([[seismic lines]]) are performed using an array of [[seismograph]]s or [[geophone]]s and an energy source.

The methods depend on the fact that seismic waves have differing velocities in different types of soil or rock. The waves are refracted when they cross the boundary between different types (or conditions) of soil or rock. The methods enable the general soil types and the approximate depth to strata boundaries, or to [[bedrock]], to be determined.