The seismic refraction method has been used extensively to determine depth-to-bedrock or depth to other seismic velocity boundaries. More recently, the seismic refraction method has been increasingly used in shallow environmental and engineering site characterisation studies In both cases, subsurface information is derived from first-arrival times rather than reflection events that are also present in refraction data.

A refraction profile is commonly composed of 2 or 3 shot points recorded on the same geophone line: 2 end-on spread shots and one split spread shot if 3 shots are recorded. Typically, with refraction analysis of first arrival travel times, the depth of investigation is limited to approximately 1/3 the length of the active receiver spread. On the other hand, the processing and interpretation of reflection events present in the refraction data allows the depth of investigation to increase to approximately the length of the spread. Also the acquisition of high-quality shallow reflection seismic data requires higher spatial sampling than co-located refraction data and the processing of shallow reflection seismic data requires careful attention to statics corrections, velocity estimation, and noise attenuation.

The example shows how SVD and F-K methods can be fruitfully combined to perform wave separation and extraction of reflected events in order to obtain a single-fold, high-resolution seismic section