REFRACTED WAVE TECHNIQUE

Refracted wave method of is most often used in engineering geophysics to study the geometry and physical properties of the surface of the rocks and determine the thickness of loose Quaternary deposits.

Seismogram of refracted waves from the explosion of 3 kg  ammonite charge at the base of receiving 360 m (site Choclon-2, Peru)

Refraction wave technique is mostly justified when clearly denominated layering of the near-surface sediments absent  and, as an effect, when there are not reflection waves on the seismic records. Investigation depth during refraction wave technique using generally consist of 25-30 % of a maximal shot-receiver distance. By thick near-surface layer of the weak soils (dry sands, peat) with  elastic wave energy great attenuation for refraction wave time-distance curve obtaining in the first breaks on the receiving base 250-400 m it is necessary to use enough powerful elastic wave sources, often the explosions, where it is permitted by the environment institutions.

Analysis of amplitudes and frequency composition of oscillations on the seismogram of refracted waves

The section of Vp  longitudinal waves  propagation velocities

An example of refraction wave record processing for Vp velocity obtaining with SeisOptim software using at the one of Choclon II areas. Investigations of the bottom interior of the future flotation waste repository of metallurgical integrated plant (Peru).

An example of the dolomite karsted surface mapping at the site of Plavinas HPP projected emergency spillway

One of the most applications of refraction wave technique is karsted areas outline in the near-surface layers of the bedrocks, represented by the halogen-carbonate sediments. In these cases the depth of investigation usually is limited  by the depth of the high-velocity bedrock top,  but physical properties variations of the bedrock weathered surface and overlaying near-surface soil layer are manifested enough distinctly.