Seismic refraction

The refraction is a method of applied geophysics. These artificial seismic waves are generated and recorded the propagation of the wave field along the earth's surface by hammer, drop weight, blowing up, vibrators or other sources. For the measurement sensors ( geophones ) are usually designed along a profile line. The distances between the geophones can in this case be less than one meter to several kilometers. On a single profile is, however, worked with a strictly defined distance. The total length of the display is a few tens of meters to more than 100 kilometers long, depending on the depth to the structure under investigation. This applies coarse that structures can be studied up to one third of the expenses length in depth.

In contrast to reflection seismics, where only the ground reflected waves are considered for the evaluation and interpretation, in which the refraction refracted energy is used ( head shaft or Mintropwelle ). The evaluation is made easier by the creation of run-time diagrams. The result is a model of the substrate showing the various layers having propagation velocities of the seismic waves.

Areas of application include geological explorations of the Earth's crust into the upper mantle into it (for example, determining the depth of mountain roots) or near-surface investigations for engineering and environmental geology or to determine the thickness of the weathering layer in conjunction with seismic reflection measurements.

A disadvantage of this method is that refracted waves are only for " normal" rate of change, that is, when the speed increases in the downward direction is generated. Assuming a layer boundary, the velocity contrast to bottom, this layer boundary remains invisible. This can lead to errors in interpretation.

• Geophysics
• Seismic