What are seismic surveys?
Seismic reflection is a technique for mapping rock layers underneath the ground. Use of this technique together with surface mapping, provides geoscientists with the necessary tools to construct 3D geological maps. It was initially used in petroleum exploration, where an accurate knowledge of the rock layers is critical to successful exploration. In recent years, the technique is being used more and more in mineral exploration as the search for deeper ore bodies continues. The technique gives a two- or three-dimensional picture of the structure of layers of sedimentary rock at depth by generating an elastic shock wave at the surface, analogous to a sound wave in fluids, and recording reflections from the rock layers by means of a linear array of detectors. The reflections are the result of differences in the acoustic impedance of rock layers (see figure). The waves were originally generated by using explosives, but in recent years mechanical vibrators have been used. Mechanical vibrato
