Of all the advances in the reflection seismic technique, surely none is more important nor has had greater impact than the invention of common-depth-point coverage, or simply, stacking.
In concept, the procedure is very simple. The distance between seismic source and receiver is varied symetrically to survey the same subsurface point several times. The observations, corrected for geometrical distortion and adjusted to datum, are then summed to obtain the average.
The reason for its outstanding success is that it provides the most powerful method for separating noise from signals of the same frequency. With one exception, all other seismic processes either eliminate both signal and the noise, or merely modify the amplitude without changing the proportion. The exception is multichannel filtering, which is also able to separate signal from noise of the same frequency, but it is effective only in areas of relatively homogeneous dip and is of little value in areas of complex structure. Under proper conditions, stacking will remove several types of noise, but it is most effective against random noise.