Seismic exploration by groups of constant frequency wave trains - involves variably weighting detected signals before recombination

摘要

A group of wave trains of constant frequency is emitted in the direction of the ground and the resulting signals are detected at a point spatially separated from the point of emission and are combined. A weighting is applied, variable with time, to the amplitude of the signals detected before this combination. This takes account of the variations in the attenuation offered by the ground as a function of frequency. The median frequencies of the wave trains may form an arithmetic progression or a geometrical progression. The emitted wave trains, may be amplitude modulated. Preferably a narrow band filter is used for the detected signal.