A new approach to enhancement of frequency bandwidth of surface seismic data

It is a common observation that seismic waves propagating through the earth are attenuated. As these elastic waves travel deeper they lose energy, in contrast to spherical spreading, where energy is spread over a wider area, and reflection and transmission of energy at interfaces, where its redistribution occurs in the upward or downward directions. This loss is frequency dependent: higher frequencies are absorbed more rapidly than lower frequencies, such that the highest frequency usually recovered on most seismic data is about 80 Hz. Moreover, absorption appears to vary with the lithology of the medium. The unconsolidated near-surface absorbs more energy than the underlying compact rocks. In the extreme case most of the energy may be absorbed in the first few hundred metres of the subsurface. It is therefore important to study absorption and to determine ways in which it can be detected in seismic data.