Extraction of a Signal by Using Cross-correlation of Ambient Seismic Noise

Ambient seismic noise has often been considered to be a useless part of a seismogram, thus being discarded as part of traditional seismic data processing. Recent developments in seismic imaging theory have verified a long-standing postulate concerning the recovery of the useful signal from ambient seismic noise. One may retrieve the impulse response function between two receivers through a cross-correlation of noise at the two receivers. Theoretically and experimentally, a random wavefield has been shown to have correlations to a Green’s function representing characteristics of the media. The Green’s functions extracted by cross-correlating long sequences of ambient seismic noise can be used to obtain information about the structure of media.