A noise shot been recorded by using explosive as the source, and a line of 47 vertical geophones. The figure on the left shows the seismic data. Data are sampled every 16 ms and the recording's duration is limited to 4 seconds. On this recording, we can see a refracted wave, a reflected arrival of strong amplitude associated to a deep reflector, and two dispersed Pseudo-Rayleigh waves characterized by low apparent velocity and by low frequency contents.

The figure shows on the right, the 2D amplitude spectrum of the seismic recording. The spectrum is presented with and without normalisation in a wavenumber k. Without normalisation , the two branches associated to two dispersed waves are clearly visible. After a normalisation, the refracted wave appears at frequencies superior to 17 Hz, and the reflected waves concentrated near the null wave number. The first branch of the Pseudo-Rayleigh mode, situated in the frequencies interval 3-10 Hz, corresponds to the slow Pseudo-Rayleigh. The second branch in the interval 10-20 Hz corresponds to the fast Pseudo-Rayleigh. These two branches are associated to the first two modes.

After group velocity and phase shift corrections, the slow Pseudo-Rayleigh wave is flattened and rendered non-dispersed. The group velocity correction is 189 m/s. The phase correction is 22 degrees. The non-dispersive Pseudo-Rayleigh wave is extracted by using SMF filter. Once estimated, the dispersion properties of the slow Pseudo-Rayleigh wave are recovered by applying opposite corrections in velocity and phase.

The video shows the noise shot before and after group velocity and the phase shift corrections. It also shows the associated 2D spectra without and normalisation in wavenumber.