We propose to analyse the dispersion for the low frequency branch.

We will successively correct the noise shot by the group velocity correction, then by the dispersion in order to render the curve (f, k) tangent to the vertical straight line k=0, at the frequency 7 Hz. Applying a phase correction or a phase shift reduces the dispersion of the mode.

It is possible to:

• Visualize the initial data by clicking on the button: init.
• Analyse the dispersion by clicking on the button: setting.
• Visualize the data after a group velocity correction of 189 m/s and a phase correction of 22 degrees by clicking on the button: Default.

We then have an approximation of the phase velocity at frequency 7 Hz. Knowing the group velocity allows to calculate the phase velocity, then the dispersion curve of the Pseudo-Rayleigh wave. After correction by the group velocity and the phase shift, the slow Pseudo-Rayleigh wave is flattened and rendered non-dispersed. It could be estimated, and then filtered by using filtering techniques such as SVD or SMF. The figure on the top left shows the variation curve of the phase velocity, relating to the frequency of the Pseudo-Rayleigh mode studied.