GNGTS 2019 - Atti del 38° Convegno Nazionale

682 GNGTS 2019 S essione 3.2 along the entire model. To obtain the true average DCs corresponding to each path, we discretized each path (every 5 m) and we computed the average slowness from 3 to 50 Hz using the DCs of the closest 1D models to each point of the discretized path. In Figs 2a and 2b, we show the true average DCs in the phase velocity-frequency and phase velocity-wavelength Fig. 1 - (a) The initial VS model. (b) The perturbation map in percentage where the black color shows a 20% negative perturbation and the white color represents a 20% positive perturbation. (c) The perturbed (true) model. Fig. 2 - The dispersion curves corresponding to the ray paths defined for the true model (Fig. 1b): (a) The phase velocities against frequency. (b) The phase velocities against wavelength.