## 4 Results and Discussion
### S-Wave Velocity Profiles  
HVSR and dispersion curves have been inverted separately, as they were obtained at different sites within the landslide. The number and the thickness of layers, as well as the range of Vs values obtained from the downhole results (see Section 4.1), have been used to constrain the parameter space in the sites around the central area of the landslide. In the case of the thickness and Vs values, an additional margin around the value ranges deduced from the boreholes has been included because the measurement points do not match exactly at the borehole sites (see Figure 3). For the sites closest to the first borehole (S1), the following model has been used: a first layer with maximum thickness of 12 m and shear-wave velocity between 150 and 550 m/s; a second layer that reaches a maximum depth between 35 and 43 m and has a Vs value between 750 and 950 m/s; and a third layer whose maximum depth reaches 45-53 m, with a Vs value of 550-750 m/s. Below this, a hard layer is configured with a minimum depth of 48 m and velocities between 900 and 1100 m/s. In the cases of the sites closest to the second borehole (S2), a four-layer model has been applied with the following characteristics: a first layer with maximum thickness of 8 m and shear-wave velocity between 150 and 550 m/s; a second layer whose maximum depth reaches 22-33 m, with Vs value of 650-750 m/s; a third layer with maximum depth and shear-wave velocity in the ranges 33-43 m. and 750-800 m/s, respectively; and a fourth layer that reaches a limit depth of 45-53 m., and a Vs of 650-700 m/s. Below, a hard layer is configured with a minimum depth of 48 m and velocities between 900 and 1000 m/s. In all cases, an additional harder layer has been added to these models in order to take into account possible deeper velocity contrasts. The profiles obtained at these two sites are shown in Figure 4, showing a remarkable similarity with the results of the downhole tests. For those sites closer to the expected border of the landslide, a simpler model has been used with two sedimentary layers over two harder layers, representing the in situ stable materials. The superficial layer is included to take into account the shallower materials, disturbed by agricultural activities. The inclusion of two harder layers allows also for adjusting the estimated model to the HVSR peaks found below 2 Hz, which might be associated with deeper contrasts. The fitting carried out by the software is based on a multimode surface-wave modeling through a vertically heterogeneous, elastic and isotropic medium. The model generation process implies the computation of the theoretical ellipticity, or dispersion curves, of the fundamental mode Rayleigh wave (forward model), and a comparison with the respective experimental curves. The similarity between the theoretical and the empirical HVSR or dispersion curves is expressed quantitatively by a misfit value. Figures 7 and 8 depict some examples of the Vs profiles estimated using the HVSR curves, and the dispersion curves obtained by the f-k method, respectively. From the estimated profiles, we can observe how the obtained results with both techniques are coherent with each other. Figure 7: HVSR inversion for six sites (see Figure 3 for location of sites). The best ellipticity and velocity models (dark grey lines), together with models lying inside the minimum misfit + 10% (dark orange) and all the tested models, are shown. The black curve and bars in the ellipticity plots are the average and standard deviation, respectively, of the experimental HVSR curve. The dashed lines in the velocity profiles indicate the search bounds. Figure 8: Dispersion curve inversion for six different sites (see Figure 3 for location of sites). The best dispersion and velocity models (dark gray lines), together with models lying inside the minimum misfit + 10% (dark orange) and all the tested models, are shown. The black curve and bars in the velocity-frequency plots are the average and standard deviation, respectively, of the experimental dispersion curve.