## 3 Analysis of Geophysical Data
### Seismic and Gravimetric Basement Depth Inversion
(**a**) adjustment of the ellipticity curve between the observed curve (black line) and the best models. (**b**) adjustment of the dispersion curve between the observed curve (black line) and the best models. (**c**) models obtained from the inversion. Black line corresponds to the best model. Figure 12: Inversion results in a point in Mejillones using ellipticity of the Rayleigh waves from the H/V curve. (**a**) adjustment of the ellipticity curve between the observed curve (black line) and the best models. (**b**) adjustment of the dispersion curve between the observed curve (black line) and the best models. (**c**) models obtained from the inversion. Black line corresponds to the best model. Figure 14: Inversion results in a point in Iquique using ellipticity of the Rayleigh waves from the H/V curve. (**a**) adjustment of the ellipticity curve between the observed curve (black line) and the best models. (**b**) adjustment of the dispersion curve between the observed curve (black line) and the best models. (**c**) models obtained from the inversion. Black line corresponds to the best model. Figure 13: Inversion results in a point in the northern fine soils in Santiago using ellipticity of the Rayleigh waves from the H/V curve. (**a**) adjustment of the ellipticity curve between the observed curve (black line) and the best models. (**b**) adjustment of the dispersion curve between the observed curve (black line) and the best models. (**c**) models obtained from the inversion. Black line corresponds to the best model. Figure 13 shows the same results for a site located in Santiago, specifically in the northern area with fine soils. This site has a seismic classification of D, with an H/V predominant period of 0.68 s and a \(V_{s,30}\) of 288 m/s. The minimum misfit value in this inversion is around 0.088. Here, there is also a good agreement in the dispersion and ellipticity curves between the observed data and the resulting models. The resulting inversion profile shows a layer of almost 1000 m/s at 50 m deep, associated with the seismic bedrock. Equation (1), using the values previously mentioned in this site, gives a depth to basement of 49 m, which is almost the same as the inversion. In terms of gravity, the residual anomaly in this site is \(-\)1.15 mGal. From the work of [PERSON] et al. [7], it is possible to estimate a density contrast between the soils and bedrock in the zone of around 0.7 ton/m\({}^{3}\). Using this value and Equation (2), the gravimetric basement in this site results in 40 m.  
On the other hand, Figure 14 shows the same results, although for a dense soil in Iquique. This site has a seismic classification of C, with an H/V predominant period of 0.25 s and a \(V_{s,30}\) of 380 m/s. The minimum misfit value in this inversion is around 0.141. The resulting inversion profile shows a layer of almost 3000 m/s at 28 m deep, associated with the seismic bedrock. The Equation (1), using the values previously mentioned in this site, gives a depth to basement of 24 m, which is close to the inversion. In terms of gravity, the residual anomaly in this site is \(-\)1.2 mGal. From the work of [PERSON] et al. [42], it is possible to estimate a density contrast between the soils and bedrock in the zone of around 0.7 ton/m\({}^{3}\). Using this value and Equation (2), the gravimetric basement in this site results in 40 m.  
Finally, Figure 15 shows three different examples of H/V curves obtained in Santiago, specifically in the southern part of the city (see black dots in the right panel of Figure 5. Santiago. Left panel: Simplified geology of the city adapted from Chilean geological map 1:1,000,000 [36]. Right panel: Main results of the geophysical campaign [7; 36; 39]. The color grid shows the gravity residuals in mGal. The color points show the H/V results. Color indicates the predominant period (T0) in seconds and the size indicates the amplitude (A0) of the H/V curve.).