## 3 Analysis of Geophysical Data
For the H/V campaigns, a 3-component 4.5 Hz Tromino(r) instrument was used to measure the ambient vibrations for at least 20 min, except for the case of Mejillones where a low frequency SARA(r) triaxial seismometer was used and measurements of more than one hour. In this investigation, the analysis was carried out following a variation of the Nakamura method [53]. This approach considers a fixed window of 60 s for the S-transform application [54] at each window. S-transform uses a mobile and scalable window for the analysis. This achieves a frequency-dependent resolution, longer/shorter windows for low/high frequencies. This optimizes the signal response, obtaining smoother results at high frequencies and a more robust mean  
Considering the shortcomings of both depth estimates, the depth-to-geological basement derived from gravity observations, and the depth-to-seismic/mechanic basement derived from H/V observations, in this work, only the raw results of each method were used to seek for possible correlations. The right panels of Figures 2-6 show the main results of these methodologies in terms of residual anomaly (gravity) and predominant period of vibration (H/V). In general, the green zones in the residual gravity anomaly illustrate the infilling sediments and the red zones show where the rock is shallow or where it outcrops. In all the figures, it is possible to see that negative residual gravity anomalies correlate with the quaternary deposits shown in the geology, indicating the presence of low to medium density soil deposits. In terms of H/V, the predominant periods are summarized by colored and different size circles in the right panels of Figures 2-6. The circle color indicates the range of the predominant period, while the size indicates the amplitude of the H/V peak (A0 values). In general, higher periods indicate higher soil thickness, although this result will depend on the average velocity of the site and possible 2-D or 3-D effects [25]. The amplitude cannot be related with the site amplification factor, although, it is related with the site impedance contrast [11; 25]. Higher amplitudes normally correlate with a higher impedance contrast between the infilling sediments and apparent bedrock. Finally, the black dots illustrate those sites where it is impossible to find a clear peak (flat curves). The H/V results show that the blue and green circles are located mainly in the zones with lower gravity residuals, which are mainly zones with higher sediment thicknesses, whereas the yellow and purple circles (lower periods) are located near the rock outcrops and red zones in the gravimetric results. Additionally, the bigger circles (higher amplitudes) are located mainly in two different zones. First, they appear in zones with large negative gravity residuals implying thick soil columns. Secondly, they are located in zones near the red gravity areas where the bedrock is probably at shallow depths, indicating a high impedance contrast between them and soil coverage. Finally, the flat curves (black dots in Figures 2-6) are located in zones where there is rock, however there are a lot of points that are over the green zones in the gravity residuals. This apparent contradiction highlights the differences, in some cases, between mechanical and geological sedimentary thickness. We will address this particular case in the discussion Section 4.