## 5 Implications and Discussion
### Relationship between the Geological Units and the Cz Thickness  
The thickness of the CZ is influenced by the type of rock. We attempted to investigate the relationship between the thickness of the CZ and the different geological units crossed by each profile. The results of the geophysical interpretation of the thickness of the CZ from the four study profiles are shown in Table 3.  
The CZ with the greatest average thickness is located in the La Torrecilla profile, with an average CZ thickness of 40-50 m. The CZ in La Torrecilla corresponds to Quaternary fluvial sediments and alluvial fan deposits (quartzite conglomerates and unconsolidated deposits formed by gravel, sands, silts and clays) [42; 49]. In the La Salud North profile, the average CZ thickness of about 35-45 m corresponds to the Qua-ternary formations (alluvial gravels and siltstones). Similarly, in the La Salud South pro-file, the mean CZ thickness of about 40-47.5 m also corresponds to the Quaternary formations (alluvial gravels and siltstones). Alluvial fan deposits are important recorders of tectonic activity. Alluvial fans develop at the edge of the sedimentary basin, and this can be evidence of tectonic activity, with faults along the edge of the basin causing uplift in the catchment area and subsidence  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Profile** & **Geological Units** & **Minimum CZ (m)** & **Maximum CZ (m)** & **Average CZ (m)** \\ \hline La Torrecilla & Quaternary fluvial sediments & & & \\  & and alluvial fan deposits & & & \\  & (quartzites conglomerates & & \\  & and unconsolidated deposits & & & \\  & formed by gravel, sands, & & & \\  & silts, and clays). & & & \\ \hline La Salud North & Quaternary formations & & & \\  & (alluvial gravels and & 30–40 & 40–50 & 35–45 \\  & siltstones). & & & \\ \hline La Salud South & Quaternary formations & & & \\  & (alluvial gravels and & 30–40 & 50–55 & 40–47.5 \\  & siltstones). & & & \\ \hline Carrascoy & The Messinian rocks are & & & \\  & associated with a weathered & & & \\  & layer of marstone as well as & & & \\  & the Red Unit and & & & \\  & Pleistocene-Quaternary & & & \\  & alluvial fan deposits. & & & \\ \hline \hline \end{tabular}
\end{table}
Table 3: Relationship between CZ thickness and the different geological units that host it.  
in the basin. Therefore, it is possible to see evidence of tectonic activity in the alluvial fan depositional succession, where the massive influx of coarse detritus into alluvial fan deposits can be interpreted as the result of tectonic activity in the form of earthquakes and uplift [83; 84].  
The Carrascoy profile has the thinnest average CZ (around 30-40 m) and includes a weathered layer of Messinian marlstone and the Red Unit and Pleistocene-Quaternary alluvial fan deposits [42; 49; 85]. The marlstone rocks are interpreted as a shallow marine zone with a fairly massive concentration of carbonate deposits so that the clastic deposits are not thick enough in the Carrascoy profile. In the North of the Carrascoy profile, the presence of the Red Unit and Pleistocene-Quarterary alluvial fan deposits can explain why the CZ thickness in the Carrascoy profile deposits does not exceed the thickness of the other three profiles.  
Finally, the values estimated for the thickness of the CZ in our study correlated well with the average 36.8 m thickness across continental areas estimated by [PERSON] and [PERSON] [11]. Therefore, we validate here the use of combined electrical and seismic methods to evaluate the thickness and characterize the CZ.