## 4 Results
### Depth to the Basement Estimation for Real Gravity Data  
The study area covers a minima and maxima latitude of 22.58 and 23.69 and minima and maxima longitude of \(-103.525\) and \(-102.625\), respectively; therefore, this area surrounds the aquifer polygon as seen in Figures 1 and 6a.  
We recollected gravity data from The Satellite Geodesy research group at the [PERSON] H. and Ida M. Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California San Diego [41]. After geophysical processing, the observed gravity data (Figure 6a) of the area of study present consistencies with the geology and the topography information of the region of interest (Figure 6b). The interpretation of these gravity anomalies is straightforward: the sedimentary rock deposits, where the Aguanaval River streams, match with the lowest gravity anomalies, where the central part of the aquifer lies; on the other hand, the highest gravity anomalies are presented at the boundaries of the aquifer because these regions act as a source for the recharge of the aquifer due to high elevation.  
The inversion result after 10 iterations of the algorithm is shown in Figure 6c. It is clear that the data have been fit for all zones, except for some regions with errors up to \(\approx\)2 mGal (see scale of Figure 6c), mostly at the regions where the gravity maximum and minimum are presented. Such errors can be reduced if the weight on the regularization is lowered; however, models with a higher roughness could be presented. As expected, the depth model presents a similar shape to the observed gravity data. A depth to the basement between 1.8 and 5.5 km is estimated, where the maximum depth is located at the central part of the aquifer limits as seen in Figure 6d for a 2D view and Figure 6e for a 3D view of the basement relief. The model does not present zero depths, which means that the basement does not crop out to the surface. Such depths are consistent with the topography and the geology of the study zone. The convergence of this result is well-behaved and fast in the same way as the synthetic example; therefore, the cost function will not be presented.  
One-directional profiles are picked for interpretation, centered at the domain of the aquifer, horizontally and vertically. The north-south profile, along a constant latitude of \(103^{\circ}\)W, suggests the presence of an inland basin filled with sedimentary rocks according to the geology of the study zone. In the same way, the west-east profile covers the aquifer perpendicularly, where such a basin is narrower. This suggests that the aquifer is elongated in the north-south direction and slightly inclined in the same direction as the aquifer's polygon.  
Figure 5: 1D profile along \(x\)-direction (**a**) for the true (red) and final (blue) depth model at \(y=201\) km. (**b**) The objective function cost (Misfit) is plotted for each iteration (10).  
Figure 6: Observed gravimetric-satellite data for the area of interest (**a**) and its topography (**b**). The synthetic data after 10 iterations of CGLS method (**c**) recovers the observed data, obtaining the final depth model of (**d**). A 3D view of the basement (kilometers) is shown in (**e**). 1D profiles were picked for interpretation for N-S orientation at longitude 103\({}^{\circ}\) W (**f**) and for W-O orientation at latitude 23.25\({}^{\circ}\) N (**g**).