## 4 Results and Discussion
### Time-Domain Electromagnetic  
For each of the measurement stations of the TDEM profile, the configuration parameters of loops, current injection, voltage, or measurement time were varied. Figure 4A shows the different induced voltage decay curves measured at station 1 (S1) for a single-loop configuration and obtained using the TEMBIN software. Figure 4: Different induced voltage curves as a function of time, all collected at station S1. Different measurement parameters were used in each of the curves (variations in Current, Voltage, Time). (**A**) The curves represent a single-loop configuration so that the transmitter area (Tx) and the receiver area (Rx) coincide (200 m \(\times\) 200 m = 40,000 m\({}^{2}\)). (**B**) The curves represent a central-loop configuration, where the same transmitter loop is maintained, but the receiver loop (Rx) has dimensions of 20 m \(\times\) 20 m; in this case, a five-wire cable and an amplifier of \(\times\)10 were used, so the effective area of Rx in this case is 20 \(\times\) 20 \(\times\) 5 \(\times\) 10 = 20,000 m\({}^{2}\). In each of the tests, the ramp time is directly proportional to the current used [46]. In our study, according to the technical specifications of the equipment, the ramp time was 12 \(\upmu\)s or 30 \(\upmu\)s, depending on whether the injected current was 1 or 8 A (for loops of 200 m \(\times\) 200 m). In station S1, when comparing the curves 'C_0.bem' and 'C_1.bem' (Figure 4A), currents of low emerge led the plateau at the top of the curve to be lower, and this increases with increasing emergence. Therefore, the information of the surface part decreases with the amplitude of the current. However, the capacity for in-depth investigation increases with the magnetic moment (\(I\ast A\)). According to [PERSON] [34]:  
\[d\sim 0.55\Big{(}\frac{I\ast A}{\sigma\ast Nr}\Big{)}^{\frac{1}{5}}\]  
where: \(d\) is depth in m, \(I\) is current of the transmitter in Amps, \(A\) the effective area of the transmitter in m\({}^{2}\), \(\sigma\) is electrical conductivity of the medium in S/m, and \(Nr\) is noise level in V/m\({}^{2}\). By keeping the surface of the transmitter loop constant (Tx = 200 m \(\times\) 200 m), the magnetic moment and the penetration capability remain proportional to the current, as deduced when curves 'C_0.bem' and 'C_1.bem' are compared (Figure 4A). Therefore, high currents are used even if information is lost near the top of the profile. Such information from very shallow depths is not relevant to the hydrogeological interpretation. Another important aspect to consider is the voltage range. We compare the response with the measurements at 0.1, 1, and 10 V at station S1 (Figure 4A). The superposition of the different curves allows us to deduce that greater stability is achieved in the depth of the induced voltage curve using low voltages as 0.1 V in the 'C_3.bem' curve of Figure 4A. Another factor analyzed was the measurement time window; longer time windows produce larger depths of investigation [34]. In our case, different time-offs at station S1 (20, 100, and 500 ms) were used. When the 'C_2.bem' and 'C_4.bem' curves are compared, times greater than 100 ms are observed, the noise level increases considerably, and the voltage values are extremely low, so time intervals in this range should be ignored due to their low reliability. All the aforementioned curves were obtained with a single loop. The readings were repeated at station S1 (Figure 4B) for the measurements with the different set-ups but using a central-loop device. As in the previous case, the data for research at deeper levels show that the magnetic moment must be increased (if the area remains constant, it will be proportional to the increase in current) and the voltage must be decreased. The measurement time was held constant at 100 ms. In all the stations indicated in the profile (Figure 2), the previously mentioned parameters were used.