## 3 Electrical Resistivity Tomography for Landslide Assessment  
The Electrical Resistivity Tomography (ERT) method is based on measuring the differences in electrical potential along a connected electrode array. By injecting current into the ground using two electrodes (metal stakes), the voltage difference in the subsurface is measured based on Ohm's Law, which provides us with indirect information on water saturation, fluid conductivity, porosity, and surface conductivity. The conductivity of the fluid, the porosity, and the surface conductivity, the latter depending on the organic matter and the clays [18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37], as well as the resistance of the soil strata, can be calculated as follows:  
\[R=U/I, \tag{1}\]  
where U is the measured voltage and I is the injected current. To obtain accurate ERT results, multiple electrodes are used to minimize measurement errors through proper data inversion [42,43]. Based on the injected current, measured voltage, and electrode configuration (Table 2), a resistivity image or pseudo-section of the subsurface is generated [44].  
The pole-dipole (Figure 10) array will be used due to its great utility for its good vertical and horizontal resolution, deep penetration, and sensitivity to both vertical and horizontal structures, according to studies by [45,46]. This method is perfect for detecting discontinuities between layers of rock and sediment in geological cross-sections of unstable terrain and also allows for the precise definition of the surface along which the breakage and displacement of the sliding mass occurred. The use of two-dimensional inversion methods is very common in landslide analysis [47], thanks to their resolution, precision, and accuracy, which make it possible to avoid erroneous data [7, 8, 9, 30, 31, 32, 33, 34, 35, 36, 37].  
\begin{table}
\begin{tabular}{c c} Electrodes & 24 \\ Interdistence (m) & 15–20–30 \({}^{*}\) \\ Delay from rising edge (s) & 0.02 \\ Acquisition period (s) & 0.3 \\ Signal Inversion Delay (s) & 0.02 \\ V (mVolts) & 5000 \\ I (mA) & 1500 \\ Array & Polo-Dipolo \\ Data Noise Tolerance (\%) & 2 \\ Number repeat & 1 \\ Sample frequency & 32,000 Hz \\ Maximum n & 22 \\ \end{tabular} \({}^{*}\)Inter-electrode distances used in ERT, 30 m for ERT-1, 15 m for ERT-2, and 120 m for ERT-3 and ERT-4.  
\end{table}
Table 2: Input data for processing.  
To classify the materials according to their resistivities (Figure 11), the resistivity values of rocks and minerals developed by [PERSON] [48] will be considered.  
Applying 3D ERT monitoring would increase the robustness of the study, as the results show that this method has the lowest false negative rate (2.412%) and the highest detection accuracy (up to 100%), surpassing traditional methods [49]. Similarly, the application of seismic methods, such as seismic refraction, multichannel analysis of surface waves (MASW-MASW-2D), multichannel analysis of microtremors (MAM or REMI), and time domain electromagnetic methods (TDEM), would expand the research to determine compatibility in the different strata and the conductivity of the materials in the study area; however, these methods would lack depth (seismic methods) and electromagnetic methods would be difficult to access.