## 2 Background and Scope
### Geophysical Background and Scope
These applications of the HVSR technique have been increasing in recent years with landslide investigations, almost always combined with drilling or other geophysical investigations such as refraction seismic and electrical tomography [7,36,37,38,39]. In a few cases [4,6], other geoelectrical surveys have been used as a reference in investigations, such as VES tests in [21], where they only apply this test type to establish the indicated correlation. In the present investigation, two different combined methods have been used. The seismic method was applied through active seismic techniques such as refraction and MASW profile techniques and HVSR seismic passive surveys. Complementarily, the geoelectrical method was proposed using the technique of VES. The VES technique has been widely used and developed over time regarding the geoelectrical method. The generation of an electric field and the measurement of its potential variation when crossing the ground allows for obtaining resistivity values that,depending on the configuration of the electrodes, can reach depths of several meters and is one of the most used geoelectric techniques in the investigation of landslides, along with electrical tomography [4]. In the seismic method, the seismic refraction technique allows, depending on the arrival time of an elastic wavefront to the receivers arranged along a profile (geophones), for determining the compression velocity \(V_{p}\) and the possible variations and changes in the composition and geometric configuration of the materials. The relatively simple test has extensive literature and knowledge and can be applied to mobilized landslide materials [3]. On the other hand, the surface waves analysis surveys of the seismic method, such as the MASW, allow, from the frequency analysis of surface and body waves, to obtain the distribution of values of the velocity of the shear wave S (\(V_{s}\)) in the analysis of a linear system of geophones with a one-dimensional distribution [40; 41]. The shear wave velocity in the ground usually complements the data obtained in the refraction seismic. The use of VES surveys as a correlation tool will be proposed without the need to carry out bore-holes (mechanical drilling) with the consequent reduction in costs and speed of execution of the study. For this, the variation between resistivity will be used as a differentiation tool. The shallow materials (less compact) and potentially in movement (sliding) present a contrast against the static rocky substrate (and of greater resistivity). Here, complementary tests will be available, such as active and passive seismic tests for model calibration. The combination of geophysical techniques, as [42] resumes, complemented with direct surveys, such as drilling, allows for determining the first parameters in landslides. Moreover, they can define the position of the rupture surfaces with considerable precision, always depending on the conditions and characteristics of the area and materials [4; 6; 28; 43]. Therefore, in order to study, in advance, the sliding zone (the material that was in movement) and define its thickness, a geophysical research campaign application has been proposed. The company scopes are to analyze different kinds of materials, obtain some knowledge about the presence of water in materials, and define the landslide rupture surface. This information could provide an early idea of the size of the landslide, materials involved in the sliding area, an approach to the focused areas, and the investigation depth in future works. These investigations will be the basis for decision-making in future actions regarding landslide research through mechanical soundings and monitoring of the event using inclinometers.