## 2 The Stage-Wise Methodology for the GHM Characterization of the Landslide Mechanisms  
Assessments of landslide mechanisms, traditionally carried out at the slope scale, integrate data characterizing the variables controlling the slope stability, as defined by [PERSON] [17], as internal and external landslide factors (Figure 3), within the framework of the physical laws that control the slope movements [10] in connection with external factors, i.e., the landslide mechanism (Figure 4). Figure 5 illustrates the main steps of the GHM analysis of the slope processes determining the landslide mechanism, which are primarily hydro-mechanical. Such an analysis can now benefit from the considerable development which has occurred in recent years of the techniques of surveying and monitoring of landslide factors (in the fields of topography and geomatics, sensor technology and digital communication), and of the digital-based construction of databases [18; 19]. Moreover, GHM analyses can now implement advanced physical-mathematical modelling of slope responses to external factors, providing knowledge about the internal and external causes of the landslides, whose identification is a prerequisite of the proper design of sustainable landslide mitigation measures [10; 20]. For slopes consisting mainly of soil, which are a reference in the present paper, the 'first failure' mechanism [12; 16; 21] can be modelled within the theoretical framework of continuum mechanics by means of several numerical strategies [22; 23; 24; 25; 26]. These are aimed at simulating the coupling between the physical (hydro-mechanical and thermodynamic) and chemical phenomena that control the slope response, in terms of a boundary value problem ([10]; Figure 5c). This is quoted to provide a perspective of how comprehensive a GHM analysis may become; moreover, in some peculiar cases, a proper and successful landslide diagnosis may necessitate taking thermal or chemical behavior into account. Hence, generally speaking, this modelling requires the solution of a system of differential equations which is representative of the phenomena controlling the slope equilibrium over time, whose number varies depending on the number of processes accounted for in the modeling. In order to predict the displacement field over time, it is necessary to integrate a system including at least the equilibrium equation (which implements the elasto-plastic constitutive law of the slope soils) and the conservation equation of pore fluid masses ([22; 27; 28]; Figure 5c), i.e., either liquid or gas. Through the solution of such a system, the modelling predicts the strain field propagation up to the 'onset' of a landslide, and provides knowledge about both the morphology and the kinematics of the landslide (style and distribution of landslide activity; [16]), as well as about its causes. Figure 4: Landslide mechanism: from the triggering action (**1**), through the development of the shear band (**2**) until the final mobilization of the landslide body (**3**). Figure 3: Landslide factors [17]. In synthesis, when an external action occurs, the stress state across the slope changes over time, satisfying the equilibrium and strain compatibility, while determining strain localizations whose distribution depends on the hydro-mechanical properties of the slope materials and on the boundary conditions. As the straining develops over time, the mobilization of the landslide body progresses, with the development of a major discontinuity within the displacement field. In general, the so-called landslide event matches a stage when the difference in displacement rate between a slope portion (i.e., the landslide body) and the rest of the slope becomes significant. The major discontinuities in the displacement field correspond to the strain localization regions, typically either traction bands, or shear bands. The shear band may become the location of a slip surface.