## 1 Introduction  
Landslides are natural phenomena as well as man-made disasters that frequently lead to loss of human life and property, as well as causing serious damage to natural resources throughout the world. These occurs because of different associated natural hazards or anthropogenic activities. Natural phenomena include meteorological changes, such as intense rainfall, prolonged rainfall, or snowmelt and again earthquakes or volcanic eruptions. Human disturbances instead include land use alteration, deforestation, carrying out excavations, changes in the slope profile, and infrastructure constructions [1]. The effects associated with the occurrence of landslides include injuries, loss of human life, significant damage to natural resources and infrastructure, such as roads, bridges, and communication lines. To limit this, the realization of the landslide susceptibility map is fundamental to identify possible preventive measures and the planning of evacuation strategies to avoid significant damage and victims. Moreover, landslide susceptibility, hazard and risk maps are of great help to planners for selecting suitable areas to implement development schemes in any area [2, 3]. Despite tremendous progress in science and technology, landslides considerably affect the socio-economic conditions of all regions of the globe. The susceptibility to landslides can be defined as the probability of the spatial occurrence of a landslide event based on the relationships between the occurrence distribution and a set of predisposing factors in a given area, such as geo-environmental thematic variables [4]. Landslides cannot be completely prevented but an accurate prediction of the landslide-susceptible areas is of particular importance since this can lead to saving natural resources as well as human lives. Landslides occur and are controlled by one or more conditioning factors, such as topography, slope, failure mechanism, intensity of rainfall, land cover, geological formation, strength of rocks, and many more [5, 6, 7]. The landslide susceptibility assessment can be tricky because of the difficult evaluation of both the spatial and temporal distribution of past events for large areas, mainly due to the limitations and gaps of historical records and geographic information [8]. Many different types of landslide risk assessment zonation techniques have been developed over the last decades. These methods can typically be labeled as being either qualitative or quantitative procedures, also called direct and indirect methods [9; 10; 11]. The qualitative approaches are inventory-based and knowledge-driven methods such as distribution analysis or inventory [12], geographic mapping [13], and map integration models [14]. They yield direct and countable results but are limited by data availability. By contrast, the qualitative approach is less complex, but the subjective estimation of experts renders its degree of confidence and the accuracy of its results questionable [15]. Direct mapping has the purpose of determining the degree of landslide susceptibility based on a qualitative approach and provides an estimate of \"where\" landslides are expected. In this approach, the experience, knowledge of the ground boundary conditions, and the evaluation of pre-existing terrain maps are taken into consideration. Precisely for these reasons, direct methods present results that are subjective since they are linked to the experience and knowledge of the personnel and present many difficulties in transcribing the phenomena due to the occurrence of particular environmental changes in certain areas [16]. This methodology usually uses factors characteristic of the locations where landslides have occurred in the past, together with an assessment of the areas with a potential to experience land sliding in the future, but with no assessment of the landslide's occurrence frequency. The reliability of landslide-susceptibility maps mainly depends on the scale of work, the quality of the data and the analysis methodology.