## 4 ETL Susceptibility Assessment in Cephalonia Based on GIS-Based Analytic Hierarchy Process  
### ETL Susceptibility Model  
In the context of landslide susceptibility assessment research, 596 thematic parameters have been used so far worldwide, which are classified into five main categories, as shown in the review by [PERSON] et al. [53]: (a) geological parameters, (b) hydrological parameters, (c) parameters related to land use, (d) morphological parameters and (e) other parameters not included in the previous categories. Figure 6: (a) Maximum distance from earthquake epicenter of disrupted slides and falls induced by historical and recent earthquakes of different magnitudes generated onshore and offshore Cephalonia versus earthquake magnitude. The dashed line is the upper bound for disrupted slides or falls by [PERSON] [7]. (b) Maximum epicentral distances of landslides triggered by historical and recent earthquakes of different magnitudes versus earthquake magnitude. The red subset comprises data from Cephalonia and the blue subset from around Greece published by [PERSON] and [PERSON] [17]. The dashed line is the upper bound for disrupted slides or falls by [PERSON] [7]. In the case of the assessment of landslide susceptibility in Cephalonia, the following parameters were used: (a) morphological parameters, including slope, slope aspect and slope curvature; (b) geological parameters, such as lithology of geological formations and distance from tectonic structures (faults and thrusts); (c) seismological parameters, including the peak ground acceleration (PGA); (d) environmental parameters including vegetation, derived from the NDVI index and the distance from the road network; (e) hydrometeorological parameters, such as the spatial distribution of rainfall and the distance from the drainage network (rivers and streams) (Figures 7 and 8; Table 3). Morphological slope controls the balance of restraining and destabilizing load forces acting on a slope [79; 80], while forces are developed to maintain a steep rather than a gentle slope. From the statistical analysis of recorded landslides throughout Greece [81], it appears that the 16-30\({}^{\circ}\) class is the most susceptible one. Among the morphological parameters, slope is widely used in landslide susceptibility models, as it is the most critical parameter that contributes to the reliable estimation of susceptibility [24; 82; 83; 84] and to the definition of non-susceptible areas [85]. Slope aspect is a very important parameter as it affects the exposure of the surface to sun and dry winds and indirectly to the flora as well as to the degree of saturation and evapotranspiration of the soil. According to [PERSON] et al. [86; 87], at northern hemisphere latitudes, where Ionian Islands are located, N- and NW-facing slopes are more prone to failures due to lower temperatures and more shade, factors that favor soil moisture retention. Figure 8: Thematic maps illustrating the environmental and hydrometeorological causal factors taken into account for the landslide susceptibility calculations. (**a**) NDVI, (**b**) yearly rainfall, (**c**) drainage network and (**d**) road network. A concave surface is more likely to suffer landslides, as after prolonged rainfall it can retain and store rainwater for longer time periods, unlike a curved surface. Additionally, a curved slope can delineate the rocky bedrock that is likely to be present in the area. Areas with positive curvature values identify curved surfaces and correspondingly negative values indicate concave surfaces. A zero curvature value indicates a flat surface. The more negative a value is, the higher the probability of landslide, while on the contrary, a surface with a positive curvature value (curved surface) is less likely to experience landslide phenomena.