## 4 ETL Susceptibility Assessment in Cephalonia Based on GIS-Based Analytic Hierarchy Process
### ETL Susceptibility Model
Due to inadequate drainage and destabilization of hillslopes by undercutting and overloading, landslides are more frequent near the road network [135]. With increasing distance from the road network, the landslide susceptibility in an area decreases. Important information on landslide susceptibility along the road network is obtained from the study of the history of such events. The road network in the study areas was derived from the topographic maps of the Hellenic Military Geographical Service in 1:50,000 scale [89; 90; 91; 92], which was then updated by using OpenStreetMap [93] (Figure 8d). After the factors were selected, they were classified into classes and rank values and standardized ratings were assigned for these classes (Table 4). In order to evaluate the relative weight of each factor, the Analytic Hierarchy Process (AHP) developed by [PERSON] [136] was selected as a decision tool. In the frame of the AHP, all factors are compared pairwise by taking into consideration the intensity of their significance and contribution to the generation of ETL, as it is derived from expert opinions, experience and knowledge gained from previous events. In the current study, the SpiceLogic Inc. Analytic Hierarchy Process Software (trial version 3.4.5) [137] was used. In total, 45 pairwise comparisons undertaking an approximate eigenvector calculation were conducted resulting in the pairwise comparison matrix, the consistency ratio and the multi-criteria utility function (Table 5; Figure 9). For the consistency ratio, [PERSON] [136] suggested that it should be less than or equal to 0.1, to accept the weights. The consistency ratio in this case, as derived from the software, is equal to 0.071, which reveals a suitable and reasonable level of consistency in the pairwise comparison that is a satisfactory value to recognize and estimate the factors weights. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Causal Factors** & **Classes** & **Rank Values** & **Standardized Ratings** & **Weights** \\ \hline \multirow{4}{*}{Slope} & Escarpments, \textgreater{}35\({}^{\circ}\) & 5 & 100 & \\  & Steep slopes, 25–35\({}^{\circ}\) & 4 & 80 & \\  & Moderately steep slopes, 15–25\({}^{\circ}\) & 3 & 60 & 0.224 \\  & Gentle slopes, 5–15\({}^{\circ}\) & 2 & 40 & \\  & Very gentle slopes, \textless{}50\({}^{\circ}\) & 1 & 20 & \\ \hline \multirow{4}{*}{PGA} & \textgreater{}530 cm/s\({}^{2}\) & 3 & 100 & \\  & 470–530 cm/s\({}^{2}\) & 2 & 67 & 0.203 \\  & \textless{}470 cm/s\({}^{2}\) & 1 & 33 & \\ \hline \multirow{4}{*}{Tectonic Structures} & \textless{}150 m from thrusts and fault & \multirow{2}{*}{3} & \multirow{2}{*}{100} & \\  & zones & & & \\ \cline{1-1}  & 150–300 m from thrusts and fault & \multirow{2}{*}{2} & \multirow{2}{*}{67} & \\ \cline{1-1}  & zones & & & \\ \cline{1-1}  & \textless{}50 m from minor faults & 1 & 33 & \\ \cline{1-1}  & All other areas & 0 & 0 & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Landslide causal factors, classes, rank values, standardized ratings and weights used in the landslide susceptibility assessment in Cephalonia. \begin{table}
\begin{tabular}{c c c c} \hline \hline