## 2 Materials and Methods
### Materials
#### 2.1.3 FR and Correlation Analysis of Predisposing Factors  
The FR values of the 14 predisposing factors were calculated to build connections between the recorded landslide grid cells and the predisposing factors [26; 49; 50; 56]. Two discrete predisposing  
Figure 3: Hydrological, lithological, and land cover factors in Shicheng County, (**a**) Distance to river, (**b**) TWI, (**c**) MNDWI, (**d**) Rock types, (**e**) NDBI, (**f**) NDVI, (**g**) Total surface radiation, (**h**) Population density index. factors, namely, distance to river and rock types, were directly used, while the other continuous predisposing factors were first divided into several subclasses, which were then used to calculate the FR values. In this study, the continuous predisposing factors were generally divided into eight subclasses using the Jenks natural break classification method [45; 49; 56]. The calculated FR values are shown in Table 1, which demonstrates that these factors play important roles in landslide occurrence in Shicheng County. Generally, a higher FR value indicates the more significant influence of a subclass of a predisposing factor on landslide occurrence. Therefore, Table 1 shows that, for example, slope values between 7.5\({}^{\circ}\) and 14.9\({}^{\circ}\) have a greater effect on landslide occurrence than other values; the closer to the river, the greater the influence on landslide occurrence. Further, metamorphic rock is more conducive to landslide occurrence comparing to other rocks. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Factors**} & \multirow{2}{*}{**Data Type**} & \multirow{2}{*}{**Value**} & \multirow{2}{*}{**Grids in Domain**} & \multicolumn{2}{c}{**Grid Proportion**} & \multirow{2}{*}{**Landslide**} & \multicolumn{1}{c}{**Grid Proportion**} & \multirow{2}{*}{**Frequency Ratio**} \\  & & & & **(\%)** & & **Number** & & **(\%)** \\ \hline \multirow{8}{*}{DEM (m)} & 0–280.9 & 450,325 & 25.6 & 833 & 30.7 & 1.200 \\  & 280.9–360.9 & 544,197 & 31.0 & 943 & 34.8 & 1.124 \\  & 360.9–454.2 & 308,108 & 17.5 & 307 & 11.3 & 0.646 \\  & 454.2–560.9 & 181,087 & 10.3 & 341 & 12.6 & 1.222 \\  & 560.9–676.4 & 127,080 & 7.2 & 199 & 7.3 & 1.016 \\  & 676.4–805.3 & 86,871 & 4.9 & 82 & 3.0 & 0.612 \\  & 805.3–969.7 & 41,033 & 2.3 & 4 & 0.1 & 0.063 \\  & 969.7–1320.1 & 18,636 & 1.1 & 0 & 0 & 0 \\ \hline \multirow{8}{*}{Slope (\({}^{\circ}\))} & 0–3.9 & 348,797 & 19.8 & 184 & 6.8 & 0.342 \\  & 3.9–7.5 & 406,976 & 23.2 & 737 & 27.2 & 1.175 \\  & 7.5–11.2 & 358,445 & 20.4 & 865 & 31.9 & 1.566 \\  & 11.2–14.9 & 258,803 & 14.7 & 516 & 19.0 & 1.293 \\  & 14.9–19.1 & 184,620 & 10.5 & 273 & 10.1 & 0.959 \\  & 19.1–23.8 & 114,448 & 6.5 & 113 & 4.2 & 0.641 \\  & 23.8–29.8 & 61,718 & 3.5 & 18 & 0.7 & 0.189 \\  & 29.8–52.8 & 23,530 & 1.3 & 3 & 0.1 & 0.083 \\ \hline \multirow{8}{*}{Aspect} & \multirow{2}{*}{Continuous} & -1 & 359 & 0.02 & 0 & 0 & 0 \\  & 0–22.5, & 204,837 & 11.7 & 258 & 9.5 & 0.817 \\  & 337.5–360 & 204,837 & 10.0 & 233 & 8.6 & 0.856 \\  & 67.5–112.5 & 212,635 & 12.1 & 439 & 16.2 & 1.339 \\  & 112.5–157.5 & 230,991 & 13.1 & 379 & 14.0 & 1.064 \\  & 157.5–202.5 & 225,837 & 12.9 & 276 & 10.2 & 0.793 \\  & 202.5–247.5 & 211,352 & 12.0 & 263 & 9.7 & 0.807 \\  & 247.5–292.5 & 239,169 & 13.6 & 464 & 17.1 & 1.259 \\ \hline \multirow{8}{*}{Relief amplitude} & 0–22.4 & 335,770 & 19.1 & 393 & 14.5 & 0.759 \\  & 22.4–38.3 & 420,761 & 23.9 & 924 & 34.1 & 1.425 \\ \cline{1-1}  & 38. 3–54.2 & 349,311 & 19.9 & 673 & 24.8 & 1.250 \\ \cline{1-1}  & 54.2–71.5 & 270,334 & 15.4 & 457 & 16.9 & 1.097 \\ \cline{1-1}  & 71.5–91.0 & 182,134 & 10.4 & 188 & 6.9 & 0.670 \\ \cline{1-1}  & 91.0–114.9 & 111,395 & 6.3 & 73 & 2.7 & 0.425 \\ \cline{1-1}  & 114.9–146.7 & 60,885 & 3.5 & 1 & 0.04 & 0.011 \\ \cline{1-1}  & 146.7–185 & 26,747 & 1.5 & 0 & 0 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Frequency ratios of landslide-related predisposing factors.