## 2 Material and Methods
### Data Preparation
#### 2.2.2 Landslide Influencing Factors  
In this study, fifteen landslide influencing factors, including altitude, slope, aspect, plan curvature, profile curvature, stream power index (SPI), sediment transport index (STI), topographic wetness index (TWI), lithology, distance to fault, distance to river, land use, normalized difference vegetation index (NDVI), soil and rainfall (Figure 3). A DEM of the Anyuan area was obtained from the ASTER GDEM Version 2 and we can produce the geomorphological factors of slope, altitude, aspect, curvature, SPI, STI and TWI by using ArcGIS and SAGA-GIS software. In Figure 3a,b, altitude was divided into seven categories of 132-282 m, 282-432 m, 432-582 m, 582-732 m, 732-882 m, 882-1032 m and \(>\)1032 m, and slope was classified to eight angles of \(<\)20.0\({}^{\circ}\), 20.0-24.6\({}^{\circ}\), 24.6-29.2\({}^{\circ}\), 29.2-33.8\({}^{\circ}\), 33.8-38.4\({}^{\circ}\), 38.4-43.0\({}^{\circ}\), 43.0-47.6\({}^{\circ}\) and \(>\)47.6\({}^{\circ}\). As previous studies, aspect was classified to nine directions in Figure 3c, including east, south, west, north, northwest, northeast, southwest, southeast and flat. Both of the plan and profile curvatures were discriminated into three categories of \(<\)\(-\)0.001, (\(-\)0.001)-(0.001) and \(>\)0.001, as shown Figure 3d,e. \begin{table}
\begin{tabular}{c l l} \hline
**No.** & \multicolumn{2}{c}{**Unit Name**} & **Lithology** \\ \hline \multirow{4}{*}{D} & Lin shan group, Shui bei group & Carbonaceous shale and coal seam \\  & Luo a group & Feldspar quartz coarse sandstone \\  & Ge xianshan group, Xishan pai unit & Granite \\  & Linsha group, Yuexing group & Granite \\  & Yu tian group, Ji long group & Residual tuff; crystalline chip \\  & Long zhou unit & Diorite \\ \hline \multirow{2}{*}{E} & Shui jiang unit, Nankeng unit & Monzogranites \\  & Gan zhou group, Zhou tian group & Basalt, calcium mirabilite and halite \\ \hline F & Yang jiaqiao group & Quartzite, siliceous rock \\ \hline \multirow{2}{*}{G} & Da long group, Le ping group, Chang xing group & Coal seam, flint limestone, siliceous rock \\  & Tao xi group & Biotite plagioclase leptynite, sericite schist \\ \hline H & Xia keng group & Granoidorite \\ \hline \multirow{2}{*}{I} & Hu cheng unit & Tonalite \\  & Gui keng unit, Shang you unit & Granite \\ \hline \multirow{2}{*}{J} & Le chang group & Slate, phyllite \\  & He zi unit & Peridoite, ophiolite, amphibolite \\ \hline K & Bacun group, Niu jiaohe group & Silty slate, carbonaceous slate \\ \hline \end{tabular} Notes: A, B, C, D, E, F, G, H, I, J and K represent the lithology classes.  
\end{table} 
Table 1: _Cont._Figure 3: _Cont_. The factors of SPI, STI and TWI were divided into seven classes in Figure 3f-h, respectively. As for the geological factors, there are eight groups in the lithological map in Figure 3i, and distance to fault was initialized to six classes of 0-500 m, 500-1000 m, 1000-1500 m, 1500-2000 m, 2000-2500 m, and \(>\)2500 m in Figure 3j. As for the hydrological factor of distance to river, it was classified to seven intervals in Figure 3k, i.e., (1) 0-150, (2) 150-300, (3) 300-450, (4) 450-600, (5) 600-750, (6) 750-900, (7) >900. The land use and NDVI can be obtained using a Landsat 7 ETM+ satellite image acquired on 12 October 2001. The values of NDVI are in the range of [\(-\)1, 1] and were separated into six classes of \(<\)-0.05, (\(-\)0.05)-0.05, 0.05-0.15, 0.15-0.25, 0.25-0.35, 0.35-0.45, and \(>\)0.45 in Figure 3l. To obtain the land use information, the supervised classification algorithm of maximum likelihood was used with the overall accuracy of 91.2%, and the study area was classified to six objects of bare, forest, grass, residential, farmland, and water in Figure 3m. Another land cover factor of soil was provided by the Institute of Soil Science, Chinese Academy of Sciences (ISSCAS), China, into 5 different types of ATc (Cumulic anthrosols), ACu (Humic acrisols), ALh (Haplic alisols), ACh (Haplic acrisols), and RGc (Calcaric regosols) in Figure 3n.