## 3 Study Area and Data Used  
The study area (Nanzheng County) lies in Shaanxi Province, China (Figure 1). It is located between longitude 106\({}^{\circ}\)30\({}^{\prime}\) and 107\({}^{\circ}\)22\({}^{\prime}\) E and latitude 32\({}^{\circ}\)24\({}^{\prime}\) to 33\({}^{\circ}\)07\({}^{\prime}\) N. It covers an area of 2823 square kilometers. The altitude of the study area is between 442 and 2410 m. The study area has a subtropical monsoon climate, with an annual average temperature of 14.2 \({}^{\circ}\)C. Rainfall is mainly concentrated from June to September and the mean annual rainfall is 909.8 mm. A landslide inventory can give insight into landslide location, dates, type, and damage caused [68; 69; 70]. In this study, the landslide inventory map was prepared on the basis of historical landslide records and satellite images (Google Earth and ZY03 images). A total of 202 landslides were identified, including 190 slides and 12 rock falls [71]. The largest landslide was more than 1,000,000 m\({}^{3}\)  
Figure 1: Study area and landslide inventory. and the smallest landslide was nearly 160 m\({}^{3}\)[70]. Finally, 141 landslides were randomly selected as training and validation datasets with a ratio of 70:30 (Figure 1). There is no clear agreement about the precise cause of landslides due to their complex nature and development. According to the latest relevant research and local geological environment characteristics [72; 73; 74; 75; 76], 16 landslide conditioning factors have been compiled: elevation, profile curvature, plan curvature, slope angle, slope aspect, stream power index (SPI), topographic wetness index (TWI), sediment transport index (STI), distance to roads, distance to rivers, distance to faults, lithology, rainfall, soil, normalized different vegetation index (NDVI), and land use. The 16 landslide susceptibility conditioning factors were converted with a resolution of \(30\times 30\) m.  
Elevation influences earth surface and topographic attributes which account for spatial variability of precipitation, soil thickness, erosion, and vegetation [38]. Profile curvature and plan curvature have significant effects on surface runoff and infiltration [77]. Slope angle is an important factor that controls the velocity of the slopes, and the slope aspect has an important effect on rainfall, wind and sunlight exposure [78]. SPI, TWI and STI are related to soil water content status, water accumulation and progress of erosion and sedimentation in a watershed, which influence landslide stability [77; 78]. In the present study, the elevation map was acquired from a \(30\times 30\) m digital elevation model (DEM) and reclassified into 10 classes: 442-600 m, 600-800 m, 800-1000 m, 1000-1200 m, 1200-1400 m, 1400-1600 m, 1600-1800 m, 1800-2000 m, 2000-2200 m, and 2200-2410 m (Figure 2a). Similarly, the profile curvature, plan curvature, slope angle, slope aspect, SPI, TWI, and STI were also extracted from the DEM by ArcGIS. In the study, the profile curvature was grouped into three classes of \(-\)14.28 to \(-\)0.05, \(-\)0.05 to 0.05, and 0.05 to 14.77 (Figure 2b). The plan curvature was divided into three categories of \(-\)14.0 to \(-\)0.05, \(-\)0.05 to 0.05, and 0.05 to 13.07 (Figure 2c). The slope angle was grouped into seven categories: 0-10\({}^{\circ}\), 10-20\({}^{\circ}\), 20-30\({}^{\circ}\), 30-40\({}^{\circ}\), 40-50\({}^{\circ}\), 50-60\({}^{\circ}\), and 60-72.83\({}^{\circ}\) (Figure 2d). The slope aspect was reclassified into nine classes (Figure 2e). The SPI values were grouped into five classes: \(<\)20, 20-40, 40-60, 60-80, and \(>\)80 (Figure 2f). The TWI was reclassified into five categories: \(<\)4, 4-5, 5-6, 6-7, and \(>\)7 (Figure 2g). The STI values were divided into five classes: \(<\)10, 10-20, 20-30, 30-40, and \(>\)40 (Figure 2h). Distance to roads, distance to rivers and distance to faults are three commonly used landslide conditioning factors, these factors are related to the infiltration and strength of slopes [79; 80].