## 2 Study Area and Data Used  
Shangnan County, Shaanxi Province, China (Figure 1) regularly suffers a great deal of damage from landslides, so was selected as a suitable site for evaluating landslide susceptibility models. The altitude in the area ranges from 189 to 2050 m above sea level (a.s.l. ), and the area and maximum slope angle are approximately 2307 km\({}^{2}\) and 65\({}^{\circ}\), respectively. The average temperature for the whole county is 14.6 \({}^{\circ}\)C, ranging between 11.1 and 15.0 \({}^{\circ}\)C for various regions. The spatial distribution of air temperature is affected by altitude. The temperature is low in the northern and southern mountainous areas, and high in the central and Danjiang River areas. Topographically, Shangnan County is a mountainous terrain in the Eastern Qinling Mountains. The altitudes in the northern and southwestern areas are higher than in the middle and southeastern areas. The study area can be divided into three geomorphological units: (I) Hilly areas with altitudes below 500 m and a relative height difference of less than 200 m; (II) low-relief areas with altitudes between 500 and 1000 m and a relative height difference between 200 and 500 m; and (III) mid-mountain zones with altitudes above 1000 m and a relative height difference greater than 500 m.  
Geologically, the study area is located at the border zone of the North China and the Yangtze plates, and spans multiple stratigraphic regions from north to south. Therefore, the lithologies of the stratum are obviously different. The strata in the region are dominated by the Archean to Ordovician periods, and Devonian and Carboniferous are partially outcropped (Figure 2). Five major faults divide the study area into distinct structural zones: (1) Shangnan-Danfeng fault (NW-SE direction); (2) Zhulinguan-Taifenglou large fault (W-E direction); (3) Banyan-Yaolinghe fault (NW-SE direction); (4) Bailuchu-Weijiatai fault (NW-SE direction); and (5) Shiliping-Sanguammao fault (W-E direction). Landslide inventory is the basis for LSM. Reliable and accurate landslide inventory data are crucial for LSM [51]. To enhance the reliability and accuracy of landslide inventory maps, a total of three techniques were used in the study: Historical reports, interpretation of aerial photographs, and extensive global positioning system (GPS) field surveys. According to landslide inventory maps in the region, a total of 348 landslides were identified (Figure 1). From these locations, 244 (70%) were randomly selected for building the models, and 104 (30%) were used for validating models. Following the development of a landslide inventory, the factors necessary to create the landslide susceptibility maps must be determined [52]. The factors used in the studies evaluating landslide susceptibility can be categorized into three major groups: Topographical, environmental, and geological. Figure 1: Location of the study area and landslide inventory. Fifteen factors (11 continuous and 4 categorical) were chosen and produced from the digital topographical maps at a 1:50,000 scale, LANDSAT-8 satellite images with a spatial resolution of 30 m, the compilation of geological maps on a 1:200,000 scale, the compilation of land use maps on a 1:100,000 scale, and soil maps on a 1:1,000,000 scale. The list of the factors used in this study are shown in Table 1. Altitude, plan curvature, profile curvature, slope angle, slope aspect, topographic wetness index (TWI), stream power index (SPI), sediment transport index (STI), distance to roads, and distance to rivers factors were determined from topographical maps. Distance to fault and lithology factors were produced from the geological maps. Normalized difference vegetation index (NDVI) was produced from the LANDSAT-8 satellite images. Land use and soil factors were extracted from land use and soil maps, respectively. Finally, a 30 m pixel size was chosen for all the factor maps (Figure 3).