## 2 Study Area and Data Processing
### Construction of Evaluation Index System  
The evaluation index system of landslides is crucial in assessing landslide hazards and evaluating susceptibility. In this study, the landslide index system is divided into two major parts: intrinsic factors and extrinsic factors. Based on the geographical conditions of Zayu County and scientific selection principles, 15 evaluation factors, such as elevation, aspect, and slope, were selected [24]. The constructed evaluation index system is illustrated in Figure 2.  
To ensure spatial consistency, the factor layers in this study were resampled to a uniform spatial resolution of 30 m. Furthermore, all factors were normalized to prevent the results from being influenced by the magnitude of the numerical values. The extraction and processing of factors were primarily conducted using the ArcGIS 10.2 and ENVI 5.3 platforms. The processed thematic maps of the factors are presented in Figure 3.  
* Elevation significantly influences the regional climate, particularly in high-altitude mountainous areas where landslides are closely dependent on elevation [25]. * Slope
* Steeper slopes generate greater shear forces, increasing landslide likelihood. * Variations in aspect lead to differences in regional climate conditions, indirectly impacting slope stability [26]. * Plane curvature and profile curvature
* Slope curvature affects the internal stress distribution, influencing landslide development. * The Terrain Ruggedness Index (TRI) is crucial for describing the earth's surface topography. * Normalized vegetation index
* The vegetation index reflects the degree of vegetation coverage [27]. Vegetation coverage can mitigate erosion and the scouring of rocks by rainwater and reduce rainwater infiltration. Conversely, vegetation roots can intrude into rocks, compromising overall stability [28]. Therefore, vegetation can have either a positive or negative impact on landslides. The calculation formula is as follows: \[NDVI=\frac{NIR-R}{NIR+R}\] (1)  
Figure 2: Structure diagram of the landslide evaluation system. where _NIR_ and \(R\) represent the spectral reflectance in the near-infrared and red bands, respectively. * Stream density River erosion and infiltration can reduce slopes' shear resistance, thereby affecting their overall stability [29]. * Topographic wetness index The Topographic Wetness Index (_TWI_) evaluates soil moisture and quantitatively assesses runoff trends. The calculation formula is as follows: \[TWI=\ln\frac{\alpha}{\tan\beta}\] (2) where \(\alpha\) is the length of the contour line per unit area, and \(\beta\) is the slope. * Normalized difference water index The Normalized Difference Water Index (_NDWI_) visually represents the distribution of rivers in the area. The calculation formula is as follows: \[NDWI=\frac{Green-NIR}{Green+NIR}\] (3) where _NIR_ and _Green_ represent the spectral reflectance in the near-infrared and green bands, respectively. * Land cover type Different land use types affect slope stability differently [30]. * Fault density and distance to faults Faults disrupt the integrity of rock masses, thereby increasing the impact of other factors on slope stability. * Road density A higher road density indicates more frequent human activities, leading to increased surface disturbances and potentially causing landslide disasters. * Rainfall Rainfall increases groundwater levels, alters the mass distribution within the soil, and changes the slope stress, thereby affecting slope stability. Intense rainfall can cause substantial soil surface erosion, directly leading to landslides. The data sources for each indicator are shown in Table 1.