# Examination of Landslide Susceptibility Modeling Using Ensemble Learning and Factor Engineering
## 2 Geological Background  
### Study Area  
The research focuses on Chongqing's southwestern region, within China's Three Gorges Reservoir area (Figure 1), spanning Fuling, Nanchuan, Zhongxian, and Fengdu districts. Positioned 172 km upstream from Chongqing's urban core and 434 km from the Three Gorges Dam, the area straddles critical tectonic boundaries: the Sichuan basin's fold belt to the northwest and the southeastern uplift zone, demarcated by Jinfoshan Mountain's northern slope. The northwestern part belongs to the Sichuan Depression and the eastern Sichuan fold belt, while the southeastern part is part of the uplift fold of southeastern Sichuan. Geologically, the area is part of the Neo-Cathaysian tectonic system, with dominant orientations of NNE, NS, and NNW, as well as some arcuate structural lines. stratigraphically, the area spans from the Cambrian of the Paleozoic to the Cretaceous of the Mesozoic, with notable gaps in the Devonian, Carboniferous, and parts of the Cretaceous. Quaternary sediments are sporadically distributed in river valleys, plains, and troughs. The Cambrian is characterized by dolomite and dolomitic limestone, the Ordovician by clastic and cracked limestone, the Silurian by limestone, the Permian by gray-to-black aluminum shale and carbonaceous shale, the Triassic by interbedded limestone, sandstone, and siltstone, and the Jurassic by brown-purple sandstone and shale. Tertiary strata are absent in the Cenozoic, while Quaternary lithology consists primarily of accumulation layers. Elevations here exceed 1400 m, presenting a deeply dissected mid-mountain landscape. The northwestern part is lower, displaying the \"red layer\" geomorphology of eastern Sichuan, with elevations generally between 500 and 1100 m, forming a shallow-cut low mountain landscape. Along the Chuanxiang Highway, the terrain consists of low mountains and trough basins, with elevations ranging from 500 to 800 m. The highest point in the study area is Fengchuiling of Jinfo Mountain at 2238 m, while the lowest point is Yutiaoyan in Qilong Township at 340 m, resulting in a relative height difference of 1898 m. Mid-mountains and low mountains dominate the topography, covering 50.71% and 48.07% of the area, respectively, with hills accounting for only 1.22%.  
The area experiences a subtropical monsoon climate, influenced by the westerlies, the Western Pacific Subtropical High, the Southwest Vortex, and the Tibetan High. Winter is dominated by northerly airflows, while summer is influenced by the southerly monsoon, with the Pacific Subtropical High often extending westward. This results in distinct seasons, significant dry and wet periods, warm winters, hot summers, ample rainfall, and a long frost-free period. Temperatures decrease and precipitation increases from northwest to southeast, forming a distinct vertical climate. The average annual temperature is 18.1 \({}^{\circ}\)C, with an average annual precipitation of 1185 mm. In 2023, the annual precipitation reached 1380.8 mm, a 38.0% increase from the previous year. The study area is part of the Yangtze River basin, with abundant water resources and a well-developed hydrological network. The Yangtze River flows northwest to northeast through the area, forming an irregular \"W\" shape, and is supplied by primary, secondary, and tertiary rivers, as well as seasonal streams. Secondary tributaries are primarily mid-mountain and high-hill water systems, with relatively gentle gradients. The Yangtze River within the study area is approximately 134 km long, with a perennial flow rate of about 13,357 cubic meters per second. The Three Gorges Reservoir causes water levels to fluctuate between a maximum of 175 m and a minimum of 145 m, with variations in the upstream flow during dry and wet periods directly impacting reservoir regulation. These changes are a significant factor in the reactivation and deformation of water-related landslides.