## 4 Case Study  
The study site is situated on Yuyao City, Zhejiang Province (Figure 6). Zhejiang Province is located on the southeast coast of China; due to its unique geographical location, complex geology, topography, and climate background, Zhejiang has become one of the most frequent regions for rainfall-induced landslides in China. According to statistics, over 82% of the landslides in the Zhejiang region are rainfall-induced landslides (soil landslides and debris flows) [29]. In the Zhejiang region, the main natural environmental factors controlling the occurrence of rainfall-induced landslides include stratigraphic lithology, Quaternary loose deposits (residual, colluvial, and alluvial layers), soil, land use, and topography (elevation, slope, aspect, and slope shape). Currently, there is still a lack of systematic or relatively complete regional data. This paper mainly analyzes the relationships between landslide distribution and stratigraphic lithology, soil texture, land use, and topography. Regarding stratigraphic lithology, areas with Tertiary basalt distribution have the highest landslide frequency per unit area, followed by Sinian volcanic rocks, granite, sandstone, sandy mudstone, Precambrian metamorphic rocks, Cambrian mudstone, muddy limestone, and Carboniferous sandstone and shale. Among various soil types, submerged paddy soil, coarse bone soil, and infiltrated paddy soil are the most prone to landslides. The distribution of landslides also varies among different land use types, with the highest landslide distribution per unit area occurring in terrace fields, drylands, tea gardens, wastelands, and forested areas. According to statistics based on 1 km\(\times\)1 km grid units, the probability of landslides is highest at an elevation of 200-400 m, with over 95% of landslides occurring on slopes with a gradient of 5-15 degrees. The influence of slope shape on landslide distribution is also significant, with over 50% occurring on convex slopes and about 45% associated with concave slopes. The survey line layout consists of three survey lines: Survey lines 1 and 2 run parallel to the direction of the landslide trend, while Survey line 3 is perpendicular to the landslide trend (Figure 7). In the results of the three survey lines, the following color-coded areas are observed: The blue area represents the Quaternary soil layer, with resistivity values less than 600 \(\Omega\cdot\)m. The yellow area above denotes the moderately weathered interface, with  
Figure 6: Field case study location. resistivity values ranging from 600 \(\Omega\cdot\)m to 1270 \(\Omega\cdot\)m. The red area indicates the complete bedrock, characterized by resistivity values exceeding 1800 \(\Omega\cdot\)m (Figure 8a). Figure 8: Resistivity profile of survey line. (**a**) results of survey line 1; (**b**) results of survey line 2; (**c**) results of survey line 3. Figure 7: Survey line layout. Figure 8b reveals a low-resistance anomaly spanning 25-45 m horizontally along survey line 2. This anomaly may lead to a separation between the left and right sides, potentially triggering a landslide. Therefore, reinforcement measures should be implemented promptly. Outside the landslide body, the resistivity images of the soil only show higher resistivity at the surface. As the depth increases, the resistivity generally shows a monotonic decrease. The resistivity values of the soil inside the landslide body differ significantly from those outside the landslide body. At the position of the sliding surface of the landslide body, the resistivity values show stratification, with noticeable differences in resistivity values above and below the sliding surface. In the profile perpendicular to the sliding direction of the landslide body, the shape of the sliding surface is approximately arc-shaped or an inverted trapezoid. The sliding surface is deepest near the central position of the landslide body, and shallowest near the sliding walls on both sides of the landslide body.