## 4 Analysis
### Initial LSP Results
#### 4.2.2 SHAP Value Analysis  
In Figure 5, SHAP values are displayed along the horizontal axis, where positive values indicate increased landslide probability and negative values suggest decreased probability. The color gradient represents the feature values, with red indicating high values and blue indicating low values. Figure 5 reveals that the NDVI, altitude, distance from roads, and slope degree are the most influential factors, consistent with the ranking in Table 2, while profile curvature, fault density, lithology, soil, and plan profile show relatively smaller impacts. Among the high-impact factors, the NDVI demonstrates the strongest influence. Higher NDVI values (shown in red, indicating dense vegetation) consistently correspond to negative SHAP values, indicating that dense vegetation significantly reduces landslide probability. Altitude shows complex effects, with lower elevations (blue in feature values) being generally associated with increased landslide likelihood, while higher elevations (red in feature values) correlate with decreased probability. For distance from roads, areas closer to roads (blue in feature values) show positive SHAP values, suggesting higher landslide susceptibility, potentially due to slope destabilization from construction activities. Slope degree exhibits a clear pattern where steeper slopes (red in feature values) strongly correlate with positive SHAP values, confirming that increased slope angles enhance landslide probability. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**LCFs** & **Class** & **Area Count** & **Landslides** & **\% of Area (E)** & **\% of Landslide (F)** & **FR = F/E** \\ \hline Altitude & Very Low & 326,157 & 3 & 38\% & 1\% & 0.01 \\  & Low & 197,596 & 11 & 23\% & 2\% & 0.08 \\  & Moderate & 131,483 & 38 & 15\% & 6\% & 0.42 \\  & High & 119,645 & 90 & 14\% & 15\% & 1.09 \\  & Very high & 77,189 & 445 & 9\% & 76\% & 8.37 \\ \hline \end{tabular}
\end{table} 
Table 4: Frequency ratio classification of initial LSP by RF model. Figure 5: SHAP values. The lower-impact factors show more subtle patterns. Profile curvature and plan profile display moderate effects, with certain curvature patterns corresponding to slightly increased landslide probability. Fault density shows minimal variation in its impact, while specific soil types and lithological characteristics demonstrate minor but detectable influences on landslide susceptibility. Further analysis of the NDVI and altitude SHAP analysis results (Figure 6a,b) reveals complex non-linear relationships with landslide susceptibility. For the NDVI (Figure 6a), a critical threshold of 0.8 was identified, where SHAP values exhibit a distinct transition pattern. SHAP values remain predominantly positive when the NDVI is below 0.8, indicating higher landslide susceptibility in areas with lower vegetation coverage. When the NDVI exceeds 0.8, the SHAP values rapidly shift to negative and stabilize, demonstrating significantly reduced landslide susceptibility. This threshold aligns with the FR analysis (Table 2), where areas with an NDVI > 0.8 only account for 13% of the relative frequency (RF), indicating a significantly lower landslide occurrence in well-vegetated areas. This NDVI threshold serves as a criterion for non-landslide sample selection in Scenario 3. The SHAP analysis plot for altitude (Figure 6b) displays a pronounced U-shaped pattern. Areas at lower altitude (0-500 m) show high positive SHAP values (1.0-1.8), possibly attributable to intensive human activities and road construction, as evidenced by the high importance of distance from roads in the SHAP analysis. This influence decreases sharply with the increase in altitude, transitioning to negative values around 700 m. Middle-altitude zones (1000-1500 m) maintain negative SHAP values between \(-\)0.5 and 0, while higher-altitude areas (>1500 m) exhibit consistent but moderate negative effects (\(-\)0.3 to \(-\)0.2).