## 3 Results and Discussion  
### Spatial Relationship Between Landslide Distribution and Conditioning Factors  
To understand the controlling mechanisms of co-seismic landslides triggered by the 2015 Gorkha Earthquake, we investigated the spatial distribution of landslide area, areal density, and number density across ten key landslide conditioning factors (LCFs). These factors include terrain morphology, seismic input, geological settings, hydrological conditions, vegetation cover, and anthropogenic influences. The spatial distribution maps are presented in Figure 11a-j, illustrating the spatial relationships between landslide metrics and key conditioning factors. Each subplot illustrates three metrics: total landslide area (gray bars), areal density (%) (gold line), and number density (1/km\({}^{2}\)) (red line), across different classes of conditioning factors. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**S. No.** & **Feature** & **VIF** & **Tolerance** \\ \hline
1 & Distance to Fault & 7.787 & 0.128 \\
2 & Elevation & 5.618 & 0.178 \\
3 & PGA & 4.937 & 0.203 \\
4 & Rainfall & 3.182 & 0.314 \\
5 & Distance to Road & 1.988 & 0.503 \\
6 & Slope & 1.838 & 0.544 \\
7 & Geology & 1.830 & 0.546 \\
8 & TWI & 1.814 & 0.551 \\
9 & SPI & 1.770 & 0.565 \\
10 & NDVI & 1.462 & 0.684 \\
11 & Distance to Stream & 1.420 & 0.704 \\
12 & Curvature & 1.209 & 0.827 \\
13 & LULC & 1.194 & 0.837 \\
14 & Aspect & 1.051 & 0.952 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Variance Inflation Factor (VIF) and Tolerance values used to assess multicollinearity among predictor variables. Figure 11: _Cont._  
Figure 11: Spatial distribution of landslide area (gray bars), areal density (%) (gold lines), and number density (1/km\({}^{2}\)) (red lines) across classes of (**a**) aspect, (**b**) curvature, (**c**) geology, (**d**) distance to road, (**e**) distance to fault, (**f**) distance to stream, (**g**) elevation, (**h**) NDVI, (**i**) PGA, and (**j**) slope. Landslides predominantly occurred on slopes ranging between 30\({}^{\circ}\) and 50\({}^{\circ}\), with the highest number density observed in the 40-50\({}^{\circ}\) class (Figure 11). This range appears to represent a critical slope threshold where gravitational stresses most effectively exceed the resisting forces. The areal density similarly peaked in the 50-60\({}^{\circ}\) range, indicating that not only were more landslides initiated on moderately steep terrain, but that they also tended to cover larger areas. In contrast, landslide occurrence notably decreased in the steepest slope class (>60\({}^{\circ}\)), likely due to the presence of exposed bedrock. Landslide frequency and area display a pronounced directional pattern, with south-facing (S) and southeast-facing (SE) slopes experiencing the highest number density (up to \(\sim\)2.0/km\({}^{2}\)) and areal coverage (around 2.5 km\({}^{2}\)), as in Figure 11. These aspects are typically exposed to higher solar radiation, which may induce surface desiccation, reduce vegetation density, and lead to diminished root cohesion, collectively weakening slope stability. In contrast, north- and northwest-facing slopes, as well as flat terrain, exhibit relatively lower landslide densities and areas, possibly due to denser vegetation, more stable moisture retention, or reduced weathering intensity. Landslides occurred predominantly on concave (negative-curvature) slopes, which showed the highest landslide area and number density, as in Figure 11. These landforms tend to accumulate water, increasing pore pressure and promoting failure. In contrast, flat surfaces exhibited minimal landslide activity, while convex slopes showed moderate susceptibility, likely due to their tendency to shed water and reduce subsurface saturation.