# Influence of Earthquakes on Landslide Susceptibility in a Seismic Prone Catchment in Central Asia
## 4 Discussion
### Relationship between Landslide Metrics and Environmental Variables  
As one of the most disastrous natural hazards, land sliding is one of the complex geomorphic processes that is affected by several triggering factors, which differ greatly from region to region [9; 36; 37]. The relative importance analysis indicated that distance to faults, precipitation, slope, and elevation were more relevant to the structure of the spatial patterns of LSI and VOL than other environmental variables. The influence of fault lines on the landscape vulnerability has been long recognised [13; 50], i.e., the closer to the fault lines, the more dangerous the landscape. The importance of precipitation was supported by the finding of [PERSON] and [PERSON] [75] who investigated the relationship between the occurrence of landslides and precipitation in Hong Kong, and concluded that a 12 h rolling precipitation is most important factor in predicting the number of landslides. Similarly, [PERSON] et al. [52] reported that intensive precipitations and rapid melting contributed to the activation of some landslides in 2017 in the Mailuu-Suu catchment. The importance of slope has been mentioned in many previous studies [8; 13; 42]. Generally, landslides do not occur on a gentle slope, as the shear stress is too low, and an increase in slope gradient can potentially raise the likelihood of land sliding [15]. A colluvial landslide event mainly occurs in the moderate slope zone, as shown in Ma [15] and Zhou [65]. However, LSI and VOL showed linear correlations with the slope in our case. The importance of elevation lies in the fact that it controls temperature and vegetation. The occurrences of landslides rose with the increase in elevation before reaching a threshold elevation, where the landslide probability decreases as a result of soil characteristics or other geotechnical parameters [13; 61]. This is in line with our findings in which the highest VOL was observed in the moderate elevation zones. As the third topographic variable used in this study, the aspect was relatively unimportant, but it was found to be important in the study of Three Gorges Reservoir in China, where the southeast aspect represented the highest occurrence probability of colluvial landslides [65]. The other two proximity variables (i.e., distance to roads and streams) were also identified as unimportant triggers in structuring the spatial patterns of LSI and VOL. Similar findings were reported by [PERSON] et al. [13] in the Krios and Krathis catchments in Greece. However, the importance of proximity variables has been found in few studies; for example, 43% of the colluvial landslides occurred within the range of 50 m from roads and 38% within the range of 200 m from streams in the Three Gorges Reservoir in China [65]. By comparing the spatial distribution of LSI along the gradients of environmental variables, LSI was found to be negatively correlated to elevation, slope, precipitation, distances to faults, roads, and streams. Such relationships reflect the importance of these environmental variables. However, the patterns of land cover can also reflect the spatial distribution of LSI. Due to the effect of vegetation, [PERSON] et al. [76] found that most cropland areas were vulnerable to landslides on the Peloponnese Peninsula in Greece. This is in contrast with our results, where the most stable zones were dominated by cropland and sparse vegetation in the downstream areas, and the unstable zones were located in the high mountain with water/snow and bare areas. The high susceptibility level in the snow and bare areas was also proven by the studies of [PERSON] et al. [37] and [PERSON] et al. [76], where the presence of rock masses does not support any vegetation in the higher slopes. Based on the same effect of vegetation, the forest cover can protect the mountainous slopes from climatic effects and mass movements as the roots hold the underneath soil and keep the slopes stable [37].