# Influence of Earthquakes on Landslide Susceptibility in a Seismic Prone Catchment in Central Asia
## 3 Results  
### Landslide Susceptibility Index and Volume of Landslide  
Maps of LSI and VOL were developed in the Mailuu-Suu catchment. The results showed that the upstream areas were more unstable than the downstream areas under the first four earthquake scenarios (namely moderate, strong, severe, and violent) (Figure 3a), whereas most areas were identified as very unstable (LSI \(\leq\) 0.5) under the extreme earthquake scenario (Figure 3a). Under the moderate scenario, most downstream areas were stable or very stable, and with the increase in earthquake strength, the entire catchment became more unstable (Figure 3a). Such patterns were also observed by comparing the average values of LSI under the five earthquake scenarios (Figure 4). These average values were calculated to be 1.02 \(\pm\) 0.60 (mean \(\pm\) standard deviation or SD), 0.81 \(\pm\) 0.38, 0.57 \(\pm\) 0.23, 0.33 \(\pm\) 0.15, and 0.23 \(\pm\) 0.14 under moderate, strong, severe, violent, and extreme earthquake scenarios, respectively (Figure 4). Each scenario was significantly different from the other four scenarios (Tukey's test, _p_! 0.05; Figure 4). Figure 3: Maps of (**a**) landslide susceptibility index and (**b**) volume of landslide under five earthquake scenarios in the Mailuu-Suu catchment. However, a significant difference in the average values of VOL was only observed between the extreme earthquake scenario (2.4 \(\times\) 10\({}^{8}\)\(\pm\) 3.1 \(\times\) 10\({}^{8}\) m\({}^{3}\)) and the other four scenarios (ranged between 2.2 \(\times\) 10\({}^{7}\) and 3.3 \(\times\) 10\({}^{7}\) m\({}^{3}\)) ([PERSON]'s test, \(p\) \(<\) 0.05; Figure 4). In other words, although the VOL rose with the increase in earthquake strength (Figure 3b), the average values of VOL were not significant different among the first four earthquake scenarios ([PERSON]'s test, \(p\) \(>\) 0.05; Figure 4). Interestingly, the areas with large VOL (colours of yellow, orange, and red in Figure 3b) were identified as mosaic clusters under the extreme earthquake scenario. Such mosaic clusters indicate the most susceptible areas to potential heavy earthquakes. The selected nine environmental variables were classified into four to eight classes (Figure 5), and the variations of LSI and VOL were then estimated among the classes for each environmental variable. In details, the average values of LSI reduced with the increase in elevation, slope, annual precipitation, distances to faults, roads, and streams (Table 3). Concerning the land cover, the areas with cropland and sparse vegetation (dominated in the downstream areas; ranged between 0.26 and 1.52) were stable, whereas water/snow and bare areas (dominated in the upstream areas; ranged between 0.10 and 0.56) were identified as unstable areas (Table 3). Concerning the soil type, it changed along the longitudinal stream networks, and therefore the average value of LSI increased along the soil type (i.e., along the longitudinal stream networks) (Table 3). However, there were no clear patterns among classes for aspect (Table 3). Figure 4: Comparisons of landslide susceptibility index and volume of landslide among five earthquake scenarios in the Mailuu-Snu catchment. The circle and square are mean values and the whisker is standard deviation. Different letters indicate significant differences between the earthquake scenarios ([PERSON]’s multiple comparison test, \(p\) \(<\) 0.05). The general patterns of VOL were slightly different from the patterns of LSI. In detail, the highest VOL was observed in moderate elevation areas (i.e., 1000-2000 m; ranged between 2.5 \(\times\) 10\({}^{7}\) and 2.6 \(\times\) 10\({}^{8}\) m\({}^{3}\)) and the lowest value was in the high elevation areas (i.e., \(>\)3000 m; ranged between 1.4 \(\times\) 10\({}^{7}\) and 1.0 \(\times\) 10\({}^{8}\) m\({}^{3}\)) (Table 3). The VOL reduced with the increase in slope, whereas an opposite pattern was observed for the annual precipitation (Table 3).