## 5 Discussion
### Importance of Landslide-Influencing Factors  
To figure out the significance of influencing elements, each factor was eliminated and the results were recalculated. New cluster results with different factors were compared with the original clustering results using the Calinski-Harabasz index, silhouette index, and Davies-Bouldin index. Nine clustering results correspond to the missing influence factors and the evaluation scores were normalized. The higher the normalized ratio is, the less important this factor is. The order of importance in this study does not represent the absolute order of the corresponding impact factors, but only represents the relative order in the study area.  
Test results can be seen in Figure 10, where the CH represents the normalized ratio of the Calinski-Harabasz index and the SI means the normalized ratio of the silhouette index. The DAV is obtained by 2 minus the normalized ratio of the Davies-Bouldin index so that the trend is the same as the other two indexes. As seen in Figure 10, the model without liquefaction obtained the lowest score, which means liquefaction is the most important factor that influences landslides in the study area. Models that exclude water depth, wave height, and soil strength obtained higher scores than those that exclude liquefaction, which means they are the second most important factors. These three elements may affect whether liquefaction happens, but none of them can predict it on their own. Consequently, these components are less significant than liquefaction, but more significant than other factors. As for sediment type, erosion, and maximum current velocity of the bottom, they are less important than the factors mentioned before. There is a great correlation between sediment types and soil strength. However, the physical and mechanical properties of the same sediment may be different because of the different depositional states and times.  
Therefore, soil strength has a greater impact on landslides. Erosion and maximum current velocity of the bottom have certain influences on the stability and strength of sediments, but are not decisive; therefore, the importance degree is relatively low. The least important factors are slope angle and human engineering activities in this study area. Slope angle has an important influence on the landslide according to previous studies [28,29], but the difference in slope angle in this study area is not large enough, and thus, the influence degree is low. As described in Section 3.2, the biggest slope angles are \(>\)1/500 radian, which is about equal to 0.11\({}^{\circ}\). However, [PERSON] [30] counted 399 cases of submarine landslide slope angles and found that the most frequent value was 3-4\({}^{\circ}\) and the average value was 5.8\({}^{\circ}\). These data are far larger than the slope value in our study area, and the average value is 50 times the maximum value in the region; thus, the slope angle is negligible and is very unimportant in the landslide evaluation of the study area. As for human engineering activities, some engineering activities, such as hydrate exploitation [31,32], can play an important role in the formation of submarine landslides, but the engineering activities in the study area are mainly offshore platforms and submarine pipelines, which are widely distributed, and therefore, their importance is very low and can be ignored.  
In conclusion, various influencing variables have varying degrees of impact influence on submarine landslide risk assessment, and the significance relies on the degree of correlation between the landslide and its distribution in the study area. The order of importance and degree of effect of variables acquired in this research only reflect one study area; the techniques described in Section 5.2 must be employed to conduct particular analyses in other study areas.