## 4 Discussion on Failure Mechanism  
The cross-bedrock fault-induced landslide is influenced by both the relative movement of the two fault blocks during fault slip and the significant plastic deformation of the overlying layer and slope soil, leading to the formation of the main rupture zone. This results in a severe degree of landslide damage and a complex evolution process and failure mechanism. By analyzing the previously summarized macroscopic slope failure characteristics, main rupture zone deformation analysis, slope body and overlying layer stress analysis, and microseismic monitoring damage analysis, the slope body failure can be divided into three stages: crack damage stage (I), crack expansion and penetration stage (II), and slope instability stage (III). Ultimately, the forms of soil failure and instability are tensile-collapse or tensile-compressive shear failure, as illustrated in Figure 14.  
Figure 12: Peak microseismic variation diagram of the slope surface. Peak microseismic variation on the slope surface during soil body rupture (**a**) at the slope crest (T1) and (**b**) at the slope toe (T2). Figure 13: Peak microseismic variation diagram of the slope body. Peak microseismic variation within the slope body during soil body rupture (**a**) at the slope crest (T1) and (**b**) at the slope toe (T2). In Stage I, both the slope crest and slope toe soil rupture tests exhibited the development of cracks in the overlying soil layer. These cracks extended upward from the bedrock fault (approximately parallel to the fault dip angle) and downward from the slope surface. The slope surface cracks developed into narrow collapse zones, and the soil, under shear stress, began to exhibit plastic deformation zones (Figure 14a,d). It can be observed that during Stage I, by utilizing the predicted crack location, placing crack gauges and microseismic sensors allows for early warning of cross-fault slope failure. In Stage II, in the slope crest and slope toe soil rupture tests, with an increase in the bedrock dislocation, the main rupture zone penetrated the soil and the slope body to the slope surface. The slope surface cracks widened, and the collapse zone expanded. The soil near the collapse zone underwent compression and plastic deformation, showing more pronounced tensile cracking deformation within the slope body, further expanding until forming a through-soil tensile crack surface. After the rupture penetrated the soil, the slope crest soil rupture test showed small overhanging faces in the main rupture zone, while the slope toe soil rupture test showed distinct ruptured shear rupture zones near the slope toe (Figure 14b,e). It can be observed that in the later part of Stage II, the slope's structure changes, and an overall sliding surface (the known through-rupture zone) appears. This enables the prediction of potential slope instability risks and provides a scientific basis for taking appropriate engineering measures. In Stage III, both the slope crest and slope toe soil rupture tests showed minimal changes in terms of the failure morphology despite the gradual increase in the bedrock dislocation. This indicates that the slope was already fully unstable, characterized by large deformation zones. The increase in bedrock dislocation caused the overhanging face in the main rupture zone in the slope crest soil rupture test to expand, resulting in the formation of a double-sided slope. Due to the steepness of the overhanging face, secondary landslides are likely under seismic activity and other conditions. In the slope toe soil rupture test, the severely ruptured shear rupture zone near the slope toe caused the upper slope body to lose support, leading to secondary landslides under the effect of self-weight and seismic activity (Figure 14c,f). In summary, the slope crest soil rupture mode had a greater impact on soil slopes.