## 4 Results and Discussion  
### SBAS-InSAR Results  
To investigate the surface motion status of the Guobu slope during 2016-2019, this study detected the surface deformation of the Guobu slope using the SBAS-InSAR technique. Based on the method described in Section 3, a time series deformation sequence of Sentinel-1A/B SAR image data was generated, resulting in a total of 28,498 deformed pixels in the studied region. The relationship between deformation rate, deformation rate precision, and pixel number is illustrated via the histograms in Figure 5. Figure 5a shows that the histogram is negatively skewed with a mean deformation of \(-45\) mm/y, indicating that some regions in the studied area are subsiding. More than 75% of the monitored points have deformation rates distributed in the range \(-20\) to \(20\) mm/y, indicating that most of the studied region is stable. Figure 5b shows that the precision of the pixel deformation rate in the entire study area is in the range of \(1\) to \(8\) mm/y, with a standard deviation of \(0.967\) mm/y. These two histograms are, to some extent, indicative of the validity and accuracy of the experimental results. We utilized ArcGIS to produce an annual average deformation velocity map of the Guobu slope and present it in Figure 6. Figure 6a exhibits the annual average deformation velocity from September 2015 to December 2019, while Figure 6b displays the cumulative deformation map at certain moments. Negative values indicate that the landslide body is moving away from the SAR sensor and vice versa. We calculated the annual cumulative deformation at the largest deformation point and listed the results in Table 2. As illustrated in Figure 6, the maximum deformation rate of the Guobu slope during September 2015 to December 2019 reached \(-447.448\) mm/y, and the maximum cumulative deformation was \(-1860\) mm. The landslide boundary was distinct and shows a \"U\" shape in the plan view. These results are consistent with the monitoring results of [PERSON] et al. [30] and [PERSON] et al. [27] in terms of spatial distribution and deformation magnitude, further confirming the reliability of our deformation monitoring results. Table 2 indicates that the movement of the Guobu slope is stable at the interannual scale, without apparent acceleration or deceleration (the 15 mm annual deformation difference can be ignored compared to the 440 mm cumulative deformation). Figure 5: (a) Histogram of deformation rate vs. number of pixels; (b) histogram of deformation rate precision vs. number of pixels. In order to comprehensively investigate the spatial deformation characteristics of the Guobu slope, a profile line denoted as AA\({}^{\prime}\) is drawn from the crest to the toe of the slope along the primary sliding direction of the deformed mass (depicted as a solid black line in Figure 6a). Subsequently, the point data collected along the profile line AA\({}^{\prime}\) are depicted in the form of a polyline graph, exhibiting the relationship between the deformation rate and elevation in the direction of the profile line, as illustrated in Figure 7. The solid blue line in Figure 7 represents the elevation along the profile line AA\({}^{\prime}\), whereas the solid red line represents the annual average deformation rate along the profile line. The dashed green line corresponds to the elevation of the design water level at 2452 m, and the dashed black line serves as an auxiliary guide to determine the elevation of the severely deformed region. Notably, the region of most severe deformation, where the annual mean deformation rate exceeds \(-400\) mm/a, is located in the upper middle section of the slope, between 2700 and 2850 m ASL. In addition, the entire slope has an annual mean deformation rate of more than \(-200\) mm/a. The annual deformation rate from the top to the bottom of the landslide body demonstrates a \"V\"-shaped variation, transitioning from gradual to quick to gradual, while the displacement of the slope surface exhibits a typical nonlinear spatial and temporal distribution.