## 4 Results
### Time-Series Deformation of the Landslide  
The time-series deformation of the landslide had adequate data for analyzing landslide evolution and failure process [30]. It was crucial to obtain these data for monitoring the Xiaomoiju landslide. Figure 10 shows the time-series deformation curves of six large deformation points in the landslide area obtained by the SBAS-InSAR method (the six points are marked in Figure 7), and the average displacement velocity is shown in Figure 7a. Based on the time-series deformation and velocity results, the deformation rate within the landslide boundary was generally above 5 cm/a, whereas the areas outside the boundary were almost <2 cm/a. The deformation values of six points from October 2017 to April 2019 (Figure 10) helped analyze the motion state quantitatively. The negative values indicate motion away from the satellite in the LOS direction, and the positive values represent motion toward the satellite. Due to the different observation angles between ascending and descending orbits, it was correct that results from ascending images showed negative values while results from descending images showed positive values. Overall, the deformation in the middle part of the slope is relatively large (Figure 10a-e) and has an average deformation of \(-10\) to \(-14\) cm/a in the ascending image results, whereas that of the toe area (Figure 10f) is relatively minor with a range of \(-6\) to \(-7\) cm/a. It is worth noting that the toe area's deformation values showed a relatively large deformation of about 2 cm/a, indicating a significant uplift in the region.  
Figure 11 shows the time-series deformation along the LOS direction based on PALSAR-2 SAR data and the SBAS-InSAR method. From November 2017 to July 2018, only a small area collapsed at the toe of the slope. There was no apparent displacement in the landslide area. Subsequently, the most apparent deformation signals occurred in the front of the slope. From October 2018 to November 2018, the cumulative deformation gradually increased in the middle part with a velocity of about 5 cm/month, and the cumulative displacement reached 18 cm. After December 2018, the deformation rate of the region in the rear edge also increased rapidly. Beforehand, there was a low deformation rate in this region. In the end, the cumulative deformation reached 20 cm by March 2019.  
Figure 9: Error analysis of three-dimensional decomposition. (**a–c**) The deformation errors (cm) of the vertical, east-west and north-south directions.  
Figure 11: SBAS-based time-series displacement on the landslide from 27 November 2017 to 18 March 2018. (**a–i**) Cumulative deformation of the landslide at nine time points since 27 November 2017.  
Figure 10: Time-series deformation of six monitoring points in the Xiaomoiju landslide. (**a–f**) time series deformation of six monitoring points marked in Figure 7a.  
We divided the motion states into Zone I, II, and III according to the deformation results (Figure 12a). Zone I corresponds to the landslide area with a deformation velocity \(>\)10 cm/a, located at the rear edge and middle regions and constituting the central crush zone. Figure 12b,c shows two local failure areas: b is the rock mass failure at the rear edge, and c is the tensile cracks by rapid slippage. Zone II is the heavy erosion area in the landslide mass, where the rock mass is severely damaged. Mainly on the left edge, the deformation velocity is \(>\)8 cm/a. The deformation velocity in Zone III is \(<\)8 cm/a, which differs from the rapid deformation zones. Therefore, signs of tensile cracks or extrusion uplift can be found in the border area. Figure 12d shows the displacement velocity profile (A-A') between Zones I and III with apparent differences in the fracture zones. Figure 12e shows the time-series curves of two points in the rapid deformation area (I) and uplift areas of the toe region.