## 4 Results and Analysis
### Ice Motion Features for Completing Lake Ice  
In order to explore the detailed temporal and spatial change of ice motion in the second stage (i.e., the lake was completely covered with ice), both time series displacements on points and along profiles were selected for analysis in this section. Five points are in Figure 3(A1)--three (P1, P2, and P3) in the northern part and two (P4 and P5) in the southern part, were selected to show accumulated displacements, as shown in Figure 8. We calculated the accumulated EW and NS components for each point, and the results are shown in Figure 8a,c,e,g,i and Figure 8b,d,f,h,j, respectively. Figure 8 shows no measurement for lack of consistency. We refer to the work of [50], who used COSI-Corr to calculate seismic deformation displacements; they excluded anomalies with Nan value and larger absolute values of deformation values from the statistics of deformation values. Therefore, we simply assume that Nan is 0 in Figure 8. Note that this assumption is not rigorous, but it does not affect our understanding of the overall the lake ice movement trend. The P1 close to the northwestern shore of the lake indicates the accumulated displacements of the EW and NS components ranging from \(-9.8\) to \(7.9\) m and \(-0.8\) to \(5.8\) m, respectively. It can be seen that the displacement trend of P1 started from the eastern direction and then changed to the western direction in the EW component. Meanwhile, in the NS component, it kept moving to the north and reached a maximum displacement of \(5.8\) m on \(12\) February 2021. P2 had a single direction of motion in both components and continued to move to the west and north, with cumulative displacement values of \(16\) and \(10\) m, respectively. The accumulative eastward movement of P3 reached \(6\) m on January 8. The displacement variation in the NS direction was smoother than in the EW direction, and the accumulated displacement from the beginning to the end of the second stage is about \(0\) m. In the EW direction, P4 had no significant change in January, but slowly moved eastward from \(2\) February 2021 until the displacement value reached \(10.9\) m; P5 presented a calm performance in the second stage and presented no significantly large displacement movement. Figure 7: (**A1–F2**) represent the results of horizontal displacement of Lake Khovsgol in the EW and NS directions in the third stage. It is superimposed on \(3\) Arc-Second Global SRTM Digital Elevation Model (DEM) with \(90\) m resolution. The graphs are basically anomalous values. The displacement values in the EW and NS directions are positive. Detailed spatial characteristics of the lake ice during the ice cover accumulation period are shown along the AA' and BB' profile lines in Figure 9. The profile line AA' indicates the spatial variation of displacement along the lake length direction, and the profile line BB' indicates the spatial variation of displacement along the lake width direction. The succession of motion values in Figure 7(A1,A2,F1,F2) is poor due to the cloud cover. Figure 9(B1,C1) shows that from 8-18 January 2021, the ice cover displacement in the EW direction changes from eastward motion to westward (from 4.2 to \(-\)4 m) and had a gentle displacement gradient, showing an overall blocky motion. In contrast, the lake ice displacement gradient in the NS direction was larger and migrated northward, always with an opposite displacement motion around the island (Figure 9(B1)). In comparison, the displacements along the AA' profile line showed relative flatness in both components between 18 and 23 January 2021. A large lake ice movement occurred from 2 to 22 February, with an increase in the number of displacement gradients, especially at the southernmost and northernmost parts of the lake (Figure 9(G1,I1,J1)). The local movement was active, the overall displacement of the lake ice shifted from overall from north to south (Figure 9(G1-J1)), and the movement of EW direction changed from east to west.