## 3 Case Study: Lishanyuan Landslide
### Early Warning Analysis  
The data collected by the two GNSS monitoring stations are used for early warning calculations by the proposed hybrid method. The thresholds of different stages are listed in Table 3. The early warning results of the two stations are shown in Figures 6 and 7. Subplots (a) in Figures 6 and 7 show the velocity and acceleration calculated for the conventional warning, and the colored bars on the top side of the figure show the warning results obtained using the single-method strategy (conventional warning), while the colored bars on the bottom side show the warning results obtained using the conservative strategy. Subplots (b) in Figures 6 and 7 show the calculated normalized tangent angles, and the colored bars on the upper side show the warning results obtained using the single-method  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Station**} & \multirow{2}{*}{**Start Time**} & \multirow{2}{*}{**End Time**} & \multicolumn{4}{c}{**Calculation Methods (mm/d)**} & \multirow{2}{*}{**Average Value (mm/d)**} \\ \cline{3-3} \cline{5-7}  & & & **CKDEM** & & **AVM** & **RFM** \\ \hline DB01 & 23 April 05:00 & 12 May 23:00 & 1.073 & 1.114 & 1.244 & 1.144 \\ DB02 & 6 May 03:00 & 13 May 00:00 & 1.726 & 1.732 & 1.754 & 1.737 \\ \hline \hline \end{tabular}
\end{table}
Table 2: The velocity of the two monitoring stations of the Lishanyuan landslide in the CDS.  
Figure 5: Cumulative displacement and velocity distribution of each monitoring station of the Lishanyuan landslide from 15 April to 23 April.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{**Time**} & \multicolumn{2}{c}{**22 April**} & \multicolumn{2}{c}{**13 May**} \\ \hline Station & DB01 & DB02 & DB01 & DB02 \\ \(S_{\text{lat}}\) (mm) & 16.5 & 21 & 16.5 & 21 \\ \(S_{\text{lat}}\) (mm) & 33 & 42 & 33 & 42 \\ \(v_{21}\) (mm/d) & 12 & 20 & 12 & 20 \\ \(v_{22}\) (mm/d) & 24 & 40 & 24 & 40 \\ \(v_{31}\) (mm/d) & 6 & 10 & 2.288 & 3.474 \\ \(v_{32}\) (mm/d) & 12 & 20 & 4.576 & 6.948 \\ \(v_{33}\) (mm/d) & 18 & 30 & 6.864 & 10.422 \\ \(v_{34}\) (mm/d) & 24 & 40 & 9.152 & 13.896 \\ \(v_{m}\) (mm/d) & / & / & 1.144 & 1.737 \\ Warning & Single-method strategy & & & \\ Strategy & (Conventional warning) & & & \\ \hline \hline \end{tabular}
\end{table}
Table 3: The thresholds of the Lishanyuan landslide.  
strategy (critical sliding early warning), while the lower side shows the warning results obtained using the conservative strategy.  
From the Figures 6 and 7, it can be found that the early warning results obtained by using the proposed method can reflect the landslide acceleration process well and have good continuity. As the two stations have the same deformation trend, we only calculate the results of LISHAN-DB02. This station is first warned by the conventional early warning method, during which, a blue warning event is triggered. After the calculation on 13 May, the LISHAN-DB02 started critical sliding early warning, and the early warning strategy was changed to the conservative strategy. Table 4 lists some key early warning events at LISHAN-DB02.  
The on-site inspection on 19 May found many cracks in the landslide body (see Figure 8), obvious slip of the slope body, soil accumulation at the landslide toe, and local small debris flows, which are consistent with the monitoring and early warning results.  
Figure 6: Early warning results of the LISHAN-DB01 monitoring station obtained by the proposed method. (**a**) Results of the conventional warning method based on velocity and acceleration. (**b**) Results of the critical sliding warning method based on the normalized tangent angle.