## 2 Study Area
### Characteristics of Crack Development  
The field investigation reveals the presence of 27 primary cracks, with LF4, LF8, and LF13 exhibiting relatively longer extensions compared to the others. The distribution of major landslide cracks is illustrated in Figure 8, and their characteristics are detailed in Table 2, with typical crack photos shown in Figure 9. Specifically, LF1 to LF20 are located below the river road and are mainly within the H1-3 landslide body, resulting from a sudden drop in the reservoir water level. Conversely, LF21 to LF27 are situated above the river road, mostly at the rear of the H1-3 landslide body, and were formed prior to the reservoir impoundment, showing a lesser correlation with the reservoir water level fluctuation.  
Figure 7: The new landslide H1-3 formed at the front edge of the landslide due to reservoir water level fluctuations.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**ID**} & \multicolumn{2}{c}{**Elevation (m)**} & \multirow{2}{*}{**Location**} & \multirow{2}{*}{**Date**} & \multirow{2}{*}{**Strike**} & \multicolumn{2}{c}{**Length (m)**} & \multirow{2}{*}{**Width**} & \multicolumn{1}{c}{**Dislocation**} & \multicolumn{1}{c}{**Crack**} \\  & & **(m)** & & & & & **(m)** & **(cm)** & **(cm)** & **Type** \\ \hline \multirow{4}{*}{LF1} & CYP04 & 1807 & Small village & \multirow{4}{*}{June 2019} & N30\({}^{\circ}\) W & \multirow{4}{*}{120} & 5 & 0.3 & Tensile \\  &CYP05 & 1804 & upstream & & & N5\({}^{\circ}\) E & 120 & 21 & 10 & Tensile \\  &CYP06 & 1800 & Below the road & & & N5\({}^{\circ}\) E & 16 & 9 & Tensile \\  &CYP08 & 1807 & & & & N5\({}^{\circ}\) E & 2.5 & 1.5 & Tensile \\  &CYP30 & 1807 & & & N14\({}^{\circ}\) E & 3 & 0.75 & Tensile \\  &CYP09 & 1800 & Below the road & & & N50\({}^{\circ}\) E & 120 & 20 & 1.5 & Tensile \\  &CYP10 & 1795 & & & N56\({}^{\circ}\) E & & 25 & 5 & Tensile \\  &CYP11 & 1785 & & & N5\({}^{\circ}\) W & \multirow{4}{*}{360} & 1.5 & 0.75 & Tensile \\  &CYP16 & 1773 & & & N5\({}^{\circ}\) E & 360 & 50 & 70 & Tensile \\  &CYP17 & 1759 & & & N59\({}^{\circ}\) E & & 40 & 40 & Tensile \\  &CYP12 & 1779 & & & N21\({}^{\circ}\) E & & 12 & 3.5 & Tensile \\ LF5 &CYP13 & 1774 & & & N40\({}^{\circ}\) E & 90 & 9 & 15 & Tensile \\  &CYP14 & 1768 & & & N15\({}^{\circ}\) E & & 4 & 2.5 & Tensile \\ LF6 &CYP15 & 1768 & & & & N13\({}^{\circ}\) E & 40 & 30 & 7.5 & Tensile \\ LF7 &CYP18 & 1750 & & & & N20\({}^{\circ}\) E & 50 & 11 & 2.5 & Tensile \\  &CYP25 & 1674 & & & & NW & 6 & 1.5 & Tensile \\  &CYP26 & 1684 & & & & SN & 60 & 20 & Tensile \\  &CYP27 & 1693 & & & N6\({}^{\circ}\) W & 195 & 30 & 50 & Tensile \\  &CYP28 & 1694 & & & N34\({}^{\circ}\) E & & 40 & 20 & Tensile \\ LF9 & CYP19 & 1679 & & & & N50\({}^{\circ}\) W & 50 & 3 & 1.5 & Tensile \\ LF10 &CYP24 & 1657 & & & N14\({}^{\circ}\) E & 40 & 25 & 1.5 & Tensile \\  &CYP20 & 1683 & & & June 2019 & N10\({}^{\circ}\) W & 10 & 1.5 & Tensile \\ LF11 &CYP21 & 1688 & & & & N70\({}^{\circ}\) W & 1.5 & 2 & Tensile \\ LF12 &CYP22 & 1676 & & & & N45\({}^{\circ}\) W & 50 & 10 & 2 & Tensile \\ LF13 &CYP23 & 1656 & & & June 2019 & N39\({}^{\circ}\) W & 450 & 3.5 & 1.5 & Tensile \\ LF14 &CYP31 & 1805 & & & & & N46\({}^{\circ}\) E & 25 & 7.5 & 2 & Tensile \\  &road & & & & & & & & \\ LF15 &CYP32 & 1807 & Road surface & April 2020 & N30\({}^{\circ}\) E & 70 & 23 & 7.5 & Tensile \\ LF21 & - & 2278 & & H\({}_{1}\) trailing edge & April 2020 & SN & 30 & 15 & 20 & Tensile \\ LF22 & - & 2256 & H\({}_{1}\) side edge & 1992 & N74\({}^{\circ}\) W & 40 & 10 & 5 & Shear \\ LF24 & - & 2240 & H\({}_{1}\) side edge & 1992 & N58\({}^{\circ}\) E & 50 & 5 & 1.5 & Shear \\ LF26 & - & 2113 & H\({}_{1}\) side edge & 1956 & - & 70 & 35 & 35 & Shear \\ LF27 & - & 2080 & H\({}_{1}\) side edge & 1956 & - & 90 & 20 & 100 & Shear \\ \hline \hline \end{tabular}
\end{table}
Table 2: Distribution and characteristics of cracks.  
Figure 8: Distribution of cracks in Cheyiping reservoir section.