## 4 Result
### Paloseismic Studies  
#### 4.2.1 Trench TC1 at Bugge  
The Yarigong fault cuts across the alluvial fans near Bugge Village, forming a well-defined and linear fault trough. We used UAV and SfM technology to obtain the topographic data along this fault segment. Trench TC1 at Bugge was excavated across the fault trough (Figure 9). The TC1 trench reveals seven stratigraphic units, listed from old to new as follows (Figure 10):  
Figure 8: (**a**) Right-lateral offset of the T2 terrace of the Ciwu River and location of the dating sample. The image was obtained using UAV photogrammetry. (**b**) Photograph showing the dating sample collection section in the T2 terrace of the Ciwu River. U1: Gray-white and yellow-brown gravel layer, containing many highly weathered granite gravel particles, with angular to sub-angular shapes. U2: Yellow-brown clay layer, containing many small gravel particles, with sizes generally less than 5 cm. U3: Deep brown silt layer, containing many gravel particles, with gravel often deposited in clusters. U4: Brown, dark gray sand and gravel mixed with yellow-brown clay clumps, with significant folding and deformation. U5: Brown sandy soil layer, containing many gravel particles. This unit gradually thins toward the west. U6: Yellow sand-gravel layer, with an especially higher accumulation of gravel at the bottom of the layer. U7: Gray soil layer. \begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Sample** & **Lab No.** & **Description** & \begin{tabular}{l} **13C/12C** \\ **(o/oo)** \\ \end{tabular} & \
\begin{tabular}{l} **Measured** \\ **Radiocarbon** \\ **Age (a BP)** \\ \end{tabular} &
\begin{tabular}{l} **Conventional** \\ **Radiocarbon** \\ **Age (cal BP)** \\ \end{tabular} \\ \hline BGC06 & 647813 & charcoal & \(-24.1\) & 620 \(\pm\) 30 & 654–550 \\ \hline BGC08 & 660112 & charcoal & \(-23.6\) & 1220 \(\pm\) 30 & 1180–1062 \\ \hline BGC11 & 647812 & charcoal & \(-25.1\) & 710 \(\pm\) 30 & 688–641 \\ \hline BGC14 & 660113 & charcoal & \(-18.1\) & 5970 \(\pm\) 30 & 6893–6731 \\ \hline BGC16 & 660114 & charcoal & \(-19.6\) & 1600 \(\pm\) 30 & 1534–1405 \\ \hline BGC26 & 647811 & charcoal & \(-22.1\) & 1940 \(\pm\) 30 & 1940–1746 \\ \hline BGC27 & 647810 & charcoal & \(-24.1\) & 3520 \(\pm\) 30 & 3880–3698 \\ \hline NDC02 & 646655 & charcoal & \(-23.6\) & 8000 \(\pm\) 30 & 9001–8754 \\ \hline NDC24 & 660115 & charcoal & \(-23.2\) & 19,080 \(\pm\) 60 & 23,109–22,903 \\ \hline NDC29 & 648911 & charcoal & \(-23.4\) & 28,290 \(\pm\) 150 & 33,010–31,860 \\ \hline NDC44 & 660116 & charcoal & \(-25.2\) & 2750 \(\pm\) 30 & 2889–2766 \\ \hline NDC53 & 648912 & charcoal & \(-23.7\) & 32,250 \(\pm\) 220 & 37,036–36,158 \\ \hline NDC55 & 660117 & charcoal & \(-22.5\) & 25,190 \(\pm\) 110 & 29,844–29,180 \\ \hline NDC59 & 648913 & charcoal & \(-22.1\) & 20,030 \(\pm\) 60 & 24,219–23,857 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Radiocarbon ages from samples collected in trenches TC1 and TC2. Figure 10: Photograph of the southern wall of the Buge trench and explanatory profile. The radiocarbon dating sample ages of the TC1 trench are detailed in Table 2.  
On the basis of an analysis of the faulted strata, sedimentation, and deformation characteristics, three paleoseismic events were identified in the TC1 trench. In event I, faults F1 and F2 displaced units U1 and U2, forming a fault scarp, and subsequently, U3 was deposited in the footwall of the fault scarp. Unit U2 is a yellow-brown clay layer, and unit U3 a dark brown silt layer. The units represent different depositional environments, and the compaction of U2 is greater than that of U3. In accordance with the results of the dating samples BGC14 from U2 and BGC27 from U3, event I is constrained to have occurred between 5970 \(\pm\) 30 a BP and 3520 \(\pm\) 30 a BP (Table 2). Event II mainly involved fault F3 displacing unit U3, forming a wedge fault zone, followed by the deposition of U4 with mixed sedimentary components.