## 2 Tectonic Setting
### Fault Characterization
#### 2.4.3 Longpan-Qiaohou Fault  
The Longpan-Qiaohou fault is characterized by a sinistral strike slip with strikes at 15\({}^{\circ}\)-20\({}^{\circ}\) and a nearly upright dip angle of 70-80\({}^{\circ}\). It starts from Longpan in Yunnan Province and passes through Baihanchang and Jianchuan to Qiaohou, and it has a total length of approximately 110 km (Figure 5a). [PERSON] et al. [47] showed that this fault could be divided into five segments: (from north to south) the Longpan-Xionggu segment, Jiuhe segment, Jianchuan segment, East Fule segment, and Qiaohou segment. The Longpan-Xionggu segment is a late Pleistocene fault, while the Jiuhe and Jianchuan segments are Holocene faults.  
Figure 5: (**a**) Seismotectonic map of the Longpan–Qiaohou fault. The red lines represent the location of the Longpan–Qiaohou fault, and the red circles represent three earthquakes occurred on this fault. (**b**) Seismic depth profiles along the Longpan–Qiaohou fault (\(M_{\text{S}}\geq 1.0\) earthquakes are from 1 January 1981 to 28 February 2018). The circles denote the earthquakes, and the colors denote the focal depth. The gray dashed line shows the 90% seismicity cutoff depth within 10 km of the fault. (**c**) Source model of the Longpan–Qiaohou fault. The blue stars represent the SPs, the red areas represent the largest asperity, and the yellow area represents the smaller asperity; the subfault size is 2 km \(\times\) 2 km [19].  
Based on the maximum credible earthquake of \(M_{\rm W}\) 7.3 and Equations (1) and (2), we obtained the rupture length and width of the Longpan-Qiaohou fault as 82 and 22.5 km, respectively. Earthqu within 10 km of the Longpan-Qiaohou fault showed that 90% of the cumulative depth distributions is 15 km (Figure 5b). Combining the results of the empirical relationship with the 90% seismic depth, the rupture width of 22 km was determined.  
Geological data have shown that the Longpan-Xionggu segment has been active since the late Pleistocene. Trench results of the pull-apart basin north of Houjing have revealed that three \(M_{\rm S}\) > 6.5 earthquakes have taken place in the Jianchuan Basin since the Holocene: 1751, 6230 \(\pm\) 130 BP, and 10737 \(\pm\) 468 BP with a recurrence interval of approximately 5300 a [48]. The strain results for southwestern Yunnan showed that the main compressive stress is close to the NNW-NW direction, and the maximum shear strain rate is around Jianchuan at approximately 1.8 \(\times\) 10\({}^{-6}\)/a. The shear deformation along the Longpan-Qiaohou fault is relatively strong [49]. The vertical deformation velocity gradient is relatively large, which indicates that the Jianchuan area is prone to accumulating stress. Furthermore, the \(b\) value of the Lijiang-Jianchuan area is 0.51, which is a low value that indicates earthquakes may occur in the future. The seismic depth distribution along the Longpan-Qiaohou fault (Figure 5b) shows that relatively few earthquakes have occurred from Jianchang to Baihanchang, which indicates that this segment may be experiencing strong stress accumulation. Thus, we set the largest asperity here (Figure 5c). To consider the worst-case scenario at the dam, we set another smaller asperity on the rupture plane closest to the dam. The sizes of the asperities were calculated using Equations (3)-(12) (Figure 5c).