## 3 Tectonic Setting
The grey circles show the historic \(M\)\(\geq\) 6.5 events, and the red circle marks the position of the \(M_{\rm S}\) 6.8 Luding earthquake. The black arrows point out the movement directions of the blocks. The black arrows point out the movement directions of the blocks. B1: Lhasa sub-block. B2: Qiangtang sub-block. B3: Sichuan–Yunnan sub-block. B4: South China sub-block. B5: Bayan Har sub-block. B6: Qaidam sub-block. B7: Qilian sub-block. B8: Ordos sub-block. B9: Alashan sub-block. B10: Tarim sub-block. (**b**) From this perspective of the Sichuan–Yunnan sub-block and its surroundings. The blue dashed lines represent the boundary of the Sichuan–Yunnan sub-block, and the solid green lines envelop our study region in this work. The grey circles show the historic \(M\)\(\geq\) 6.5 events, and the red star marks the \(M_{\rm S}\) 6.8 Luding earthquake. F1: Xianshui He fault belt, F2: Anning He fault belt, F3: Zemu He fault belt, F4: Daling Shan fault belt, F5: Longmen Shan fault belt. Lastly, the Daliang Shan fault belt (F4 in Figure 1b), located east of the Anning He fault, is characterized by sinistral strike-slip movement. Since the Holocene Period, its slip rate has been recorded at approximately 3-4 mm/a [40; 42; 43; 44; 45]. Recent GPS analyses further highlight its evolving seismic potential by revealing substantial slip deficits and a strong potential for significant earthquakes [47]. The Luding earthquake, registering a magnitude of 6.8, struck in the Moxi area, located in the southeastern part of the Xianshui He fault belt. This area forms a crucial link between the northern termini of the Anning He and Daliang Shan fault belts [44; 48]. The southeastern segment of the Xianshui He fault zone is notable for having one of the longest intervals without seismic activity in the history of the fault [25; 49; 50]. The accumulated strain, calculated from the slip rate and the elapsed time since the last significant event, is estimated to be between 2.3 and 3.2 m [49]. This led researchers, prior to the earthquake, to classify this segment as a high-risk area for a major seismic event, potentially reaching magnitudes of 7.0 to 7.37 [49; 50]. The study region, outlined by polygons with blue lines in Figure 2, is situated in the northern portion of the eastern boundary of the Sichuan-Yunnan sub-block. The 2022 Luding \(M_{\rm S}\) 6.8 earthquake occurred centrally within this designated area. This area encompasses not only a section of the southern Longmen Shan fault belt but also the Xianshui He, Anning He, Zemu He, and Daliang Shan fault belts in its core. Collectively, these fault belts form the northern segment of the eastern boundary of the Sichuan-Yunnan sub-block, sharing a common dynamism and movement pattern--a left-lateral strike-slip motion attributed to the southeastward shift of the Qinghai-Tibet Plateau. The completion of the \"post-disaster reconstruction project\" following the 2009 Wenchuan \(M_{\rm W}\) 7.9 earthquake significantly enhanced earthquake monitoring capabilities in Sichuan [51]. To ensure data completeness and continuity, the year 2009 was selected as the starting point for our analysis. Figure 2: Map of the \(M_{\rm L}\geq 1.5\) epicenters from 2009 to May 2022 in the Sichuan region (grey circles), active faults (red lines), stations used in earthquake relocating (green triangles), and the study region in this paper (blue lines). The yellow star shows the epicenter of the \(M_{\rm S}\) 6.8 Luding earthquake on 5 September 2022. The red star shows the epicenter of the \(M_{\rm S}\) 8.0 Wenchuan earthquake on 12 May 2008. F1: Xianshui He fault belt, F2: Anning He fault belt, F3: Zemu He fault belt, F4: Daliang Shan fault belt, F5: Longmen Shan fault belt, F6: Jinsha Jiang fault belt, F7: Huaying Shan fault belt.