Strong Earthquake Activity over Long Time Scales on the Xianshuihe Fault Zone: Insights from Paleoearthquake and Historical Earthquake Data

Earthquake activity is the transient release of the stress in the earth, which mainly occurred in the active fault zones and shows the characteristics of quasi-periodic recurrence. The history of strong earthquake activities in the block boundary zone serves as a crucial basis for analyzing the overall deformation of blocks, the tectonic movements and evolution of boundary zones, and assessing the potential for future strong earthquakes. This history is of significant scientific importance for in-depth studies on the mechanisms of strong earthquake generation within continental block boundaries. This study focuses on the Xianshuihe Fault Zone, which is an important part of the eastern boundary of the Sichuan-Yunnan rhombic block. Based on the paleoearthquake records and by integrating multiple types of evidence revealed from multiple trenches, we have constrained strong earthquake events along the fault zone and reconstructed the temporal sequences of strong earthquake activities for different faults, and the earthquake records are extended to the 10,000-year scale. In light of the short recurrence intervals and relatively moderate magnitudes inferred from historical earthquake records, we further classify paleoearthquake events over the past 5000 years using statistical techniques such as cluster analysis, to reconstruct a more robust and reliable chronology of strong earthquake activities. On this basis, we constructed a spatiotemporal distribution map of strong earthquake activities along the Xianshuihe Fault Zone over the past ten thousand years. By analyzing the recurrence patterns and clustering migration behaviors of strong earthquake activities, we conducted a preliminary assessment of the potential risk of future large earthquakes along the Xianshuihe Fault Zone.