Insight into long-term seismic behavior from an 8500-year paleoseismic record on the Altyn Tagh fault, Northwest China

Unveiling the earthquake recurrence behavior of active faults and their controlling factors, as well as the potential maximum earthquake sizes that have occurred along these faults, is essential for regional seismic hazard assessment and disaster mitigation. One effective approach to achieve this is to obtain long-term seismic records and compare paleoseismic data from various sites along the fault. In this study, we excavated a 13.5-m-deep trench at the Wuzunxiao site on the Altyn Tagh fault (ATF) and identified thirteen paleoearthquakes over the past 8500 years. The average recurrence interval (RI) of these events is 601± 529 yr with a coefficient of variation (COV) of 0.90, indicating a weak quasi-periodic (irregular) recurrence. Comparison of our paleoseismic data at the Wuzunxiao site with other records along the central ATF indicates that up to 17–36% of the seismic events are shared with the adjacent Xorkoli section, breaching the Pingding Shan geometric barrier. This probability is comparable to the passing probability estimated by a logistic model constructed from fine-scale historical surface rupture maps. The irregular recurrence behavior of paleoearthquakes in the Wuzunxiao section, as well as the alternating occurrence of multi-section joint ruptures and single-section ruptures revealed by paleoseismic data comparisons, is likely controlled by the Pingding Shan earthquake gate.