Long-term Earthquake Cycle along the eastern Altyn Tagh Fault, China

Identifying earthquake recurrence times and slip distributions over the span of many seismic cycles is key to understand fault-rupture processes and to better assess the seismic hazard. In this study, we used three paleoseismological excavations along the Aksai segment of the Altyn Tagh Fault (ATF) to document preserved evidence of past earthquakes in the sedimentological record such as vertical offset, fault cracks, and folding. We integrated these findings with previous studies on the Annanba and Xorxoli segments in order to build a larger-scale rupture history of the ATF. We reported nine large paleo-earthquakes and three of these with ground rupture expression along the whole three segments (∼ 400 km). Based on a Bayesian approach we present 95-percentile range ages of 6149 – 5285 BC, 5296 – 4563 BC, 3026 – 2677, 2469 - 2254 BC, 2069 - 1964 BC, 1184 – 709 BC, 270 – 635 AD, 875 – 1325 AD and 1491 - 1741. Furthermore, we used high-resolution satellite imagery to measure horizontal offsets recorded in the morphology, which are associated with potential co-seismic deformation. We find that the mean recurrence time is 1171±425yr with a COV of ∼0.31 suggesting a quasi-periodic behavior with a characteristic slip motion based on the similar distribution of fault offsets. The last event seems to be strongly expressed in Xorxoli segment and also found along the Aksai segment, although we could not identify it along the Annanba bend. Whereas, the penultimate event and the two before this appear to well correlate across the Aksai, Annanba and Xorxoli segments. Thus, being strong candidates for the three largest and successive earthquakes along the ATF (roughly rupture longitude ≥ 350 km). Variations in the COVs along the eastern Altyn Tagh Fault accounts for the important control of local structural complexity and/or slip rate variations on the rupture behavior of major fault systems.