A lacustrine sediment perspective on the seismic cycle in Southeast Tibet

The Tibetan Plateau formation, resulting from the collision between India and Eurasia, is accompanied by significant seismic activity. Along its SE margin, the sinistral Xianshuihe fault is one of the most active faults in China. To understand the seismic cycle and estimate subsequent hazards, long-term records extending beyond historical archives are required. In Kangding's restraining bend, fault partitioning leads to seismic activity being distributed across four branches, exposing significant population and critical infrastructures to seismic hazards. To document the long-term patterns of fault activity, we identified seismically-triggered event deposits in three mountain lakes near the fault, using a multiproxy approach, including CT scanning, grain-size analysis, and XRF core scanning, associated with chronology based on palaeomagnetism, short-lived radionuclides, and radiocarbon ages. Our investigation across three sites (Yari Acuo, Yalatuo, Mugecuo) distributed over 30 km of the fault, revealed varying sensitivities to seismic events over the past ~300 years. Based on these different sensitivities to record earthquakes, this multi-site approach allowed us to relocate historical earthquakes based on sediment core evidence. However, the high frequency of events and the uncertainties in age models limit our ability to unambiguously attribute the oldest deposits to specific events. The recently retrieved 3.6 m-long core from Lake Yalatuo, on which we will apply similar analyses, appears more promising to reconstruct the long-term regional palaeoseismological record and discuss the Xianshuihe fault seismic cycle.