Paleoseismic study of the east Kalpintage fault in southwest Tianshan based on deformation of alluvial fans and 10Be dating

Multiple earthquakes produced by thrusting deformation have been recorded over the last century in the Tianshan area. Paleoseismic studies are very important in the exploration of the active quaternary tectonics and the risk assessment of great earthquakes in the Tianshan orogenic region. However, in this area, paleoseismic research is still lacking because of the lack of samples dated by C-14 or optically stimulated luminescence (OSL) methods. We determined the ages of the alluvial fans by Be-10 terrestrial cosmogenic nuclide (TCN) dating, measured the surface deformation of the fault scarp in a GPS survey, and evaluated the vertical displacements of the events in trenches in the east Kalpintage fault in the southwest Tianshan region. We estimated the displacement and recurrence intervals of the paleoseismic events and constrained the errors of the Be-10 ages and slip rates using a Monte Carlo simulation method. Our study suggests that each paleoseismic event shows a similar displacement of similar to 1.5 m with a recurrence interval of similar to 5 kyr in the east Kalpintage fault. The calculated slip rate is 0.31(+0.21/-0.18) mm/yr. In such arid regions with large areas of coarse gravel that lack C-14 or OSL samples, the integration of TCN dating, geomorphic deformation survey, and trenching methods is a reliable alternative for studying the active regional tectonics.