Paleoseismic study of the east Kalpintage fault in southwest Tianshan based on deformation of alluvial fans and 10 Be 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 14 C or optically stimulated luminescence (OSL) methods. We determined the ages of the alluvial fans by 10 Be 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 10 Be ages and slip rates using a Monte Carlo simulation method. Our study suggests that each paleoseismic event shows a similar displacement of ~1.5 m with a recurrence interval of ~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 14 C or OSL samples, the integration of TCN dating, geomorphic deformation survey, and trenching methods is a reliable alternative for studying the active regional tectonics. Copyright Springer Science+Business Media Dordrecht 2013