Late Quaternary deformation of the Longquan anticline in the Longmenshan thrust belt, eastern Tibet, and its tectonic implication

• We investigated fluvial terraces on the Longquan Shan in the eastern edge of LSTB.
• Geomorphic evidences are indicative of the Longquan anticline activity.
• It has been shortening at a rate of ∼1.47 mm/yr in NW–SE direction.
• Our results support the hypothesis that drive inflation of the crust uplifts in the Longmen Shan.

The 2008 Mw 7.9 Wenchuan earthquake and 2013 Mw 6.6 Lushan earthquake are a consequence of ongoing India–Tibet collision and reflect the growth of the Longmenshan thrust belt (LSTB). Assessing seismic hazards associated with the Longquan anticline and its contribution to crustal shortening of the LSTB requires understanding of its fold structure and activity. To address this, the geometry of fluvial terraces across the anticline was surveyed and measured by real-time kinematic (RTK), and these terraces were dated by using radiocarbon with accelerator mass spectrometry (AMS) and optical stimulated luminescence (OSL) methods. Interpretation of seismic reflection profiles suggest that the Longquan anticline grows laterally through kink-band migration and a total cumulative shortening is about 1.13 km in NW–SE direction. Combining with previous studies of depth of decollement, this yields a crustal shortening rate of ∼1.47 mm/yr in NW–SE direction and constrains the time of initiation of the Longquan anticline deformation to 1–2 Ma in the late Pliocene.Obviously, our result indicate that the Longquan anticline is active and potentially seismogenic, and that it should be incorporated into current regional seismic hazard models for the highly populated area of Sichuan basin.