Co-seismic ground-shortening structures produced by the 2008 Mw 7.9 Wenchuan earthquake, China

Abstract

We observed ground-shortening structures produced by the 2008 M w 7.9 Wenchuan earthquake along the 285-km-long Wenchuan co-seismic surface rupture zone. The structures are characterized by co-seismic thrusting and folding structures that include thrust fault scarps, flexure-slip folds, and mole tracks. Fold structures are generally developed within alluvial deposits, river channel deposits, and sealed road surfaces, mainly restricted to within a < 100-m-wide corridor (generally < 50 m) about the co-seismic thrusting fault scarp along the co-seismic surface rupture zone. The amount of co-seismic horizontal ground shortening accommodated by co-seismic thrusting and folding ranges from 0.1 up to 7.3 m (generally 1–3 m), consistent with GPS observations. Our results, combined with geological and GPS data, confirm that present-day shortening strain upon the eastern marginal zone of the Tibetan Plateau is mainly released by seismic thrusting–folding along active faults within the Longmen Shan Thrust Belt.