Reevaluation of surface rupture parameters of the 5·12 Wenchuan earthquake and its tectonic implication for Tibetan uplift

Parameters of earthquake surface ruptures are fundamental constraints for earthquake rupture process inversion and for seismic risk assessment of similar active faults.Based on in-situ measurements at the key observation sites along the earthquake surface ruptures using Total Stations and differential GPS receivers, interpretation of high resolution satellite images and tectonic landform analysis for preexisting fault scarps, the parameters, such as rupture length and its maximum offsets, of the 5·12 Wenchuan earthquake surface rupture zone are reassessed. The results indicate that its length reaches 240 km and the maximum coseismic vertical offset is ～6.5 m measured at north Qushan Town, while its right-lateral slip is ～4.9 m at south Pingtong Town.The maximum vertical offset corresponds to a crustal shortening of ～7 m, and this implies that structural transformation from crustal shortening in the Longmenshan to the uplift along the Longmenshan thrust belt may be responsible for the growth of high topography along the eastern margin of the Tibetan Plateau.