Rivaling the Himalaya in relief, the Longmen Shan is probably one of the most enigmaticmountain ranges in the world: high mountains reach more than 4000 m relief but without adjacentforeland subsidence and with only slow active convergence. What are geological and geodynamic processesthat built the Longmen Shan? Coseismic deformation associated with the 2008 Wenchuan earthquake couldhold clues to answer these questions. The primary features associated with the 2008 Wenchuan earthquakerupture have been narrowly distributed coseismic deformation and predominantly vertical displacementsthat could be interpreted as the result of slips on high-angle listric seismogenic faults. Deep sounding seismicreflection profiling across the seismogenic faults indeed reveals high-angle listric reverse faulting in thebrittle upper crust and east-dipping reflectors that we interpret as ductile shearing, in the viscous lower crust.In conjunction with a visco-elastic finite element modeling of coseismic displacements associated with theWenchuan earthquake, we show that the high-angle listric nature of earthquake faults produces insignificanthorizontal shortening across the fault and facilitates upward slips along the fault that both explain thelocalized coseismic deformation and vertical displacement, as well as the presence of high mountainswithout adjacent foreland flexure. We suggest that the formation of the Longmen Shan may be betterunderstood in terms of partitioned lithospheric pure-shear thickening in which upward high-angle listricfaulting of brittle upper crust is linked to thickening of the more viscous lithospheric mantle throughdownward ductile shearing of rheologically deformable lower crust.