Abstract:By using the least-square method constrained by the co-seismic deformations of the Wenchuan earthquake derived from GPS, we inverse the slip models, with and without considering ramp-decollement separately. Based on the slip models obtained, we simulate the co-seismic gravity changes. The results show that the co-seismic horizontal deformation of the GPS stations and the gravity changes of the gravity stations modeled by the slip model with ramp-decollement are both closer to the actual measurements. This verifies that a large-scale nearly horizontal ramp-decollement,which existed at the southern part of the mid-fracture of the Longmenshan, has participated in the co-seismic slip of Wenchuan earthquake.