Abstract:By collecting and processing the data of GPS continuous observation stations in Nepal and GPS reference stations in southern Tibet of China, we obtain the GPS horizontal deformation field three years after the 2015 MW7.8 earthquake in Nepal, which shows that the post-earthquake deformation is mainly distributed in the northern part of Nepal and the border area between China and Nepal, and that deformation in the east-west direction is small, while deformation in the north-south direction is large. The whole earthquake continues to move south, and the maximum post-earthquake displacement is about 10.93 cm. The theoretical surface displacement calculated by the pore elastic rebound model is far less than the GPS observation value, which cannot explain the post-earthquake deformation observed by GPS. The post-earthquake residual slip distribution inversed by the post-earthquake residual slip model shows that the post-earthquake residual slip is mainly concentrated in the downdip extension part of the fault, and the spatial distribution is wide. The seismic moment released by the residual slip is 1.09×1020 Nm. The theoretical surface deformation caused by viscoelasticity in the forward modeling of PSGRN/PSCMP shows that the viscoelasticity relaxation model cannot explain near-field GPS observations, but its movement direction is consistent with the GPS observations in the far-field region. After inversion using the combined mechanism model of viscoelastic relaxation and post-earthquake residual slip, the seismic moment released by residual slip is reduced to 1.08×1020 Nm, and the spatial distribution is more concentrated. The results show that the inversion results of the combined mechanism model are closer to those of the stress driven model on the basis of ensuring the fitting accuracy of the model.
YAO Weizheng,XU Keke,ZHU Xulin et al. Postseismic Deformation and Dynamic Mechanism Associated with the 2015 MW7.8 Nepal Earthquake from GPS Observation[J]. jgg, 2021, 41(8): 833-840.