Abstract: On April 25th 2015, M_S8.1 Nepal earthquake occurred in the Himala earthquake belt that locates in the south margin of the Tibetan Plateau. We analyzed the continuous GPS data from Crustal Movement Observation Network of China and Nepal continuous GPS network. We firstly adopted the multi-scales wavelet method to investigate the pre-seismic effect of tectonic activities on the new set GPS stations, and corrected the coordinate time series of GPS sites. Then,retrieved the postseismic deformations in these time series, and studied the effects of the afterslip based on logarithmic model and visco-ealstic relaxation based on exponential model induced by this event. The parameters of three poseismic deformation models including afterslip, viscoelastic relaxion and the combination of both were inverted by MCMC algorithm of Bayesion frame, showing that observed postseismic deformation involved at least two different mechanisms. We found that the postseismic deformation was featured with variable temporal scales, and controlled by effects of both the afterslip and visco-ealstic relaxation. The charasteristic time of exponential model is 876.623 a, with a viscosity of 8.30×10²⁰ Pa·s. The inverted cumulative deformation shows that this effect is ongoing along the main fault, while the seismic risk in the upper part of unruptured area still deserved further attention.

Key words: 2015 Nepal earthquake, GPS, Bayesian framewor, Logarithmic model, Exponential model, Multi-scale characteristic