Abstract:Based on the theory of rectangular dislocation and the seismic wave inversion in the elastic-viscoelastic stratified half-space, combined with the average velocity of the crust-upper mantle in the study area, PSGRN/PSCMP software is used to simulate the 2012 Sumatra MW8.6 earthquake co-seismic effect, taking into account the surface deformation and seismic effects of gravity changes from the 2004 MW9.1 earthquake. At the same time, the annual variation rates of post-earthquake deformation and gravity are given. The coseismic deformation and gravity change show the left-lateral strike-slip characteristics of the seismogenic fault; the changes mainly focus on the fault; the redistribution of seawater quality has a significant effect on the vertical displacement and coseismic gravity change. The mean annual rate of change after 50 years reveals the changes of surface deformation and gravity change. The average deformation in the near field after 50 years is 10 mm/year. The average annual deformation of the far-field is less than 1 mm/a, and the average annual variation of gravity is generally less than 0.1 μGal/a. The horizontal deformation changes obviously within 400 years after the earthquake. The rate gradually decreases and stabilizes after 800 years. The vertical displacement and gravity change are particularly notable within 100 years after the earthquake, and the rate of change rapidly decayed, and basically remained unchanged after 400 years.