Post-seismic gravity change modelling based on non-linear power-law upper mantle rheology

Abstract

SUMMARY Post-seismic gravity change modelling is commonly based on earth model with Newtonian linear rheology. Here, we present a novel way of modelling post-seismic gravity change by using a non-linear power-law rheology earth model. The method is constructed based on the framework of spectral finite element method (SFEM). SFEM has been proven practical for the purpose of modelling gravity change occurring during megathrust earthquakes. Our method implements the strain rate expression of non-linear power-law rheology into the mathematical framework of SFEM. Using our method, simulations of geoid change caused by synthetic point source earthquakes were made. The results revealed the potential of using non-linear power-law rheology for the explanation of rapid gravity changes in the beginning of the post-seismic epoch. Further on, we computed the post-seismic gravity change of the 2011 M9.0 Tohoku-Oki earthquake based on Maxwell non-linear power-law rheology in the upper mantle. It demonstrated the potential of power-law upper mantle flow as a possible candidate for the explanation of post-seismic gravity change after the earthquake occurs. However, a Maxwell non-linear power-law rheology alone is insufficient for the explanation of the post-seismic gravity change occurred.