A rheological model of post-seismic response due to 2004 sumatra-andaman earthquake: contribution from low viscosity lithosphere

Abstract

The Sumatra earthquake on December 26, 2004 provided an excellent opportunity to investigate the post-seismic crustal deformation and thereby understand the rheology of the crust and mantle. Subsequent to this earthquake, we monitored the post-seismic deformation at strategically located five continuous GPS sites in Andaman and Nicobar region. The post-seismic transients are obtained and the viscoelastic modeling has been carried out. Post-seismic flow below a depth of 55–60 km with low viscosity of the order of 1019 Pa S can explain observed far field motion. There is also a contribution from upper mantle to post-seismic deformation which follows power law rheology. These results lead us to infer that the Sumatra-Andaman mechanical lithosphere is about at ~55 km depth.