Global co-seismic displacements caused by the 2004 Sumatra-Andaman earthquake (Mw 9.1)

This paper presents and discusses the global co-seismic displacements caused by the 2004 Sumatra-Andaman earthquake, using quasi-static dislocation theory for a spherically symmetric earth model (Sun et al., 1996). Theoretical calculations are performed with a heterogeneous slip distribution fault model based on Ammon et al. (2005). Results show that the co-seismic horizontal displacements are large to the north-east and south-west of the fault plane. Even as far as 6000 km from the epicenter, more than 1 millimeter co-seismic horizontal displacements raised from the earthquake. This paper has three contributions: to validate the fault model (Ammon et al., 2005) by geodetic data; to interpret the displacements observed by GPS; and to provide a reference for other researchers or for other geodetic applications. Overall, the modelled and observed displacements basically agree with each other in both the near field and far field. The calculated displacements are a generally smaller than the observed ones, since considerable moment is released by slow-slips and/or aftershocks which has not been included in the fault model. Key words: The 2004 Sumatra-Andaman earthquake, co-seismic displacement, dislocation theory. 1