Plate Boundary Deformation Following the December 26, 2004 Andaman–Sumatra Earthquake Revealed by GPS Observations and Seismic Moment Tensors

To investigate the transient strain rate of postseismic deformation associated with the highly devastating December 26, 2004 Andaman–Sumatra earthquake (M_w 9.3), a combined analysis have been done using GPS data and Seismic Moment Tensors (SMT) acquired from Andaman–Nicobar–Sumatra regions during 2005–2007. The displacement estimated during postseismic periods 2005–2006 and 2006–2007 with respect to ITRF2008 and Indian Reference Frame, display dominating arc-normal active deformation in the southern part close to epicenter, and arc-parallel deformation towards the northern part of the Andaman–Nicobar–Sumatra Subduction Zone (ANSSZ). The principal strain rates during 2005–2006 periods indicate larger strain accumulation and decreased rate of strain during 2006–2007 with a maximum arc-normal compression on southern part of ANSSZ and a changing trend of arc-parallel extension towards the central and northern part along the ANSSZ. Stress inversion using SMT also indicate compressive horizontal stress in the southern part and extensional stress towards the central and northern part of the study area, and a remarkable agreement with GPS derived strain rate pattern.