Crustal deformation following the 2004 Sumatra-Andaman earthquake in the northern Sumatra region (Preliminary Report)

To detect the postseismic deformation following the 2004 Sumatra-Andaman earthquake, we have repeated the continuous GPS measurements in Banda Aceh, northern Sumatra, Indonesia since 10th February 2005. A ground deformation of 25.5+-0.8cm toward south, 26.6+-0.5cm toward west and 0.6+-1.8cm uplift is detected until 18th November. As the direction of the deformation is toward Sunda trench and it is the same as the direction of the co-seismic deformation observed at Banda Aceh, a southwestward displacement of 36.9cm is postseismic displacement following the 2004 Sumatra-Andaman earthquake. Based on the relative motion between 2 continuous GPS sites along the trench normal, afterslip occurred at up-dip extension of coseismic fault