Insight into the 2004 Sumatra-Andaman earthquake from GPS measurements in southeast Asia


Vigny, C., W. Simons, S. Abu, R. Bamphenyu, C. Satirapod, N. Choosakul, C. Subarya, A. Socquet, K. Omar, H. Abidin and B.A.C. Ambrosius

Nature, vol 436, 14/07/05, pp201-206,doi:10.1038/nature03937, 2005




Data collected by about 60 mostly continuously recording GPS sites in SE Asia depict the crustal deformation inflicted by the 26 December 2004 earthquake at an unprecedented large scale. Small, but significant co-seismic jumps, are clearly detected more than 3000km away from the earthquake epicentre. The nearest sites, yet more than 400km away, show displacements larger than 10cm. Here we show that the rupture must be at least 1000km long and that non-homogenous slip is required to fit the large displacement gradients revealed by GPS. Kinematic analysis of the GPS recordings indicates that the centroid of released deformation is located at least 200km north of the seismological epicentre. It also provides evidence that the rupture propagated northward fast enough so that stations in northern Thailand reached their final positions less than 10 minutes after the earthquake, hence ruling out the hypothesis of a silent slow aseismic rupture.