Preliminary analyses of the 12/26/2004 Mw 9.0 Earthquake in Indonesia

The main shock on December 26, 2004 is the large green dot and seven days of aftershocks are smaller green dots. More recent earthquakes are shown on top of earlier events. Two permanent GPS stations, SAMP and NTUS, are also shown.

Coseismic offsets on the east coast of Sumatra

Dr. Jeff Freymueller (University of Alaska) has analyzed the most recent data from the CGPS site SAMP (Sampali, Medan, Sumatra), located on the east coast of Sumatra. The solutions for the coseismic offset below represent the average of one week before and one week after the quake. Pre-quake solutions use JPL final orbits, post-quake use JPL rapid, and all solutions have been independently transformed to ITRF2000.

Displacement (east-north-up):  132 mm, 17 mm, -17 mm
Formal uncertainty is about 3 mm, but not necessarily scaled sensibly.

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Freymueller writes, "The plot is a baseline time series and represents fairly rapid solutions that can be improved. I suspect that there is a real post-seismic signal in the east component. There may be displacements at some of the IGS sites, but if so they are small and will require more care to resolve. Nevertheless, it is at least one displacement that can be added to a seismic slip model."