Rupture Process of the 2004 Sumatra-Andaman Earthquake
The 26 December 2004 Sumatra-Andaman earthquake initiated slowly, with small slip and a slow rupture speed for the first 40 to 60 seconds. Then the rupture expanded at a speed of about 2.5 kilometers per second toward the north northwest, extending 1200 to 1300 kilometers along the Andaman trough. Peak displacements reached ~15 meters along a 600-kilometer segment of the plate boundary offshore of northwestern Sumatra and the southern Nicobar islands. Slip was less in the northern 400 to 500 kilometers of the aftershock zone, and at least some slip in that region may have occurred on a time scale beyond the seismic band.
Additional Information© 2005 American Association for the Advancement of Science. Received 14 March 2005; accepted 27 April 2005. We acknowledge the efforts of those associated with the collection of data made freely available through the Federation of Digital Broadband Seismographic Networks. Seismic waveform data were obtained from the Incorporated Research Institutions for Seismology (IRIS) Data Management System. This work was supported in part by NSF contracts EAR-0125595 and EAR-0337491, USGS contract 04HQGR0038, and the California Institute of Technology Tectonics Observatory. S.N. was supported in part by the Outstanding Young Scientists Program of the National Science Foundation of China (40425005).
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