Frictional afterslip following the 2005 Nias-Simeulue earthquake, Sumatra

Ya Ju Hsu, Mark Simons, Jean Philippe Avouac, John Galeteka, Kerry Sieh, Mohamed Chlieh, Danny Natawidjaja, Linatte Prawirodirdjo, Yehuda Bock

Research output: Contribution to journalArticlepeer-review

433 Citations (Scopus)


Continuously recording Global Positioning System stations near the 28 March 2005 rupture of the Sunda megathrust [moment magnitude (Mw) 8.7] show that the earthquake triggered aseismic frictional afterslip on the subduction megathrust with a major fraction of this slip in the up-dip direction from the main rupture. Eleven months after the main shock, afterslip continues at rates several times the average interseismic rate, resulting in deformation equivalent to at least a Mw 8.2 earthquake. In general, along-strike variations in frictional behavior appear to persist over multiple earthquake cycles. Aftershocks cluster along the boundary between the region of coseismic slip and the up-dip creeping zone. We observe that the cumulative number of aftershocks increases linearly with postseismic displacements; this finding suggests that the temporal evolution of aftershocks is governed by afterslip.

Original languageEnglish
Pages (from-to)1921-1926
Number of pages6
Issue number5782
Publication statusPublished (in print/issue) - 30 Jun 2006


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