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Authors: McCloskey, J.* 
Antonioli, A.* 
Piatanesi, A.* 
Sieh, K.* 
Steacy, S.* 
Nalbant, S.* 
Cocco, M.* 
Giunchi, C.* 
Huang, J. D.* 
Dunlop, P.* 
Title: Tsunami threat in the Indian Ocean from a future megathrust earthquake west of Sumatra
Issue Date: 2007
DOI: 10.1016/j.epsl.2007.09.034
Keywords: tsunami
Subject Classification04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics 
Abstract: Several independent indicators imply a high probability of a great (MN8) earthquake rupture of the subduction megathrust 14 under the Mentawai Islands of West Sumatra. The human consequences of such an event depend crucially on its tsunamigenic 15 potential, which in turn depends on unpredictable details of slip distribution on the megathrust and how resulting seafloor 16 movements and the propagating tsunami waves interact with bathymetry. Here we address the forward problem by modelling about 17 1000 possible complex earthquake ruptures and calculating the seafloor displacements and tsunami wave height distributions that 18 would result from the most likely 100 or so, as judged by reference to paleogeodetic data. Additionally we carry out a systematic 19 study of the importance of the location of maximum slip with respect to the morphology of the fore-arc complex. Our results 20 indicate a generally smaller regional tsunami hazard than was realised in Aceh during the December 2004 event, though more than 21 20% of simulations result in tsunami wave heights of more than 5 m for the southern Sumatran cities of Padang and Bengkulu. The 22 extreme events in these simulations produce results which are consistent with recent deterministic studies. The study confirms the 23 sensitivity of predicted wave heights to the distribution of slip even for events with similar moment and reproduces Plafker's rule of 24 thumb. Additionally we show that the maximum wave height observed at a single location scales with the magnitude though data 25 for all magnitudes exhibit extreme variability. Finally, we show that for any coastal location in the near field of the earthquake, 26 despite the complexity of the earthquake rupture simulations and the large range of magnitudes modelled, the timing of inundation 27 is constant to first order and the maximum height of the modelled waves is directly proportional to the vertical coseismic 28 displacement experienced at that point. These results may assist in developing tsunami preparedness strategies around the Indian 29 Ocean and in particular along the coasts of western Sumatra.
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