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Mega-earthquakes rupture flat megathrusts

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Science  25 Nov 2016:
Vol. 354, Issue 6315, pp. 1027-1031
DOI: 10.1126/science.aag0482

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Mega-earthquakes go the flat way

Megathrust faults in subduction zones cause large and damaging earthquakes. Bletery et al. argue that certain geometric features of the subduction zones relate to earthquake size. The key parameter is the curvature of the megathrust. Larger earthquakes occur where the subducting slab is flatter, providing a rough metric for estimating where mega-earthquakes may occur in the future.

Science, this issue p. 1027

Abstract

The 2004 Sumatra-Andaman and 2011 Tohoku-Oki earthquakes highlighted gaps in our understanding of mega-earthquake rupture processes and the factors controlling their global distribution: A fast convergence rate and young buoyant lithosphere are not required to produce mega-earthquakes. We calculated the curvature along the major subduction zones of the world, showing that mega-earthquakes preferentially rupture flat (low-curvature) interfaces. A simplified analytic model demonstrates that heterogeneity in shear strength increases with curvature. Shear strength on flat megathrusts is more homogeneous, and hence more likely to be exceeded simultaneously over large areas, than on highly curved faults.

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