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Preliminary analyses of the Mw 8.6 Sumatra earthquake of April 11, 2012 have been obtained from both back-projection of high-frequency seismic waveforms and modelling of longer period waveforms:
This earthquake broke two records: it is the largest strike-slip earthquake ever recorded, as well as the largest intra-plate earthquake. What's more, its magnitude 8.2 aftershock is the second largest!
The rupture occurred not along the plate boundary, but within the oceanic plate that is subducting along the Sumatra trench.
This rupture has activated a complex set of conjugate faults, probably controlled by the fabric of the oceanic plate.
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Video of the rupture propagation - based on seismic data from Japan networks. The white star is the mainshock epicenter and the green circles are the epicenters of the first day of aftershocks. Time is shown on top. The trench and coastline are shown by white curves.
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