n sumatra outer rise earthquakes

looks like we just got some late aftershocks to the 2004 Sumatra-Andaman subduction zone earthquake. on 2012 April 11, there was a swarm of activity, with an Mw 8.6 and an Mw 8.1 event with strike slip focal mechanisms and moment tensors.

the 8.6 is directly updip of the region of maximum slip from the 2004 Great earthquake. the 8.2 is updip from the 2005 Great earthquake. Todays two earthquakes are likely on one or two of the many fracture zones that strike generally north-south in the India-Australia plate. one of the better known fzs is the Investigator fracture zone, several hundred kms to the east of these epicenters.

the fzs are thought to partly contribute to the segmentation of the subduction zone offshore sumatra. i have composed a map that shows Sumatera, the islands (forearc), the 2004 earthquake slip (in cm) modeled by Chlieh et al., 2007, some bathymetry with some structures labeled, and the epicenters of the two largest earthquakes from today mentioned above. my map

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