Seismic evidence for broken oceanic crust in the 2004 Sumatra earthquake epicentral region

The 2004 Sumatra earthquake was one of the largest events to occur in a subduction zone in the past 50 years. Seismic reflection data for this subduction zone reveal thrust faults cutting across the entire oceanic crust. This observation, coupled with the hypocentres of aftershocks, suggests that the megathrust—the interface between the Indo-Australian plate and the Sunda plate—currently lies in the oceanic mantle.