Should the whole of this stretch break in a single event the magnitude could be similar to the December 2004 earthquake. old and has a present convergence rate of 6.81 cm/yr, while the crust off Java has ages of 70 100m.y.Hamilton,1979 Ghoseetal. The subducting oceanic crust of to day off Sumatra is 4660 m.y. AMR similar to that before the December 2004 and March 2005 events is found for a 750 km stretch of the southeastern Sumatra and western Java subduction system suggesting that it is close to failure. changes in slab geometry can also be the result of the subduction of oceanic crust of different ages and with different rates. ian slab along the Sumatra-Java trench, an accretionary wedge, the outer arc ridge forming the backstop Pubellier et al., 1992 Samuel and Harbury, 1996, the Bengkulu-Mantawai forearc basins off Sumatra and the Java forearc basin in front of the volcanic arc. No AMR is found for the region of the 1833 Sumatran earthquake suggesting that an event in this region in the near future is unlikely. Less clear AMR is associated with the regions north of Sumatra around the Nicobar and Andaman islands where rupture in the December 2004 earthquake was less vigorous. The effect is clearest for the epicentral regions with less than a 2% probability that it could occur in a random catalogue. Below northern Sumatra, we find that the slab is folded at depth, exhibiting geometry similar to that of the volcanic arc and the trench at the surface. Below northern Sumatra, we find that the slab is folded at depth, exhibiting geometry similar to that of the volcanic arc and the trench at the surface. AMR can be identified in the regions around the Sumatra Subduction system that must have been stressed before the 26 December 2004 and 28 March 2005 earthquakes. New data provided by the 20042005 SumatraAndaman great earthquake sequences allow us to image with improved detail the Pwave velocity structure beneath Sumatra and adjacent regions. In contrast, recent work has suggested that Accelerated Moment Release (AMR) can help to identify when a stretch of fault is approaching failure without any knowledge of the seismic history of the region. However, in practice the large uncertainties in the seismic histories of most tectonically active regions limit this approach since a stress increase is only important when a fault is already close to failure. A promising approach to assessing seismic hazards has been to combine the concept of seismic gaps with Coulomb-stress change modeling to refine short-term earthquake probability estimates.
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