QuakeSeg · Controls on Megathrust Earthquake Segmentation

Great subduction earthquakes (with a moment Magnitude of Mw >8) rupture an area of a few thousand square kilometres along a convergent continental margin with coseismic slip up to some tens of meters. However, at certain locations along the continental margin earthquake rupture is suddenly arrested. The spatial extent of the rupture area controls the magnitude of the earthquake and therefore its destructiveness. The recent powerful megathrust earthquakes in Sumatra (2004, 2005), Chile (2010) and Japan (2011) showed that the factors that control extent and limitations of rupture during such earthquakes are highly complex and thus only poorly understood at the moment. This holds true, although the phenomenon of earthquake segmentation has been observed for decades and in spite of the socio-economic impact of this type of earthquake and their associated tsunamis. The overall aim of this project is to increase the understanding of factors that control the area and extent of earthquake rupture and by this also the magnitude of the earthquake. Marine seismic and bathymetry data across earthquake segment boundaries worldwide will be analyzed in order to document structural and morphological variations of the upper overriding and the lower subducting plate which impact on or reflect changes in the physical properties of the plate interface and thus control earthquake segmentation. The output will be an improved understanding of earthquake segmentation at active continental margins. This, in turn, is beneficial for global hazard assessment and mitigation efforts in regions that expect powerful subduction earthquakes in the future.