![]() The Earthquake Research Institute (University of Tokyo) has calculated the tsunami magnitude for the 2004 Indian Ocean tsunami and has shown that it is consistent with such a high magnitude earthquake. The size of 2004 Indian Ocean local tsunami is consistent with the size of local tsunamis generated by other earthquakes of similar magnitude, for example the 1964 Great Alaska earthquake and tsunami. In contrast, the intensity of local tsunamis from normal tsunamigenic earthquakes do not trend exactly with magnitude. Although the local tsunamis from tsunami earthquakes (solid dots on plot) are larger than would generally be expected from earthquake magnitude alone, local tsunami intensity trends linearly with magnitude. These earthquakes tend to rupture the interplate thrust near where it approaches the sea floor at the trench. The term tsunami earthquake refers to anomalous earthquakes, in which the tsunami is larger than expected from the magnitude of the earthquake. Near the earthquake source, local tsunami size increases with the magnitude of the earthquake, although there is significant variability in this relationship. The plot shows local tsunami intensity (a function of maximum tsunami runup) plotted against the moment magnitude of the earthquake (Mw) for a number of tsunamis that occurred in the past century. A magnitude of M=9.1 seems to be most appropriate for tsunami studies as ascertained from analysis of seismograms and geodetic data (Banerjee et al., 2007 Chlieh et al., 2007). ![]() Because of the size and complexity of this earthquake, it has been difficult to assign a precise magnitude. The magnitude (M) of a submarine earthquake is, in most cases, the most important factor that determines the size of a tsunami. major strike slip faults in the overriding plate of the subduction zone.īase map of the Sumatra subduction zone showing seismicity associated with the 2004 Sumatra-Andaman earthquake.Figure based on info from the USGS Earthquake Hazards Program.the epicenter of the Decemmainshock, and.the interplate thrust where it interesects the sea floor along the Sunda trench,.The map, based on info from the USGS Earthquake Hazards Program, shows: Where the interplate thrust intersects the sea floor is marked by the Sunda trench that can traced along an arc from Burma in the north to Java in the south. This fault lies below the southwestern part of Sumatra and the Andaman Islands. ![]() ![]() ![]() The interface between the two plates results in a large fault, termed an interplate thrust or megathrust. The DecemM=9.1 Sumatra-Andaman earthquake occurred along a tectonic subduction zone in which the India Plate, an oceanic plate, is being subducted beneath the Burma micro-plate, part of the larger Sunda plate. This figure is taken from the online edition of This Dynamic Earth General diagram of an oceanic subduction zone. Sumatra and the Andaman Islands are part of an island arc. ![]()
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