The displacement of the ground surface will be related to, but somewhat less than, the displacement on the earthquake fault at depth. What was the maximum displacement of the sea bottom above the magnitude 9.0 earthquake source off the west coast of northern Sumatra? The maximum displacement estimated from a preliminary study of the seismic body waves is 20 meters. What was the maximum displacement on the rupture surface between the plates from the magnitude 9.0 earthquake off the west coast of northern Sumatra? North of this arc, tectonic complexity increases, with converging plate fragments forming multiple subduction zones mainly oriented noth-south that in turn produce the Sulawesi-Sangihe volcanoes on the west and Halmahera on the east of the collision zone.Īndaman Island lies in a very active earthquake zone. To the NNW, the basaltic volcanism results from short spreading centers, and to the east the Banda Arc reflects Pacific Ocean crust sub ducted westward. This arc includes 76 percent of the region's volcanoes, and those on either end are tectonically more complex. What is the plate tectonic setting of Andaman Island?Īndaman Island and the great sweep of the Sunda Arc, over 3,000 kilometers from NW Sumatra to the Banda Sea, results from the subduction of Indian Ocean crust beneath the Asian Plate. An early estimate from the study of elastic waves show the majority of slip was concentrated in the southernmost 400 km of the rupture. The aftershocks suggest that the earthquake rupture had a maximum length of 1200 - 1300 km parallel to the Sunda trench and a width of over 100 km perpendicular to the earthquake source. What was the size of the fault that produced the magnitude 9.0 earthquake off the west coast of northern Sumatra?Īn initial estimate of the size of the rupture that caused the earthquake is obtained from the length of the aftershock zone, the dimensions of historical earthquakes, and a study of the elastic waves generated by the earthquake. How much energy was released by the magnitude 9.0 earthquake off the west coast of northern Sumatra?Įs 20X10^17 Joules, or 475,000 kilotons (475 megatons) of TNT, or the equivalent of 23,000 Nagasaki bombs. In northern Sumatra, which lies almost above the fault, shaking may have been experienced for up to several minutes. The exact length of time that people felt the shaking varied from place to place, depending on their distance to the fault, and other factors, such as what type of bedrock they were on, what the crustal structure was below them and between them and the fault, etc. The actual rupture duration on the fault (the time it took for the earthquake to take place on the fault and rupture the entire length) was approximately 3 to 4 minutes. How long did the magnitude 9.0 earthquake off the west coast of northern Sumatra shake? (What was the duration?)
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