Sumatran earthquake of September 2009
The Sumatra earthquake of September 2009 was a powerful undersea earthquake off the coast of the Indonesian island of Sumatra . It occurred on September 30 at 5:16:10 p.m. local time (10:16:10 a.m. UTC ). The hypocenter of the quake was at a depth of 80–90 km, about 60 km west-northwest of Padang , about 475 km south-southwest of Kuala Lumpur and 960 km northwest of Jakarta . It reached a magnitude of 7.6 M w on the moment magnitude scale and is therefore comparable in strength to the San Francisco earthquake of 1906 or the earthquake in Kashmir in 2005 .
Several hundred people were killed in the earthquake as many houses collapsed. The relief work was made more difficult by another earthquake with a magnitude of 6.6 M w with an epicenter 250 km further southeast about 15 hours later.
Tectonic overview
The Sumatra earthquake on September 30, 2009 occurred in connection with the oblique thrust at the nearby plate boundary between the Australian and Eurasian plates at the Sunda Trench . At the epicenter of the earthquake, the Australian Plate is moving northeast in relation to the Sunda Plate at a rate of about 65 millimeters per year.
The subduction zone around the immediate area of the island of Siberut off the coast of Padang has not experienced any major earthquakes in the recent past. It last tore in 1797 in an earthquake measuring 8.5 M or more. At that time the Australian plate had slipped around ten meters below the Sunda plate in this area and thus relieved the tension. In view of the speed with which both plates move against each other, this relief has now been more than used up.
About 250 km further south, a 250 km long section of the plate boundary slid during the Sumatra earthquake series of September 2007 (up to M w = 8.5), while around 300 km further north a 350 km long section during the Sumatra earthquake of March 2005 ( M w = 8.7) slipped. At the location of the earthquake on September 30, the plate boundary at a shallower depth was the scene of a series of several earthquakes with a strength of M w = 5-6. It is not clear whether these quakes at the time are related to the earthquake of September 30th, which occurred at a much greater depth.
Due to the location of the hypocenter at a depth of 80 km, it is likely that the earthquake originated within the submerged Australian plate. The earthquake hypocenter was deeper than typical subduction earthquakes, which generally occur at a depth of less than 50 km. It is therefore likely that the mantle of the Australian plate ruptured during this deep earthquake.
The earthquake of September 30th did not lead to a rupture of the subduction zone in the area of the Mentawai Islands , so that the risk of a large earthquake with a moment magnitude of over M w = 8.5 was not reduced.
Individual evidence
- ↑ a b c d M 7.6 - southern Sumatra, Indonesia. United States Geological Survey , accessed January 5, 2020 .
- ↑ a b c J. McCloskey, D. Lange; F. Tilmann; SS Nalbant; AF Bell; DH Natawidjaja; A. Rietbrock: The September 2009 Padang earthquake . In: Nature Geoscience . 3, No. 2, 2010, pp. 70-71. doi : 10.1038 / ngeo753 .
- ↑ Indonesia quake deaths pass 500 ( English ) BBC News . October 1, 2009. Retrieved October 1, 2009.
- ↑ Magnitude 7.6 - SOUTHERN SUMATRA, INDONESIA - summary ( English ) United States Geological Survey . September 30, 2009. Archived from the original on October 1, 2009. Retrieved October 1, 2009.
