2005 Sumatra earthquake
Background Information
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 Epicentre map from NOAA |
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| Date | March 28, 2005 |
|---|---|
| Magnitude | 8.7 Mw |
| Depth | 30km |
| Epicenter | 2°04′35″N 97°00′58″E |
| Countries or regions | Indonesia |
| Casualties | 1,300 |
The 2005 Sumatra earthquake, referred to as the Nias Earthquake by the scientific community, was a major earthquake on 28 March, 2005, located off the west coast of northern Sumatra, Indonesia. Approximately 1,300 people were killed by the earthquake, mostly on the island of Nias. The event caused panic in the region, which had previously been devastated by the massive tsunami triggered by the 2004 Indian Ocean earthquake, but this earthquake generated a relatively tiny tsunami that caused limited damage. It was the 4th most powerful earthquake since 1964.
The earthquake occurred at 16:09:36 UTC (11:09:36 P.M. local time) on March 28, 2005. The hypocenter was located at 2°04′35″N 97°00′58″E, 30 km (18.6 miles) below the surface of the Indian Ocean, where subduction is forcing the Indo-Australian Plate to the south-west under the Eurasian plate Sunda edge. The area is 200 km west of Sibolga, Sumatra, or 1,400 km northwest of Jakarta, roughly halfway between the islands of Nias and Simeulue. Seismic recordings give the earthquake a magnitude of about 8.7, and effects were felt as far away as Bangkok, Thailand, a distance of 1,000 km.
Earthquake and damage
The earthquake lasted for about two minutes in total. In the twenty-four hours immediately after the event, there were eight major aftershocks, measuring between 5.5 and 6.0. A debate arose among seismologists over whether this should be considered an aftershock of the December 2004 event, or a "triggered earthquake" as it was larger than typical aftershocks but on the same fault.
On the Indonesian island of Nias, off the coast of Sumatra, hundreds of buildings were destroyed by the earthquake. The death toll on Nias was at least one thousand, with 220 dying in Gunungsitoli, the island's largest town. Nearly half of Gunungsitoli's population (27,000) fled the town.
The earthquake was strongly felt across the island of Sumatra, and caused widespread power outages in the Indonesian city of Banda Aceh, already devastated by the December 2004 tsunami, and prompted thousands to flee their homes and seek higher ground.
It was also strongly felt along the west coast of Thailand and Malaysia, and in Kuala Lumpur high-rise buildings were evacuated. The earthquake was felt less strongly in the Maldives, India, and Sri Lanka.
Tsunami
The earthquake caused great concern around the Indian Ocean that it might trigger a tsunami similar to the massive one generated three months earlier by the 2004 Indian Ocean earthquake on December 26, 2004. Evacuations were carried out in coastal regions of Thailand, Malaysia, and Sri Lanka. This earthquake, however, produced a relatively tiny tsunami. A three-meter tsunami caused moderate damage to port and airport facilities on Simeulue, and a two-meter tsunami was recorded on the west coast of Nias. Much smaller waves, most detectable only in tide gauge recording systems, were recorded across the Indian Ocean; for example, a 25 cm wave was recorded at Colombo, Sri Lanka.
Tsunami warnings were issued by the Pacific Tsunami Warning Centre, operated by the US National Oceanic and Atmospheric Administration (NOAA) , and by the government of Thailand. There were initial concerns that a major tsunami could be generated, particularly travelling south from the event's hypocenter.
Portions of Thailand's southern coast were evacuated as a precaution, and NOAA advised an evacuation of 965 km (600 miles) of coastline in Sumatra. Evacuations also occurred in the northern Malaysian states of Penang and Kedah, as well as the eastern coast of Sri Lanka, where ten people were killed in the confusion of the evacuation. Many of the southern states of India were also put on high alert; all of these areas had seen significant damage from December's tsunami. After the detection of a minor tsunami south of the epicenter, including a 30 cm tsunami on Australia's Cocos Islands, the island states of Mauritius, Madagascar, and the Seychelles in the Indian Ocean issued warnings to their populations.
Although tsunami warning systems for the region had been actively discussed before the December 2004 earthquake, none had yet been implemented in the Indian Ocean.
Humanitarian response
The United Nations worked with the Indonesian government to take further actions to prevent a possible catastrophe after the strong earthquake, and the US State Department has announced that it will help countries affected by a possible tsunami. The government of India announced aid of USD 2 million for the earthquake victims.
Australia announced it would provide AUD 1 million in emergency aid, and, at the request of the Indonesian Government, dispatched Australian Defence Force medical teams and equipment to Nias. The Australian naval ship HMAS Kanimbla , having only recently left Aceh, was redeployed to the region from Singapore. At about 9:30 (UTC) 2 April 2005, one of Kanimbla's two Sea King helicopters, Shark 02, crashed on the island of Nias while taking medical personnel to a village. Nine personnel were killed, and two others sustained injuries but were rescued from the site by the other helicopter. The crash occurred one day before a state visit by President Susilo Bambang Yudhoyono to Australia, where he and Prime Minister of Australia John Howard expressed mutual sorrow for their countries' losses.
