October 2010 Sumatra earthquake and tsunami

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Mentawai Islands

Many villages on the islands were affected by the tsunami that reached a height of three meters and swept far inland to 600 meters. The tsunami caused devastation were left homeless by the more than 20,000 people. 435 victims of the natural disaster were confirmed, more than a hundred are still missing. The following rescue and relief operation was initially hampered by bad weather and the remoteness of the islands, which also contributed to the tentative announcement of the number of victims.

Tectonic overview

The epicenter of the earthquake was about 240 kilometers west of Bengkulu and 280 km south of Padang near the Mentawai Islands, southwest of Südpagai. First, the United States Geological Survey (USGS ) reported that the hypocenter was at a depth of 33 km, but later revised this figure to 20.6 km. The intensity of the earthquake was MM IV in Bengkulu and MM III in Padang.

The island of Sumatra is located above the Sunda mega- thrusts, the zone in which meet the subducting Australian plate and the over -shifting Sunda plate. The movement in this subduction zone is responsible for a number of large mega -thrust earthquakes. The last sequence of large earthquakes in the area began with the Indian Ocean tsunami in 2004 and includes the undersea earthquake off Sumatra in 2005 and the Sumatra earthquake of March and September 2007. The earthquake of October 2010 was probably the result of a thrust fault at or near the plate boundary. In terms of the potential seismic risk of the Sunda Trench can be divided into several segments. The southern segment is located on the south side of the island of Siberut. The fracture-zone earthquake of 25 October 2010 is within this southern segment. Historical earthquakes in this section were, among others, the Sumatra earthquake of 1797 and the Sumatra earthquake of 1833 with a magnitude of Mw ~ 9.0.

In contrast to 2004, the triggered tsunami was not directed westward and did not concern thus a number of other riparian states of Indiks. It was also noted that the earthquake could be a strong aftershock of the much larger Sumatra earthquake of September 2007.

The earthquake occurred about seven hours after the eruption of Mount Merapi on the Indonesian island of Java. Due to the distance between the epicenter and the volcano, the two events are probably not in direct communication.

Effects

The effects of the earthquake were felt most on the upstream Sumatra Mentawai Islands. On the island Südpagai of the earthquake, tsunami reached a height of three meters and swept to 600 M into the interior. According to Indonesian officials were in the more than twenty hit by the tsunami towns of more than 20,000 residents homeless, with about 4000 households are affected. The coastal village Betu Monga on Südpagai was destroyed by the tsunami and many of its residents are missing. Many inhabitants of the villages and Peurogat Beleerakso were reported missing. Eighty percent of the houses in the village Muntei Baru on Nordpagei were damaged or destroyed.

A spokesman for the Indonesian Agency for Meteorology, Climatology and Geophysics ( BMKG ) announced that the earthquake was also felt in several cities in Sumatra, but no damage or casualties were reported. The Mentawai Islands have the coast of Sumatra shielded from the full force of the tsunami.

On October 30, the death toll was specify by earthquake and tsunami impact with 435, 110 more were still missing, it being assumed that many of them were flushed by the tidal wave out to sea.

Due to bad weather and rough seas were relief workers, the area initially not reach. The Indonesian military has been ordered to march, and international aid organizations have initiated relief efforts. The first aid teams met two days after the earthquake on 27 October a site.

Problems with the Tsunami Early Warning System

The BMKG issued a based on seismographic data tsunami warning. The alarm was broadcast by radio and proclaimed over loudspeakers of mosques, prompting thousands to flee to Sumatra on higher -lying country. The alarm was later revoked; some officials stated, however, that the installed after the 2004 tsunami tsunami warning system does not completely work. Two of the buoys at sea had been vandalized and did not work. These allegations were denied by the German side. The head of the German -Indonesian Tsunami Early Warning System ( GITEWS ) said that the system had " worked very well," only one of the sensors had failed, and his failure did not affect the functioning of the system. However, the epicenter of the earthquake was so close to the islands that a warning was in any case too late, because the tsunami took only five to ten minutes to reach the islands.

Aftershocks

Since the initial earthquake several aftershocks were recorded, of which the most significant are the following:

  • 5.0 - October 25 15:21:12 UTC
  • 6.1 - October 25 19:37:30 UTC
  • 4.9 - October 25 22:10:03 UTC
  • 6.2 - October 25 22:59:53 UTC
  • 5.3 - October 26 10:51:25 UTC
  • 5.3 - October 26 11:33:21 UTC
  • 5.0 - October 26 19:40:41 UTC
  • 5.0 - October 26 23:09:47 UTC
  • 5.8 - October 26 23:45:38 UTC
Bengkulu (city) September 2007 Sumatra earthquakes North Pagai List of earthquakes in Indonesia
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