This 8.7M quake was centered off the West coast of Northern Sumatra. Earthquakes over Magnitude 8 are classified as "Great" Earthquakes. "Great" quakes are relatively rare and usually very destructive. By comparison, this earthquake was considerably larger than the 1906 San Francisco earthquake and indeed larger than any seen in the US outside of Alaska. Of course damage from any quake is due to a number of factors including density of population, building methods and materials, local geology and the duration of shaking. This quake struck at 4:09 PM (GMT) or 11:09 PM local time. Shaking lasted 3 minutes, which is a long time for an earthquake. There have been at least 518 people confirmed killed and thousands displaced. A few people were pulled alive from the rubble after 4 days. Worst hit was the island of Nias, where electricity and water supplies have been disrupted. Roads and runways across the island have large cracks across them and are in many cases unusable. Also hard hit was the nearby island of Simeulue. Fires have raged unchecked with fire fighting equipment buried in rubble.
Aid has been arriving from around the world. Some teams were already in place in nearby Aceh from the December quake and tsunami. Some of the areas devastaed then have seen more damage from this quake. Tsunami warnings went out around the Indian Ocean and people were evacuated from coastal areas in Sri Lanka, India, Thailand, Malaysia and Indonesia. However this time there was no tsunami.
This earthquake occured on a neighboring section of the same subduction zone that caused the December 26, 2004 tsunami. Scientists had been concerned that that quake would increase the pressure on parts of the zone that had not moved and this appears to be what happened here. This map shows the relationship between these two quakes and two other quakes that have occured in the same area in the past. You can see quite clearly how different sections of this zone will move at different times.
(See the Plate Tectonics page for more information on these processes.) The US Geological Survey (USGS) is an invaluable resource in understanding and tracking earthquakes. Here is the USGS report on this earthquake
See also the following news stories:
- Oxfam reports quake island damage(BBC 3/29/05)
- In pictures: Indian Ocean quake(BBC 3/29/05)
- Indonesian quake death toll hits 518(Australian ABC News)
- Nine feared dead in quake crash (BBC 4/2/05)
- Quake rescuers abandon city search (CNN 4/1/05)
- Traditional houses outlast new in Indonesia quake (CNN 4/1/05)