Scientists predict a large quake will come from beneath Siberut

Flickr/Erik B

[JAKARTA] The powerful earthquake that hit Padang, Indonesia, last September was not the massive quake that earth scientists have predicted, warn researchers.

Writing in Nature Geoscience this week (17 January) they say that the quake, which measured 7.6 on the moment magnitude scale (similar to the Richter scale) and killed more than 1,000 people, may actually have increased the chances of the disastrous, tsunami-causing quake predicted for the region.

This is because the Padang earthquake failed to relieve the stress on the Sunda megathrust — the fault line where the Eurasian and Indo-Australian tectonic plates meet — which stretches 5,500 kilometres from Myanmar to north of Australia, running along the southwestern side of the island of Sumatra.

The megathrust has caused numerous large earthquakes, most recently the one in 2004 that caused the Indian Ocean tsunami and led to 200,000 deaths.

A small segment of the fault line, under the island of Siberut, has not been ruptured for 200 years. The researchers predict that the next large earthquake will come from this area — and is likely to be the type that causes a tsunami.

The Padang earthquake, along with those in the region in 2005 and 2007, has added to the stress in the area — making it more fragile and vulnerable to earthquakes (see Tsunami quake 'increased risk of further disasters' and Indonesia 'faces fresh risk of quake and tsunami').

"[An earthquake] could reach eight on the Richter scale in a time not far away from now," Danny Hilman Natawidjaja, an author of the paper from the Indonesian Institute of Sciences, told SciDev.Net.

Areas most at risk are the coastal parts of southwest Sumatra, including the cities of Padang and Bengkulu, and the Mentawai islands off Sumatra of Pagai, Siberut and Sipora, he said.

Zulfahmi Arrasuli, a senior natural disaster volunteer in Padang, said that many people in the city do not know what to do if a tsunami or earthquake occurs.

And many government programmes for community preparedness reach only 20 per cent of the people they need to, he added.

Natawidjaja said large-scale evaluations of disaster preparedness must take place. "First of all it is important for Padang governance and central government to anticipate this matter. The other [challenge] is how to make communities ready to counter the disaster," he said.

Another problem is a lack of coordination between government and foreign groups running disaster preparedness programmes, he added.

Link to abstract in Nature Geoscience