JAKARTA, 12 March 2008 (IRIN) - The Indonesian province of West Sumatra has experienced several earthquakes over the past fortnight since a 7.3 quake on 25 February sparked a tsunami alert, stirring up fears that another massive quake might strike this seismically active region.

The almost daily quakes have centered on Padang, West Sumatra's capital, and the Mentawai islands off the coast. Some scientists fear another devastating disaster such as in December 2004, in which more than 230,000 people across Asia were killed.

But scientists are divided over when the next big one might strike. US-based geologist, Kerry Sieh, from the California Institute of Technology, believes the quakes and tremors since 25 February are signs of increasing stress.

"Significant pieces are starting to break. But whether that means a magnitude nine tomorrow or 20 years from now, we cannot tell," Sieh told a Singapore daily, the Straits Times.

"Still, these earthquakes are clearly driving the Sunda mega-thrust closer to failure, accelerating things," said Sieh, who has been studying the Sumatra fault for more than a decade.

The stress is caused by the Sunda plate, which stretches from Sumatra to eastern Indonesia, pushing into the Indian Oceanic and Australian plates, according to geologists. The cracks along a segment of the Sunda mega-thrust caused the Aceh tsunami of 2004 and the Nias quake of 2005.

"For a quake with a magnitude of at least 8.5 we can say that something like this will occur within 200 years with almost 100 percent accuracy. But to say this might happen in the next 20 years, I think we can only predict that with 10 percent accuracy," Andes Suharjono, a geologist in the disaster unit of the Metereology and Geophysics Board (BMG), told IRIN. These predictions are based on studying the history of the quakes in this region, he said.

"This is a natural phenomenon. The mega-thrust wants to stabilise and to stabilise it wants to release energy ... so we can expect quakes anywhere along this fault-line, even in eastern Indonesia," said Suharjono.

He admitted the frequent quake warnings and the tsunami alert were making West Sumatrans nervous, and it would be less stressful if the government's meteorology agency could predict more accurately whether a quake would set off a tsunami or not.

In an effort to do this, he said the government was installing tsunami buoys. To date only two buoys have been installed but there are plans for another 19 to be placed in the next few years.

In addition, a network of tide-measuring machines is needed. If they were in place the BMG could more easily predict where on Sumatra's 1,000km coastline a tsunami might strike, said Suharjono.

Disaster preparedness

In Padang, residents admit to feeling edgy. "Every day there is a quake and it feels like the buildings will collapse; everyone is very tense," said Handewi, a hotel employee.

However, they are better equipped than most to deal with a quake, and even a tsunami. Almost 200,000 people have received training on how and where to evacuate, since a local NGO, Tsunami Alert Community (KOGAMI), began disaster preparedness training sessions in 2005.

"Before, if there was a big quake people used to panic, but now they know to check any information about quakes, such as on local radio stations, and they don't panic," says Achmad Ansyari Siregar from KOGAMI.

Nonetheless, although Padang is more quake ready than most other Indonesian cities, it sits on flat, sandy plains and the roads and bridges leading to higher ground are narrow.

Sudi Prayitno, a former UN consultant on disaster management for the UN Office for the Coordination of Humanitarian Affairs (OCHA), who is head of the Legal Aid Foundation in Padang, told IRIN, "If you look at evacuation routes for the Padang area, they don't have the capacity for people to evacuate the 7-10km into the hills to high ground." In fact, after an earthquake on 12 September, there was a three-hour jam of cars trying to get up into the hills, said authorities.

KOGAMI estimates that some 400,000 people in Padang are at risk in a large-scale tsunami, and is lobbying the government to widen roads and bridges. In response, the government has promised to create another evacuation route, and also nominate several tall buildings to be used in the event of a tsunami.

mk/bj/mw

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