Fault line that caused 2004 tsunami ruptured 20 times in Feb

The fault line that spawned the 2004 Indian Ocean tsunami has ruptured nearly 20 times this month, with three strong quakes in the last 24 hours alone. The activity shows the stress the seam is under and could be a harbinger of worse to come, scientists warn.

Mr Sieh and other scientists using Global Positioning System transmitters to measure the uplift of the quakes say another massive temblor sometime in the next 100 years or so is likely, but they cannot give an exact prediction.

The fault line is the seam in the earth where the Eurasian and Pacific tectonic plates have been pushing against each other for millions of years, causing huge pressure to build up. It runs the length of the west coast of Sumatra about 200 km offshore.

The 2004 earthquake off Aceh province in northwest Sumatra had a magnitude of 9.2, making it the most powerful temblor in four decades. It triggered a tsunami that killed 230,000 people in 12 Indian Ocean countries, more than half in Indonesia.

Three months after the Asian tsunami, a magnitude 8.6 quake further down the seam killed 1,000 people, while in September last year, an 8.7 quake opposite Bengkulu province damaged thousands of homes, killed about 25 people and sent a 3m tsunami crashing into nearby coastlines.

The most recent events have occurred opposite Bengkulu. Last Wednesday, a magnitude 7.4 quake killed three people and damaged scores of houses. Since Sunday, four other events strong enough to prompt tsunami warnings by international agencies have jolted the region.

They are best seen as part of a chain that began in 2004, the stability of the fault has been disturbed.