Mega-quake building off Indonesia

As the search for survivors from the Haiti earthquake continues, experts warn another devasting earthquake and tsunami could strike off the island of Sumatra.

The group, led by a prominent scientist who predicted a 2005 Sumatran quake with uncanny accuracy, issued the warning in a letter to the journal Nature Geoscience.

The peril comes from a relentless build-up of pressure over the last two centuries on a section of the Sunda Trench, one of the world's most notorious earthquake zones, which runs parallel to the western Sumatra coast, they say.

This section, named after the Mentawai islands, "is near failure," the letter warned bluntly.

"The threat of a great tsunamigenic earthquake with a magnitude of more than 8.5 on the Mentawai patch is unabated ... There is potential for loss of life on the scale of the 2004 Indian Ocean tsunami."

The letter gave no timeframe for this event but warned starkly of the danger for Padang, a city of 850,000 people that lies broadside to the risky segment.

"The threat from such an event is clear and the need for urgent mitigating action remains extremely high," it says.

More than 220,000 people lost their lives in the killer wave of 26 December 2004 when a 9.3-magnitude earthquake, occurring farther north on the Sunda Trench, ruptured the boundary where the Australian plate of Earth's crust plunges beneath the Eurasian plate.
Previous predictions

The authors of the letter are led by Professor John McCloskey of the Environmental Sciences Research Institute at the University of Ulster, Northern Ireland.

In March 2005, McCloskey warned that the 2004 Boxing Day quake had built up major stress in an adjoining part of the fault to the south. He declared a temblor in the region of 8.5 magnitude with the capacity to generate a tsunami was imminent and urged the authorities to beef up preparations.

Such predictions are extraordinarily rare in the world of seismology. Knowledge of where earthquakes strike is extensive, but the ability to say when they will occur remains elusive.

But McCloskey was proven right within two weeks. On 28 March 2005, a quake measuring 8.6 erupted at Simeulue island, generating a three-metre tsunami.

In the letter to Nature Geoscience, his team explain their calculations for the vulnerable Mentawai segment in the aftermath of a 7.6-magnitude quake that occurred 60 kilometres near Padang on 30 September last year, killing more than 1000 people.