SYDNEY - A massive undersea earthquake is long overdue beneath the Mentawai islands in Indonesia and could trigger another deadly tsunami, said scientists mapping one of the world's most quake-prone zones.
The announcement comes near the five-year anniversary of the Indian Ocean tsunami, which struck Dec. 26, 2004, and killed around 226,000 people. The possible new tsunami would probably be smaller but may be very deadly as it would hit Sumatra's densely populated coast.
"The size of the tsunami may not be as big, but the problem is the size of the population is about three times as great," Kerry Sieh, director of the Singapore-based Earth Observatory, told Reuters.
A major quake measuring around 8.6 magnitude is expected beneath Siberut Island, along the Sunda megathrust, where the Indo-Australian tectonic plate butts up against the Eurasian plate - one of the world's most active fault lines.
When the big quake will strike is not known.
"We say most likely in the next few decades. Thirty seconds to 30 years, somewhere in there," said Sieh, who has studied geological records showing that for 700 years, major quakes have occurred along the Sunda megathrust every 200 years.
There have been three major quake cycles: the late 1300s, the 1600s, and between 1797 and 1833.
"The timing between those three sequences is about two centuries," said Sieh, adding a section of the megathrust under Siberut has not ruptured for 200 years, so it is due to slip and cause a major quake.