Washington, Dec 4 : A new research has suggested that a devastating "megathrust" earthquake could occur at any time off the Indonesian island of Sumatra.
Using GPS, field measurements, radar data and seismological records, a team of international researchers investigated the parameters and reconstructed the events of two massive earthquakes, measuring 8.4 and 7.9 on the Richter scale, which occurred in the Mentawai area in 2007.
Previous models of how earthquakes work had suggested that the same fault would rupture in the same way and at regular, predictable time intervals.
But, the researchers found that the 2007 quakes ruptured only a fraction of the area affected by the giant 1833 earthquake, indicating that a tectonic plate boundary can rupture in different patterns depending on local differences in stress.
"What we see here is that the 2007 earthquake had at least a very big overlap with the 1833 earthquake, but it was very much smaller; in other words, it was an entirely different earthquake," said John McCloskey, a geophysicist at the University of Ulster, UK.
The GPS data enabled the researchers to create a map of the fault zone, showing which parts were locked tight and which parts were slipping freely.
This allowed them to estimate where the most strain has built up, and where the next big rupture is most likely to occur.
The results suggested that the 2007 events released only a quarter of the energy that had accumulated since 1833, leaving enough pent-up energy to trigger another giant earthquake at any time.
This event could be anything between magnitude 8.2 and over 9, according to McCloskey.
According to geologist Jean-Philippe Avouac, director of the Tectonics Observatory at the California Institute of Technology (Caltech), "There's still enough strain to create another major earthquake in that region.
We may have to wait a long time, but there's no reason to think it's over."