14 DAY TRIAL // A new research performed by Caltech experts indicates that the threat of a major earthquake in the region of one of the world's most active faults located in Sumatra is extremely high. The area has been affected many times by such monster-magnitude events, the most recent having taken place in September last year - two earthquakes, one of 8.4, the other of 7.9 in magnitude - occurring within an interval of 12 hours. But this is far from being over, claim the specialists.
On the 26th of December 2004, a behemoth quake of 9.2 magnitude hit Sumatra's western coast, causing a massive tsunami wave across the Indian ocean. The region is a quake heaven because this is where a tectonic plate dips under another, accumulating a lot of stress. One year later, in 2005, another occurred, this time of a magnitude of 8.6, just to the south of the previous one, and exactly in the same spot as that in 1861, releasing a stuck portion of the tectonic plate and some of the tension. The Mentawai area investigated by the Caltech team was shaken by an 8.8 quake in 1797 and a 9.1 in 1833.
Based on data obtained from an array of GPS stations named Sumatra Geodetic Array (SuGAr), as well as seismological records, remote sensing data, and field measurements, the scientists deduced that most of the stress had not been released yet. "In fact," explained Ali Ozgun Konca, the main author of the paper, as quoted by Eurekalert, "we saw release of only a quarter of the moment needed to make up for the accumulated deficit over the past two centuries". This is because the fault's activity, either calm or violent, is determined by factors such as its temperature variations or the water amount in the crust.
"The 2007 quakes occurred in the right place at the right time," shared Caltech's Jean-Philippe Avouac, cited by Discovery. "They were not a surprise. What was a surprise was that those earthquakes were way smaller than we expected. It was what we call a partial rupture. 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," he stated, adding that "We could potentially have another quake larger than 8.5 tomorrow. Or we might have to wait a few decades, but the energy is available now".