Scientists have discovered new evidence pointing out an increase in strain beneath Bangladesh that can potentially affect at least 140 million people in the region as a direct result of a massive earthquake.
According to a paper published in the journal Nature Geoscience, the newly identified threat is a subduction zone. This zone occurs when plates of heavy ocean crust slowly dive offshore beneath the lighter rocks of adjoining continents, or under other parts of the seafloor. All the most massive earthquakes known to occur on Earth occur in subduction zones, including the Indian Ocean quake and tsunami that took the life of some 230,000 people in 2004 and the 2011 Tohoku quake and tsunami off Japan that swept away more than 20,000 and caused the Fukushima nuclear disaster.
Previously, researchers thought that the plate boundary in and around Bangladesh to sliding vertically. However, new evidences suggest that a subduction is occurring below the surface over the past decade and part of the juncture is locked and loading up with stress. When this stress is to be release, the researchers believe it will cause a massive shaking likely to be larger than 8.2, and could reach a magnitude of 9.
"We don't know how long it will take to build up steam, because we don't know how long it was since the last one," said Michael Steckler, a geophysicist at Columbia University's Lamont-Doherty Earth Observatory and lead author of the paper, in a statement. "We can't say it's imminent or another 500 years. But we can definitely see it building."
The worst case scenario for Bangladesh and its neighboring countries is when the strain has been building for much longer; the zone could jump horizontally by up to 30 meters, or almost 100 feet. At present, the built up stress in the zone, assuming a steady motion over the past 400 years, could produce about 5.5 meters or 18 feet of horizontal jump. The best case scenario is when only a part of the zone slip, creating a much smaller quake.