Megathrust earthquake: Ticking time bomb

July 13, 2016

Megathrust earthquake: Ticking time bomb

A massive earthquake called an "active megathrust fault" is posing a genuine threat to southern Asia.

And if the modelling is correct, this earthquake could be at least as devastating as the 2011 quake which devastated Japan and took 16,000 lives.

The discovery of the hidden geographic fault lurking under southern Asia could unleash a magnitude 9.0 quake, placing up to 140 million people at risk in the most densely-populated place on earth, researchers fear.

The study of the area took more than a decade and detected the massive fault beneath Bangladesh, parts of India and Myanmar.

The research, the first to use GPS data collected from Bangladeshi tracking stations, suggests the northeastern corner of the Indian subcontinent is on a collision course with Asia.

Traffic at the central part of Dhaka, Bangladesh. Dhaka is one of the most overpopulated cities in the world and new research indicates a devastating earthquake may be lurking below it. Photo / Getty

The tectonic plates far beneath the earth's surface are covered in layers of sediment more than 20m thick, and the study models suggest at the upper levels they are stuck in a pile-up, one thrusting under the other in a 'megathrust' which may have been under stress for more than 400 years.

Researchers believe the area is spring-loaded to buckle and rupture under the strain. But because their discovery is relatively recent, they have no idea when, or if, the fault will give way and trigger a 8.2 to 9.0 megaquake.

"We don't know if it's tomorrow or if it's not going to be for another 500 years," study co-author Michael Steckler, a geophysicist at the Lamont-Doherty Earth Observatory at Columbia University in New York City said in an article on the university website.

Solid red line indicates an area of about 62,000 square kilometres that could move during a subduction-zone earthquake, affecting 140 million people or more. Image / Chris Small/Lamont-Doherty Earth Observatory

"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. But we can definitely see it building."

The research team estimates 140 million people live within 100km of the fault, including about 17 million in the area around low-lying Dhaka region of Bangladesh, which Steckler says already has problems with poor construction, making it hugely at risk of building collapse should a quake of large magnitude hit the region.

Overcrowding would make it difficult to rescue survivors in the event of an earthquake.

"Right now, the streets are clogged with traffic such that it's impossible to drive around Dhaka on a normal day," Steckler said. "If you fill the streets with debris, it's really going to be impossible to get supplies and rescue equipment and things like that around," Steckler told Live Science.

The research team is now building a more detailed map of the shape of the fault, as well as looking at historical tsunami data to understand how often megathrust earthquakes occur, Steckler said.

The March 11, 2011 Japan earthquake, with a magnitude of 9.0 struck off Japan's northeastern shore and was the most powerful to ever hit the island country.

The quake triggered a devastating tsunami which struck the area with waves of up to 40m, tearing apart villages and towns, flattening homes and carrying ships inland, before sucking back to out to sea carrying debris, vehicles and bodies in its wake.

Damage to the Fukushima Daiichi Nuclear Power Plant completed a deadly treble of disaster, contaminating an area which continues to see more than 100,000 displaced locals living as evacuees.

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