According to a news release from McGill University, researchers have revealed the cause of the deadly 2011 tsunami in Japan.

The tsunami, which impacted Japan’s Tohoku region in March 2011, was touched off by a submarine earthquake much bigger than anything geologists had anticipated in that zone.

New research published in the journal Science offers new information on what led to the powerful displacement of the seafloor off the northeastern coast of Japan. The research also implies that other zones in the northwest Pacific may be at risk of similar massive earthquakes.

Twenty-seven scientists from 10 countries took part in a 50-day expedition in 2012. The researchers drilled three holes in the Japan Trench area to examine the rupture zone of the 2011 earthquake, a fault in the ocean floor where two of the planet’s major tectonic plates meet.

The joint where the Pacific and North American plates meet creates what is called a “subduction” zone, with the North American plate riding over the edge of the Pacific plate. The Pacific plate bends and descends deep into the earth, creating the Japan Trench.

Geologists have long thought that deep beneath the seafloor, motions of the plates can produce a lot of elastic rebound. Closer to the surface of the seafloor, this rebound effect was believed to subside.

Until 2011, the biggest displacement of plates ever documented along a fault took place in 1960 off the coast of Chile. In the Chile earthquake, the slip was 20 meters compared to 30 to 50 meters in the Tohoku earthquake. According to researchers, the slip actually amplified as the subterranean rupture advanced towards the seafloor. The rupture pushed up the seafloor, causing the deadly tsunami.

The results of 2012’s drilling by the Chikyu expedition show several factors that help give reason for this surprisingly extreme slip between the two tectonic plates.

The fault itself is extremely thin — less than five meters thick in the area investigated.

“To our knowledge, it’s the thinnest plate boundary on Earth,” said McGill University geologist Christie Rowe in a statement.

The researchers also found that the clay deposits that fill the narrow fault are comprised of very fine sediment.

“It’s the slipperiest clay you can imagine,” noted Rowe. “If you rub it between your fingers, it feels like a lubricant.”

The finding of this strange clay in the Tohoku slip zone implies that other subduction zones in the northwest Pacific where this kind of clay exists may be able to produce similar, large earthquakes.

The researchers utilized specially constructed deep-water drilling equipment that allowed them to drill more than 800 meters beneath the sea floor, in an area where the water is approximately 6,900 meters deep.

The drill traveled for six hours with core samples from the fault back to the surface.

“We X-rayed the core as soon as it came on board, so the geochemists could get their water sample before oxygen was able to penetrate inside the pores of the sediment,” Rowe added.

What do you think of the findings? Share your thoughts in the comments section.