Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Deep-Sea Study Reveals Cause of 2011 Tsunami

06.12.2013
Drilling in Japan Trench by international scientific team finds unusually thin, slippery geological fault

The devastating tsunami that struck Japan’s Tohoku region in March 2011 was touched off by a submarine earthquake far more massive than anything geologists had expected in that zone.


JAMSTEC/IODP

An international team of scientists has concluded that an unusually thin and slippery geological fault where the North American plate rides over the edge of the Pacific plate caused a massive displacement of the seafloor off the coast of Japan in March 2011, touching off the devastating tsunami that struck the Tohoku region.

Now, a team of scientists including McGill University geologist Christie Rowe, has published a set of studies in the journal Science that shed light on what caused the dramatic displacement of the seafloor off the northeastern coast of Japan. The findings also suggest that other zones in the northwest Pacific may be at risk of similar huge earthquakes.

Prof. Rowe, of McGill’s Department of Earth & Planetary Sciences, was one of 27 scientists from 10 countries who participated in a 50-day expedition in 2012 on the Japanese drilling vessel Chikyu. The team drilled three holes in the Japan Trench area to study the rupture zone of the 2011 earthquake, a fault in the ocean floor where two of the Earth’s major tectonic plates meet, deep beneath the surface of the Pacific Ocean.

The joint where the Pacific and North American plates meet forms what is known as a “subduction” zone, with the North American plate riding over the edge of the Pacific plate. The latter plate bends and plunges deep into the earth, forming the Japan Trench.

The conventional view among geologists has been that deep beneath the seafloor, where rocks are strong, movements of the plates can generate a lot of elastic rebound. Closer to the surface of the seafloor, where rocks are softer and less compressed, this rebound effect was thought to taper off.

Until 2011, the largest displacement of plates ever recorded along a fault occurred in 1960 off the coast of Chile, where a powerful earthquake displaced the seafloor plates by an average of 20 metres. In the Tohoku earthquake, the slip amounted to 30 to 50 metres – and the slip actually grew bigger as the subterranean rupture approached the seafloor. This runaway rupture thrust up the seafloor, touching off the horrifying tsunami.

The results of last year’s drilling by the Chikyu expedition, outlined in the Science papers published Dec. 6, reveal several factors that help account for this unexpectedly violent slip between the two tectonic plates.

For one thing, the fault, itself, is very thin – less than five metres thick in the area sampled. “To our knowledge, it’s the thinnest plate boundary on Earth,” Rowe says. By contrast, California’s San Andreas fault is several kilometers thick in places.

The scientists also discovered that the clay deposits that fill the narrow fault are made of extremely fine sediment. “It’s the slipperiest clay you can imagine,” says Rowe. “If you rub it between your fingers, it feels like a lubricant.”

The discovery of this unusual clay in the Tohoku slip zone suggests that other subduction zones in the northwest Pacific where this type of clay is present – from Russia’s Kamchatka peninsula to the Aleutian Islands – may be capable of generating similar, huge earthquakes, Rowe adds.

To conduct the studies, the scientists used specially designed deep-water drilling equipment that enabled them to drill more than 800 metres beneath the sea floor, in an area where the water is around 6,900 metres deep. No hole had ever before been drilled that deep in an area of similar water depth. At those extraordinary depths, it took six hours from the time the drill pulled core samples from the fault until it reached the ship.

During night shifts on deck, Rowe was in charge of deciding which sections of drill core would go to geochemists for water sampling, and which would go to geologists for studies of the sediment and deformation structures. “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.”

The expedition was supported by member countries of the Integrated Ocean Drilling Program (particularly Japan and the US), and Canadian participants were supported by the European Consortium for Ocean Research Drilling, of which Canada is a member.

Link to the expedition website: http://www.jamstec.go.jp/chikyu/exp343/e/

Chris Chipello | Newswise
Further information:
http://www.mcgill.ca

More articles from Earth Sciences:

nachricht NASA eyes Pineapple Express soaking California
24.02.2017 | NASA/Goddard Space Flight Center

nachricht 'Quartz' crystals at the Earth's core power its magnetic field
23.02.2017 | Tokyo Institute of Technology

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Stingless bees have their nests protected by soldiers

24.02.2017 | Life Sciences

New risk factors for anxiety disorders

24.02.2017 | Life Sciences

MWC 2017: 5G Capital Berlin

24.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>