Japan study implications for under-sea zones around New Zealand

February 8, 2013
Japan study implications for under-sea zones around New Zealand
A new study about the 2011 Japan tsunami in the internationally respected journal Science has implications for New Zealand, says a University of Otago scientist who

A new study about the 2011 Japan tsunami in the internationally respected journal Science has implications for New Zealand, says a University of Otago scientist who contributed to the study, Dr Virginia Toy.

The major finding confirmed by the analyses reported in the paper, published today, is that the massive 2011 earthquake in Japan released nearly all of the stress that had built up along the in that region.

Researchers had suspected that this release happened to some degree, based on observations that the sea floor moved nearly 50 meters during the earthquake.

To test the hypothesis the study authors, led by Weiren Lin from the Kochi Institute for Core Sample Research in Japan, analysed fracture orientations they could see in "resistivity images" from three large drilled into the crust across the plate interface where the earthquake occurred.

The team obtained their material from an expedition last year in which Dr Toy, from Otago's Department of Geology, travelled on the Chikyu as part of JFAST, the Japan Trench Fast .

Dr Toy was a representative of an Australia-New Zealand International Consortium (IODP) consortium called ANZIC – a group made up of universities and from both nations.

This project aimed to drill into the subduction fault that slipped in May 2011, generating a magnitude 9 earthquake, and the huge seafloor displacement that caused a that devastated the Sendai coast.

Dr Toy says the scientific aim was to sample the fault materials and make measurements related to the frictional strength of the fault surface, to help understand why there was such a large displacement.
 
She says the resulting study in Science has found that there was near total release of stress (i.e. pressure, or force, resulting from tectonic plate motions) in the crust in the wedge materials above the when the 2011 earthquake in Japan occurred.

"This is significant because most earthquake faults only release a small portion (typically 10%) of the stress in the crust around them, not nearly 100% as in this case," she says.

"Also, such a high proportion of stress was probably released because the fault materials were particularly frictionally weak or slippery."

She adds that the results suggest that subduction zone faults in other locations, including around New Zealand, need to be more carefully examined. New Zealand has "so much of its coastline exposed to the Pacific Ocean, which is ringed by subduction zones, for example in Tonga-Kermadec, Hikurangi and Chile."

"If the materials in the fault planes are similar to those in the Trench, it is likely they will also be very frictionally weak and therefore that we can also expect very large seafloor displacements when they slip,"

"It means that we should be prepared for other similar subduction zones to generate very large tsunami."

View the paper abstract via the Science website.

Explore further: Chikyu to set sail for IODP expedition: Japan trench fast drilling project

Related Stories

Deep-ocean researchers target tsunami zone near Japan

January 17, 2008

Rice University Earth scientist Dale Sawyer and colleagues last month reported the discovery of a strong variation in the tectonic stresses in a region of the Pacific Ocean notorious for generating devastating earthquakes ...

Recommended for you

Multinationals act on ocean-clogging plastics

January 16, 2017

Forty of the world's biggest companies assembled in Davos agreed on Monday to come up with cleaner ways to make and consume plastic as waste threatens the global eco-system, especially in oceans.

Tracking Antarctic adaptations in diatoms

January 16, 2017

Diatoms are a common type of photosynthetic microorganism, found in many environments from marine to soil; in the oceans, they are responsible for more than a third of the global ocean carbon captured during photosynthesis. ...

Study tracks 'memory' of soil moisture

January 16, 2017

The top 2 inches of topsoil on all of Earth's landmasses contains an infinitesimal fraction of the planet's water—less than one-thousandth of a percent. Yet because of its position at the interface between the land and ...

How the darkness and the cold killed the dinosaurs

January 16, 2017

66 million years ago, the sudden extinction of the dinosaurs started the ascent of the mammals, ultimately resulting in humankind's reign on Earth. Climate scientists have now reconstructed how tiny droplets of sulfuric acid ...

Soil pores, carbon stores, and breathing microbes

January 16, 2017

Researchers at the Pacific Northwest National Laboratory (PNNL) recently studied how moisture influences soil heterotrophic respiration. That's the breathing-like process by which microbes convert dead organic carbon in the ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.