Scientists probing the fault zone

THE TEAM: An international team of scientists and engineers preparing highly-specialised instruments to be deployed on the seafloor off the east coast of the North Island. From left are Pete LIljegren (Columbia University), Laura Wallace (GNS Science), Neville Palmer (GNS Science), Carlos Becerril (Columbia University), Spahr Webb (Columbia University), Yusuke Yamashita (Kyoto University), and Ted Koczynski (Columbia University). Picture by Margaret Low

An international team of scientists set off last weekend to place earthquake monitoring instruments along New Zealand’s largest fault, the Hikurangi subduction zone.

About 40 instruments will record seismic movement and information that will help better understanding of the earthquake and tsunami potential for the zone, which runs along the North Island’s east coast.

“What we can learn about this fault and how it moves will help us understand and prepare for the next great earthquake,” says GNS Science expedition leader Dr Daniel Barker.

Subduction zones are where most of the world’s deadliest earthquakes, volcanoes and tsunamis occur — such as Sumatra (2004) and northern Japan (2011) magnitude 9 earthquakes and tsunami.

GNS Science is leading the operation aboard NIWA’s research ship R/V Tangaroa, and the instruments will be placed off Gisborne, Hawke’s Bay, and Wairarapa.

“This plate boundary has the potential to produce powerful earthquakes and tsunamis, so this research is a priority for New Zealand geoscientists,” says project leader Dr Laura Wallace.

One of the instrument types used is a seafloor pressure sensor. These will record the upward or downward movement of the seabed, detect “slow-motion earthquakes” offshore, and could also provide evidence about how the zone might behave in a large earthquake.

The team will deploy two arrays of precision seafloor transponders to track horizontal movement of the seafloor, and several ocean bottom seismometers.

“We expect that the instruments will record many hundreds of small earthquakes that cannot be accurately located with land-based instruments,” Dr Wallace says.

The expedition includes scientists from GNS Science, Victoria University of Wellington, Lamont Doherty Earth Observatory (US), Scripps Institution of Oceanography (US), as well as Tohoku, Kyoto and Tokyo Universities in Japan.

“Because so many interesting things are occurring on the Hikurangi subduction zone, New Zealand provides an ideal natural laboratory to deploy these instruments”, says Professor Spahr Webb of Columbia University.