18 Oct 2017

Scientists on quake fact-finding mission

2:47 pm on 18 October 2017

Scientists from four countries will start dropping highly sensitive devices off the east coast of the North Island on Tuesday to measure movements in the Earth's crust.

Scientists Dan Bassett, Dan Barker, and Katie Jacobs, all of GNS Science, with some of the recording instruments that will be placed on the seafloor off the East Coast as part of the project to study the Hikurangi subduction zone.

Scientists Dan Bassett, Dan Barker, and Katie Jacobs, all of GNS Science, with some of the recording instruments that will be placed on the seafloor off the East Coast. Photo: Supplied / Margaret Low, GNS Science

There will be 100 of the devices, known as seismometers, which will be dropped from NIWA's research ship Tangaroa, to help scientists learn more about tectonic movement in what is called the Hikurangi subduction zone.

This marks the boundary of the Pacific and Australian tectonic plates, and is one of this country's most significant faultlines.

GNS Science said the plate was capable of producing a 8.5-magnitude earthquake - a shake big enough to cause massive damage and generate a tsunami.

The project involves scientists from New Zealand, Japan, the US, and the UK, and is aimed at better understanding the potential threat from the Hikurangi subduction zone.

In addition to the seafloor instruments, scientists will deploy more than 200 land-based seismic instruments across the Raukumara Peninsula.

The land and sea based instruments will record echoes from both naturally occurring earthquakes and from acoustic signals generated by a US research ship anchored offshore.

Images will then be created of the Earth's crust down to a depth of 30km, using technology similar to a CAT scan.

GNS said some of these images would be three-dimensional.

They would help scientists determine the physical properties of rock that grind against each other as the Pacific and Australian tectonic plates move past each other.

They would also find out how the plates sometimes get locked together, which builds up seismic pressure.

New Zealand project leader Stuart Henrys said the data would help understand why different areas of the plate boundary were behaving so differently.

"Some parts of the plate interface slide past each other every year or so, in events called slow earthquakes," Dr Henrys said.

"But other parts appear to be stuck fast and are storing energy for a future large earthquake."

Lead US investigator Harm Van Avendonk said the project would produce detailed images of the entire fault system across that part of the North Island.

"A better understanding of what causes the marked differences in tectonic behaviour on this plate boundary will help New Zealand government agencies in their efforts to reduce the danger posed by earthquakes and tsunami in this area," Dr Van Avendonk said.

"What makes subduction zones rupture in huge, tsunami-generating earthquakes is one of the most pressing questions facing Earth scientists today."

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