Tangaroa diverts to undertake earthquake survey

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23 July 2013

NIWA is diverting its flagship research vessel Tangaroa to undertake survey work in the Cook Strait following the earthquakes in Marlborough and Wellington in recent days.

The Tangaroa has been stationed off the Marlborough coast mapping an area of the Pegasus Basin as part of a Ministry of Business, Innovation and Employment-funded (MBIE) Ocean Survey 2020 project.

The ship is currently heading to the Cook Strait and will spend part of tomorrow taking measurements using a multi-beam echo-sounder to determine whether the earthquakes have triggered any landslides in the Cook Strait Canyon.

The canyon starts just 10 kilometres off the coast and plunges from a depth of 150 metres to 3000 metres south of Cape Palliser. The canyon is the most prominent undersea feature of the Cook Strait and is scarred by numerous large submarine landslides and active faults.

NIWA marine geologist Scott Nodder said the Tangaroa survey would enable new data to be collected that would help quantify the landslide and tsunami risk to New Zealand's coastal communities.

"We have previously identified an area of potential instability in the middle of the canyon and this will give us the opportunity to see if there have been any changes," he said.

The ship will also survey an area crossing the earthquake epicentre to determine if there have been any changes to the sea floor due to near-surface faulting.

The work will take less than half a day to complete and the Tangaroa is expected to return to its Wellington base tomorrow afternoon, weather permitting.

NIWA acknowledges the co-operation of MBIE in enabling the diversion to take place.

"This won't give us all the answers but it will provide us some new information that will help us determine if the recent earthquake activity has caused any significant changes to the sea-floor due to either submarine landsliding or fault rupture."

NIWA scientists are also working with GNS Science staff to determine on which faultline the earthquake occurred and its relationship to the large Wellington faultline.

The planned survey tracks for RV Tangaroa to determine if recent earthquakes have caused any sea-floor changes in the Cook Strait Canyon and on the Marlborough shelf. [NIWA]
Distribution of active faults in the Cook Strait region, with slip rates (red, in mm/y). The red arrow in the centre of the figure shows the direction and magnitude (in mm/y) of the motion of the Pacific Plate, relative to the Australian Plate. Onshore faults from GNS Science and offshore faults from NIWA. [Philip Barnes(NIWA)/It’s Our Fault(GNS)]