New fault line discovered in Wellington Harbour

A previously unknown fault in Wellington Harbour has been discovered, but scientists say it is unlikely to increase the capital’s known risk of earthquake damage.

Credit: Aiden Wojtas (Flickr)
Credit: Aiden Wojtas (Flickr)

The Aotea fault, named for its proximity to Aotea Quay, was found by NIWA (National Institute of Water and Atmospheric Research) marine geologists mapping the area between the Cook Strait Ferry terminal and Point Jerningham as part of the It’s Our Fault research programme led by GNS Science.

The fault is thought to be capable of earthquakes in the order of magnitude M6.3 to M7.1, with evidence that at least two large, surface-rupturing quakes have occurred in the last 10,000 years.

GNS scientist Russ Van Dissen explains in a NIWA press release that the new fault does not appreciably increase the overall ground-shaking hazard in Wellington.

“Any ground-shaking that this fault could produce is already considered in Wellington’s seismic hazard calculations. So it is already accounted for in the building code,” he says.

A combination of seismic surveys and borehole drilling over the past two years has enabled researchers to pinpoint the path and extent of the new fault, which is hidden from view beneath a layer of seafloor sediment.

The fault stops short of joining up with the much larger Wellington fault, which runs down the Hutt Valley along State Highway 2. At the southern end, a one metre-high scarp can be seen on the seafloor within 300 metres of the shoreline.

Researchers believe the Aotea fault continues inland, possibly as far as the South Coast, though its path has yet to be traced. Information about potential damage from surface rupture along the length of the fault would be useful in infrastructure planning.

In a Wellington City Council press release, Mayor Celia Wade-Brown says that she is keen that additional funding be found for scientists to continue geological mapping on land as this will help in understanding the fault’s precise location and characteristics. She emphasises, however, that Wellingtonians should not be unnecessarily alarmed.

“The Capital City is a safe city. Wellington is well-prepared for natural hazards,” she says.

Click below to hear a recording of the press conference and Q&A at NIWA announcing full details of the findings.

Speakers include Philip Barnes (NIWA), Celia Wade-Brown (Mayor of Wellington), Russ VanDissen (GNS) and Neville Brown (WCC).

The new fault has been widely covered in New Zealand and global media:

New Zealand Herald: New Wellington fault line discovered
ONE News: Wellington Harbour faultline makes businesses nervous ‘Aotea’ fault line found under Wellington
Radio NZ: Fault line could run under capital
The Press: Wellington’s fault find prompts grim warning
Radio NZ: New fault won’t hit capital insurance
NewstalkZB: New fault line unlikely to change insurance premiums
3News: Wade-Brown: Wellington buildings could handle fault’s quake
TV3 Campbell LiveShould Auckland become the capital?
ABC News: New earthquake fault line found in New Zealand’s capital Wellington capable of major tremors
9News Australia: Major new fault line capable of generating 7.1 magnitude earthquakes found under New Zealand capital
The Guardian: NZ capital won’t be moved despite Wellington fault line discovery, says PM
The Borneo Post: Major new fault found in New Zealand capital
RIA Novosti: Wellington Becomes One of the Most Seismologically Active Places on Earth
Outlook India: Major Earthquake-Prone Fault Found in NZ Capital
The News Nigeria: New Zealand capital reveals new geological fault line
Japan Times: New fault line discovered in New Zealand could generate 7.1 quake