Experts plan for Alpine Fault 'mega-quake'

According to scientists the Alpine Fault is due to rupture every 300 years (Newshub.)
According to scientists the Alpine Fault is due to rupture every 300 years (Newshub.)

A team of experts has been tasked with creating an action plan for an Alpine Fault mega-quake, thought to be due within the next 60 years.

The fault line along the South Island ruptures roughly every 300 years and the last time was 299 years ago.

However, GNS Science earthquake geologist Dr Robert Langridge told Mark Sainsbury it doesn't mean it'll go next year.

"It's a question of when," he says, "when we say it's 300 years of course there's an uncertainty around that of about plus or minus 60 years."

The emergency management project will receive $500m in funding over two years.

The rupture of the Alpine Fault along a length of 200km will cause very strong shaking for a couple of minutes, Mr Langridge says.

"The shaking in the Southern Alps would actually be very strong and cause a lot of rock falls and rock avalanches all around the various catchments.

"One side of the plate will move seven or eight metres to the east or west and you'll also see about one to two metres of vertical movement."

He says the intensity would lessen as it reached the Canterbury region and the South Island wouldn't be split in two.

Mr Langridge says it's "absolutely" survivalable, but would be catastrophic in places.

"I'm not panicking about it...but in terms of statistical probabilities there's about a 30 percent chance in the next 50 years this event will happen. That's actually a reasonably high value when you're talking about geological events."

Quake scientists in January tried to get an X-ray-like image of the Alpine Fault (Newshub.)

Environment Southland Emergency Management manager Angus McKay says the scientists are investigating what the likely scenario is in terms of magnitude and effects.

"The idea is we develop a coordinated response plan so that if and when the Alpine Fault does rupture we all work together to try and respond and recover."

"It makes a big difference if it ruptures starting from the north to the south or from the south up to the north. Depending on which way it goes depends on the way the energy flows through the South Island," he says.

"We're going to have to look at the whole of the South Island and come up with a solution to it."

He says the fault rupturing may affect Wellington as well.

Mr McKay says at the end of the two years the group is hoping to have a good response plan, as well as an ongoing "steering" group to take the plan forward.

Director of the Ministry of Civil Defence and Emergency Management, Sarah Stuart-Black says it's an exciting and important project.

"We're really looking at how do we ensure we can be flexible and agile on the day in order to support affected communities.

"We never know when an earthquake is going to happen...but what we do know in New Zealand is that we experience earthquakes regularly."

The project also shows communities Civil Defence is continuing to improve and adjust, which should give some reassurance.

The Southern Alps run through the Alpine Fault (Newshub.)