The Alpine Fault is a geological fault that runs almost the entire length of New Zealand's South Island. YouTube / GNS Science
It may be the largest earthquake in our lifetimes – and probably our children’s lifetimes too. Today, emergency planners in Parliament begin an exercise aimed at readying New Zealand for a major event on the Alpine Fault. Here’s what to know.
Stretching 600km up the western side of the South Island, between Milford Sound and Marlborough, it marks the boundary between the colliding Pacific and Australian plates.
The latest estimates say there’s a 75 per cent chance of a major rupture within the next 50 years – and the probability of that quake measuring more than 8.0 is at 82 per cent.
Big ruptures along the fault occur around once every three centuries.
2017 was the 300th anniversary of what is thought to have been a magnitude eight quake that moved one side of the fault by about 8m in a matter of seconds.
The Alpine Fault runs several hundred kilometres from near Milford Sound all the way to Nelson Lakes National Park. Photo / North and South
What would it be like?
A large rupture could be catastrophic, stranding about 10,000 and killing and injuring many.
Studies have suggested a big quake – perhaps lasting two minutes – could also block South Island highways in over 120 places and cost the economy about $10 billion.
The most intense shaking would be felt on the West Coast – within 10km of the fault – with horizontal movement of up to eight metres.
“Rocks and landslides will be coming down off the Alps,” Otago University’s Dr Caroline Orchiston earlier told the Herald, “so if you’re anywhere near the mountains, it’ll be very loud.”
What have we been doing to prepare?
Orchiston and colleagues have been helping ready New Zealand through AF8 – a collaborative programme bringing together scientists and emergency managers.
The statutory responsibility, however, lies with the National Emergency Management Agency (Nema) and regional Civil Defence groups.
Today will be the first of three days over which Nema will run its Exercise Rū Whenua – a nationwide drill testing our response and recovery plans for an Alpine Fault scenario.
“The exercise will also be an opportunity to test or practice some of the lessons identified from the response to the North Island severe weather events in 2023,” Nema says.
For the rest of us, the message for what to do in a major quake remains the same: drop to your hands and knees, cover your head and neck, and hold on to your shelter.
Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.
