Focus on Hikurangi zone as quake experts plan for 'big one'

The Hikurangi subduction zone off the East Coast of the North Island and the southern section of the Alpine Fault are the two earthquake zones that give New Zealand the most trouble, district councillors learned yesterday.

Subduction zones are where tectonic plates collide.

Tararua District Council resilience manager Paddy Driver gave councillors an update on research and planning for "the big one", highlighting the Hikurangi subduction zone.

"This is the one which is going to bite us more," he said.

Paddy Driver, of the Tararua District Council, demonstrates how the Pacific and Australian tectonic plates could cause an earthquake and tsunami. Photo / Christine McKay

"The Alpine Fault has moved 30m in a thousand years, but when it lets go, the result is catastrophic."

Mr Driver explained how the Alpine Fault ruptured approximately every 300 years, the last time in 1717.

"It's due to rupture in the next 50 years and will affect most of the South Island and parts of the North Island," he said.

"But it's the Hikurangi subduction zone which we are planning for, with Exercise Hikurangi later in the year.

"There is a five-year research programme under way investigating the plates in the zone and slow-slip earthquakes.

"Every hour or so there is a small earthquake happening off Porangahau and while that's happening it's fine. But the minute they stop, we've got trouble."

On land, earthquake fault-line monitoring devices are based at Dannevirke, Weber and Akitio, as well as around the country as part of a major scientific programme.

"There's a lot of money being put into trying to map the subduction zones, with $22 million from the New Zealand Government and $40m from the United States," Mr Driver said.

A Japanese scientist on an $800,000 Rutherford Scholarship has been modelling a scenario of an 8.4 magnitude earthquake, centred on Waipukurau.

His research will form the basis of Exercise Hikurangi, when the district council's emergency operations centre in Dannevirke will be activated.

"It will help us to be ready if something like this happens," Mr Driver said.

However, councillor Jim Crispin admitted these briefings made him nervous.

"The last time we had one of these [briefings] I never slept in a month," he said.