Chance of another large quake in next month falls

2:46 pm on 22 February 2017

The chance of another large earthquake within the next month has dropped to 18 percent, the country's geological hazard monitoring service says.

Seismograph

A seismograph on display in the GeoNet briefing room (file) Photo: RNZ / Alison Ballance

GeoNet modelling forecasts show a downward movement in aftershocks since the magnitude 7.8 earthquake in Kaikōura last November, but a spokesperson said people needed to remain prepared for the possibility of one or more large quakes striking at any time.

The agency has been monitoring aftershocks since the November quake, created by the rupture of nine large faultlines in north Canterbury and south Marlborough.

It said the chance of a magnitude 6 to 6.9 quake happening within the next month had dropped from 25 percent, from the latest forecast in January, and while it was a step in the right direction, it did not mean the country was in the clear.

GeoNet said another big earthquake was still "well within the probabilities in our models", and an 18 percent chance in a month was still a concerning probability, meaning the public needed to continue to be prepared for earthquakes.

Up until Monday this week, there have been 13,626 quakes since Kaikōura. Four of them were of magnitude 6 or greater.

GNS principal scientist Kelvin Berryman said there had been ongoing analysis of the faultline ruptures, which was helping them to complete a picture for what could happen next.

"One aspect that has moved along a bit is the thinking about 'what next'. We are increasingly thinking New Zealand might be in a period of heightened earthquakes - a bit like the period 1929-1942.

"This has implications not just for the Kaikōura aftershock zone stretching up to eastern North Island, but for the country as a whole," Dr Berryman said.

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