The next big one? Geonet reveals quake risks for 2018 and next decade

Latest earthquake forecasts show there is a 2 per cent to 14 per cent, or "very unlikely" chance of a large earthquake occurring in central New Zealand over the next year, but an increased chance of a large event in the next decade.

Geonet has released 1 and 10 year earthquake forecasts, using a new modelling system looking at how slow slip events might impact future earthquakes to improve accuracy.

The process looked at earthquake models as well as the impact of slow slip events. Evidence of earthquake clustering over the past few thousand years was used to revise the estimated likelihood of large events occurring.

GNS Science seismologist Dr Matt Gerstenberger said the forecasting showed the likelihood of a magnitude 7 or above earthquake occurring within the next year in central North Island was "very unlikely" - with a 2-14 per cent chance.

The organisation's best estimate was 6 per cent, which was a one in 16 chance. While this was lower than at this time last year - following the 2016 Kaikōura earthquake the probability was greater than 20 per cent - it was up on years prior to this.

"So that's increased from what we would have said prior to the Kaikoura event. And it's already quite a high probability area," Gerstenberger said.

GNS earthquake forecasts looked at predictions for central North Island, as shown by the yellow box. Photo / Geonet

GNS scientists met with experts from Japan, Taiwan and the US to create these estimates, which Gerstenberger said was useful for building upon their own knowledge.

The team also created an estimate of how likely a large earthquake was within the next 10 years. The best estimate of a large-scale earthquake happening in central New Zealand in this time period was 30 per cent.

Gerstenberger said these estimates factored in a new range of models, looking at slow slip events.

Slow slip events, he said, were earthquakes that happened on the interface of tectonic plates. They could take from one week to six months to occur.

They weren't generally felt while they were occurring, he said but GNS typically detected them through GSP stations. They could alter the landscape, causing the land to move various distances.

Three of these slow slip events were triggered following the Kaikoura earthquake last November. Gerstenberger said this prompted the group to improve their knowledge in this area.

"The question is, what impact do these events have on future earthquakes?"

They did not yet know the full-blown impact of how these events changed or impacted on future earthquakes but a study of activity over the Hikurangi Margin following the 2016 Kaikoura event had built upon knowledge in this area.

"The main thing that has come out of that was that there was some impact from those slips on future events.. But it's lessened. It isn't huge."