New Zealand earthquakes: Modelling forecasts which quakes could strike over next 30 days

The three strong earthquakes which struck near New Zealand on Friday could be followed by more severe ones soon - including the chance of a "significantly larger earthquake".

GeoNet has developed three scenarios for earthquakes that might happen over the next 30 days.

While it's uncertain how large they could be, or when they could strike, it says statistical modelling can help know what could happen next.

"Earthquakes that generate tsunami impacting the northern part of Aotearoa-New Zealand are possible in any of these scenarios," GeoNet says on its website.

"We expect there to be more felt earthquakes, particularly in the East Cape. The region considered for these scenarios extends from the central Kermadec region north of the March 5 M8.1 earthquake to offshore East Coast Aotearoa-New Zealand within the next 30 days, because this area of activity is closest to the land and people."

The three scenarios

Scenario One - Very likely (up to 90 percent within the next 30 days)

GeoNet says the most likely scenario is we will see more earthquakes smaller than the ones which struck on March 5, however these will decrease in frequency over the next 30 days.

"This includes the potential for earthquakes in the M7.0-M7.9 range (more than 80 percent probability within the next 30 days)," it says.

"Larger earthquakes are more likely to occur in the central Kermadecs, near the northern part of the sequence. Similar sequences to these have occurred in this region in the last 50 years including a central Kermadecs M8.0 in 1976 and M7.7 in 1986."

Scenario Two - Very unlikely (15 percent or less within the next 30 days)

The next most likely scenario is a similar-sized earthquake of around M8.0.

"Should this occur, it is much more likely to be in the central Kermadecs, but it is still possible for it to happen near the East Cape," GeoNet says.

"Earthquakes of this size can occur on either the subduction interface or farther away as an 'outer rise' earthquake on the incoming Pacific plate, east of the subduction zone."

Scenario Three - Extremely unlikely (1 percent or less within the next 30 days)

GeoNet says a much less likely scenario is that the recent earthquakes will trigger a "significantly larger earthquake" within the next 30 days - which could be M8.5 or greater.

"For example, an earthquake could occur on the Kermadec subduction interface in the central Kermadecs," it says.

"This scenario is very complex and when combined with the current uncertainty in our models, we cannot confidently put a probability estimate on it occurring; however, our models suggest this is even less likely to occur near the location of the March 5th East Cape M7.1 earthquake, including the Hikurangi Subduction Zone.

"Although it is still extremely unlikely, the chances of this occurring have increased since the M8.1 earthquake."