A bigger follow-up to a magnitude 7.1 quake in the East Cape is unlikely, but it can't be ruled out, Geonet says.
On Friday morning a 7.1-magnitude quake caused a 30cm tsunami and had people heading for high ground - although there were no reports of major damage or injuries.
GeoNet's forecast aftershock zone. Photo: GeoNet
A steady string of aftershocks, including some over magnitude 5, have followed.
Looking at what was likely to happen in the next month, seismologists at Geonet say the most likely scenario - about 90 per cent odds - is the rattling will continue for the next month at decreasing levels, although that could include some tremors of between magnitude 6.0 and 6.9.
Geonet's Sara McBride said the 7.1 Waitangi Day quake in 1995 - near the East Cape - was followed by two years of tremors.
But, Geonet says there's also a 10 per cent chance another magnitude 7.0 to 7.9 quake will strike the area in the next 30 days.
"This earthquake may be onshore or offshore but close enough to cause severe shaking on land. Also there is a possibility of an earthquake either north or south of the M7.1 mainshock area," Ms McBride said.
And although its "very unlikely", Geonet says it can't rule out the possibility a quake of magnitude 8.0 or greater may strike.
An earthquake of magnitude 8.0 or greater is "very unlikely" according to GeoNet. Photo: GeoNet/Getty
"This scenario is similar to what occurred in the Tohoku earthquake in Japan in 2011. Although it is still very unlikely, the chances of this occurring have increased slightly since the M7.1 earthquake."
It said the chance of a magnitude 6.0 and 6.9 striking the area in the next 30 days was about 50 per cent.