More than 1700 aftershocks have rocked central New Zealand since the devastating magnitude 7.5 Kaikoura earthquake.

Geonet said there had been 1718 tremors by noon today since the initial quake, which struck in the early hours of Monday morning.

There had been 37 earthquakes alone in the past hour, and a massive 336 tremors since midnight.

More than 20 had been over magnitude 4.

In a night of constant tremors the South Island was rocked by more than 300 earthquakes.


GNS scientist John Ristau said statistically this was normal aftershock activity given the size of the quake.

"We expect lots of large magnitude aftershocks of 5 and above and lots of small ones. In this case lots of the large aftershocks are triggering their own aftershocks."

Ristau said nothing was greater than magnitude 5 last night but a couple of stronger magnitude 4 quakes would have caused a third consecutive night of sleeplessness for quake-ravaged parts of central New Zealand.