Scientists have discovered Wellington is being hit by a magnitude 7 earthquake - but it cannot be felt.
The Kapiti slow-slip event, or silent quake, would be the largest earthquake to hit the region in 150 years.
It is occuring 40 kilometres below ground over an area spanning more than 100km, from Levin to the Marlborough Sounds.
GNS seismologist scientist Caroline Holden says the region is moving eastwards by a tenth of a millimetre a day.
She says slow-slip quakes have also been recorded in Manawatu, Hawke's Bay and Gisborne.