The quake was centred near Eketahuna in Wairarapa, at a depth of 73km, just before 4pm (not off Castlepoint as thought initially).
It was felt as a long, rolling quake which lasted nearly a minute. The quake was followed by three aftershocks of magnitude 4.3, 4.2 and 4.6, around 20 to 30 kilometres deep.
At Wellington Airport, a giant eagle hanging from the roof of Wellington Airport to promote the Hobbit trilogy has fallen because of the shock.
The National Radio programme was off air for several minutes because of the quake and train services were suspended until the railway tracks could be inspected and judged to be safe.
There were no immediate reports of injuries or deaths in the quake.
But there are reports of rockfall in the Manawatau Gorge. TranzMetro has suspended all train services in the capital and is replacing them with buses.
Meanwhile, photos posted to Twitter show the eagle installed at Wellington Airport to promote The Hobbit: Desolation of Smaug has fallen down.