A magnitude 5.8 earthquake occurred centred 25 km south-east of Tokoroa on Saturday.
GNS Science says the quake was at a depth of 197km at 7.19am.
Initial reports show it was felt from Wellington to Gisborne.
GNS Science initially reported a magnitude 6.0 quake but later downgraded it.
Vulcanologist Gill Jolly said the quake was unlikely to have been felt near the epicentre.
The quake was followed by aftershocks of magnitude 2.6 and 3.7 at a similar depth, centred around Tokoroa, and a magnitude 3.3 near Tauranga.
Police say there have been no reports of damage.