People described hanging on to doorways and diving for cover when the quake struck the country.
GeoNet reported the tremor, which hit at 10.36pm, was centred 230km deep and was 60km south of the Taranaki town of Opunake.
People from Bay of Plenty to Otago reported feeling it.
The first quake was followed nine minutes later by a 4.6 shake at the same depth, 70km south of Opunake.
GNS Science duty seismologist Lara Bland said the 7.0 quake was the largest to strike the Taranaki Bight area for the past 100 to 120 years.
It was related to the subduction zone where the Pacific tectonic plate was being driven under the Australian plate, she said.
The quake probably happened on the Pacific plate, which dipped down deeply, she said, occurring because the plate was hard and brittle.
That was also partly why it had been felt so widely, as the energy travelled "efficiently" back up the plate to the surface.
It was a good-sized shake but the depth and distance offshore limited its impact, Bland said.
While large quakes in the area weren't unheard of, "they aren't often that big," she said.
I live relatively close to the epicentre and the whole house began to shake from side to side and rattle. But it definitely was one of those rolling quakes. Earthquakes are nothing new in my area (there was a 3.4 this morning) and I have felt smaller ones before but this was something different.