It is one of the largest earthquakes in New Zealand since a Magnitude 7.8 tremor struck near Kaikoura in November 2016, which killed two people.
Geonet tweeted soon after the quake.
"That was a very widely felt earthquake. We hope you are all okay. More information soon."
There is no tsunami threat, Civil Defence has confirmed.
The sitting of Parliament was suspended to allow time for a check of the buildings and staff.
Herald readers around New Zealand have reported their quake experience.
Olivia Allison felt the quake in Palmerston North.
"Wholly crap we just had an epic quake in Palmy. First Big one since I've been back. Just keeps going," she said on Twitter.
The Hits presenter Brodie Kane also tweeted from Christchurch.
"So I actually woke from a nap into the earthquake and it wasn't even in the same island as me," she said.
"That was a get under the table and hold on tight kind of earthquake here in Welly! Shake rattle and roll," said Al's Show Biz on Twitter.
Tejinder Chawla wrote: "I felt the earthquake in Wellington Wills street. Felt it 1st time and was little shaky ... as almost dropped my coffee on me."
A North Canterbury resident said the quake was "quite noticeable" and Christchurch woman Alesha Boon said "Christchurch Hospital rocked and rolled like a boat for what seemed like ages."
In Whanganui Rachel Stewart tweeted: "Few pictures fell off the wall here in rural Whanganui."
"Loud and violent and long-ish," she said. "The dog's run off into the bush, and the cat even stopped eating his raw fish. For a minute."
The quake was felt strongly in Hastings. One woman said the carpark was "rolling underneath me at Countdown".
Napier resident Jonathon Smith said he grabbed his dogs, hopped in his car and left immediately. "I live right by the coast so we were scared there was going to be a tsunami."
"The first one was quite short and sharp and then there was a pause and I thought it might be over then there was a stronger shake that went on for about 30 seconds. "
Wellington resident Kasey MacKinnon - who has just moved up from Christchurch - said it went on for a while. "Biggest one I've felt in a long time and first one since moving to Wellington two months ago."
Donna Field said she felt "quite a significant shake in Greytown Wairarapa. Went for about 30 seconds. Made the building creak and sway back and forth. "
Wellington Fire and Emergency spokesman said no injuries or damaged had been reported in the area as of yet.
Wellington's Metlink says bus, train and ferry services are operating normally.
A Christchurch Fire and Emergency spokesman said his whole office based in the CBD felt the quake. "It was quite a significant shake but no damage or injuries have been reported yet."