Did you feel the big quake? Send your story, photos or video here.
Prime Minister John Key says, in principle, New Zealand is well placed to withstand the costs of another major earthquake.
Aftershocks continue to plague Wellington and the top of the South Island after yesterday's 6.5 magnitude jolt which struck in the Cook Strait at 5.09pm.
More than 100 aftershocks have been recorded since, including a 5.0 which hit 15km east of Seddon at 10.47 this morning.
GNS Science says there's a 20 per cent chance of a tremor greater than 6 hitting the same region in the next week.
Prime Minister John Key has assured quake-hit Wellingtonians the Government will do its "very best'' to ensure they get the support they need.
Mr Key had a brief stand-up with media before visiting the Wellington Regional Emergency Management Office for an update on earthquake damage from Civil Defence controller Bruce Pepperell.
Mr Key also met Wellington Mayor Celia Wade-Brown and Greater Wellington Regional Council chairwoman Fran Wild.
He was still to get an update on any fiscal impact of yesterday's earthquake but said, in principal, New Zealand could afford to pay for the damage caused by another earthquake.
"There's nothing at the moment that's been advised to me that would indicate there's substantial fiscal risk to the Crown, we know that the Earthquake Commission fund really has nothing in it from the last time I looked at it.
"The Government just backs that up anyway, we have a strong balance sheet - we're in a much better shape than pretty much any OECD country in the event that we need to rely on the Crown,'' Mr Key said.
"We have one of the lowest levels of debt in the OECD.''
Mr Key said the damage from yesterday's earthquake was not on the same scale as the Christchurch quakes.
He would still fly to South Korea this evening for a bilateral meeting with President Park Guen-hye.
"Every trip we take is fluid and in the end we can reassess those and if there was a reason not to go, or not to go to the Solomons on Wednesday obviously we wouldn't go.
"At this point there isn't anything that would stop us doing that.
"I understand completely that Wellingtonians feel anxious and nervous, but all I can say is that we'll be doing the very best we can to make sure that they get the support that they need.
Mr Key said his office in the Beehive was "a bit beaten up''.
"Bottles of wine smashed and a few bits and pieces,'' he said.
Mr Key had not been able to assess the damage to Premier House yet.
Workers told: Stay away from the central city
Wellington City Council is now advising workers to stay clear of the central city for the rest of the day while inspectors continue to assess buildings for earthquake damage.
Earlier, the council had urged workers not to return until noon, however at a press conference this morning, Mayor Celia Wade-Brown said these inspections were taking longer than first thought.
Four people were injured during yesterday's big 20 second-long tremor.
Inspections are continuing around the capital after the long shake, which blew out windows, cracked concrete and caused buildings to sway.
Ms Wade-Brown said building inspectors were making visual assessments of CBD buildings as well as more detailed inspections of council buildings but she said it was up to individual business owners to ensure the safety of their properties.
Did you feel the big quake? Send your story, photos or video here.
15 metre wide chunk of land disappears at wharf
A huge chunk of land fell into Wellington harbour and disappeared during yesterday's magnitude 6.5 earthquake, and the city's harbourmaster fears more damage will occur if the quakes continue.
Mike Price was out this morning assessing the damage, with the south side of the Thorndon Container Terminal worst affected.
"The port's okay, the ferries are operating but the most visible manifestation seems to be up the side of the container terminal where there's a huge chunk of land about 15 metres wide that has just dropped off into the harbour and disappeared,'' he told Radio New Zealand.
"That's a chunk of seawall, half the road, those recreational fishing shelters that were there, all disappeared. Gone.''
The area had been cordoned off.
"The state of some of that road down there, if there's another one this big, that will be gone as well. It's not a good place to stand.''
A shipping container and a large amount of debris had also fallen into the water.
"There's a lot debris - masses of what looks like polystyrene and blocks of timber - floating in the harbour. We put an old oil boom around that last night to hold it all in so it's all still there this morning.''
The container had been tied to the shore.
New Zealand Herald photographer Mark Mitchell said the port was in "a bit of a mess''.
"A huge portion of the reclaimed land has actually collapsed into the sea,'' he said.
"It looks like what a riverbank would if it collapsed.''
600 extra calls to emergency services
Police said it had been a quiet night in the capital.
Acting District Commander Superintendent Sue Schwalger said police maintained a careful watch over the city and resumed normal policing activities shortly after the main cordons were removed.
"I'm pleased to say there have been no arrests for anything related to yesterday's earthquake. Traffic flows into the city are lighter than usual this morning so it is good to see commuters appear to be heeding advice to delay their travel to the city.''
The 111 communications centre at Wellington Central police station received around 600 extra calls between 5pm and 7pm yesterday following the 6.5 earthquake.
Ms Schwalger said extra police were posted in the city overnight and today they would continue to help engineers and council staff as a street-by-street check of the CBD was carried out.
One man was knocked out and received minor injuries after a television fell and another person attached to a medical machine was treated by ambulance staff after being shaken out of bed. Two people were treated in hospital for minor injuries.
The St John communications centre also received a number of calls from people with chest pains and anxiety, although nothing life-threatening.
At Hutt Hospital, a section of ceiling collapsed in the third floor of the community health building and four people were evacuated.
Power was cut during the quakes to 3500 homes but restored within an hour.
Wellington Airport was temporarily closed while a runway check was carried out. All suburban trains were cancelled until further notice and KiwiRail said there would be no bus replacements.
Witness: It was terrifying
April Ferrino was in a fifth-floor apartment on Lambton Quay when the big quake hit.
"I'm from Austin, Texas, so we're used to other natural disasters - tornadoes, hurricanes. Earthquakes are extremely terrifying because you can't predict them.
"Things started falling off the shelves. It was terrifying. I felt the first tremor this morning, which was a slow rumbling ... but this one was a jolt. It was extremely terrifying."
Around the city, several buildings were evacuated after reports of structural damage. At the Mercure Hotel, 76 people were led to safety after the sixth floor partially collapsed.
A police officer at the scene said the building had dropped up to 50mm in the stairwell on the southern side. Police had also moved 140 people from a building behind the hotel and 50 from nearby student accommodation because of fears for the Mercure's "potential collapse".
Leaks force evacuations
About 100 people, including Ahmed Bhari, his wife Azreen and young son Eadayat, were evacuated from The Aitken on Mulgrave apartment block due to extensive flooding.
"It was very scary," Mr Bhari said, "and now my family have moved to a motel for two nights. It really shook, so it was very scary."
Nelson Fernandes, 44, returned to his flat to find it already evacuated.
"There was a major water leak and the whole apartment, seven levels, got cleared out," he said. "It's terrible.
"There was one cafe down below that was totally damaged. It was soaking, all the floors; we had tiles falling off the roof. There is so much damage it is absolutely terrible. I have never felt anything like that."
A burst pipe flooded the Central on Willis apartment of Sunny Gupta, aged 26. "It burst on my level, level eight, and the whole apartment was full of water and we actually had to take our pants off and run through the leaking stuff."
The water spread right down to the ground floor and residents were asked to find other accommodation.
The software engineer spoke of cracks on the walls and fallen roof tiles. Crockery and electronics had smashed. "It was very, very scary."
Sarah Bennett, who lives in a hilltop house, said it was the worst quake she had felt. "You usually only get a bit of a jiggle, but this was a hula dance," she said.
The CBD was temporarily locked down after streets were littered with glass from broken windows. Workers kept people away in case another quake struck and loosened the glass that was left.
The city's library was thrown into disarray as hundreds of books hurtled from the shelves onto the floor, and at the port, a large crack appeared in the concrete.
Quake swarms likely to stick around - expert
The faultline causing the quakes has a history of producing "swarms" and Victoria University professor of geophysics Euan Smith said it was likely the current swarm would continue for some time.
He said yesterday's seismic activity was similar to a swarm of 30 smaller earthquakes which struck Wellington in January 1950.
"They could go on, as the 1950 swarm did for a month. Or they could be all over, though I think that's very unlikely," he said.
Seddon residents inspect damage
Many residents report the inside of their homes are trashed, their chimneys are damaged, and one man says the piles of his house are damaged.
Newstalk ZB reporter Adam Walker is there this morning, and says the most obvious damage has been the rock fall around State Highway 1.
"I've seen about 20 slips from about 40 kilometres outside of Seddon.
"In terms of damage to the township, there's been a number of fallen chimneys, and there's been reports of at least one house that has been severely damaged.''
The aftershocks - which are expected to continue for some days - are something Marlborough Emergency Services Manager Gary Spence says they can not do much about.
"That's just the way it is.
An evacuation centre was set up at the Awatere Rugby Club in Seddon and some people gathered there last night.
A police spokesman there had been some damage and landslips in Seddon township.
"It's kind of strange, because some places are getting quite a major after-shake (sic) and not too far away they're getting nothing.''
Gary Spence expects people will be up early to inspect the damage.
''(They'll) double check their properties and that sort of stuff, and more importantly make sure that they go and look at their emergency kit or a getaway bag.''
Main quake widely felt around country
Chrissie Small, from Blenheim, said she suffered motion sickness during the big tremor.
"Seems there's a quake every four minutes at the moment but they're small ones ... Poor Seddon is bearing the brunt ... I hope it's nearing its end."
People in Napier reported the earthquake as a long shaking, while Gisborne woman Jennifer Cockayne felt it as a rolling sort of quake that seemed "like a wobble rather than a shunt" which left her with an uncomfortable feeling.
Some as far north as Auckland felt the rocking. Manoj Bangia was sitting with friends in a Pakuranga living room when the house started shaking. "We all felt our heads dizzy. [It] lasted for 10 to 20 seconds before we came out of the house."
A couple on the 26th floor at the Metropolis apartments in Auckland's CBD said they also felt the quake as their building started creaking. At first, they thought it was the wind, but because it was a still night they assumed it was an earthquake.
In Canterbury, a resident described the quake as a "lazy roller" that rattled the nerves.
In New Plymouth, Michael Riley said: "It was the biggest earthquake I have ever felt."
Herald: Anna Leask, Amelia Wade, Morgan Tait, Vaimoana Tapaleao, Alanah Eriksen, Isaac Davison, Natalie Akoorie, Audrey Young and Paul Harper.
APNZ: Teuila Fuatai, Kate Shuttleworth, Daniel Richardson.