A cliff has collapsed near the Christchurch beach suburb of Sumner following a 5.7 magnitude quake, but there are no reports of serious injuries.
The quake struck shortly after 1pm today and was initially reported as 5.9 magnitude by GeoNet. GeoNet rates the quake as severe.
St John district operations manager Canterbury Dion Rosario says shortly after the quake it began to receive a sharp increase in calls. That has since returned to normal.
Mayor Lianne Dalziel says cliffs collapsed at Whitewash Heads, Sumner and on Wakefield Ave on the eastern side of Richmond Hill.
"What we have to take from this is our city is stronger than it was five years ago and it's better able to respond," Ms Dalziel said.
Ms Dalziel says people will feel vulnerable.
"It really is a real set-back psychologically for the city," she said.
Prime Minister John Key said it was good news there was no loss of life or injuries.
He said the new buildings in Christchurch are stronger and people should not be concerned the quake was a whole knew thing in its own right. It was connected to the previous quakes.
There should be a very high confidence for Cantabrians but it's a very sharp reminder for them, he said.
Christchurch Hospital reports no increase above normal in patients and it's checking minor damage to its buildings.
It's moving mothers and babies from Burwood Hospital in the eastern suburbs as a precaution.
Pictures have emerged of a cliff face crumbing into the sea at Sumner Beach.
A spokesman for Sumner Surf Life Saving Club says roads along the beach front and across to the popular surf beach Taylors Mistake initially remained open, and he had not heard reports of anyone injured by falling rubble.
Both surf clubs intended to form a sea patrol to check no boaties or walkers had been caught by falling rubble around the cliffs.
Everyone was "a bit freaked out", he said.
Sumner was badly hit by the 6.3 magnitude February 22, 2011 quake, and three people died there out of the city total of 185.
Shipping containers are still used to protect the main access road to the suburb from falling rubble.
Shopping malls and the university were evacuated as a precaution. The Press building on Gloucester St was evacuated, after items fell over and computer monitors smashed. Two people died in the former Press building in the 2011 quake in the city.
This quake was centred 15km east of Christchurch and was 15km deep - with people as far north as Palmerston North and as far south as Dunedin reporting they felt it.
The unwelcome quake comes just a week out from the fifth anniversary of the 6.3 magnitude February 22, 2011 quake that killed 185 people.
St John ambulance said while they had not received reports of serious injuries or damage, a number of people had fallen in the quake.
Minor damage has been reported in New Brighton, including flooding and power lines pulled from a house.
GeoNet spokeswoman Anna Kaiser said the quake was centred slightly offshore and was to the east of a sequence of quakes since the so-called Darfield quake damaged Christchurch.
She said quakes had been progressively moving eastwards and this one was centred in a similar spot to a quake in December 2011.
"Absolutely they're linked to the earthquakes five years ago. This earthquake is certainly part of the same thing," she said.
She said there would be many aftershocks because today's quake was shallow.
There had been landslides and liquefaction reported, she said.
The fire service says the liquefaction is at Pines Beach.
Orion Energy says about 500 customers lost power in northeast Christchurch and Piper Valley on Banks Peninsula. The fire service had advised people to stay off roads and avoid non-essential travel. Numerous crashes were reported to police.
The city has experienced aftershocks, with a 3.5 magnitude quake and a 3.0 quake recorded shortly after. A magnitude 4.0 aftershock was recorded after 6pm and scientists say there is a 50 percent chance of another quake above 5.
People trying to contact loved ones had been concerned as phone systems were overloaded. Telecommunications company Spark said it had 10 cellphone sites out in the city following the quake.
"Grabbed the TV to stop it falling, books off, car alarms set off by it in the neighbourhood," Belinda McCammon tweeted.
Shaun Rolston of marquee and event hire company Happyhire says he was in the middle of a wedding consult when the earthquake hit.
"I was not in New Zealand during the last big ones," he says. "Things were falling over everywhere, nearly had the speaker system fall on us – very scary."
Other people reported roof tiles falling off a building and goods fallen from shelves.
"Suddenly the air all full of sirens and birds," another person tweeted.
Flights out of Christchurch Airport have not been affected by the quake.
The Lyttelton Tunnel, which links the city to its port, has been checked and is open. The airport has remained open.
An NZTA spokeswoman says all highways remain open and bridges have been checked.
The quake did not stop Lydia Ko's progress towards the defence of her New Zealand Women's Open golf title.
Ko was just 10 minutes from teeing off in the final round of the event at Clearwater Resort when the quake rumbled for 10 to 15 seconds.
Denmark's Emily Pedersen responded to the quake by making an eagle on the par-5 second hole.
There is no tsunami threat to New Zealand, according to the Ministry of Civil Defence and Emergency Management.
Newshub. / NZN