A series of large earthquakes has jolted the South Island.
A quake measuring 6.7 on the Richter scale struck early this morning, followed by aftershocks, including a fifth measuring 6.2 at 10.28am.
The fifth one was 50km west of Milford Sound and at a depth of 5km.
There were 287 reports of the quake on the GNS website within half an hour of the quake and it was felt from Westport to Dunedin.
Claire Hesselin was at work in central Dunedin when the quake happened, knocking over water bottles and gently swaying the lights.
"Some people felt it and some people were oblivious," Ms Hesselin said.
She said the quake lasted for about 20 or 30 seconds.
The other quakes measured between 4.6 and 4.9.
Seismometres will be installed in Fiordland to measure the size, depth and aftershocks of today's quake.
GNS Science seismologist Bryan Field said aftershocks could continue for several weeks after a large earthquake.
"This looks to be a particularly rich aftershock sequence that should yield useful information about stresses in the earths crust in the Fiordland region," Mr Field said.
He said there were dozens of aftershocks with half-a-dozen big enough to be felt widely in the southern part of the South Island this morning.
The first quake was felt strongly but there were no immediate reports of damage or injury.
GNS Science duty seismologist Mark Chadwick said the quake, which struck at 1.29am, was centred 60km from Milford Sound at a depth of 24km.
"Fortunately it's slightly offshore from Fiordland so there's not too much infrastructure down there to damage," he said.
A 4.6 magnitude aftershock followed at 2.50am.
Like the initial quake it was centred 60km west of Milford but was shallower, at a depth of 5km, GNS Science said.
There was no tsunami risk to New Zealand from this morning's earthquakes.
The quake has been reported by 580 people on the GNS website. Reports have come in from as far north as Ashhurst in the Manawatu.
John Hamilton, director of the Ministry of Civil Defence and Emergency Management, said the ministry had received information about the earthquake from the Pacific Tsunami Warning Centre (PTWC) in Hawaii and GNS Science in New Zealand.
PTWC issued a bulletin stating that there was no tsunami risk to Pacific coastlines and GNS Science confirmed there was no localised tsunami.
Southland Civil Defence officer Tom Shaw said civil defence staff at Milford had inspected the area as thoroughly as was possible in the dark immediately after the quake and there were no signs of damage to buildings or structures.
However, the earthquake was felt very strongly in that area as well as across the region and further afield, he said.
Invercargill Civil Defence officer, Bill Obers, said he had not received any reports of structural damage in the immediate aftermath of the quake.
Staff from the Southland Civil Defence Emergency Management Group were also monitoring the situation.
Milford Sound Development Authority operations manager Dave Inwood said he was at the Freshwater Bay visitor centre when the fourth 6.2 aftershock struck just before 10.30am.
The centre was busy with tourists waiting to take cruises on Milford Sound or sightseeing trips, but no one took much notice, Mr Inwood said.
"I'm not sure if the tourists thought they were on a floating structure or not, but nobody showed any interest in moving," he said.
"We all just stood there and watched as the building shook. It was just very gentle."
Mr Inwood said a number of Milford tourism managers were out at 1.30am to check for damage to buildings and equipment.
"But there was no damage to buildings and no threat to life and limb," he said.
Mr Inwood described the first quake as "just a good shake" throughout the Milford area.
"It's certainly rock and roll here today."
Transit New Zealand Central Otago area engineer John Jarvis said contractors were out inspecting roads and bridges in the area shortly after the quake and noticed "nothing significant".
Mr Jarvis said there may have been the "odd rockfall" and contractors would clear debris as it was reported.
"We've got people out on the road doing regular inspections, but we haven't got any reports of any significant damage at all," he said.
A spokesman from the police southern communications centre in Christchurch said police had received calls from many people in the lower South Island since the quake, but no damage or injuries had been reported.
GNS Science said the magnitude was preliminary at this stage.
"It's a tricky business with large earthquakes," Mr Chadwick said.
"The problem we have is that we're too close, so when we estimate magnitudes we're using data that's coming from nearby instruments and sometimes the shaking is so much that they can overload."
The US Geological Survey had recorded a magnitude of 6.8 for this morning's quake.
Mr Chadwick said the final magnitude was likely to be between 6.6 and 6.8.
YOUR EXPERIENCES OF THE QUAKE:
I'm staying in a close-to-downtown hotel in Queenstown, on Frankton Road. I woke up at 1.32 am with the bed rocking quite hard, and shifting noises - cracking sounds - in the room. There was, however, no damage). It lasted over a minute, then some very minor movement until five minutes later when there was more quite strong movement, though not as strong as the first time). My first ever reasonably big earthquake (I'm not a Kiwi) - very exciting!
- Tanya Tintner
While most people weren't affected too much by the earthquake I had an interesting experience in the early hours of this morning. I am in my third trimester of pregnancy and was unable to stop my belly from wobbling around when the quake hit. My baby's response was to kick me as much as possible. I wouldn't be surprised if the rumblings would've been enough to send a few woman into the early stages of labour.
- with NZPA