A severe earthquake, centred near Hanmer Springs, has shaken much of the country and has been followed by numerous aftershocks today.
The Ministry of Civil Defence and Emergency Management this afternoon cancelled the tsunami warning that had been in place since this morning's 7.5 magnitude earthquake.
The quake was 16km deep and struck at 12.02am.
Here's what you need to know:
Clarence River warning
People living near the Clarence River north of Kaikoura were this afternoon urged to move to higher grounds due to concerns the river may breach its banks.
Initial reports from a helicopter flyover have found the river had partially breached, and the volume of water was less than earlier thought.
Tsunami threat
The tsunami marine and beach threat that was in place from Wellington to Banks Peninsula has now been cancelled.
But the Ministry of Civil Defence and Emergency Management said coasts may still experience unusual, strong currents and sea level fluctuations lasting for several more hours.
People are advised to stay vigilant in and around coastal waters.
Rail services, ferry crossings cancelled
KiwiRail says it expects to reopen the main trunk line between Palmerston North and Wellington and its staff have spent the day inspecting Wellington's passenger network.
In the South Island, rail services are running again between Christchurch and Invercargill, but the line between Picton and Christchurch will be closed for several days. The TranzAlpine is not running.
In Wellington, Civil Defence says no trains are running and no buses will replace them today.
Cook Strait ferry sailings have resumed.
Authorities say people should stay away from central Wellington for at least the rest of the day because forecast high winds could dislodge materials from buildings damaged in the quakes.
Tenants of commercial buildings should contact the property owners.
Wellington regional controller Bruce Pepperell says early indications are that a number of major buildings are showing signs of structural stress and there may be a mess and disruption inside some buildings - particularly on higher floors.
The council says no trains will be running and there are no replacement bus services. Inspections are under way of bridges and tunnels around the region.
Schools, universities
The Education Ministry said 276 schools closed out of the 524 in Wellington, Nelson-Marlborough and Canterbury.
In addition Victoria University, Massey University's Wellington campus, and the polytechnics in Wellington, Porirua, and Nelson are closed.
The Ministry of Education said most of them should reopen tomorrow.
NZQA today postponed scholarship exams at all centres.
The Qualifications Authority said students who missed their NCEA exams today or who felt their performance was impaired by the disruption of the earthquakes would be able to apply for a derived grade based on their performance in other assessments during the year.
Road damage 20km south of Clarence Photo: RNZ / Rebekah Parsons-King
Road closures
Road and engineering crews will be working through the night in parts of the upper South Island, assessing earthquake damage to roads and bridges.
An alternative inland state highway route has been re-established between Picton and Christchurch, via Murchison and the Lewis Pass.
The coast road, State Highway 1, north and south of Kaikoura has been badly damaged, cutting off the town.
- SH1 Seddon to Cheviot. Road closed.
- SH7 Waipara to Springs Junction. Road open but the route is down to one lane in places.
- SH7A Springs Junction to Hanmer Springs. Closed overnight but expected to reopen in the morning.
The Hurunui District Council says Rotherham and Waiau are isolated by slips and damage to the Parnassus overbridge.
Several bridges in Marlborough have suffered serious structural damage and have been closed.
Meanwhile, Wellington Airport is open after an inspection showed the runway was undamaged.
Power and phone outages
In North Canterbury, power has been restored to houses in Kaikoura and Hanmer Springs, but 1200 homes in the Culverden and Cheviot areas remain without power.
In Marlborough, about 800 houses are still without power, Marlborough Lines says it hopes to have power restored to most customers shortly. But there are many faults on the lines in the Awatere, Seddon and Ward areas, and road closures will make access difficult.
In the Hutt Valley 1000 homes remain without power, but the power company was hoping they would be be restored about 5pm.
In the capital - initially 25,000 homes - mostly in the Hutt Valley - were without power following this morning's quake.
Wellington Electricity Lines says crews have been working to restore power to homes in the Naenae, Waterloo and Haywood's areas.
On the West Coast about 1800 households are still affected by cuts.
About 30,000 homes across Taranaki, Whanganui, Manawatu and Wairarapa lost power but they are slowly being restored, with only about 1000 still without supply.
Spark says its phone networks in Clarence, Kaikoura, Weld Cone, Waiau and Eltham in the South Island have been affected. People should text rather than call if possible, it says.
Phone networks in Kaikoura and Blenheim are experiencing the most significant connection problems with damage to the landline network and power cuts to mobile cell sites around the area.
Spark is organising for staff to be flown to the affected areas but people may have limited or no access to landline, broadband and mobile services including the 111 emergency operator service for sometime yet.
However, local phone calls and a localised emergency 111 line are available in Kaikoura.
Water
In Kaikoura, which is cut off from the north and south, about three days' supply of fresh water are left.
Residents in North Canterbury are being urged to boil or treat all water before drinking, brushing teeth or using it for food preparation.
The Canterbury District Health Board says that includes water from taps and tankers. It says water can also be treated by adding just under a quarter of a teaspoon of household bleach per 2 litres of water and leaving for 30 minutes.
People are being urged to avoid contact with waterways and surface that may be contaminated with sewage.
People in Havelock are being asked to conserve water due to a power cut at the pumping station. Picton residents are asked to conserve water as one of the town's reservoirs is leaking.
A precautionary boil water notice has been issued for all residents of the Hurunui District.
People in Raglan in Waikato are also being advised to boil their drinking water for the next three days after the town supply became discoloured following the quake.
And residents are being advised to continue conserving water; only using it for drinking.
Help centres, welfare
Bad weather is hampering the delivery of supplies by helicopter into Kaikoura this evening.
Civil Defence national controller David Coetzee says flights have now been stopped and he expects them to resume in the morning.
However, the Defence Force is sending a ship to evacuate tourists and residents in Kaikoura, and to bring aid supplies to quake-affected areas.
HMNZS Canterbury will sail to Kaikoura overnight from Auckland, picking up supplies on the way.
The vessel should arrive at Kaikoura by Wednesday, but this depends on the weather and stopover times.
About 100 people are expected to spend the night in the evacuation centre in Kaikoura.
Sir Mark Solomon, the Kaiwhakahaere of Ngāti Kuri in Kaikoura, says anyone in the area who needs shelter or food can head to Ngāi Tahu's Takahanga Marae.
Health Minister Jonathan Coleman says local health services are coping well. He says the new Kaikoura hospital, known as Kaikoura Health, hasn't been damaged by the severe quake and aftershocks.
The Nelson Marlborough District Health Board says inspections have shown that hospitals in Nelson and Wairau are safe and services are running normally, but encourages people to contact their GP initially if they have any health concerns.
It says the Marlborough Health Hub in Blenheim sustained some damage and its services are now being provided at Wairau Hospital. Some pharmacies in Blenheim are closed today but those in Picton and Nelson are open as usual.
Federated Farmers is encouraging people in rural areas struck by the earthquake to ring 0800 FARMING so that they can get a clearer idea of who needs help.
WorkSafe is urging businesses to have their premises checked if they notice cracks in buildings as a result of this morning's earthquakes.
The Insurance Council is urging property owners to report damage after the earthquake and include photos of any damage to contents and property with their claim.