A magnitude 6.8 earthquake hit the east coast of the North Island on Thursday night sending tremors up and down the country.
Warwick Smith from GNS Science says the earthquake struck at 8:55pm and was centred below the ocean 50 kilometres south-east of Gisborne, at an equidistance between Gisbourne and Mahia.
He says although it was a large magnitude, it was located offshore at a depth of 40km and the effects are not as significant as they could have been.
The tremor was felt as far south as Christchurch but most reports came from around Hawke's Bay.
There were reports of damage in the CBD with roofs caving in but there are no known casualties.
Shortly after the quake the Director of the Ministry of Civil Defence & Emergency Management, John Hamilton, said that the National Crisis Management Centre had been activated to monitor the situation in Gisborne and assess if government assistance is required.
Police and the Gisborne council are continuing to ascertain the extent of the damage.
Council spokesperson Vance Walker says it appears that damage is light, mainly to roofing columns and interruption to power supplies.
The earthquake was described by Walker as a series of sharp shocks, a lull and then more shocks.
One resident told ONE News reporter Beth Roche that the jolt was so big that her husband fell over.
Following the quake the roads were reportedly packed with traffic and locals were advised to stay where they were, unless injury, occurred so as to allow emergency services ease of access around the city.
Gisborne Hospital reported minor water damage.
The hospital is functioning and able to receive and admit patients. No patients were injured during the earthquake and all patients are safe.
The hospital has opened a call centre for anyone with concerns and is advising anyone with minor injuries to see their GP rather than go to the hospital.
Phone communications were also severely affected. As of late Thursday night Telecom said its full system was not yet operational, but was working on restoring it fully.
Some cellphone sites are running off battery power, and any earlier overloading problems have eased.
The standby sewerage system has kicked in and the council has advised that water is still working and can be accessed by the public. However, Civil Defence says as there is a likelihood of aftershocks, residents should turn off their electricity, water and gas as a precaution.
Being close to the sea many Gisborne residents were concerned about the risk of Tsunami and many fled to high ground.
However, the GNS Science convened tsunami expert panel has assessed the data received and there is no evidence of a tsunami having been generated.
Thursday night's earthquake follows a 4.1 magnitude tremor which struck 10 kilometres north of Matata in the Bay of Plenty overnight on Wednesday.
This smaller, shallower quake was also felt in Whakatane, and at Lake Rotoma.
New Zealand scientists record around 14,000 earthquakes a year, of which around 20 top 5.0 on the Richter scale.
The last fatal earthquake was in 1968 when an earthquake measuring 7.1 on the Richter scale killed three people on the South Island's West Coast.