The Sunday evening quake injured two people, opened up sinkholes in the quake-prone country and damaged some buildings.
The U.S. Geological Survey said the quake, trailed by at least two smaller aftershocks, was centered in the Cook Strait at a depth of about 10.5 miles, about 34 miles south-southwest of Wellington, between New Zealand's northern and southern islands. The capital lies on the boundary between the Pacific and the Australian tectonic plates.
Wellington Mayor Celia Wade-Brown warned residents to be careful and "expect disruption," CNN reported.
"On the whole, most infrastructure and most buildings have been unaffected -- but we will obviously have engineers and experts double-checking the condition of infrastructure after daybreak," Wade-Brown said in a statement Monday.
The BBC reported the quake also damaged Wellington's Parliament building. Officials said there was no risk of a tsunami.
The report quoted a Wellington resident that there were some power cuts in the city and in nearby suburbs.
The New Zealand Herald, quoting experts, said the damage in Wellington could have been worse but did not rule more aftershocks as the fault line causing quakes in Cook Strait has a history of producing "swarms" of quakes.
"In general New Zealand is very resilient to this type of earthquake. This type of shaking occurring in other countries with very brittle buildings might have caused a lot more mayhem than today," one expert told the Herald.
In February 2011, Christchurch on the South Island, the country's second largest city, was devastated by a 6.3-magnitude earthquake in which 185 people died.