DOC staff flew into Fiordland National Park at first light to check on registered trampers and one-day visitor structures before focusing on the quake's epicentre and surrounding huts and tracks, Te Anau acting area manager Andrew Cudby said.

The trampers were leaving the park on foot and were expected out at some stage today, Mr Cudby said.

There had been some slips but no major damage, and the ground would be monitored over coming months.

Visitors to the park should report any ground or slip concerns, he said.

DOC staff in the field had been contacted and were unharmed.

The controller of Southland's civil defence emergency management group, Neil Cruickshank, activated the region's emergency operations centre to assess damage reports and said the region had been given "a good shake" .

"Phone services were down in east Invercargill and power was out for some time in the suburb of Otatara because of the earthquake," he said.

Civil Defence staff flew over the epicentre today but found little damage.

They would continue to monitor and assess the aftermath, he said.

Mr Cruickshank said anyone worried about the structural integrity of their building should contact their local council.

More than 14,000 earthquakes are recorded in New Zealand annually, but only about 20 are stronger than 5 on the Richter scale.

The Inangahua earthquake on the West Coast in 1968 measured 7.1 and killed three people.

The previous strongest recorded Fiordland earthquake, near the mouth of Doubtful Sound in August 2003, measured 7.1 and caused considerable damage in Te Anau.

The Earthquake Commission received almost 3000 claims totalling $10.5 million.

- NZPA