Hundreds of survivors stranded by a huge earthquake that struck central New Zealand three days ago reached Christchurch on a naval ship early on Thursday, as engineers in the capital, Wellington, assessed the state of dozens of damaged buildings.

About 450 tourists and residents from the small seaside town of Kaikoura were taken by the New Zealand navy's multi-role vessel HMNZS Canterbury to Christchurch, the South Island's largest city, overnight.

Most tourists had continued their journeys, but about 130 people were being housed temporarily in Canterbury University's student halls.

A student volunteer army, formed after a 7.8 magnitude tremor that killed 185 people in Christchurch in 2011, had mobilised to help the evacuees, university spokeswoman Margaret Agnew said.

"They've set up to feed people, house people, they've got all the facilities they need," she said.

"We've set them up with Wi-Fi, that was one of the things they were asking for."

Kaikoura, a fishing community and popular whale-watching base ringed by steep mountains, had been completely cut off by large landslides that covered road and rail links.

Air Force NH90 helicopters joined a fleet of private helicopters that have ferried hundreds more people from the town to Christchurch and outlying areas 150 kilometres south over the past two days.

Workers cleared an emergency inland road into Kaikoura, allowing water and other supplies to be trucked in for the first time.

Two people were killed and dozens injured by the magnitude 7.8 quake - two nearly simultaneous tremors that ruptured fault lines across the top of the ruggedly beautiful South Island.

The timing of the quake - shortly after midnight on Sunday - combined with the epicentre being in a sparsely populated region prevented a higher toll, authorities said.

A tsunami alert that followed sent many rushing for higher ground before the threat was lowered.

In Wellington, authorities said as many as 60 buildings had suffered structural damage, including properties housing Statistics New Zealand and the Defence Force.

Another multi-storey building near the Parliament complex would have to be taken down, engineers said.

Wellington is bisected by several fault lines, and large areas of its business district are built on reclaimed land, raising questions about building practices in the capital, despite some of the world's strictest codes.

"There are some sites that are really not suitable for certain types of structures. For example, I would seriously question putting a hospital or essential services on reclaimed land," Paul Campbell, the president of the New Zealand Structural Engineering Society, told Radio New Zealand.

The force of the tremor was most evident in the upper South Island, where parts of the coast moved metres and geological features were altered.

A popular New Zealand fur seal colony near Kaikoura, where pups could often be seen playing in a waterfall in a nearby stream, was destroyed by a landslide, Department of Conversation officials said.

A team of volunteers rescued thousands of abalone, a large shellfish known locally as paua, that had been left high and dry when sections of the rocky coast were shunted metres out of the water by the force of the quake.

Civil Defence warned people to stay away from the Hapuku and Ure rivers, further north, where landslides from the earthquakes had blocked the rivers.

"There is a 150 metre high dam caused by the earthquakes which could rapidly fail, spilling water and debris from the new 'lake' over (or through) the dam due to heavy rain and building pressure," Civil Defence Canterbury said on its Facebook page.

Storms lashed the region on Thursday and seismologists were still recording hundreds of aftershocks: about 2000 have rattled the region since the initial tremor shortly after midnight on Sunday.

The New Zealand government has announced a $7.5 million wage subsidy to help quake-hit businesses in and around Kaikoura.

The announcement comes after Prime Minister John Key expressed fears about the impact of the earthquake on the tourist town, with State Highway 1 likely to be out of action for months.

Economic Development Minister Steven Joyce said the road was "unlikely to open for many weeks and possibly months", stranding the business sectors of Kaikoura and other small towns in the area.

"On top of that, the earthquake has had a massive negative effect on the fisheries industry in the district. It is clear that if we don't move quickly, much of the employment in the area will dry up."

Reuters, stuff.co.nz