Key Points:

Gisborne has suffered more extensive damage than initially thought following last night's 6.8 magnitude earthquake.

A state of emergency was declared after the quake, which hit about 8.55pm yesterday and was centred 50km offshore southeast of Gisborne and 40km deep. It was followed this morning by aftershocks measuring 4.2 and 4.5 on the Richter Scale.

Gisborne District Council (GDC) public information manager Vance Walker told NZPA it had been hoped the central business district (CBD) would be reopened by midday but that had not happened.

"The damage has been a bit more extensive than what we initially thought," he told NZPA.

"We've had to revise our target of opening the CBD fully from 12 midday today until probably mid-afternoon."

An apartment building and two shops had partially collapsed, roofs caved in, water tanks and winery vats burst and gaping holes opened up in roadways. Four houses had been damaged, including one under construction.

Only 11 people reported injuries as a result of the quake.

The council confirmed one elderly woman died of a suspected heart attack around the time the quake struck. The Ministry of Social Development was contacting all pensioners within the area to see how they were going. Anyone with welfare concerns could call the ministry on 0800 779 997.

The Earthquake Commission (EQC) had received 167 claims following the quake, and it was expected many more would be received.

EQC insurance manager Lance Dixon said anyone with house or contents insurance automatically had EQC cover, and had up to three months to lodge a claim. He urged people to check their houses for possible damage and said if possible, it was best to take photos before moving anything or tidying up.

"That makes assessment of the claim easier," Mr Dixon said.

"Crockery and glass breakages can be cleared up but don't throw them away yet. Only throw away perishable items."

Insurance Council chief executive Chris Ryan said insurance assessors were on the ground assessing damage, which included structural damage to commercial properties, broken windows, damaged fireplaces and a range of other interior damage.

"While no estimates for the cost of this earthquake have been established yet, it's now clear losses for insured people from this latest Gisborne quake will be significantly less than the 1987 Bay of Plenty earthquake near Edgecumbe which, on inflation-adjusted terms, would have cost $391 million for insured New Zealanders alone," Mr Ryan said.

Initial impressions were that larger, older buildings were the most severely affected.

Meanwhile, Pak'n Save Gisborne owner Hamish Walton estimated stock losses would cost tens of thousands of dollars.

About 75-80 shoppers and staff were in the supermarket when the quake hit, and it was "quite dramatic".

"All of the racking in our stores is designed to move in these sort of situations - but if you don't know that, it can be quite frightening," he said.

"The front of the wine department collapsed onto the floor, but everything that fell was below shoulder level. There was never any danger to anybody."

Pernod Ricard New Zealand, formerly Montana Wines, has three wineries in the area, all of which suffered damage.

"At this stage it is still too early to determine the full extent of the damage. However the vineyards themselves look to be unaffected by the earthquake," managing director Fabian Partigliani said.

"We do know there has been some wine losses and tank damage."