KEY POINTS:
Vulcanologists are warning tourists and other visitors that a shallow quake close to White Island early today means they should stay away from the island this weekend.
Two significant tremors in the early hours of the morning were followed by one of the biggest quakes felt in the area for some time: a 5.4 magnitude shake at 9.06 am, centred 10km southwest of the volcano and just 5km deep.
In Tauranga, workers in multi-storey buildings described a "slow and rolling" quake which made the buildings sway.
"There has been no immediate response from the volcano," said GNS Science volcano surveillance co-ordinator Brad Scott.
But the large number of aftershocks meant that any seismic response might be difficult to see for several hours.
"We would recommend no visits to the island for the next 48-72 hours," he said.
"The potential for eruptive activity will be higher during that period."
After that period, the risk level might fall.
He said today's quake was a tectonic type earthquake - common in the outer Bay of Plenty. Weak volcanic tremor and low frequency volcanic earthquakes are both common at White Island, which is New Zealand's biggest volcano.
On Thursday afternoon there was a 3.7 magnitude quake 10km north of Gisborne.
If today's quake was followed by increased volcanic activity, there was likely to be an increase in gas output, and scientists might fly over the island to check on the emissions.
The active crater at White Island is occupied by a crater lake that formed during eruptions over the past 40 years.
The last White Island eruption, in 2000, occurred from a vent that is now beneath the lake.
Between 1976 and 1993 White Island was more active than at any time in the past few hundred years, and ash from its 1998 eruptions was recorded as far inland as Rotorua.
Sited 48km offshore, the island has been built up by continuous volcanic activity over the past 150,000 years, and though about 70 per cent of the volcano is underwater, it is the largest volcanic structure in New Zealand.
More than 10,000 people visit White Island every year with four helicopter operators taking visitors to the island from Rotorua and Whakatane. Some launch operators, mostly based in Whakatane, run charter trips to the island.
An internet camera trained on the island's crater can be seen here
- NZPA
