Quake and tsunami near Tonga

A 7.8-magnitude earthquake struck central Tonga this morning, creating a local tsunami which may have caused damage.

Although there are few reports from Tonga so far, a small tsunami of less than half a metre was observed at Niue (east of Tonga) and at Pago Pago in American Samoa (north of Tonga).

There were initial warnings that a tsunami could affect New Zealand, Fiji and Hawaii, but all warnings have now been cancelled.

It was not immediately clear what damage was caused by the quake but a report on Sky Television said it was felt in several Tongan islands. A resident told Sky he felt tremors lasting over 30 seconds.

The quake hit 170km northeast of the Tongan capital Nuku'alofa at 3.26am (NZT), at a depth of 38km, the New Zealand Institute of Geological and Nuclear Sciences (GNS) said.

The epicentre was near the Ha'apai islands in central Tonga, approximately 2150km northeast of Auckland.

The quake was reported by GNS as magnitude 8.1, but the Pacific Tsunami Warning Centre in Hawaii later said it measured 7.8 on the Richer scale.

The Tsunami Warning Centre issued warnings for countries in the region at 3.42am, saying at the time it did not know whether the quake actually generated a tsunami. If it did, it could have hit Fiji at 5.13am and Gisborne at 6.21am.

The Centre later cancelled all warnings, and said New Zealand would likely experience half-metre swells only.

Niue registered a 0.21m wave at 4.03am and Pago Pago registered a 0.15m wave at 4.36am, according to data on the Tsunami Warning Centre website.

A message posted on the website at 5.36am said:

"Sea level readings indicate a tsunami was generated. It may have been destructive along coasts near the earthquake epicentre. For those areas - when no major waves are observed for two hours after the estimated time of arrival or damaging waves have not occurred for at least two hours then local authorities can assume the threat is passed.

"Danger to boats and coastal structures can continue for several hours due to rapid currents. as local conditions can cause a wide variation in tsunami wave action the all clear determination must be made by local authorities.

"No tsunami threat exists for other coastal areas in the Pacific although some other areas may experience small sea level changes."

- NZPA, REUTERS, NZHERALD STAFF