Mass quake brings New Zealand closer to Australia

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(Xinhua/Agencies)
Updated: 2009-07-23 10:22

WELLINGTON: The 7.8 magnitude quake which was centered in New Zealand's Fiordland appeared to have twisted the South Island out of shape, moving it closer to Australia, scientists said on Wednesday.

The quake last Wednesday night was the largest to strike New Zealand in 78 years.

According to the Land Information's New Zealand-GeoNet global positioning system, the Fiordland town of Te Anau is now 10 cm closer to Australia, Bluff by 3 cm, Alexandra by 2 cm and Dunedin by 1 cm.

The South Island's southwest tip Puysegur Point is 30 cm closer.

Scientists said the South Island will gradually move back to where it was before the quake -- but that process will take hundreds of years.

Aerial inspection of the forested fiords near the quake's epicentre showed few land slips or other signs of damage.

This was partly because the type of rupture at the boundaries of the Australian and Pacific plates meant the energy from the quake was largely directed westwards towards the sea rather than inland towards the nearest towns.

The type of quake, known as a subduction thrust rupture, also meant the quake produced lower frequency shaking, felt as a rolling motion, rather than sharp jolts which would have caused more damage.

New Zealand frequently suffers earthquakes because it marks the meeting point of the Australian and Pacific continental plates.

Earthquake scientist Ken Gledhill of GNS Science said the latest quake may have brought forward a major quake on the offshore section of the Alpine fault, off the coast of Fiordland in the Tasman Sea.

"There could easily be another large earthquake in another part of that region. We can't predict that obviously."

The latest quake was the biggest since February 2, 1931 when a 7.8 quake killed at least 256 people in the North Island city of Napier.

The biggest quake recorded here measured 8.2 and caused major damage in 1855 in the fledgling European settlement that later became the capital Wellington.

The latest quake was unusual in striking right on the boundary of the Australian and Pacific plates and will be important in researching earthquake hazards, Gledhill said.