July 16 (Bloomberg) -- New Zealand escaped serious damage after a magnitude-7.8 earthquake struck off South Island, triggering a tsunami alert that extended to Australia.

The quake, which hit at 9:22 p.m. local time yesterday, was the largest since 1931, when a temblor the same size on North Island killed 256 people, the largest loss of life from an earthquake in the country’s history, seismological monitor GeoNet said.

“We’ve got really minimal damage,” Sergeant Brock Davis of Invercargill Police said by telephone today. Power lines came down in the city of 50,000 people, which lies 150 kilometers (93 miles) southeast of the epicenter, and a water main burst in the nearby town of Winton, he said.

The tsunami warning was in force for about 2 1/2 hours in New Zealand and canceled after a wave measuring 17 centimeters was recorded, according to the government’s GNS Science research group. Australian authorities issued emergency warnings for coastal areas in the states of New South Wales and Victoria.

On Lord Howe Island, 770 kilometers northeast of Sydney, about 125 people were evacuated to higher ground, Greg Pierce, acting chief executive officer of the island’s administrative board, said by telephone.

“We managed to relocate people who had been evacuated to lodges and private homes,” Pierce said. Lord Howe has about 350 permanent residents and can host a maximum of 400 tourists at a time, he said.

A theater performance at the pavilion next to Sydney’s Bondi beach was canceled last night because of the tsunami warning.

Threat Passed

Australia’s Bureau of Meteorology said, although the main tsunami threat has passed, “small unusual waves and currents and abnormal tides may still affect some beaches, harbors and coastal waterways for many hours or even days.”

The United Nations helped develop an improved international warning system with strategically placed buoys after a magnitude 9.1 earthquake off the coast of Aceh in northern Sumatra in December 2004 triggered a tsunami that devastated coastal communities in countries across the Indian Ocean, killing more than 220,000 people.

Yesterday’s quake struck at a depth of 12 kilometers, according to the U.S. Geological Survey. It put the magnitude at 7.6, 0.2 lower than the measurement provided by GeoNet.

Shook Buildings

The temblor shook buildings as far away as Christchurch, the biggest city on the South Island and 532 kilometers to the northeast of the epicenter.

It was followed by at least seven aftershocks, including a magnitude-5.4 quake at 11:44 a.m. local time, the USGS said.

The region closest to the epicenter is sparsely populated forest and bushland, Sergeant Davis said. Civil defense officials will check the area for landslides, he added.

The Department of Conservation advised hikers planning a trip into the Fiordland National Park to wait until teams have checked on potential damage to huts, bridges and roads.

Meridian Energy Ltd.’s Manapouri Power Station near the epicenter was operating normally after the earthquake, company spokeswoman Claire Shaw said by telephone late yesterday.

Rio Tinto Plc’s Tiwai Point aluminum-smelting plant on New Zealand’s Tiwai peninsula wasn’t affected by the quake, General Manager Paul Hemburrow said.

To contact the reporters on this story: Ed Johnson in Sydney at ejohnson28@bloomberg.net; Heather Langan at hlangan@bloomberg.net.

Last Updated: July 16, 2009 01:16 EDT