Christchurch hit by new earthquakes

Dust rises from rocks falling from a cliff in the Christchurch suburb of Sumner moments after the earthquake struck (Reuters)

A series of strong earthquakes struck Christchurch, New Zealand, today, rattling buildings, sending goods tumbling from shelves and prompting terrified Christmas shoppers to flee into the streets.

There was no tsunami alert issued and the city appeared to have been spared major damage.

One person was injured at a city mall and four people had to be rescued after being trapped by a rock fall, police said.

But there were no immediate reports of serious injuries or widespread damage in the city, which is still recovering from the devastating February earthquake that killed 182 people and destroyed much of the central city area.

The first 5.8-magnitude quake struck in the afternoon, 16 miles north of Christchurch and 2.5 miles deep, the US Geological Survey said. Minutes later, a 5.3-magnitude aftershock hit and about an hour after that, the city was shaken by another 5.8-magnitude temblor. Both aftershocks were less than three miles deep.

The Pacific Tsunami Warning Centre did not issue an alert.

The city's airport was evacuated after the first quake and all city malls shut down as a precaution.

Warwick Isaacs, demolitions manager for the Canterbury Earthquake Recovery Authority, said most buildings had been evacuated "as an emergency measure".

The area has recorded more than 7,000 earthquakes since a magnitude-7 quake rocked the city on September 4 last year. That quake did not cause any deaths.

Rock falls had occurred in one area and there was liquefaction - when an earthquake forces underground water up through loose soil - in several places, Mr Isaacs told New Zealand's National Radio.

"There has been quite a lot of stuff falling out of cupboards, off shelves in shops and that sort of thing, again," he said.

Mr Isaacs said his immediate concern was for demolition workers involved in tearing down buildings wrecked in previous quakes.

"It ... started slow then really got going. It was a big swaying one but not as jolting or as violent as in February," resident Rita Langley said.

"Everyone seems fairly chilled, though the traffic build-up sounds like a beehive that has just been kicked as everyone leaves (the) town (centre)."

The shaking was severe in the nearby port town of Lyttelton, the epicentre of the February 22 quake.

"We stayed inside until the shaking stopped. Then most people went out into the street outside," resident Andrew Turner said. "People are emotionally shocked by what happened this afternoon."

About 15,000 homes were without power after electricity lines were felled in the city's eastern suburbs. Sewage services were also cut. Hundreds of miles of sewer and fresh water lines have been repaired in the city since the February quake.

One partly-demolished building and a vacant house collapsed after today's quakes, police said.

Central City Business Association manager Paul Lonsdale said the quakes came at the worst possible time for retailers, with people rushing to finish their Christmas shopping.

Despite the sizeable quakes, there was no visible damage in the central business district, where 28 stores have reopened in containers after their buildings were wrecked by the February quake, he said.