'Explosive' aftershocks hit weary city

The Community of the Sacred Name centre was damaged in yesterday's biggest aftershock. Photo / Simon Baker

A series of explosive aftershocks near central Christchurch collapsed walls, trapped people in buildings and cut power yesterday.

Jittery residents relived the scare of September 4's 7.1 magnitude earthquake as a large jolt woke them at 2am.

A shallow quake at 10.30am cleared stores filled with Boxing Day shoppers.

The mid-morning aftershock was 4.9 magnitude, the largest since mid-November.

By 7.30 last night there had been 16 aftershocks - nine of which were 3.5 magnitude or above.

The latest aftershocks were a magnitude 4.4 quake at a shallow depth of 3 kilometres just after midnight today followed by magnitude 3.0 aftershock at a depth of 6 kilometres, at 2am both located close to the centre of Christchurch.

Yesterday's shocks prompted bargain-hunters to rush on to central city streets, several blocks of which were later cordoned off because authorities were concerned about unstable structures.

Chris Rudge, who was near City Mall during the shocks, said the successive quakes felt like dynamite being set off 100m below his feet.

"But it wasn't like the quakes in September, where you could hear them rolling in from the countryside. They came without warning, in big thumps, and echoed around the buildings.

"Once the bricks started falling off buildings, and glass was breaking, we moved to the middle of the street. It was not a great feeling, being in the city, and wondering how big the next one would be."

No one was injured, but the Fire Service reported some "life-risk" incidents. In Cashel Mall, doors were jammed by the shocks, trapping people in stairwells.

Heavy masonry broke off Christchurch Cathedral in the heart of the city and fell into Cathedral Square, which was crowded with cruise ship tourists at the time.

Water, wastewater and stormwater networks were undamaged.

Mr Rudge said that despite scientists' warnings that aftershocks would continue for months, the latest quakes wore down residents' spirits.

"When you get a series like this, the same emotions return. My daughter says she doesn't want to sleep in her room again tonight."

Lianne Farquhar was in a changing room in Riccarton Mall when the largest aftershock hit.

When she ran out into the mall, she saw many shoppers rushing for the exits.

"It was quite surreal. People were panicking but it was quiet. They had dropped shopping bags, some were crying, people were looking for people they knew."

The mall had some ceiling damage, and several shops closed to clean up.

Ms Farquhar said the first aftershock in the early hours of the morning "made the loudest sound imaginable". She lived in a third-storey apartment in the city centre.

Two blocks and several individual buildings were cordoned off downtown yesterday, as authorities inspected buildings and shielded people from falling debris. The cordons were gradually reduced in the late afternoon.

The restrictions were a cruel blow for retailers on one of the busiest trading days of the year.

Christchurch City police area commander Inspector Derek Erasmus said: "We understand how much of a disruption this is, but our first priority has to be on making sure people are safe."

Fire Service spokesman Dan Coward said engineers were hoping to complete their inspections by last night.

Officials had been swamped by 200 callouts related to the aftershocks, mostly for alarms that had been set off, but also for gas leaks and small fires.

The worst damage was in Cashel Mall, where an internal wall collapsed and building parapets crumbled.

Power to 40,000 residents in Papanui, St Albans and Fendalton was cut. Orion said it was restored within an hour, with no major damage to its network. Suburban Christchurch was not badly affected.

GNS Science duty seismologist John Ristau said the largest aftershock was shallow and close to the central city and therefore likely to cause damage.

"This one and the sequence after it serve as a rude reminder that the aftershocks continue, and will continue for months."