Two families at a welfare centre in the Christchurch suburb of Linwood are battling gastroenteritis with health authorities concerned the infection was due to contaminated water.

Nearly 100 aftershocks have hit so far hit the Canterbury region, and an expert is warning the biggest one could still be to come.

Slips and surface flooding are causing havoc for motorists in the lower North Island as heavy rain and gale force winds sweep the region.

Tracking today's events as they happen on Day Three of the Christchurch earthquake disaster.

John Key today said an estimated 100,000 homes were damaged by Saturday's 7.1-magnitude earthquake - nearly half of all dwellings in the Canterbury region.

In Christchurch, everyone has a story to tell. When the quake hit at 4.30am on Saturday, many turned to social media. Read their stories.

This afternoon's 4.5 magnitude aftershock has pushed a number of damaged Christchurch buildings over the edge, including one housing a leading radio news network.

Many central city businesses cannot open until the damage from the earthquake is fully assessed, and some workers are worried about losing pay.

Anyone caught looting in the wake of Christchurch's devastating earthquake would be harshly treated by the courts, a judge warned today.

Saturday's earthquake could prove to be the tipping point for some businesses already squeezed by the recession, a Christchurch business leader says.

A severe heavy rain and gale weather warning is in place for much of the country as widespread flooding affects farmers.

There have been nearly 5,000 insurance claims made already as a result of the Christchurch earthquake, says the Earthquake Commission. Here's how to make a claim.

About 60 streets across Christchurch are still without water this morning as aftershocks continue to shake the city after Saturday's earthquake.

The emotional trauma of the Christchurch earthquake may not surface for weeks or even months, says a psychologist.

It wasn't just humans shaken by the big quake - hundreds of terrified pets fled during the tremors.

Savage winds battered Canterbury this morning as the province only just begins to pick itself up after Saturday's devastating earthquake.

Chris de Freitas says risk-management planning can help society in practical and economic ways.

The abiding memory of Xavier Trousselot-Rhodes before an earthquake threw him out of his second-storey bedroom was of the house screaming.

The Christchurch earthquake took scientists by surprise, as it revealed a new faultline in a territory not known for seismic activity.