ChristChurch Cathedral appears to have suffered further serious damage in the rash of Friday afternoon Christchurch quakes.

CERA boss Roger Sutton surveyed the city from the air during the afternoon – and he told a 5.30pm Friday press conference that it looked as though the cathedral had sustained further damage.

The Dean of the Cathedral, the Very Rev Peter Beck, said he understands that "some areas have deteriorated significantly."

Clouds of mortar dust were seen rising from the already-severely damaged west end of the cathedral, where the Rose Window once stood.

Dean Beck says there were no workers on the cathedral site when yesterday's jolts came.

He says the extent and consequences of the further damage are not yet clear, and that the Cathedral will remain cordoned off while assessments take place. 

Dean Beck says the diocese will work with CERA to make sure that all the relevant assessments are undertaken as quickly as possible.

"As we've said throughout, our first priority is people's safety. Once we have further information, we'll make sure that our wider Christchurch community is updated."

Meanwhile, Bishop Victoria Matthews has instructed that all Christmas weekend church services in the greater Christchurch area be held outdoors.

Where midnight Christmas Eve vigil services are concerned, she suggested parishioners “BYOT” – Bring Your Own Torch.

Diocesan communication officer Philip Baldwin reports minor damage to a church hall in Kaiapoi.

The first 5.8 earthquake struck at 1:58pm, and was followed by a swarm of powerful aftershocks. The one which struck 80 minutes later, for instance, was rated at 6 on the Richter scale and centred just 10km east of Christchurch.