Christchurch was "inevitably going to be brought to its knees" by an earthquake because of the nature of the ground it stands on, a scientist says.

Some residents in the earthquake zone may be without power until the end of the week, says lines company Orion.

"It's essentially a ghost town. You can see utter devastation," said Prime Minister John Key.

The Herald's photographers have captured amazing scenes from the aftermath of September 4's magnitude 7.1 earthquake.

Audrey Young visits one of Christchurch's oldest houses, and finds it still standing.

Weather analyst Philip Duncan gives his account of the Christchurch earthquake.

Readers' photos from the aftermath of Saturday's magnitude 7.1 quake. Click here to send us your pictures and video

"It was like a giant had picked up our house and was just shaking it, shaking and shaking," said one resident.

The 7.1 magnitude tremor that shook the South Island caused the most damage since the 1931 earthquake that flattened Napier.

The displaced of Christchurch were last night in makeshift shelters across the city, fearful of waking up again to more violent tremors.

They were partying, working, sleeping - then came 90 minutes of terror they will never forget. This is their story.

Kyle Scott and Liz Blatch still had their wedding at Darfield's Oak historic homestead only hours after the 7.1 earthquake.

A formal curfew is now officially in place in the Christchurch central business district until 7am and those who breach it may be arrested, say police.

Geologists say today's earthquake had an epicentre 10km south-east of Darfield, but so far they have not been able to link it to a known fault line.

Prime Minister John Key has completed a flyover of Christchurch in order to assess the damage wreaked by this morning's earthquake.

Residents of Darfield - the epicentre of the quake - share their stories of what it was like when the big one hit.

Looming bad weather and a fear that electricity may be out for days is worrying Canterbury farmers in the wake of this morning's quake.

Photos from the 7.1 magnitude earthquake in Christchurch this morning.