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.

Craters opened up at a Kaiapoi motorcamp during this morning's earthquake, with caravans sinking up to their axles.

The cost of damage from today's devastating quake could be as much as $2 billion, Earthquake Commission chief executive Ian Simpson says.

An historic pub in the South Canterbury town of Temuka has been badly damaged by today's earthquake and the proprietor is unsure when it will reopen.

It struck in the wee small hours, a rumbling roar and intense swaying that lasted for the best part of a minute.

Christchurch Mayor Bob Parker says there is "significant structural damage" to his city after this morning's 7.1 quake, with some eastern suburbs facing possible evacuation.

Vodafone is advising customers in Christchurch to keep cellphone calls sort, or preferably use SMS messages.

The magnitude 7.1 earthquake which struck Christchurch about 4.30am today rates among the top dozen to hit New Zealand.

Christchurch residents are recounting terrifying ordeals during this morning's 7.1 magnitude earthquake.

Read the 10 things you should (and should not) do after an earthquake has hit your area.

Hundreds felt a 'sharp, short jolt' which has reportedly caused some damage in Whanganui.