Specialised search teams tunnel through the darkness to find survivors of the quake.

The level of liquefaction after Tuesday's 6.3 magnitude aftershock dwarfs the amount caused by the original earthquake that hit Christchurch in September, Mayor Bob Parker says.

A 52-year-old man is in a stable condition after having both legs amputated by a visiting surgeon at the PGC building.

Police have delayed releasing the names of those confirmed dead and for whom there are serious concerns.

There is no possibility of survivors in the rubble of the Christchurch Cathedral, police said this afternoon.

Rescuers have found no survivors at two Christchurch CBD buildings where signs of life were reported this morning, the Fire Service says.

The family of a woman feared dead in the earthquake has suffered another cruel blow with her home being burgled while her children waited for news.

Search and rescue staff are moving into the suburbs of Christchurch looking for the dead and injured from Tuesday's earthquake. The official death toll this morning stands at 72.

Prime Minister John Key has not ruled out imposing an earthquake levy similar to the flood levy brought in Queensland.

Hope is fading for hundreds of people missing for a second night after the Christchurch earthquake.

Their task is to enter highly restricted and prohibited areas, putting their lives on the line to save others.