As the earth began shaking violently beneath her feet, hotel supervisor Jovy Servitillo knew she was in trouble - she was on the 23rd floor of the tallest building in Christchurch.

Mrs Servitillo is the apartment supervisor at the Hotel Grand Chancellor which was last night on the verge of collapsing and threatening to destroy neighbouring buildings.

The quake demolished the hotel stairwell and left a gaping hole, trapping Mrs Servitillo for five hours in the dark with hotel guests.

"We could feel the building sinking. It was so terrifying."

She texted family members to say she was alive and to alert rescue teams. Eventually, a crane winched a platform up to the group - who squeezed through a crack in the wall to reach the waiting arms of rescuers high above the streets.

About 30 others were also rescued from the hotel, which will inevitably collapse.

Mayor Bob Parker said if it did not fall on its own, it will have to be pulled down.

"This is a massive high-rise hotel, a very heavy building ... a collapse will take out a number of buildings ... when it hits the ground, it will generate a big release of energy that will translate into a ground wave, a shockwave, an earthquake that will ripple through the CBD."

The hotel moved up to 2m horizontally in a short period yesterday and was last night leaning distinctly off-centre.

Blocks around the building have been evacuated.

Repairs were under way at the $30 million block before Tuesday's quake.

Frank Delli Cicchi, the group general manager of Singapore owner Grand Hotels International, said minor damage on September 4 was being repaired and the fixup was about three weeks into its programme.

Cracked windows, cracks in partition walls and warped floors were being fixed, he said.

But the problems after September 4 were only minor. Yesterday, he was devastated to see the state of the Christchurch hotel, which still had guests' passports and luggage inside.

"It's a terrible state of affairs for everybody.

"If it's coming down, that's the way it has to be. It's bricks and mortar and it's more important there are no injuries or casualties. We've owned it since 1995. It was an office building converted to a hotel," he said of the block.

The building was fully insured. Many of the hotel's guests had gathered in Hagley Park on Tuesday night, Wellington-based Mr Delli Cicchi said.

"Most of them were in tour groups so they were out for the day. Everything was in their rooms," he said.

The hotel employed 150 to 200 staff, depending on the season, and they would be paid. Mr Delli Cicchi said staff would continue to receive salaries and the group's priority was guest and employee safety.