A Liverpool man living in Christchurch has said the ground "melted" beneath him moments after the earthquake hit.
Seventy five people are confirmed dead and more than 300 are missing after the earthquake struck at a shallow depth of 5km (3.1 miles) on Tuesday lunchtime.
Paul White, from Woolton, emigrated to New Zealand three years ago.
He was at work when the quake hit, but when he went outside he said the concrete he was standing on turned to mud and he was forced to flee.
"We all dived under the desk for about 10 or 15 seconds, there were loads of laptops, monitors and that kind of thing flying around the place," he said.
"As soon as it settled down we gave it another 10 seconds then hot-footed it out of there really."
He said he and his colleagues were standing in a nearby car park when it started oozing mud.
"Just beneath our feet on the concrete car park, suddenly big cracks appeared and mud just started oozing out," he said.
Cliff 'sheared off'
"It all poured out of every hole. Ten seconds it was up, then before we know it we're all a foot deep in mud."
Mr White, who lives in the suburb of Sumner with his wife Cathy and three daughters, aged 4, 7 and 10, said it took a while to find out they were all well as mobile phone reception was affected.
"The radio was all I had really," he said.
"The first 10-20 minutes people are just trying to find out what's going on.
"I was trying to text Cathy and find out what was going on. My texts kept bouncing back as there was no reception."
He said a large part of the landmark cliff - which is about 100m from their home - sheared off, landing on residencies and businesses.
His house is still standing, but the interior has been ruined. He and his family are now staying with friends about 100km away.
He said: "Talking to my eldest daughter, she said all she remembers is looking behind her and seeing a big dust cloud and just freaking out.
"That basically was the cliff falling apart."
Hundreds of search and rescue personnel, police, fire service staff, soldiers and volunteers have been scrambling to find survivors trapped under the rubble in Christchurch, many using only their bare hands.
New Zealand Prime Minister John Key has declared a national state of emergency.
The authorities have also imposed a night-time curfew in the worst-affected areas of the city.