Laura Campbell told CNN she was at work at the bottom of a six-story building when the earthquake struck. She described seeing "windows blowing out, bricks falling down, people screaming, the whole nine yards."
"It was bloody serious," said Campbell, who was trying to walk home. "I'm worried about what I'm going to find down the road."
The U.S. Geological Survey said the quake struck just before 1 p.m. Tuesday (7 p.m. Monday ET), and a 5.6-magnitude aftershock struck about 15 minutes later. The U.S.G.S. recorded a second 5.5-magnitude aftershock shortly before 3 p.m. local time.
The New Zealand Herald reported that phone lines in the area were out, including the city's emergency 111 service, roads were cracked -- in some cases lifted as much as a meter (1 yard) -- and water mains had burst, flooding several streets.
Witness Philip Gregan said he was attending a joint U.S.- New Zealand conference when the earthquake struck.
"I'm seeing a lot of damage in buildings, there are glass and bricks in the road. I've seen one collapsed bridge and there's a lot of water from broken water mains," he told CNN. "I saw one (injured) person in the back of a police car and one of our colleagues saw a person crushed by falling debris, so there are definitely dead."
New Zealand's transit authority told TVNZ that it had been unable to reach its staff in Christchurch and at the Lyttleton Tunnel, which is near the epicenter.
Christchurch police told TVNZ that the city's 106-year-old Cathedral of the Blessed Sacrament was badly damaged, and a Herald reporter said that half the building had collapsed.
Camera footage aired by the station showed piles of stone lying atop crushed chairs on the floor of the cathedral with light shining through the collapsed tower above the sanctuary.
