Lyttelton was shaken to its core by the earthquake, with most of its heritage buildings in the city centre left in a heap of rubble - however, it was believed last night there was no loss of life.

Rachel Lister, a Lyttelton resident, said she had never been so scared in her life.

"It's pretty scary. I consider myself a pretty staunch person but I was a blithering wreck in the doorway for a good 20 minutes afterwards; not able to move because there'd be another one."

Ms Lister, a 28-year-old intern doctor, said when she felt the first quake she ran to the front doorway, but the frame had buckled.

"I couldn't get it open so I had to get to the next door, but I tripped over on the way because it was such a big shake. It was hard to walk. It was hard to get around and it felt like it went on forever."

It took Ms Lister more than 40 minutes to compose herself before she could go outside.

"I then ran outside to check on our elderly nextdoor neighbour to see if she was okay."

As she went through the town, she saw five or six buildings in the centre of town that had been completely flattened.

"Thankfully there hadn't been any fatalities, there was just one chap who'd been scalded when his hot water pipe exploded. But apart from him, everyone's doing pretty well, under the circumstances."

Ms Lister said her house was full of broken objects, and was without power.

"There's china all over the floor, the microwave's fallen off the wall, all the paintings are off the wall, light fixtures have fallen down and the veranda's walked about a metre away from the house."

Jared Adam, a 23-year-old student from Lyttelton, said from what he had seen about half of the buildings there had been badly damaged.

"Most of the larger concrete buildings have all fallen down ... a lot of the places got fully ripped apart. My place doesn't really look that good but I don't really want to sleep in the rain, so you've just got to deal with it."

He said people had started to camp on a grassy area above the local school, and the emergency accommodation at the Lyttelton Recreation Centre was extremely full.

Lyttelton Port is partially functioning, but it will take at least 24 hours for staff to assess the extent of earthquake damage to wharves and other infrastructure .

Lyttelton Tunnel was closed after rock falls, but it reopened to emergency vehicles about 6.30pm.

It will remain closed to normal traffic until a safety assessment is carried out today.