A woman who was among the group of rafters camping by the Clarence River when Monday's earthquake struck has spoken about their "fortunate" journey to safety.

Deirdre Lusby told the Herald today how her rafting trip with 13 other women took a sudden turn two days in when they were woken by the 7.5 magnitude quake at 12.02am on Monday.

"I was woken by a thunderous noise.

"It was really loud...at first I thought it was a train going right by us."

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Lusby said one of the woman woke up with a large crack beside her tent and a branch through the fly.

Guides moved the group along the river to a big, flat paddock where they slept on a tarpaulin in the open, Lusby said.

But they had a sleepless night.

"There were severe aftershocks as we lay there," she said.

Lusby said they then moved a few hours down the river.

"We noticed lots of huge slips and rockfalls...we could see dust where more rocks were coming down with every aftershock as we rafted."

The group finally set up camp at Muzzle Station, where they had TV and internet access and discovered slips had dammed the river at Muzzle Station

"We realised it wasn't safe to keep rafting after that."

The group spent another night in tents, battered by rain and wind, before being evacuated by chopper on Tuesday, then driving to Blenheim.

"We were very fortunate compared to others," said Lusby.

Civil Defence evacuated all residents in the area surrounding the Clarence River on Monday afternoon as a surge of water up to 15m high rushed downstream after breaking through the earthquake debris that had slid into the river.