A major aftershock measuring 5.1 on the Richter scale hit Christchurch at 7.45 a.m. with a depth of only six kilometres.
It was a "devastating, vicious sharp blow" for local people, Mayor Bob Parker told Newstalkzb.
Residents were beginning to feel that the aftershocks were easing off and they were starting to relax.
"It is like living in a maelstrom. My guts is just churning up here. When will this thing end?" he said.
"We have got staff in tears, we have got fire engines going through the middle of the city again, power is out and a lot of people are appearing very, very churned up by that.”
He was thankful that the aftershock had been short, as the shallowness made it a terrifying experience.
Broker Ricky Robinson has been unable to work since his business premises were yellow carded for structural safety reasons.
It was incredible, he said, that the city was still experiencing such strong aftershocks so long after Saturday's devastating earthquake.
Civil Defence Director John Hamilton said today in the Quake Information Update that aftershocks, which could reach as high as magnitude 6, are expected to continue for the next week or more.
The state of emergency has been extended for another week.
