Christchurch last night felt its biggest aftershock since February 22 - when the catastrophic earthquake hit the city - on the day Moon Man Ken Ring predicted a big tremor - though experts say there is no scientific link.

The 5.1-magnitude tremor jolted the city at 9.47pm. It was centred 10km east of Christchurch and was 10km deep, GNS Science said.

It followed four minutes after another of magnitude 3, 10km west of Lyttelton at a shallow 5km.

Three other aftershocks also hit the city yesterday, at 1.42am (3.2), 8.57am (3.1) and 10.05pm (2.9).

Police said there had been no immediate reports of extra damage.

One person in Avonhead said on Twitter they could feel their house "twisting" during the 5.1 aftershock, which she said lasted a number of seconds.

But many people were still sceptical about Mr Ring's predictions, saying the heavy aftershock was just a coincidence. Mr Ring had earlier been called reckless and irresponsible for predicting a large earthquake would hit the South Island yesterday.

His prediction left many Cantabrians on edge, with thousands leaving the city over the weekend and many others stockpiling food and water and withdrawing cash from their banks.

"It's reckless and irresponsible for people like Ken Ring to be speculating on the timing of future major earthquakes with no scientific basis," said Environment Minister Nick Smith, who attended a "non-event" lunch organised by the NZ Skeptics at the Sign of the Kiwi cafe on the Port Hills in Christchurch to mock the prediction.

"Cantabrians have been through enough trauma without charlatans preying on people's natural fears."

Mr Ring made his prediction of a "quake for the history books" on the site three days after the first Canterbury earthquake last September, saying: "The morning of 20 March 2011 sees the South Island again in a big earthquake risk."

He said the moon would be at its closest to Earth this year at 9.44am.

In addition to the aftershocks that hit Christchurch yesterday, two shakes of magnitude 4.6 and 4.3 hit South Canterbury, near Twizel, in the early afternoon.

Dr Smith, a geotechnical engineer, said: "I can appreciate that people are frustrated that scientists and engineers cannot give black and white assurances on if and when another major earthquake may occur, but false claims only make the situation worse."

He said the advice from GNS Science was that the risk of a quake of magnitude 6 or larger in Christchurch was no different to that of Wellington, and would lessen in the coming months. Mr Ring was scaremongering.

NZ Skeptics spokeswoman Vicki Hyde said: "People are just giving too much credit to a man who's making pseudo-predictions that don't come true. How many times must he get it wrong for people to realise that in all his predictions, Ken is guessing."

Christchurch resident Durgadas Verma-Lingham said on Facebook the 5.1 aftershock was bound to happen and it was simply a large jolt, which was normal after a strong earthquake.

"I conclude that his theory is complete nonsense! Even astrologically, I see nothing special to suggest his theories are even remotely correct in the slightest!"

Sharon Davis posted on Twitter that the aftershock was long and noisy and said everyone was "a bit on edge with the predictions - Mr Ring's predictions may have been rubbished by the experts, but those who left Christchurch at the weekend said it was better to take precautions".

* 6.3 Feb 22, 12.51pm. More than 170 killed.

* 5.0 Feb 22,7.43pm.

* 4.9 Mar 6,3.43am.

* 5.1 Last night, 9.47pm. The biggest aftershock since February 22 quake.