Tremors will last for some time, GNS says

Christchurch will continue to be rocked by earthquakes for years, a GNS scientist says.

The city and surrounding areas were hit by a series of strong quakes this afternoon.

The National Crisis Management Centre under the Beehive in Wellington was activated following the quakes.

From inside the centre, Ken Gledhill said he series of earthquakes in Canterbury, including the fatal event in February, were all the result of the initial quake in September last year.

Such events happened every few thousand years and so there was not too much information about them, he said.

"You could say that they wouldn't have happened if the September event hadn't of happened, or at least they wouldn't have happened yet.

"Because you wrench a big fault in the earth's surface and you rearrange all the countryside around and what we're seeing is it sort of readjusting."

But the readjustment was not happening in a normal pattern, but rather as a series of earthquakes over an extended period, he said.

And that could go on for years.

"It's not comforting to the poor people of Christchurch at all, but series of events like this probably only take place every few thousand years but we're in the middle of it at the moment."

The good news is the aftershocks are likely to diminish in magnitude over time, Gledhill said.

The first quake - magnitude 5.8 quake, 8km deep and centred 20km north east of Lyttelton - struck at 1.58pm. The US Geological Service said it was followed by a magnitude 5.3 quake at 2.06pm, and GeoNet reported the largest magnitude 6 quake struck at 3.18pm. The last quake was just 6km deep and centred 10km east of Christchurch.

"It's been pretty quiet in Christchurch over the last few months, it's dropped right down, this will just be like it's been shaken up again and it will have to settle down again."

Civil Defence controller David Coetzee said the most significant issue in Christchurch after today's quakes was anxiety and stress.

At least two people were reported injured and there were new reports of rock fall and liquefaction in the eastern suburbs, he said.

Phone services, including landlines, were intermittent and people were advised to send text messages rather than call.

"We take these things as serious until we have a good grip on what's going on."

However a state of emergency was unlikely to be put in place, Coetzee said.

The people of Christchurch had been through a lot and stress and anxiety were the main issues being reported by the District Health Board, he said.

"People are really stressing and feeling the psychological affect of this."

Coetzee was on the phone to staff in Christchurch when the second aftershock hit.

He said they had to stop the conversation for a short time.

"That is normal, it was quite a significant shake and we will have aftershocks followed by this one again."

Civil Defence advice for people in Christchurch was :
* Stay calm
* Call 111 in emergencies
* Call the council call centre for concerns about utilities
* Look after each other
* Check on your neighbours
* Text, don't call
* Stay safe

- Fairfax NZ