Quakes no reason to panic, says expert

Two quakes that shook the region were part of "normal plate activity", not a sign the big one is coming, a Palmerston North scientist says.

The first quake yesterday at 7.04am, with a magnitude of 5.1, was centred 10km south of Palmerston North and was 40km deep.

It lasted 10 to 15 seconds and was felt by residents in Manawatu, Wellington and Taranaki.

An aftershock was felt in Palmerston North at 8.05am, measured 4.3 on the Richter scale and struck in the same spot and at a similar depth.

Massey University earth scientist Bob Stewart said it was not necessarily a sign the "big one" was coming.

"It's part of the normal earthquake activity. This would be just one of the many we expect along this sector."

Dr Stewart said he experienced the quakes differently at his Pahiatua Track home than inner city residents did.

He felt no more than a couple of severe jolts and a bit of swaying because his home was on the solid rock of the ranges.

Earthquakes were ground condition-dependent, he said. "The softer the ground, the more it amplifies the seismic energy."

The morning shakes would have felt more significant to those still lying in bed or up storeys high, Dr Stewart said.

"I knew something had happened because the local cock pheasant had started squawking again."

Palmerston North, like Wellington, was in a moderately high-risk zone but it did not have the potential to be cut off from other regions as the capital would be in the event of a major quake, he said.

Horizons emergency manager Shane Bayley said Manawatu's defence bases and good access to north and south districts meant it was better placed to cope with an earthquake emergency.

"There are big airfields and a defence force right on our doorstep."

But despite all those factors, people still needed to be prepared for power, water and sewerage outages in the event of a quake.

"Our region is not immune to them [quakes] and there are a number of fault lines in the region," Mr Bayley said.

Police, ambulance and fire services met with the defence force, district health boards and councils to work through emergency management issues every six weeks, he said.

A KiwiRail spokesman confirmed there was no damage to railway lines in the quake area.

There were no reports of injury or damage.