Another major quake possible

There is a nearly-30 percent chance of another magnitude 6 earthquake striking central New Zealand in the next 24 hours, scientists say.

Duty seismologist Anna Kaiser, said that more aftershocks were to be expected after a major jolt.

"Obviously after a big event like this there is an increased probability of aftershocks and an increased probability of one of a similar magnitude," she said.

"We have had our statistical seismologists running the numbers and they estimate that in the 24 hours following this event there's a 28 per cent chance of a magnitude 6 or greater.

"That will go down if nothing happens."

She said this afternoon's quake at 6.6 was bigger than the June quake and was centred 30 kilometres south-west of that event.

"This one occurred on land whereas the previous one was over water. It is closer to the town of Seddon," she said

She said peak ground acceleration was recorded at 0.75 of gravity.

By comparison, the Christchurch February 2011 earthquake recorded peak ground accelerations of more than 2g, while the strongest readings for the July 21 quakes were approximately 0.2g at Ward, about 16km south east of the epicentre, and up to 0.16g in Wellington and Porirua.

"This one was certainly a lot higher than that and that's reflective of the fact the epicentre was on land and closer to the stations," she said.