Aftershocks hit Canterbury after 5.1 magnitude quake

Canterbury residents have been rolled by nine aftershocks since last night's magnitude 5.1 quake.

About 4000 people reportedly felt the quake centred 30 kilometres west of Methven.

It struck at 9.21pm.

Dr Jonathan Hanson, seismologist at GNS Science, told Morning Report it was not expecting significant damage from the quake.

He said people close to the epicentre would have felt a sharp shake but further away it would have been a moderate rolling earthquake.

"It would have given people a good shake," Dr Hanson said.

"People who would have gone to bed early would have felt a good jolt."

Hanson said the aftershock pattern was in keeping with a moderate earthquake with the largest aftershock measuring magnitude 3.

"This is in keeping with what we'd expect from a quake of this magnitude. Aftershocks are a normal occurrence after pretty much any earthquake.

"We'd expect them to tail off over the next few days."

He said the aftershocks helped GNS map out which faultline the quake had occurred on.