'Unusually large' earthquakes rattle Australia

Two earthquakes hit northern NSW of a size that was unusual for the region, according to seismologists. Photo / Thinkstock

Two earthquakes struck northern NSW last night, and were felt in Tamworth, Gunnedah and Coonabarabran and in areas more than 100km away.

A 4.2 magnitude quake struck at Lake Keepit, northeast of Gunnedah, at 9.31pm (11.31pm New Zealand time) on Friday, Geoscience Australia said.

It had a depth of 17km.

A similar sized earthquake nearby struck about two minutes earlier, the Australian Seismological Centre says.

The centre's director Kevin McCue said these were the first earthquakes greater than magnitude 4 to strike inland northern NSW since December 1969, when a magnitude 5 quake struck near Coonabarabran.

Mr McCue said the Friday night quakes were felt as far as Coonabarabran, 120km from the epicentre, as well as in Tamworth and Gunnedah.

"I was talking to people up there. All the glass was jiggling in cupboards,'' he told AAP.

"It's unusual to have an earthquake of this size.''

He said it's unlikely the quakes caused structural damage to homes in major towns, but some may have cracked walls or chimneys.

Twitter accounts have come in from Tamworth, Manilla and Gunnedah.

Seismologist Dr Michael Phillips, who lives 5km from Coonabarabran, said his wife Claire Milton, a doctor, and their eight-year-old son Max felt the earthquakes in their farmhouse.

"They heard and felt it,'' he told AAP.

"The china in the cabinet was rattling and my son's bunk bed was banging on the wall.

"The whole house was rattling and shaking - it lasted 30 seconds.''

Dr Phillips, who is also a physicist, said the size of the earthquakes had overwhelmed his seismological measuring equipment.

"It was too much for the instrument,'' Dr Phillips said, adding it was likely that one of the earthquakes was an aftershock.