Geoscience Australia confirmed an earthquake measuring 2.8 on the Richter scale was recorded 40km offshore and at a depth of 14km at about 7.45pm.

Duty seismologist for Geoscience Australia, Marko Maldoni, said there were several reports from residents indicating the earthquake was strong enough to briefly shake houses in the Harrington area.

"Earthquakes are not common in this particular area," Mr Maldoni said.

"There are stress fields across the earth's crust and every now and then that stress is released. There are a few fault lines in this part of the world but there have only been four earthquakes between Port Macquarie and Taree recorded in the last 20 years."

Mr Maldoni said earthquakes below magnitude 3 are generally not felt, but the Mid-North Coast's sandy geology increases the sensitivity to earth movement.

"It is a lot easier to feel tremors on sandy terrain as it amplifies seismic waves," Mr Maldoni explained.

So are their likely to be after shocks, or a quake greater in magnitude.

Mr Maldoni said not likely, but earthquakes are a random phenomenon and can't be predicted.

"We really are in the lap of the gods. The odds are there won't be another earthquake in Harrington tomorrow. But we can't say there will be more, and we can't say there won't be any."