Geoscience Australia said the tremor, measuring 3.3 on the Richter scale, struck at 3.24am yesterday.

The epicentre was about a kilometre from shore at the northern end of Mungo Brush, north of

Hawks Nest.

Herald readers reported hearing one or two loud booms, and windows shaking for about 10 seconds.

"Staying in a two-storey house at Hawks Nest and woke to two loud bangs and the bed and windows shaking," a reader told www.theherald.com.au.

"[I] thought someone had driven into the side of the house."

A Salamander Bay resident said he was awake when the quake struck.

"Heard a boom in the distance, followed by a few seconds later the bedroom windows shaking for about five to 10 seconds."

The quake was also felt by people in Newcastle and Lake Macquarie.

Geoscience Australia revised its reading from 3.4 on the richter scale when it became apparent the quake had struck only a kilometre from the coastline.

Seismologist Dr Jonathan Bathgate said a 3.3 quake was relatively minor.

"It happened much closer to the shore that we first though, which explains why it was so strongly felt at places like Anna Bay, Fingal Bay and Soldiers Point," Dr Bathgate said.

"We wouldn't expect damage from an earthquake of that size."

Dr Bathgate said the earthquake followed two quakes to hit the Hunter region, in 1998 and 2001, that measured 2.6 on the richter scale.

The largest earthquake to hit the region, the 1989 Newcastle earthquake, measured 5.6.

"The Newcastle area is not particularly prone to earthquakes," Dr Bathgate said.