Guanaba Gorge
Guanaba Gorge
Authorities are baffled by a mystery explosion that shook the ground around Guanaba, west of the Gold Coast, last night.

A spokesman for the seismological office in Brisbane said their instruments had not recorded any ground shockwaves, despite dozens of residents reporting hearing a loud noise and vibrations.

The spokesman said a sonic boom, made by an aircraft going through the sound barrier, may have been the cause.

''There's nothing seismic on the records,'' he said.

''I've looked through continuous data from our recorder at Beenleigh around the estimated time of the shock waves and nothing has appeared, which means it wasn't an earthquake but there are still other possibilities.

''We've previously had a history of things reported from people in that area that they thought was an earthquake and we've tracked it down to a sonic boom.''

Air force jets are the only planes capable of breaking the sound barrier and there has so far been no response to inquiries to the air force base at Amberley.

The seismology office spokesman said he believed air force pilots were not supposed to exceed the speed of sound over land, but sometimes it happened just before they headed their aircraft offshore.

''The results are people will feel windows shaking, that kind of thing,'' he said.

''Our instruments only pick up sound and ground vibrations.

''My understanding is that they're only allowed to break the sound barrier when flying over the ocean but over land they're not allowed to go that fast.''