Tuesday, February 15, 2005

Freak thunderclap heralds coldest February day
Melbourne Herald Sun, Australia - Feb 2, 2005
Milanda Rout

This report is a bit old but the story is still interesting

"A FREAK clap of thunder exploded over Melbourne early yesterday, waking thousands of sleeping residents across a 90km zone.

The sound wave travelled from Melton to Rosebud in four minutes.

It shook houses in its wake and vibrations caused by the thunder were recorded at five seismic testing stations.

The big bang was a prelude to Melbourne's coldest February day on record. The mercury barely nudged 13C as the city surpassed its average rainfall for February with 46mm in 48 hours.

The thunderclap frightened hundreds and generated a flurry of theories over what caused it -- from an earthquake to a sonic boom from a jet, or even a meteor.

"It sounded like a train come through the house," said Campbellfield resident Bill Brown of the tremor.

"The kettle and the toaster were jumping on the counter.

"The whole house was shaking and I was bloody frightened."

Seismology Research Centre director Gary Gibson said the big bang was not caused by an earthquake but rather a freak clap of thunder.

He said it started in Toolern Vale, near Melton, about 3.07am when a single lightning bolt struck. It destroyed a power pole just metres from houses.
Mr Gibson said a massive burst of thunder exploded as a result of the lightning, creating a powerful sound wave that travelled about 1km each three seconds.

"It's like an explosion going off and the sound waves going in all different directions," he said.

The vibrations were first recorded by testing stations in Mount Macedon 69 seconds after the lightning strike.

The sound wave then registered at Tullamarine, followed by Richmond and Belgrave.

Residents in Rosebud were the last to feel the vibrations, four minutes after the initial thunderclap to the city's west.

Mr Gibson said the vibrations measured less than one on the Richter scale.

Toolern Vale resident Michael Maxey said he was woken about 3am by the enormous bang.

"It was unbelievable. I was too scared to get out of bed," he said.

Mr Maxey, 37, said the house shook and trembled for 20 seconds.

He went outside and realised a power pole just 200m from his house had exploded after being struck by the lightning.

Big bang: lightning blew apart this 22,000 volt power pole in the middle of the night leaving nearby Toolern Vale residents fearing a bomb had exploded or a plane had crashed.Picture: Trevor Pinder