Australians left rattled by tremors in the bush

Earthquakes near a small country town in southern Australia have left residents fearing bigger and more devastating tremors.

Simon Calder rents a house less than one kilometre from the epicentre of the earthquakes that struck Korumburra.

KORUMBURRA, AUSTRALIA // Two earthquakes near a small country town in southern Australia have left residents fearing that friction deep within the Earth's crust could unleash bigger and more devastating tremors. A flurry of unusual seismic activity five kilometres from Korumburra, south-east of Melbourne, has jolted homes and buildings, with scientists warning there is no way of predicting when and if more violent subterranean vibrations will occur.

Korumburra, a town of 5,000 people, was rocked by a 4.6-magnitude earthquake in early March, with a second similarly sized event taking place 12 days later. Spiro Spiliopolous, of Geoscience Australia, a government-run agency, said "inter-plate seismicity" was to blame for the sudden shaking of the ground in a normally tranquil corner of the state of Victoria that escaped the recent bush fires. "The causes of the earthquakes are the stresses which are built up in the Australian crust," he said.

"The Australian plate is moving to the north and colliding with the Eurasian plate and to our east we have the Pacific plate, which is colliding with the Australian plate. "The collisions and interactions create stresses and they build up and are released at points of weakness or faults in the Australian plate." Geoscience Australia has calculated that the pair of earthquakes occurred at a depth of about 10km in the Earth's crust. "A few square kilometres of fault has moved and that creates waves, which radiate out from that location," he said.

The epicentre of both quakes is less than one kilometre from Simon Calder's rented weatherboard home, which sits at the end of a rough track that winds through undulating sheep and cattle country, a short drive from Korumburra. "The first one I was sitting out the back having a drink and it started to rumble," said Mr Calder, who deals in scrap metal. "I could feel my chair moving. The trees were moving and the house shook. It was a bit freaky because I've never been in one.

"We've had a few more rumbles and we might get another one," he said. Back in town, what the dark recesses of the Earth might have in store for this quiet farming community has become a major talking point. "People are predicting all sorts of mayhem," said Frank Van Dinter, a Dutch-born former electrician. "The big one could be 20 years away. Look at San Francisco - they are still waiting." Seismologists have said the region would usually experience an earthquake of 4.5 or greater every two years, and although the occurrence of two shocks within a few weeks was out of the ordinary, there was no need to panic. "We don't see this very often, but it is not something we are unduly worried about. It is just one of those statistical fluctuations," Mr Spiliopolous said.

Although no one was injured and no major damage caused, the Korumburra rumblings have left their mark on the town, with residents able to recall the events with great clarity. "The first one was like a sonic boom," Mr Van Dinter said. "The most recent one was much quicker. A very loud bang, but the shock only lasted about 10 seconds. We had nine aftershocks, so something is happening. "I'd sooner go through an earthquake - maybe not much stronger than that - rather than a bush fire or floods."

At the Korumburra Middle Hotel, staff had just finished serving dinner when the first quake struck about 10pm. "It did feel like a truck hitting the hotel," said Philip Botte, 31, the manager. "I thought something serious was happening and everything was moving, then all the lights went out. "It lasted for about 10 seconds and then we were all in darkness and just wondering what to do.The roof and the walls were creaking and it felt like there were very, very high winds moving the building."

Natasha Verdon, 36, who works in a bar, was watching television at a friend's house 15km away when the seismic waves reverberated through the ground. "It was quite scary," she said. "The whole house shook and the power went off. A lot of people are waiting for the big one." Among those who fear the worst is Phyllis Nico, who said the minor aftershocks that followed the two earthquakes had left her feeling scared and vulnerable.

"Every time you feel a little one, you think 'oh no, what is going to happen now?' You tense yourself and it's not just me, I've spoken to other people and they feel the same. "All I could think of was those poor people in the big earthquake in China. Good heavens, how did they cope with an eight-point-whatever it was? "I knew this wasn't anything like that, but you appreciate how terrifying it must be for people who are in big earthquakes. We were frightened, but it must be a horrible sensation to be in something really serious," Mrs Nico said.

Australia's most devastating earthquake hit the port city of Newcastle north of Sydney in Dec 1989. It measured 5.6 on the Richter magnitude scale and claimed 13 lives. [e-mail]