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Australia Due for a Big One:

Australia Due for a Big One: Seismologist
December 26, 2007
The Age - Melbourne

A LARGE earthquake measuring at least six on the Richter scale appears to be overdue in Australia, after another relatively quiet year on the seismic front.

Australia's Newcastle shaker struck New South Wales Dec. 28, 1989 causing immense damage. This 5.6 earthquake killed 13 people, injured hundreds more, ruined 70,000 buildings, left 1,000 people homeless and caused over $4 billion ($US3.5 billion) in damages. In today's money, that would be about $US5 billion.)

Nationwide this year, 191 earthquakes have been recorded, just under the 209 reported last year.

The strongest so far, which occurred at Western Australia's Shark Bay in February, had a magnitude of 5.3.

But it has been a slightly bumpier year for Victoria, where there was a rise in the number of earthquakes after recent annual tallies plummeted to single-digit figures.

Across the state, there have been 18 quakes this year — the strongest with a magnitude of 3.5 south of Warburton — up from eight quakes the previous year, and four in 2005.

Earthquakes measuring three or above were also reported at Boolarra South in the Strzelecki Ranges, Mount Baw Baw and a site north-east of Foster.

Seismologist Clive Collins, of Geoscience Australia, said variations in the number of earthquakes from year to year were normal, but it had been "reasonably quiet" in Australia for some time.

"We usually get a magnitude six or above every four years, but we haven't had one since 1997," he said. "Just on the law of averages, we are due for one somewhere."

Australia's earthquake hot spots include the south-east — from Tasmania through to northern NSW — South Australia's Flinders Ranges, as well as the south-west corner of WA.

The continent sits on a plate of the Earth's crust that is moving northwards into the Asian plate, causing a build-up of stress in the rocks.

"Basically the continent's getting squeezed," Mr Collins said.

But around the world, earthquake-prone regions such as California and New Zealand — which was struck by a powerful 6.8 earthquake last week — are mostly found on the boundaries of tectonic plates that are colliding with each other.

The most damaging earthquake in Australia's recent history was in Newcastle in 1989, when a quake measuring 5.6 killed 13 people and left a damage bill of billions of dollars.

1&2 Dare To Prepare1st Ed., 1999, Holly Drennan Deyo, page 32