for National Geographic News
The most damaging earthquake in Australia's history was caused by humans, new research says.
The magnitude-5.6 quake that struck Newcastle in New South Wales on December 28, 1989, killed 13 people, injured 160, and caused 3.5 billion U.S. dollars worth of damage (Australia map).
That quake was triggered by changes in tectonic forces caused by 200 years of underground coal mining, according to a study by Christian D. Klose of Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York.
The quake wasn't enormous, but Australia isn't generally considered to be seismically active and the city's buildings weren't designed to withstand a temblor of that magnitude, Klose said.
All told, he added, the monetary damage done by the earthquake exceeded the total value of the coal extracted in the area.
Klose presented his findings at a meeting of the American Geophysical Union in San Francisco, California, last month.
The removal of millions of tons of coal from the area caused much of the stress that triggered the Newcastle quake, Klose said. (Related: "Mountaintop Mining Raises Debate in Coal Country" [January 13, 2006].)
But even more significant was groundwater pumping needed to keep the mines from flooding.
"For each ton of coal produced, 4.3 times more water was extracted," Klose said.
Other mining operations, he added, sometimes require as much as 150 tons of water to be removed for each ton of coal produced.
"So this is on the low end," he said.
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