Coal Mining Causing Earthquakes, Study Says

[Dover]

Coal Mining Causing Earthquakes, Study Says
Richard A. Lovett
for National Geographic News

January 3, 2007
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.

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" .) ..cont'd

http://news.nationalgeographic.com/news/2007/01/070103-mine-quake.html

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Earthquake rattles Canadian mining town

29 Nov 2006 17:48:28 GMT
Source: Reuters

TORONTO, Nov 29 (Reuters) - A small earthquake that awoke residents in a northern Ontario city early on Wednesday did not cause any damage or injuries, officials said, though one major mining company said it was still conducting precautionary inspections.

An earthquake of magnitude of 4.1 struck the mining town of Sudbury, about 390 km (240 miles) north of Toronto, at 2:22 a.m. (0722 GMT) on Wednesday and was followed by a pair of aftershocks at 2:36 a.m. and 2:38 a.m..

Officials said the earthquake was a little stronger than the area is used to but not totally unexpected as the region is known for scattered earthquake activity.

..con't

http://www.alertnet.org/thenews/newsdesk/N29208629.htm

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Evidence Used in Identifying Routine Mining Seismicity

USGS/NEIC personnel identify mine explosions and roof collapses induced by longwall mining on the basis of the following evidence:

1. Computed locations -- Locations of many of the provisionally identified explosions occur within or near well-known mining districts that have large surface mines, and provisionally identified explosions occur where other similar size events have regularly occurred at the same time of day. Roof collapses that are large enough to be detected and located by our procedure are much less numerous in our catalogs than explosions: they are identified by virtue of occurring in groups in the neighborhoods of some underground coal-mines that use longwall technology.

2. Time of day -- Mine explosions tend to be set off during local daytime hours, even if the mines are operating 24 hours a day.

3. Seismic waveforms -- Seismograms at a given station for explosions at the same mine tend to be similar from event-to-event, both in the relative times and amplitudes of different seismic phases within each seismogram and in the absolute amplitudes of the seismic phases. Seismograms may have the general characteristics expected for mine explosions -- emergent beginning of phases due to ripple-firing, no S, presence of Rg phase.

cont'd

http://neic.usgs.gov/neis/mineblast/evidence.html