Attention has been focused lately on the risk of earthquakes from human activity.

A number of studies suggest that geothermal drilling, mining, groundwater-extraction or injection, reservoir filling, nuclear explosions, and enormous manmade structures may all be responsible for seismic events.

(Photo: Shutterstock.com)

In recent years, though, rumors have been swirling that geothermal explorations put the public at higher risk of earthquakes.  While this is true of certain Enhanced Geothermal Systems techniques, such as deep drilling and artificial rock fracturing, that’s a small part of the geothermal picture. 

Micro-quakes are just what they sound like: tiny. Thousands of these micro-quakes have been touched off at geothermal sites, said Dr. Ernest Majer in Power Magazine, but “none of them large enough to cause any major damage.” 

And the other side of the coin: it’s not just geothermal that can set off quakes. Mining is at least as big of a culprit.

Dr. Christian D. Klose, of the Lamont-Doherty Earth Observatory at Columbia University in New York, identified more than 200 studies showing “human-induced stresses could have reactivated preexisting faults,” many of them rating high on the Richter scale and caused serious destruction.  Klose referred to these human catalysts as “geo-mechanical pollution.” 

(Photo: Shutterstock.com)

In 2007, Klose identified mining operations as a chief instigator, with its drastic impacts on groundwater. Some mines, he said, have to pump as much as 150 tons of water for each ton of minerals produced.

Australia had its most devastating quake in 1989, in Newcastle, which Klose attributed to two centuries of coal mining in the area.  The damage from the single disaster, he calculated, was greater than the value of the mine over its entire lifespan.

The Newcastle quake rated 5.6, compared to Australia’s worst geothermal quake of 3.7.  The region in Australia had not previously been prone to seismic disturbance.  However, as Klose had written in 2005, “after an earthquake occurs the probability of another earthquake increases dramatically in a source area with no prior seismicity.”  Like a concussion to the brain, we may not have realized the full extent of damage from the one disruption.

Dr. Klose has a publication currently under peer review, titled “Human-triggered earthquakes and their impact on human security.”

Science Magazine, in 2006, ran an article saying that the weight of skyscrapers may be a trigger.  Initial interest was sparked in 2005, after a series of quakes struck directly below Taipei 101, the world’s (then) tallest building in Taiwan. 

In June 1974, an earthquake rocked a limestone quarry in Wappingers Falls, New York. Researchers determined from “all of the available evidence” that the events were “triggered by crustal unloading associated with quarrying operations.”

The geothermal-triggered Basel quake registered at 3.4, and resulted in some minor structural damage in the area.  Geopower Basel, the company running geothermal operations there, said it had informed the local authorities of possible quakes.

The Department of Energy has allocated $350 million from the Recovery Act to geothermal power, and tied those funds to new monitoring to ensure safey (see accompanying article).  American geothermal companies now have plenty of incentive, and resources, to address the potential of geo-hazards. 

(Photo: Shutterstock.com)

“There is no simple answer with regard to geothermal energy production and human triggered earthquakes,” Dr. Klose said.  “It all depends on the geology, tectonic situation and production plan.”

Public safety always comes down to public enforcement.  In the energy industry, this is becoming clear in agencies like the Army Corps of Engineers, whose sweeping “rubber stamp” approval (Nation Wide Permit 21) of environmentally hazardous projects is drawing more criticism.

Governing authorities must keep permitting and operating regulations on par with science.  And they must strictly enforce them.

 

 

 

Resources

1.  Patel, Sonal.  “Assessing the Earthquake Risk of Enhanced Geothermal Systems.”  Power Magazine.  http://www.powermag.com/renewables/geothermal/Assessing-the-Earthquake-Risk-of-Enhanced-Geothermal-Systems_2309_p3.html.

2.  “Quarry-caused earthquake.” Science News.  00368423, Vol. 108, Issue 18.  01 November 1975.

3.  Klose, Christian D.  “Shallow Seismicity in Stable Continental Regions (SRCs):  Implications for Earthquake Hazards.”  Submitted to AGU fall meeting.  Reference no: 531.  17 May 2005. 

4.  Klose, Christian D.  “Mine Water Discharge and Flooding:  A Cause of Severe Earthquakes.”  26 June 2007.

5.  National Geographic News.  “Coal mining causing earthquakes, study says.”  03 Jan 2007.

6.  Burns, Shirley Stewart.  Bringing Down the Mountains.  West Virginia University Press.  Morgantown, WV, p.2.  2007.

7.  Holden, Constance.  “Giving the Earth a Poke.”  Science Magazine.  Volume 310, Issue 5755, p.1764.  16 Dec 2005.

8.  SwissInfo.ch.  “Manmade tremor shakes Basel.”  09 Dec 2006. 

9.  Department of Energy.  “American Recovery and Reinvestment Act.”  23 Nov 2009.  Accessed:  07 Dec 2009.  .