The Danger of Digging Deeper: geothermal maddness
source: http://bldgblog.blogspot.com/2009/06/danger-of-digging-deeper.html
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- leahl
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"Artificial earthquakes triggered by deep-crust drilling operations have always been of interest here, and The New York Times brings the idea back into the media cycle today with a new article – complete with a sidebar titled "The Danger of Digging Deeper."
Don't miss the interactive graphic.So the scene this time is the countryside two hours north of San Francisco, with a company called AltaRock. "Residents of the region, which straddles Lake and Sonoma Counties," we read, "have already been protesting swarms of smaller earthquakes set off by a less geologically invasive set of energy projects there. AltaRock officials said that they chose the spot in part because the history of mostly small quakes reassured them that the risks were limited."
Serious seismic problems arise when you begin to tap into – and then break through – very deep rocks. The reference case for The New York Times here is something that happened in Basel, Switzerland, back in 2006 (a seismic event mentioned briefly in The BLDGBLOG Book). The specific drilling technique used in Basel, we read, was one that "created earthquakes because it requires injecting water at great pressure down drilled holes to fracture the deep bedrock."
The opening of each fracture is, literally, a tiny earthquake in which subterranean stresses rip apart a weak vein, crack or fault in the rock. The high-pressure water can be thought of loosely as a lubricant that makes it easier for those forces to slide the earth along the weak points, creating a web or network of fractures.
A very similar technique, however, will soon be put into widespread use in northern California. There, in the foggy hills and forests, AltaRock "has received its permit from the federal Bureau of Land Management to drill its first hole on land leased to the Northern California Power Agency, but still awaits a second permit to fracture rock."
One resident awesomely points out: “If they were creating tornadoes, they would be shut down immediately. But because it’s under the ground, where you can’t see it, and somewhat conjectural, they keep doing it.”
more at the link as well as some fabulous images
Don't miss the interactive graphic.So the scene this time is the countryside two hours north of San Francisco, with a company called AltaRock. "Residents of the region, which straddles Lake and Sonoma Counties," we read, "have already been protesting swarms of smaller earthquakes set off by a less geologically invasive set of energy projects there. AltaRock officials said that they chose the spot in part because the history of mostly small quakes reassured them that the risks were limited."
Serious seismic problems arise when you begin to tap into – and then break through – very deep rocks. The reference case for The New York Times here is something that happened in Basel, Switzerland, back in 2006 (a seismic event mentioned briefly in The BLDGBLOG Book). The specific drilling technique used in Basel, we read, was one that "created earthquakes because it requires injecting water at great pressure down drilled holes to fracture the deep bedrock."
The opening of each fracture is, literally, a tiny earthquake in which subterranean stresses rip apart a weak vein, crack or fault in the rock. The high-pressure water can be thought of loosely as a lubricant that makes it easier for those forces to slide the earth along the weak points, creating a web or network of fractures.
A very similar technique, however, will soon be put into widespread use in northern California. There, in the foggy hills and forests, AltaRock "has received its permit from the federal Bureau of Land Management to drill its first hole on land leased to the Northern California Power Agency, but still awaits a second permit to fracture rock."
One resident awesomely points out: “If they were creating tornadoes, they would be shut down immediately. But because it’s under the ground, where you can’t see it, and somewhat conjectural, they keep doing it.”
more at the link as well as some fabulous images
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- Green, Earth and Science, san francisco, sanfrancisconews
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- Green, Earth and Science, Environment, Climate Change, 3 more
