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Earthquakes: The Other Side of Drilling for Geothermal Power

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The estimated temperature of 3.7 miles underground. Red areas have 392 degrees Fahrenheit (200 Celsius).

Geothermal technology surely is one of the cleanest technologies available to us, extracting clean heat from the hot underground. This energy source is often seen as inexhaustible, and its benefits seem to outweigh its weak points. For decades, geothermal companies have been drilling into Earth’s crust at depths of over 4-5km.

You can’t just dig anywhere to find real, efficient, abundant geothermal energy – it has to be an area where the crust is thinner, so to reach the outer core. If you want to heat up your home, for example, you don’t need to dig that low; a few tens of meters are enough. Still, if you’d like more, you have to go deep.

Going that deep implies nothing bad at a first glance, but taking a second look above everything, you can cause an earthquake. That’s what happened in Basel, Switzerland just a few years ago, and that’s what’s beginning to happen 90 miles from San Francisco, in Anderson Springs. The drilling in Basel caused a magnitude 3.4 geothermal earthquake.

Scientific American digs into this matter in an interview with U.S. Geological Survey Earthquake Hazards Team seismologist David Oppenheimer, who is based in Menlo Park, Calif., just a couple hours south of Anderson Springs area. Mr. Oppenheimer explains how geothermal drilling can be made safe and how measures are being taken to prevent geothermal earthquakes from happening. Still, if they happen, he says, they’re guaranteed not to exceed 2 Richter-scale degrees.

The project in Anderson Springs has big stakes: the U.S. Department of Energy has already chipped in $36 million for AltaRock’s project. In an effort to drive down the price of renewable energy, Google has financed it with up $6.25 million, the Times reported.

The phenomena is the following, as explained by David Oppenheimer: “Here’s what we know: You can think about The Geysers-the upper three miles (4.8 kilometers) of crust-as a sponge, and the sponge is wet. Now we’re taking fluid out of the sponge, and we’re taking heat out of the sponge. When you dry out a sponge, it contracts. The Geysers is contracting. From the data, we can see it pulling in, which means that it’s changing the stress field around it. Surrounding the field are some active faults, which have the capacity for some larger earthquakes. So one day one of the tectonic faults is going to move.

Every source of energy seems to have its drawbacks: we know them for oil, wind mills can disturb the birds and the wind activity, biofuels cause starvation in the long run, and here’s the geothermal drilling kicking in. These facts are known for decades, but the winning technology is the one who will manage to naturally minimize all the side effects. In my opinion, solar is the most promising. All we have is to capture what we are “given”, and do what we want with it.

With all the technological advancements going on, and despite all the efficiency increasing from year to year, we still consume more and more, because the efficiency can make us afford this consumption. There is a critical point, though, where nature will say “Stop!”, and then we’ll stop. Will it be geothermal earthquakes, or floods, or global warming, I don’t know. All I know is that, from time to time, we have to keep our money into our pockets and stop spending so much energy. I must say that the Earth seems to be alive, with the risk of being non-scientific. Alive in a different way, at least.

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3 COMMENTS

  1. “You can’t just dig anywhere to find real, efficient, abundant geothermal energy…”

    No, you just have to dig deeper in some areas than in others. That means that it will be less expensive to install dry rock geothermal in some places than in others.

    Right now we have the ability to dig deep with smaller diameter holes as we search for oil. There’s work to be done on building larger diameter drilling rigs for geothermal. But that’s almost certainly a short term engineering problem.

    “90 miles from San Francisco, in Anderson Springs. The drilling in Basel caused a magnitude 3.4 geothermal earthquake.”

    Ninety miles from SF is a huge distance. The 1989 Loma Prieta earthquake was measured at 6.9. There was no damage 90 miles away.

    The strongest quakes triggered by geothermal and oil drilling have been <4.0. We experience about 49,000 quakes of this intensity per year.

    "Now we’re taking fluid out of the sponge, and we’re taking heat out of the sponge. When you dry out a sponge, it contracts."

    Hot rock geothermal does not "take fluid out of the sponge", it puts fluid in. And that may be what causes the small tremors. Liquids are lubricants and if there are rocks under pressure in the area, but not moving due to friction, then introducing a lubricant could allow slippage.

    "nature will say “Stop!”, and then we’ll stop. Will it be geothermal earthquakes, or floods, or global warming, I don’t know. All I know is that, from time to time, we have to keep our money into our pockets and stop spending so much energy."

    No, we need to spend a lot of money on energy. Right now.

    We need to spend lots of money in order to shut down plants that burn coal to produce electricity.

    But at the same time we also need to spend money to reduce our per capita energy use. Energy conservation can help us use a lot less energy while not lowering our standard of living.

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