Auros (auros) wrote,

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Geothermal Earthquakes

The New York Times had an article last month, that I missed until now, about the Alta Rock deep geothermal project up in the area of The Geysers, a current geothermal field. They discuss the numerous small quakes that are already created by the expansion and contraction of rock in the area as water is injected (causing cooling and contraction of the rocks, opening fissures), as steam is created (creating pressure that further expands the fissures and creates new cracks), and as the steam is extracted (relieving pressure).

They also have a story about a similar deep well in the vicinity of Basel, Switzerland, that seems to have caused some significant shaking. The article feels to me a bit overwrought in its descriptions of the problems in Basel. They play up how terrifying the quake was, and barely mention the fact that nobody got hurt. Not even people standing directly over the borehole. This sounds to me like an argument for building your geothermal projects out in a rural area, rather than right by a major city. Alta Rock's project is, in fact, far from any major city, suburb, or exurb.

A lot of people seem to be scared that the Alta Rock project might set off a truly major quake. Color me skeptical. Major quakes happen when pressure builds up along a fault line for a very long time, and then the energy is all released at once. Having numerous small quakes sounds, to me, like a good thing. If it really turns out that we can induce quakes, it might actually be a good idea to start doing so at significant stress points along the major fault lines, on an ongoing basis. The fact that this happens to be a method for producing extremely high-temperature / high-pressure steam, which can generate a lot of energy, is an added bonus.

Geothermal is, IMHO, one of the more promising sources of base load energy generation; if we have to provide some relocation funding, or funding for people to build houses that can withstand small quakes on a regular basis, fine. But I don't think we ought to have the "paper of record" suggesting that it's going to cause a huge quake that will knock down San Francisco when it seems equally-or-more likely that it will actually help relieve pressure through small quakes, reducing the chance of a "Big One".

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