Crack in the World 2

Intrepid reader Dan takes me to task for my last post, and we engaged in a slightly overheated exchange. No word yet on consequent earth tremors. I was a bit harsh in my reply, so Dan, I apologize.

I posted on a New York Times story about AltaRock, a company experimenting in Northern California on the use geothermal energy as a possible source of electricity. Apparently the process can cause earthquakes, and the Times story indicated that AltaRock had ceased drilling for that reason. Dan says this:

I hate to burst your bubble with reason, but the suspension of operations at The Geysers was not due to earthquakes, but rather do to drilling problems inherent in felsite, a very brittle rock which is very difficult to drill. The earthquake hysteria you quote originated from a NY Times article referencing a barely perceptible quake (yes, 3.4 is barely perceptible) that occured due to a similar, albiet poorly managed, geothermal research project on the other side of the globe. The Geysers project never reached the target depth to even begin the experiment. And yes, The Geysers, as well as much of California, experiences earthquakes every single day. Most residents understand that process, even children. A very few create hysteria blaming earthquakes on everything from weather to homosexuality - the adults do that, not the children.

Dan is apparently saying that the experiments in the area north of San Francisco called "the Geysers" did not in fact cause earthquakes. Unfortunately he provides no links or references so I cannot check his information.

Well, I went back and reviewed the Scientific American article I linked to in the original post. The article included an interview with U.S. Geological Survey Earthquake Hazards Team seismologist David Oppenheimer. He sounds like the kind of person who would know about this. The technology used in the Geysers involves pumping water into deep, hot rock in order to fracture it and create steam. Here is what he says about the earthquakes:

What they need to do, from an engineering perspective, is keep the size of the fractures small. So they will control the [water] flow rates and pressures to make sure it doesn't become a runaway earthquake.

We've been monitoring [The Geysers] since 1975. All the earthquakes we see there are [human] induced. When they move production into a new area, earthquakes start there, and when they stop production, the earthquakes stop.

They've been inducing earthquakes since the 1960s, and the largest has been less than a [magnitude] 4.5. Earthquakes are occurring in many, many fractures. So that's very different than if you go south to the Bay Area with the San Andreas Fault. For earthquakes larger than 6.0 to happen, you need a big fault. Therefore, it's unlikely they'll intersect a large fault and trigger a larger earthquake.

The threshold goal for the earthquakes is 2.0 or lower. They don't want a repeat of Basel, Switzerland.

I don't know what Dan's expertise is, but if Oppenheimer is right then the geothermal experiments in the Geysers has been inducing earthquakes for quite some time. That bit about "when they stop production, the earthquakes stop," is reason, Dan. And Oppenheimer clearly indicates that it is possible for the process to trigger a "runaway earthquake" if it goes wrong. That sounds bad to me.

My point, however, was not that the experiments ought to be halted, let alone that we should not invest in geothermal energy. In fact, I wrote that "I am all for experimenting with such energy sources." I include in that wind power, solar power, and biofuels.

I posted about the earthquake thing because it is a rocking good story, and because it indicates something important to the current debate on green energy. However successful the experiments at the Geysers may be, they aren't close to the point that they can provide more than a very marginal contribution to our energy needs. The same is true of wind power, solar power, and biofuels. I have no love of big oil; I would be happy to see viable alternative sources of energy come online; but I also like to see things the way they are.

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An earthquake (also known as a quake, tremor, temblor or seismic activity) is the result of a sudden release of energy in the Earth's crust that creates seismic waves. Earthquakes are recorded with a seismometer, also known as a seismograph. The moment magnitude (or the related and mostly obsolete Richter magnitude) of an earthquake is conventionally reported, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale.

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