oh, there's an editorial in nature ( http://www.nature.com/nature/journal/v462/n7275/full/462848a... ) about how this could cause earthquakes? awesome. well, nothing worth doing is risk-free, right? also I love how when google funds something now, they also do it. it seems that all of the investigators were SMU people but because google.org paid for it, now it was discovered by google as well. ;)
'Fraking' has caused earth quakes in the uk, where they are trying to extract the gas down there. https://en.wikipedia.org/wiki/Hydraulic_fracturing But that is a slightly different thing to geothermal drilling. You're basically drilling 4km down, and putting a big pipe in. Then you run water through it, which heats the water. There have been no earth quakes caused in Australian drilling for geo thermal plants to my…
There was a serious earthquake in Switzerland caused by geothermal plants (not gas extraction). I believe minor ones have also occurred in the US. My understanding is that the risk is very manageable, though.