There have been numerous trials that had to be stopped because of the triggered earthquakes... Geothermal is not so easy.

Was going to mention that point: http://www.seismo.ethz.ch/en/knowledge/geothermal-energy-ear...

The worst earthquake that was induced that way was 3.5, but given that one of the quakes happened in an area that had a catastrophic earthquake in the Middle Ages, some caution might be warranted: https://en.wikipedia.org/wiki/1356_Basel_earthquake