Induced seismicity in Basel led to suspension of its hot dry rock enhanced geothermal systems project.
[1] Basel, Switzerland sits atop a historically active fault and most of the city was destroyed in a magnitude 6.5 earthquake in 1356.
But the Basel project, although it had established an operational approach for addressing induced earthquakes, had not performed a thorough seismic risk assessment before starting geothermal stimulation.
[5][6][7] In all, between December 2006 and March 2007, the six borehole seismometers installed near the Basel injection well recorded more than 13,500 potential events connected with the geothermal project.
[3] Trip points of Richter magnitudeML 2.9 and a peak ground velocity of 5 millimeters per second were established by the project as independent criteria for a "red alert" that entailed halting fluid injection and bleeding-off to minimum wellhead pressure.
The six borehole seismometers installed near the Basel injection well to monitor the natural background seismicity and the geothermal stimulation recorded more than 13,500 potential events connected with the geothermal project, from which 3,124 were of sufficient quality to permit [hypocenter] determinations in the period 2–12 December 2006,[3] which spanned the main stimulation and the decline in the event rate.