Small Earthquake in Basel on 29. June 2013

On Saturday, 29 June 2013 at 11:11 local time the SED recorded an earthquake of magnitude 1.7 in Basel. The earthquake occurred very close to the site of the now terminated deep geothermal project (Deep heat mining DHM Basel) at a depth of approx. 4 km (based on relative relocation using previous events). It was sporadically felt in Basel but did not cause any damage.

Saturday's event is directly related to the region stimulated in December 2006, as comparison with earlier events induced by the hydraulic stimulation of the DHM project in December 2006 show. This event is the strongest to occur in the geothermal project reservoir area since November 2007.

The occurrence of such micro-events is not unusual. Model calculations show that the seismic activity in the stimulated area will decrease continually, but that it will take approximately between 8 to 15 years until it returns back to pre-stimulation levels. Similar events will occasionally occur during this period.

The image shows the location of the event (bold red circle) relative to earlier events in a depth cross-section looking north-northwest and centered on the bottom of the borehole casing. Blue: Events during the stimulation 2006; black: after the termination of the stimulation in Dec. 2006; green: events in 2007; red: events in 2010, 2012, 2013. The circle diameter scales with earthquake magnitude.