Earthquakes in Switzerland and surrounding regions during 2013

This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2013. During this period, 699 earthquakes and 208 quarry blasts were detected and located in the region under consideration. With a total of 18 events with local magnitudes M-L a parts per thousand yen 2.5, the seismic activity in the year 2013 was slightly below the average over the previous 38 years. Most noteworthy were the two earthquake sequences of St. Gallen (SG) in July and Balzers (FL) in December. The former was induced by reservoir stimulation operations at the St. Gallen geothermal project. The maximum local magnitude in the sequence was 3.5, comparable in size with the M-L 3.4 event induced by stimulation operations below Basel in 2006. The sequence of Balzers was associated with an M-L 4.1 earthquake in the border region to Liechtenstein. More than 30 aftershocks with magnitudes ranging between M-L -0.2 and M-L 3.7 were detected in the month following the mainshock. The M-L 3.5 St. Gallen and the M-L 4.1 Balzers earthquakes were widely felt by the public but no reports on damages are known. The maximum intensity for both events was IV.