On 13 April 2014, the Swiss Seismological Service (SED) registered two earthquakes near Diemtigen in the Berner Oberland, which later turned out to mark the start of an earthquake swarm, comprising a further 260 quakes in the region up to the end of 2014. Three of these (detailed below) were strong enough to be felt by local inhabitants, but no damage was caused:
- 10 May 2014, 03:43, magnitude 2.7
- 25 June 2014, 11:33, magnitude 2.6
- 15 October 2014, 21:36, magnitude 3.2
The swarm started subsiding substantially in January 2015, disappearing almost completely over the next few months before intensifying again in mid-July. This culminated in another palpable earthquake, with a magnitude of 2.7, occurring at 20:34 on 15 August.
The 'Diemtigen Swarm' is one of the most active earthquake swarms ever recorded by the SED, and between June 2014 and April 2015 it set up three mobile seismic stations in the region to investigate it more closely. Initial analysis indicates that the earthquakes occurred in a steep planar fracture zone measuring 400 by 700 metres roughly 9 kilometres beneath the Earth's surface. Highly sensitive instruments have detected earthquakes with a magnitude of -1.5 there. Between January 2014 and September 2015 around 2,300 microearthquakes were registered, providing an extremely detailed picture of the activity associated with the swarm (see frequently asked questions "What does minus magnitude mean?" and "What is microseismicity?".