Over several months starting in February 1964, hundreds of earthquakes occurred in the Sarnen region. The two largest quakes, with magnitudes of 4.8 and 5.3 respectively, hit the region on 17 February and 14 March. The damage caused totalled around CHF 16 million at present value.
The earthquakes caused most damage in the municipalities of Sarnen and Kerns, where hardly any houses were left unscathed. The reason for this is that the geological substratum around Sarnen consists of marine and alluvial deposits and the subsoil around Kerns comprises sediment. These types of substrata tend to amplify seismic waves.
Although no fatalities or serious casualties resulted, there was real fear of an even stronger earthquake and several schools and churches were closed as a precautionary measure. However, after a few months the earthquake swarm petered out without any further major earthquakes occurring.
Looking at the past shows that Central Switzerland has experienced more than its fair share of earthquakes. Numerous historical events, including some high-intensity earthquakes, are well documented and have been investigated. One particular feature of the region is that phases of high earthquake activity alternate with longer quiet periods.
Noteworthy events include the series of 10 earthquakes occurring in the Altfdorf region in 1774, 11 verified earthquake events in the Sarnen region in 1777, and 19 felt and verified earthquakes occurring again in the main Obwalden Valley in 1917. Thus, the lack of seismic activity in the area since the earthquake swarm in 1964 constitutes a quiet period in the region's history.