An earthquake with a local magnitude of 4.3 occurred on Saturday 1st July 2017 at 10:10 (local time) close to Château d’Oex (VD) at a shallow depth, approximately 4km. It was strongly felt in the epicentral region (Pays-d’Enhaut). Slight damages are probable in this region. It was felt in the canton Vaud, Fribourg, in the Valais and in canton Bern. More than 1300 testimonies were posted on our website in 2 hours.
The seismicity in this zone has been elevated since 2016 and several events up to magnitude 2.7 were felt in 2016 and 2017, the last one on 13th May. Saturday’s earthquake was clearly stronger. The M4.3 is part of a sequence that we expect will continue with lower magnitude events that will last for weeks, or even months. Some of them, like that at 11:29 (magnitude 2.6) will be felt in the epicentral region, and the population should expect additional quakes in the coming days. An event as strong as that of Saturday or even stronger cannot be ruled out but has a relatively low probability.
The earthquake is related to the rupture of a normal fault (extension) oriented E-W, as the previous events recorded since 2016. A broadband moment tensor inversion also suggests a shallow event with moment magnitude Mw4.0 and a normal focal mechanism. The station SCOD in the town of Château d'Oex recorded a strong motion acceleration of 1.5m/s2 – this is the second largest instrumental recording in Switzerland.
Historically, this region has been hit by an earthquake in 1770 also close to Château d’Oex, for which the magnitude was estimated to 5.2 and the epicentral intensity of VI (obtained from the damages). By comparison, Saturday’s earthquake has an epicentral intensity of V.
In Switzerland, an earthquake of magnitude greater than 4 occurs on average every year. Another earthquake of magnitude 4.6 occurred in March this year in canton Glarus with relatively similar consequences across a larger area.
The colored squares on the map show where the earthquake was felt and reported to us. In the background, the instrumentally recorded intensity is shown.