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News Archive 2018

2018-02-08

Using seismic measuring devices to record avalanches

Using seismic measuring devices to record avalanches

Avalanches pose a danger to mountain villages and snow sports enthusiasts. Some recent avalanches have provided important information for reliably assessing avalanche danger. However, since many avalanches fall at night or in uninhabited areas, there is often uncertainty about when they occurred and how many actually swept down into the valleys below. A joint project by the Swiss Seismological Service (SED) at the ETH Zurich and the WSL Institute for Snow and Avalanche Research (SLF) showed that seismic measurements could help determine such facts.

However, there were a number of difficulties to overcome. Unlike earthquakes, the signals associated with avalanches have neither a clear beginning nor distinct wave phases. This makes avalanche falls hard to detect using conventional seismic methods. Furthermore, signal quality suffers from the continuous motion of descending avalanches. So researchers at the SED developed a computer model that uses special methods to process these signals. The model was tested on more than 350 real avalanches recorded by the SLF above Davos in 2012.

The results are promising: the computer model automatically recorded over 90% of all avalanche falls. Fine-tuning their detection would necessitate deploying a higher number of sensors in a more sophisticated configuration. The SED, in collaboration with the SLF, now intends to further investigate this and thereby make an important contribution towards forecasting avalanche danger.

Publication: Heck, M., Hammer, C., van Herwijnen, A., Schweizer, J., and Fäh, D.: Automatic detection of snow avalanches in continuous seismic data using hidden Markov models, Nat. Hazards Earth Syst. Sci., 18, 383-396, https://doi.org/10.5194/nhess-18-383-2018, 2018.

2018-02-01

[Available in DE / FR] Erneutes Erdbeben bei Bludenz (A)

Am Donnerstag, den 1. Februar 2018, hat sich um 02:47 Uhr (Lokalzeit) ein Erdbeben der Magnitude 4.1 ca. 10 km östlich von Bludenz ereignet. Bludenz liegt am nördlichen Ende des Montafon-Tals im Bundesland Vorarlberg in Österreich. Das Erdbeben wurde nach ersten Analysen ziemlich nahe an der Oberfläche lokalisiert, die Tiefe ist aber aufgrund der Entfernung zu den nächsten Messstationen nur sehr unsicher zu bestimmen. Bei einem Erdbeben dieser Stärke sind kleinere Schäden in der Nähe des Epizentrums nicht auszuschliessen.

 

Gemäss den Berichten, welche auf unserer Webseite in der ersten Stunde nach dem Erdbeben eingegangen sind, war das Erdbeben auch in Liechtenstein und in weiten Teilen der (Ost-)Schweiz, insbesondere in den Kantonen St. Gallen und Graubünden deutlich spürbar. Schäden sind in der Schweiz keine zu erwarten.

Dies ist das zweite deutlich verspürte Beben im Silvretta-Gebirge innerhalb der letzten zwei Wochen. Schon am 17. Januar 2018 hatte sich 13 km östlich von Bludenz ein Erdbeben mit einer Magnitude von 4.1 ereignet, das in der Schweiz (vor allem in der Ostschweiz) deutlich verspürt wurde.

2018-01-25

Earthquakes in Switzerland in 2017: an overview

Seismic events in 2017 once again showed that Switzerland is an earthquake country. There were two widely felt earthquakes with magnitudes above 4 and hundreds of aftershocks. Furthermore, the Swiss Seismological Service (SED) at ETH Zurich recorded more small quakes than ever before. In all, some 1'230 earthquakes were registered in Switzerland and its neighbouring countries in 2017.

On 3 March 2017, Switzerland was shaken by the strongest earthquake in more than 10 years. The earthquake with a magnitude of 4.6 occurred near Urnerboden in the border area between Uri, Schwyz and Glarus. It was felt in many parts of Switzerland and caused some minor damage to buildings near the epicentre and 100 aftershocks. The last earthquake larger than this, with a magnitude of 4.9, occurred on 8 September 2005 near Vallorcine (France) just across the Swiss border close to Martigny (VS). A second widely felt earthquake in 2017 took place on 1 July near Château-d'Oex (VD). This earthquake had a magnitude of 4.3 and triggered approximately 240 aftershocks, some of which were also felt.

Overall, in 2017 the SED registered and located more events than ever before: around 1'230 earthquakes in Switzerland and its neighbouring countries. More than 700 of these were microearthquakes, with magnitudes of less than 1.0 to -0.4. Such earthquakes are becoming increasingly “visible” in some parts of the country thanks to the improvement of Switzerland's seismic measuring system, which is making an important contribution towards gaining a deeper understanding of the structures and processes in the country's subsurface. In 2017, 23 earthquakes occurred with magnitudes of 2.5 or higher, in line with the average for the past 42 years. The earthquake activity was concentrated mainly in the Valais, Grisons and the area along the Alpine front.

Furthermore, earthquakes were clearly felt last year by sections of the Swiss population near Vallorcine (France) on 20 March (magnitude 3.0), near Sion (VS) on 2 June and 5 August (with magnitudes of 3.3 and 2.4 respectively), as well as near Zug (ZG) on 21 November (magnitude 3.3).

Year-by-year fluctuations in earthquake frequency are normal and do not permit conclusive forecasts of future seismicity. As a rule, damaging earthquakes with a magnitude of 6 occur in Switzerland once in every 50 to 150 years. The probability of this occurring in 2018 is therefore about 1 percent.

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2018-01-17

[Available in DE / FR] Erdbeben bei Bludenz (A) auch in der Schweiz deutlich verspürt

[Available in DE / FR] Erdbeben bei Bludenz (A) auch in der Schweiz deutlich verspürt

Am Mittwoch, 17. Januar 2018 hat sich um 20:07 Uhr (Lokalzeit) ein Erdbeben der Magnitude 4.1 13 km östlich von Bludenz (Vorarlberg, Österreich) ereignet. Bludenz ist das nördliche Ende des 39 km langen Montafon-Tals. Das Erdbeben war nach ersten Analysen ziemlich oberflächennah, die Tiefe ist aber aufgrund der Entfernung zu den nächsten Messstationen nur sehr unsicher zu bestimmen. Kleinere Schäden sind bei einem Erdbeben dieser Stärke in der Nähe des Epizentrums vereinzelt möglich.

Das Beben war auch in weiten Teilen der (Ost-)Schweiz, insbesondere im Raum St.Gallen (56 km Entfernung zum Epizentrum) deutlich spürbar.

Erdbeben sind im Silvretta-Gebirge keine Seltenheit. Bereits am 8. Januar 2018 hatte sich an der Grenze zwischen Vorarlberg und Tirol ein leichtes Erdbeben mit einer Magnitude von 2.9 ereignet, das in der Region schwach verspürt wurde.