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Item: Evaluation of an Avalanche Triggered by a Local Earthquake at the Vallée de la Sionne (Switzerland) Experimental Site

• • Title: Evaluation of an Avalanche Triggered by a Local Earthquake at the Vallée de la Sionne (Switzerland) Experimental Site

    Proceedings: International Snow Science Workshop Grenoble – Chamonix Mont-Blanc - October 07-11, 2013

    Authors:

    • C. Pérez- Guillén  [ Grup d’Allaus (RISKNAT), Universitat de Barcelona, Barcelona, Spain ]
    • E. Suriñach  [ Grup d’Allaus (RISKNAT), Universitat de Barcelona, Barcelona, Spain ]
    • G. Furdada  [ Grup d’Allaus (RISKNAT), Universitat de Barcelona, Barcelona, Spain ]
    • M. Hiller  [ WSL Institute for Snow and Avalanche Research SLF, Davos Switzerland ]
    • M. Tapia  [ Laboratori d'Estudis Geofísics Eduard Fontserè - Institut d'Estudis Catalans (LEGEF-IEC) ]

    Date: 2013-10-07

    Abstract: The snow avalanche group of the University of Barcelona in a collaboration with the SLF (Institute for Snow and Avalanche Research, Davos (Suiza)) monitors snow avalanches using infrasonic and seismic measurements at the experimental site of Vallée de la Sionne (VDLS). Snow avalanches are infrasonic and seismic sources in movement. The friction between the lower parts of the avalanche and the snow cover is the main source of the seismic signals. However, the interaction between the external parts of the avalanche (saltation and powder parts) with the air produces the main source of the infrasonic signal. Our installation allows us to record not only snow avalanches but also earthquakes, explosions and other seismic and infrasonic sources. On 6 December 2010, the snow avalanche alarm system of VDLS was triggered by a local earthquake 43 km from VDLS (ML 3.1; 6:41:24 UTC) with the hypocenter in France (46.05 N; 6.94 E; 3 km). At first, this alert was not considered as an avalanche because no data were recorded by the routine monitoring instruments. A subsequent analysis of the infrasonic and seismic data showed that seconds after the arrival of the earthquake a signal generated by an avalanche appeared. This avalanche did not descend along the main channel but along the secondary one. The analysis of the data of this avalanche probably triggered by the earthquake is presented. The study of the characteristics of the infrasound data allows us to delimit the interval time of the release of the avalanche. Subsequently, values of the ground vibration (PGA, Ia, Td) produced by this earthquake are compared with those of other earthquakes that did not trigger an avalanche. Finally, the weather and snow conditions of the days on which these events occurred are compared and evaluated according to the quantification of stability conditions. It may be concluded that the snowpack conditions are a determining factor in avalanche formation.

    Object ID: ISSW13_paper_O4-08.pdf

    Language of Article: English

    Presenter(s): Unknown

    Keywords: avalanche, earthquake, seismic data, infrasound, snow stability factor

    Page Number(s): 183-190

    Subjects: snow avalanche snowpack conditions seismic detection of avalanches

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