Frequency content evolution of snow avalanche seismic signals

Seismic signals generated by avalanches have been recorded by the avalanche team of the Universitat de Barcelona at the Vallee de la Sionne experimental site ( Switzerland) since 1998. During these years avalanches of varying size and flow were recorded by two sensors located at different positions. In the present paper we show the general features of the running spectra of the seismic signals for the different type of recorded avalanches. Using this method we are able not only to detect avalanches with low amplitude signals but also to distinguish between avalanches and other seismic sources (i.e., local earthquakes) which have the same frequency content but a different frequency evolution.