On the characterization of seismic signals generated by snow avalanches for monitoring purposes

Seismic signals from artificially released avalanches were studied in an attempt to characterize them for avalanche-monitoring purposes. The seismic signals generated by different sizes and types of avalanches were recorded and analyzed ill the time and frequency domains. Synchronized recordings of the corresponding seismic signals and the video images of the evolution of the avalanches were obtained together with a detailed cartography. Characteristic signatures in the frequency and time domains were found to depend on the characteristics of the avalanche path and measuring location, but to be mostly independent of avalanche size. The source of the different parts, of the recorded seismic signals was determined. A relationship was observed between the avalanche size and the amplitude of the signals. Given the presence of local site effects, a prior seismic characterization of the avalanche path in relation to the recording sites is necessary for monitoring purposes. Moreover, it was found that sliding slabs in the early, phase of acceleration produce little seismic energy, resulting in a time lapse between the observable start of the avalanche and the arrival of the detectable seismic waves at the receiving station.