Determinación de la velocidad de avalanchas de nieve mediante datos sísmicos

Abstract

Seismic instrumentation has proved to be a reliable tool for snow avalanche detection. In this approach, besides the detection skills of our system we pretend to go one step further. We aim to infer a physical parameter of the avalanche from seismic measurements. Specifically, we present a method to determine the propagation speed of snow avalanches using seismic techniques. The possible damage produced by an avalanche depends essentially on its size and speed. Unluckily the knowledge of these basic physical parameters is limited due to the difficulty of conducting measurements in the harsh winter weather conditions that usually accompany this phenomenon and the nature of the phenomenon itself. The method for avalanche speed determination presented is based on cross-correlation and time-frequency analysis techniques on seismic data. The data used came from Ryggfonn (Norway), the avalanche experimental site operated by the Norwegian Geotechnical Institute (NGI). The seismic waves are recorded by a set of 6 geophones buried along the main avalanche path. This method has been successfully applied to seismic data from 12 distinct avalanches. In the present document we examine the speed of the most well documented event, an avalanche artificially released on 16-04-2005. The availability of independent speed measurements for this event allowed a valuable comparison. The speeds obtained from seismic data are contrasted with speed estimates from CW-radar, pressure plate measurements and video images. In that case our method proved to be successful and robust, as validated by the above comparisons.