2022 Volume 84 Issue 5 Pages 421-432
We tried infrasonic monitoring of snow avalanche at Mt. Fuji. We installed infrasound sensors, a thermometer-probe snow-depth meter, and seismometers for two winter seasons from 2018 to 2020 and made integrated analyses of their data. Although no significant snow avalanche event occurred during our observation, we found many infrasound waveforms similar to the reported snow avalanche infrasound. Because the infrasound events accompanied little seismic power, we inferred surface phenomena, if not necessarily snow avalanches, generated them. The events’ occurrences were concentrated during and right after snow-falls and during snow melting. The infrasonic array analyses of the 2019-2020 dataset exhibited most of the events are from the north slopes below the observation site. From the summit direction, continuous infrasonic noise was frequently detected, by which detecting events from there might have been difficult. This study has shown that the multi-parameter observation method is practical and useful in the severe environment of Mt. Fuji in winter. Also, it revealed the particular problems of infrasound observation at the huge volcanic edifice. We expect our results will help design future observations.
