11:30 AM - 11:45 AM
[MTT38-09] An attempt to detect infrasound emitted from avalanches at Mt. Shiribetsu, Hokkaido
Keywords:Infrasound, Mt.Shiribetsu, Avalanche, Helicopter, Wheel Loader
There is no early detecting system for avalanches immediately after their occurrence, such as earthquake early warning. Meanwhile, it has been reported that infrasound is generated from avalanches, when avalanches are observed from distant locations, it will lead to disaster prevention and mitigation. In this study, infrasound observations for the purpose of avalanche detection were conducted from December 2022 to the end of March 2023 at Mt. Shiribetsu in Hokkaido. A sensor, INFRA-SOUND-SENSOR ADX III-INF04LE (manufactured by SAYA Inc), was installed in a helicopter hangar located approximately 3 km from Mt. Shiribetsu.
We investigated time series of infrasound data and spectrograms together with a flight timetable. The sound with about 6 Pa at maximum were detected around the helicopter's takeoff and landing time. We found that the sound appeared in all frequency bands. A few minutes before the landing time, frequency shifts were often observed indicating that the helicopter made the circle. From the shift, it could be estimate the velocity of the helicopter. Furthermore, we found that characteristic spectrums were often observed around 7:00 a.m. The spectrums show periodic shock-like fluctuations and continuous noise around 10 Hz. Since the clearing snow were often done at that window, those sound were emitted from the wheel loader. Those sounds show the wheel loader moving back and forth between.
As mentioned above, it is difficult to identify the sound from avalanches under the noisy environment with a single infrasound sensor. Therefore, we employed satellite imagery to detect the location and time of the avalanche. The results indicate that the avalanche could occur between 9 March 2023 to 15 March 2023. Since the satellite observed the mountain once a day and the cloud cover the mountain, it is hard to identify exact time of the avalanche. Because of this situation, the infrasound emitted from the avalanche has not yet been identified and is still being analyzed.
In order to conduct array observations to identify avalanches using infrasound sensors only, three infrasound sensors were installed in November 2023 around Mt. Shiribetsu. The differences in time of arrival are obtained with correlation analysis using infrasound data obtained by three sensors. As the results, position and occurrence time of the avalanches are estimated. Observations will be conducted until the end of March 2024 to attempt avalanche detection.
We investigated time series of infrasound data and spectrograms together with a flight timetable. The sound with about 6 Pa at maximum were detected around the helicopter's takeoff and landing time. We found that the sound appeared in all frequency bands. A few minutes before the landing time, frequency shifts were often observed indicating that the helicopter made the circle. From the shift, it could be estimate the velocity of the helicopter. Furthermore, we found that characteristic spectrums were often observed around 7:00 a.m. The spectrums show periodic shock-like fluctuations and continuous noise around 10 Hz. Since the clearing snow were often done at that window, those sound were emitted from the wheel loader. Those sounds show the wheel loader moving back and forth between.
As mentioned above, it is difficult to identify the sound from avalanches under the noisy environment with a single infrasound sensor. Therefore, we employed satellite imagery to detect the location and time of the avalanche. The results indicate that the avalanche could occur between 9 March 2023 to 15 March 2023. Since the satellite observed the mountain once a day and the cloud cover the mountain, it is hard to identify exact time of the avalanche. Because of this situation, the infrasound emitted from the avalanche has not yet been identified and is still being analyzed.
In order to conduct array observations to identify avalanches using infrasound sensors only, three infrasound sensors were installed in November 2023 around Mt. Shiribetsu. The differences in time of arrival are obtained with correlation analysis using infrasound data obtained by three sensors. As the results, position and occurrence time of the avalanches are estimated. Observations will be conducted until the end of March 2024 to attempt avalanche detection.