3:30 PM - 5:00 PM
[SVC32-P03] Investigation of Ashfall Survey Methods during Volcanic Eruptions at Hakusan Volcano
Keywords:volcanic eruption, emergency survey, ash fall survey, normalcy preparation
Hakusan Volcano is an active volcano with an elevation of 2702 m located on the border between Ishikawa and Gifu prefectures. Hakusan volcano has erupted at least 23 times in the past 10,000 years, with a small pyroclastic flow occurring in the 1554 eruption. In recent years, volcanic earthquakes have occurred with epicenters near the summit. In March 2021, the Hakusan Volcanic Eruption Emergency Mitigation Sabo Plan was published, and it was assumed that ash fall from a phreatic eruption would reach approximately 12 km from the crater, and from a magmatic eruption, approximately 38 km from the crater. The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) is making preparations from normal times, as an emergency survey for debris flows caused by volcanic eruptions. In this paper, we will introduce a study of ash fall survey methods during volcanic eruptions at Hakusan volcano.
During a volcanic eruption, it is necessary to confirm the location of the crater and the extent of ash accumulation by aerial survey using a helicopter. In order to ensure prompt and efficient surveys in the event of a volcanic eruption, we have studied the flight routes around Hakusan volcano, the establishment of survey points, and the confirmation points for each survey point, and have developed a register of helicopter survey points. In the field survey on the ground, since the survey is required to efficiently draw isopleths of ash fall thickness (i.e., isopachs), the ash fall area is delimited by a mesh and ash fall survey points are set. The mesh size is 2 km for phreatic eruptions and 5 km for magmatic eruptions. Because there are few roads around Hakusan volcano, there are many cases where ashfall survey points cannot be set even if a mesh is set. Ash fall survey points are listed in a ledger by location, and in addition to latitude and longitude, a map code that can be used with a car navigation system is also included, along with photographs of the site. On the other hand, a method using existing surveillance cameras is also being considered as a way to quickly assess the ash fall thickness without conducting a field survey. A surveillance camera ledger is being made for each camera, which lists the height of structures, white lines on roads, and other representative objects that can be used to determine ash fall thickness. This method can be used not only for ash fall surveys, but also for snow surveys during snowy eruptions. Training is also conducted for staff of MLIT members to ensure prompt response in the event of a volcanic eruption. Training is conducted on actual activities such as surveying ash fall using actual volcanic ash, estimating the extent of ash fall from helicopter images, and drawing isopleths of ash fall thickness based on the results of field surveys. Since the roads around Hakusan volcano are limited and it may not be possible to conduct ash fall surveys from the ground, it will be necessary to study ash fall survey methods using UAVs and satellite images in the future.
During a volcanic eruption, it is necessary to confirm the location of the crater and the extent of ash accumulation by aerial survey using a helicopter. In order to ensure prompt and efficient surveys in the event of a volcanic eruption, we have studied the flight routes around Hakusan volcano, the establishment of survey points, and the confirmation points for each survey point, and have developed a register of helicopter survey points. In the field survey on the ground, since the survey is required to efficiently draw isopleths of ash fall thickness (i.e., isopachs), the ash fall area is delimited by a mesh and ash fall survey points are set. The mesh size is 2 km for phreatic eruptions and 5 km for magmatic eruptions. Because there are few roads around Hakusan volcano, there are many cases where ashfall survey points cannot be set even if a mesh is set. Ash fall survey points are listed in a ledger by location, and in addition to latitude and longitude, a map code that can be used with a car navigation system is also included, along with photographs of the site. On the other hand, a method using existing surveillance cameras is also being considered as a way to quickly assess the ash fall thickness without conducting a field survey. A surveillance camera ledger is being made for each camera, which lists the height of structures, white lines on roads, and other representative objects that can be used to determine ash fall thickness. This method can be used not only for ash fall surveys, but also for snow surveys during snowy eruptions. Training is also conducted for staff of MLIT members to ensure prompt response in the event of a volcanic eruption. Training is conducted on actual activities such as surveying ash fall using actual volcanic ash, estimating the extent of ash fall from helicopter images, and drawing isopleths of ash fall thickness based on the results of field surveys. Since the roads around Hakusan volcano are limited and it may not be possible to conduct ash fall surveys from the ground, it will be necessary to study ash fall survey methods using UAVs and satellite images in the future.