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[SVC31-03] Issue of volcanic warning, eruption occurrence and volcanic activity evaluation in Japan
Keywords:volcanic warning, eruption occurrence, volcanic activity evaluation
17 years have passed since the Japan Meteorological Agency began issuing volcanic forecasts and volcanic warnings on December 1, 2007. During this time, there have been many eruptions and volcanic warnings issued. We report here on a comprehensive summary of whether volcanic warnings have been issued at the appropriate time in response to eruption activity.
We investigated cases where volcanic forecasts were raised to volcanic warnings between December 1, 2007 and February 15, 2025 for volcanoes under constant observation. The survey covered 73 cases at 22 volcanoes. Of these, 69 cases from 21 volcanoes were examined to see whether eruptions occurred (hit), or did not occur (fault) during the volcanic warning, or eruptions occurred without the volcanic warning (miss). The results were 14 hits (20%), 45 faults (65%), and 10 misses (15%). Among volcanoes that have issued five or more volcanic warnings, Asamayama and Asosan had a relatively high rate of the hits.
However, in volcanoes such as Sakurajima, where eruption activity has continued for a long period, we cannot appropriately evaluate. Therefore, we investigated the percentage of days of the hits, the faults, and the misses relative to the number of days for which volcanic warnings were issued. The hits rate is 0.5% (16/2945) for Asamayama, 30.3% (597/1973) for Asosan, and 59.9% (3761/6281) for Sakurajima. From the above, we can see that the hits rate is lower for volcanoes with less frequent eruptions.
A volcanic warning is issued when it is determined that an eruption is imminent, and shows the area requiring caution. Therefore, it is therefore more important, but also more difficult, to issue an appropriate volcanic warning when no eruption is occurring than when eruptions are continuous or intermittent. Further research in volcanic activity evaluation is needed to improve the accuracy of volcanic warnings for volcanoes that erupt infrequently.
We investigated cases where volcanic forecasts were raised to volcanic warnings between December 1, 2007 and February 15, 2025 for volcanoes under constant observation. The survey covered 73 cases at 22 volcanoes. Of these, 69 cases from 21 volcanoes were examined to see whether eruptions occurred (hit), or did not occur (fault) during the volcanic warning, or eruptions occurred without the volcanic warning (miss). The results were 14 hits (20%), 45 faults (65%), and 10 misses (15%). Among volcanoes that have issued five or more volcanic warnings, Asamayama and Asosan had a relatively high rate of the hits.
However, in volcanoes such as Sakurajima, where eruption activity has continued for a long period, we cannot appropriately evaluate. Therefore, we investigated the percentage of days of the hits, the faults, and the misses relative to the number of days for which volcanic warnings were issued. The hits rate is 0.5% (16/2945) for Asamayama, 30.3% (597/1973) for Asosan, and 59.9% (3761/6281) for Sakurajima. From the above, we can see that the hits rate is lower for volcanoes with less frequent eruptions.
A volcanic warning is issued when it is determined that an eruption is imminent, and shows the area requiring caution. Therefore, it is therefore more important, but also more difficult, to issue an appropriate volcanic warning when no eruption is occurring than when eruptions are continuous or intermittent. Further research in volcanic activity evaluation is needed to improve the accuracy of volcanic warnings for volcanoes that erupt infrequently.