1:45 PM - 3:15 PM
[O08-P05] Research to predict the distribution of ash fall during the next major eruption of Sakurajima Volcano III
Keywords:Sakurajima Volcano, Wind direction , Ashfall distribution
This year marks 110 years since the Sakurajima volcano erupted in 1914. According to previous research, the magma chamber beneath Sakurajima is about 90% filled with magma, and it is predicted that the Sakurajima volcano will erupt in a major manner within the next few decades. In order to find out in which direction ash would fall depending on the time of year if Sakurajima Volcano were to have a major eruption, we investigated trends in wind direction over Sakurajima. During the three years up until last year, the seniors revealed the following. The data analyzed is from 2013 to 2022. When we divided the data into three heights: 0-5km, 5-20km, and 20-40km and examined the trends in wind direction, we found the following trends. From 0 to 5km, there is a lot of wind from the west, but the wind direction varies widely. It was found that winds were mostly from the west between 5km and 20km, and winds were mostly from the east between 20km and 40km, and wind direction trends varied depending on height. We obtained and utilized altitude-specific wind direction data published on the Kagoshima Local Meteorological Observatory web page twice a day at 9:00 and 21:00. When we contacted the Kagoshima Local Meteorological Observatory, they said that there was almost no difference between the wind direction over Sakurajima and the wind data observed at the meteorological observatory, and that they were using it for daily ashfall forecasts, so we used this data as the wind direction over Sakurajima. I decided to use it for research. The data used this time was 34,732 items from January 2012 to the end of December of the same year. If we predict that the next major eruption of Sakurajima Volcano will be on the same scale as the Taisho eruption 110 years ago, the plume of smoke from a major eruption is expected to rise to an altitude of 15 km. Therefore, in our research, we focused on wind data from 0 to 20 km. Results from January to December 2012 at 9:00 a.m. showed that in the summer months of July to September, winds were mainly blowing from the south, and at other times, winds were blowing mainly from the west to southwest. The 9:00 p.m. results from January to December 2012 showed almost the same trends as the 9:00 a.m. data. However, from November to March, the height is almost constant due to the westerly wind. The reason for this is thought to be the influence of the jet stream.
During the Taisho eruption 110 years ago, more than 30 cm of ash was observed in Kirishima City. The most intense eruptive activity was from January to February 1914 (Kagoshima Prefectural Museum 1985), but eruptive activity has continued intermittently since then, and ash fall from summer eruptive activity has caused damage to Kirishima City. It is thought that there was a considerable amount of ash fall. Therefore, to summarize our current research, when a major eruption of Sakurajima occurs from July to September, ash fall is expected to mainly head toward Kirishima City. At other times, tephra is expected to fall toward the Osumi Peninsula. Kirishima City should take measures now in anticipation of a major eruption occurring during the summer months from July to September.
During the Taisho eruption 110 years ago, more than 30 cm of ash was observed in Kirishima City. The most intense eruptive activity was from January to February 1914 (Kagoshima Prefectural Museum 1985), but eruptive activity has continued intermittently since then, and ash fall from summer eruptive activity has caused damage to Kirishima City. It is thought that there was a considerable amount of ash fall. Therefore, to summarize our current research, when a major eruption of Sakurajima occurs from July to September, ash fall is expected to mainly head toward Kirishima City. At other times, tephra is expected to fall toward the Osumi Peninsula. Kirishima City should take measures now in anticipation of a major eruption occurring during the summer months from July to September.