5:15 PM - 7:15 PM
[SVC32-P27] Vertical ground deformation of Sakurajima volcano measured by precise leveling survey (results of the Nov. 2024 survey)
Keywords:Sakurajima volcano, precise leveling survey, vertical ground deformation
We conducted the precise leveling survey in Sakurajima volcano, southwest Japan in November 2024. The leveling routes measured in this survey are about 23 km long in total, including Sakurajima western flank route and Sakurajima northern flank route. These leveling routes were measured during the period from November 6 to 15. Mean square errors of the conducted survey were achieved with a good accuracy ranging from ±0.21 to ±0.23 mm/km.
From the measured data, we calculated the relative height of each benchmark referring to the reference benchmark BM.S.17 which is located at the western coast of Sakurajima. The calculated relative heights of the benchmarks were then compared with those of the previous survey conducted in November 2023 (Yamamoto et al., 2024), resulting in the relative vertical displacements of the benchmarks during the period from November 2023 to November 2024.
The resultant displacements indicate the remarkable ground subsidence (-11.4 mm at maximum) at benchmarks around the central part of Sakurajima. The ground subsidence is also detected at benchmarks near the northern part of Sakurajima, implying that the magma storage at the magma reservoir beneath Aira caldera was not significant during the period from November 2023 to November 2024. From the preliminary analysis based on Mogi's model, deflation source is located beneath the central part of Sakurajima. The results indicate that the pressure decrease is suggested at the magma reservoir beneath Minamidake crater. In the presentation, we will report the results using the leveling data of wider area around Aira caldera.
From the measured data, we calculated the relative height of each benchmark referring to the reference benchmark BM.S.17 which is located at the western coast of Sakurajima. The calculated relative heights of the benchmarks were then compared with those of the previous survey conducted in November 2023 (Yamamoto et al., 2024), resulting in the relative vertical displacements of the benchmarks during the period from November 2023 to November 2024.
The resultant displacements indicate the remarkable ground subsidence (-11.4 mm at maximum) at benchmarks around the central part of Sakurajima. The ground subsidence is also detected at benchmarks near the northern part of Sakurajima, implying that the magma storage at the magma reservoir beneath Aira caldera was not significant during the period from November 2023 to November 2024. From the preliminary analysis based on Mogi's model, deflation source is located beneath the central part of Sakurajima. The results indicate that the pressure decrease is suggested at the magma reservoir beneath Minamidake crater. In the presentation, we will report the results using the leveling data of wider area around Aira caldera.