11:15 AM - 11:30 AM
[SVC26-09] Vertical ground deformation of Sakurajima volcano measured by precise leveling survey (results of the Nov. 2023 survey)
Keywords:Sakurajima volcano, precise leveling survey, vertical ground deformation
We conducted the precise leveling survey in Sakurajima volcano, southwest Japan in November 2023. 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 17. Mean square errors of the conducted survey were achieved with a good accuracy ranging from ±0.21 to ±0.24 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 2022 (Yamamoto et al., 2023), resulting in the relative vertical displacements of the benchmarks during the period from November 2022 to November 2023.
The resultant displacements indicate the ground uplift (5.8 mm at maximum) at benchmarks near the northern part of Sakurajima. It is suggested that the magma storage at the magma reservoir beneath Aira caldera is progressing during the period from November 2022 to November 2023. On the other hand, the minor ground subsidence is seen at benchmarks around the central part of Sakurajima, implying that the pressure decrease at the magma reservoir beneath Minamidake crater is not remarkable during the period. From the preliminary analysis based on Mogi’s model, inflation and deflation sources are located beneath Aira caldera and beneath Minamidake crater, respectively.
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 2022 (Yamamoto et al., 2023), resulting in the relative vertical displacements of the benchmarks during the period from November 2022 to November 2023.
The resultant displacements indicate the ground uplift (5.8 mm at maximum) at benchmarks near the northern part of Sakurajima. It is suggested that the magma storage at the magma reservoir beneath Aira caldera is progressing during the period from November 2022 to November 2023. On the other hand, the minor ground subsidence is seen at benchmarks around the central part of Sakurajima, implying that the pressure decrease at the magma reservoir beneath Minamidake crater is not remarkable during the period. From the preliminary analysis based on Mogi’s model, inflation and deflation sources are located beneath Aira caldera and beneath Minamidake crater, respectively.