[SVC38-P37] Vertical ground deformation in Sakurajima volcano measured by precise leveling survey (during Nov. 2017 - Nov. 2018)
Keywords:Sakurajima volcano, precise leveling survey, vertical ground deformation
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 2017 (Yamamoto et al., 2018), resulting in the relative vertical displacements of the benchmarks during the period from November 2017 to November 2018.
The resultant displacements indicate the ground subsidence (-6.2 mm at maximum) at benchmarks around the central part of Sakurajima. The ground subsidence is also detected at benchmarks along Sakurajima northern flank route, suggesting that the inflation of the magma reservoir beneath Aira caldera was not remarkable during the period between November 2017 and November 2018. From the preliminary analysis based on a spherical source model (Mogi, 1958), the deflation source is located beneath Minamidake crater. The results indicate that the pressure decrease is suggested at the magma reservoir beneath Minamidake caused by the eruptive magma ejection.