桜島火山における繰り返し相対重力測定（2023年10～11月および2024年3月）

Abstract

Relative gravity values were repeatedly measured at 27 gravity points around Sakurajima Volcano in October-November 2023 and March 2024, to monitor spatiotemporal mass variations associated with volcanic activity. The gravity points include 8 points where gravity values were measured for the first time in the last 10 years. The gravity values obtained from 1998 to 2024 showed a clear increase of up to +5.6 μGal/yr at the central part of the volcano. The gravity increase can be explained by the point mass increase of 1.4×10¹⁰ kg/yr under the center of the volcano at a depth of 4.0 km below sea level. This result implies that volcanic mass continuously increases under Sakurajima Volcano, even during the quiet period of eruptive activities at the Minami-dake crater.