The Inflation-deflation History of Aira Caldera for the Last 120 Years and the Possibility of a Forthcoming Large Eruption at Sakurajima Volcano(＜Special Section＞Sakurajima Special Issue)

Abstract

In order to assess the potential for future eruptive activity at Sakurajima volcano, southern Japan, ground deformation around northern Kagoshima Bay (i.e., Aira caldera), especially the height change between leveling stations 2474 and 2480, was re-analyzed. Prior to the large eruption in 1914 at Sakurajima volcano, a remarkable inflation was confirmed at Aira caldera, based on re-surveyed data that were not referred to in previous investigations. Considering those data, the upper limit of the magma storage at Aira caldera just before the 1914 eruption could be obtained. Although the 1914 eruption accompanied a remarkable deflation at Aira caldera, magma started to accumulate again and was likely to have exceeded the level observed in 1900 (14 years before the large eruption). Around the early 1970s, it approached the level before the 1914 eruption. After the ground uplift stopped and slightly reversed during a period of extremely frequent explosions at Sakurajima volcano in the 1970s and 1980s, the inflation seems to again be approaching the inferred level before the 1914 eruption, suggesting the possibility of the next large eruption. In addition, inconsistencies between the inferred amounts of magma supply and observed volumes of erupted materials were discussed and left for further study.