A dense Global Navigation Satellite System (GNSS) network has been deployed at Sakurajima volcano since 1995 and extends to the surrounding area of the Aira caldera. The ground deformation obtained by GNSS observation corresponds to transient eruptive activity of Sakurajima volcano, which has produced frequent vulcanian eruptions since 1955. Inflation of the volcano was detected prior to the increase in vulcanian eruptions in 1999, and resumption of the eruptions at the Showa crater. Magma intrusion events and an increase in eruptions in late 2009, late 2011, and early 2015 suggest the existence of an open-conduit system from the Aira caldera to the vents at the summit area of the Minamidake cone, through the sub reservoir beneath the older Kitadake cone. Ground deformation induced by sudden dike intrusion is different from that of previous intrusions, as revealed by the dense GNSS network. GNSS data are useful in evaluating and forecasting volcanic activity, and are available to grasp the advection and diffusion of volcanic ash.

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