Aira caldera is one of the most active and hazardous calderas in the world. It is home to the Kirishima volcanoes, a group of active volcanoes at the north end of Aira caldera. One of these volcanoes, Shinmoedake, has produced two strong magneto-phreatic eruptions, separated by almost 300 years. Starting in December 2009, active diving and inflation before the outbreak were noticed. A series of sub-plinian events then occurred from January 19th to the 31st (Brothelande E., et al, 2018). The first phase (eruption climax) was accompanied by a strong co-eruptive deflation.