Time dependent modeling of the magma chambers in Aira caldera and Kirishima volcanoes, Japan

Volcanic activity is strongly correlated with volume change in magma reservoir. It is very important to estimate time evolution of magma reservoir for hazard estimation. For that purpose, a dense GNSS network was installed in Japan and in operation for the last two decades (Sagiya, 2004). The GNSS network covers south Kyushu, southwest Japan, where many active volcanoes exist. Aira caldera and Kirishima volcanoes are located in south Kyushu, southwest Japan. Aira caldera is one of the most active volcanoes with an active cone of Sakurajima. Kirishima is a group of volcanoes north of Aira caldera. It is proposed that the magmatic systems are connected between Aira caldera and Kirishima area based on GNSS data (Brothelande et al., 2018). It is quite important to investigate time evolution of magma chamber beneath Aira caldera and Kirishima area in unison to get insight into the magmatic system in these areas. Global Navigation Satellite system detects ground displacements in the region of Aira caldera, Sakurajima and Kirishima volcanoes. We estimate the time evolution of the Mogi sources beneath Aira caldera, Sakurajima, and Kirishima volcanoes by applying the time dependent inversion to the position time series. The locations of the Mogi sources are adopted from the preceding studies (Nakao et al., 2013). The result shows the long-term inflation of the Mogi sources in Aira caldera and Sakurajima volcano with fluctuation over time. The magma chamber deflated in the long-term from 1996 to 2008 and inflated rapidly before and after the eruption of Kirishima volcanoes in 2011 and 2018. At the time of the 2011 and 2018 eruption, the Mogi source is estimated to have shrunk with the volume change estimated to be 12×106 in 2011 and 7×106 m3 in 2018, respectively. Charging, discharging, and recharging processes at the time of the 2011 and 2018 eruptions indicate a possibility of eruption prediction in Kirisima volcanoes. Inflation speed of the mama chamber in Aira caldera slowed down at the time of recharging of Kirishima magma chamber in 2011, as is pointed out by Brothelande et al. (2018). At the time of charging of Kirishima magma chamber before the 2018 eruption, inflation speed of the mama chamber in Aira caldera slowed down. It remains to be solved the connectivity hypothesis between Aira caldera and Kirishima volcanoes.