Figure 1

Overview of the monitoring system and the eruption sequences at Shinmoe-dake. (a) A map of Kirishima volcanic group in southwestern Japan (the white square in the inset: Goole Earth, Data SIO. NOAA.U.S. Navy NGA GEBCO). The white triangles indicate Shinmoe-dake and Iwo-yama. The colored circles are seismic stations used in this study, and white markers show other seismic stations. The vertices of the black triangle are the GEONET stations calculating the areal strain⁴³, which represents the deep inflation beneath the asterisk⁴⁰. The star indicates the epicenters of deep low-frequency earthquakes, whose rate correlated with the inflation at the asterisk⁴⁴. (b) A schematic representation of Shinmoe-dake eruption sequences^34,41. ① The August 2008 phreatic eruption, ② minor phreatic eruptions, ③ the main phase of the 2011 eruption, ④ the end of the 2011 eruption, ⑤ the 2017 eruption, ⑥the main phase of the 2018 eruption, ⑦ the April 2018 phreatic eruption at Iwo-yama, and ⑧ the end of the 2018 eruption. The purple, light-gray, and dark-gray clouds indicate phreatic, ash-forming, and vulcanian eruptions, respectively.