LAUSR

We present deformation measurements of the Kirishima volcanic complex from ALOS and ALOS‐2 Interferometric Synthetic Aperture Radar (InSAR) time series during 2006–2019. Shinmoe‐dake deflated ∼6 cm during the 2008–2010 phreatic eruptions and inflated ∼5 cm prior to the 2017 magmatic eruption. Iwo‐yama inflated ∼19 cm within the crater since January 2015 and ∼7 cm around the southern and western vents since 4 months before the 2018 eruption. These deformations can be modeled as ellipsoids at ∼700 m depth beneath Shinmoe‐dake and as a sphere on top of an ellipsoid at ∼130 and ∼340 m depths beneath Iwo‐yama. Combining geodetic, geoelectric, geochemical, and petrological analysis, we interpret the hydrothermal origin of the deflation at Shinmoe‐dake and inflation at Iwo‐yama; the hydrothermal–magmatic transition during the 2011 Shinmoe‐dake eruption; and water‐boiling and bottom‐up pressurization as driving mechanisms of the inflation at Iwo‐yama. The study highlights the imaging potential of InSAR time series on complex hydrothermal systems.