Ground Surface Displacement of Kirishima Volcano Group Detected by ALOS-2 InSAR Time Series Analysis and Effect of Atmospheric Noise Reduction

Abstract

We applied InSAR time series analysis using ALOS-2 data (September 2014 to October 2017) to the Kirishima volcano group, and successfully detected localized and slow ground surface displacement around Mt. Shinmoe and Mt. Iwo. Mt Shinmoe had slowly inflated for two years or more, and it can be explained well by reaccumulation of magma at a shallow source beneath the crater which was estimated to have deflated between November 2011 and May 2013. Such localized and slow displacement is difficult to be detected by other methods than InSAR time series analysis. We also investigated the effect of atmospheric noise reduction using a numerical weather model. The numerical weather model significantly mitigated a stratification component of the atmospheric noise, which has a seasonal and topographical correlation. Without the numerical weather model, the seasonal atmospheric noise may leak into the time series of displacement, even if a spatio-temporal filter is applied, possibly resulting in an incorrect assessment of volcanic activities.