Volcanic inflation of Mount Hokkaido-Komagatake, Japan, determined from a dense GPS array

We installed and have been operating a dense GPS array with low power consumption single frequency GPS receivers around Mount Hokkaido‐Komagatake volcano, southwestern Hokkaido, Japan, since 2000. Data were collected continuously and analyzed together with the Geographical Survey Institute of Japan's nationwide continuous GPS network data. The analysis of daily baseline length changes for two years indicate a steady inflation of the volcanic body with 10−7/yr extensional strain. A pressure source was estimated at 2.4 km depth beneath the summit area with a volumetric increase rate of 4.86 × 105 m3/yr. The depth of the pressure source is in good agreement with the one expected from petrological study. Integrated magma volume has reached up to 2.6 × 107 m3 if the inflation rate is possibly extrapolated back to the last magmatic eruption. Our results strongly suggest a steady magma accumulation at the reservoir beneath this volcano and an increasing potential to the next eruption near future.