12:00 PM - 12:15 PM
[SVC26-12] Analysis of volcano deformation source of Izu-Oshima volcano using a volcano deformation calculation system considering volcanic topography
Keywords:Izu-Oshima, volcano deformation, GNSS
Volcano deformation data obtained from observation stations installed around volcanic craters are important for evaluating volcanic activity. In recent years, the Japan Meteorological Agency (JMA) has been installing GNSS and tilt meter station at volcanoes. These observation stations captured volcano deformation data that suggest activities of shallow pressure sources. However, since the observation stations around volcanic craters were installed on steep volcanic edifice, the observed deformation data were affected by the topography. Therefore, considering this effect when analyzing these data is important. We have developed a program to numerically calculate volcano deformation considering the volcanic topography. Applying this program to Izu-Oshima volcano, we investigated the effect of volcano topography on the estimated depth of pressure sources. As a result, when the pressure source was shallower than sea level, the depth of estimated pressure source is shallow if topography was not taken into account (Kawaguchi, 2023, JpGU). In this presentation, we report on the application of this program to GNSS observation data installed by the Meteorological Research Institute (MRI) on Izu-Oshima volcano to estimate the pressure source beneath the summit area of Miharayama.
The MRI has installed many GNSS stations on Izu-Oshima volcano to observe ground deformation associated with volcanic activity. Three of these stations are located near the summit crater of Miharayama. We analyzed pressure source using the daily coordinate values obtained from the observed data at each station.
Our volcano deformation calculation program could numerically calculate volcano deformation for arbitrary volcanic shapes and pressure source geometry using the boundary element method. The mesh model for volcanic topography is made from the 10-meter mesh digital elevation model provided by the Geospatial Information Authority of Japan (GSI). We consider both spherical and ellipsoidal pressure sources in the analysis.
The observed data from the stations around the summit of Miharayama, a consistent trend of the shortening of baseline length and subsidence against the caldera rim were observed. This suggests the deflation source in the shallow part beneath the summit area. We estimate the pressure source just below the summit of Miharayama by comparing the observed data with numerical calculation results. In the case of a spherical pressure source, the depth of pressure source was estimated to be 200–300 m below sea level with a volume change rate of -4×104 m3/yr. In the case of sill-shaped pressure source, the depth of pressure source was estimated to be near 0 m which was shallower than in the case of spherical pressure source.
The MRI has installed many GNSS stations on Izu-Oshima volcano to observe ground deformation associated with volcanic activity. Three of these stations are located near the summit crater of Miharayama. We analyzed pressure source using the daily coordinate values obtained from the observed data at each station.
Our volcano deformation calculation program could numerically calculate volcano deformation for arbitrary volcanic shapes and pressure source geometry using the boundary element method. The mesh model for volcanic topography is made from the 10-meter mesh digital elevation model provided by the Geospatial Information Authority of Japan (GSI). We consider both spherical and ellipsoidal pressure sources in the analysis.
The observed data from the stations around the summit of Miharayama, a consistent trend of the shortening of baseline length and subsidence against the caldera rim were observed. This suggests the deflation source in the shallow part beneath the summit area. We estimate the pressure source just below the summit of Miharayama by comparing the observed data with numerical calculation results. In the case of a spherical pressure source, the depth of pressure source was estimated to be 200–300 m below sea level with a volume change rate of -4×104 m3/yr. In the case of sill-shaped pressure source, the depth of pressure source was estimated to be near 0 m which was shallower than in the case of spherical pressure source.