1:45 PM - 3:15 PM
[SVC33-P02] Development of volcano deformation calculation system considering volcanic topography (2)
Keywords:volcano deformation, BEM, Izu-Oshima
Volcano deformation data is important for evaluating volcanic activity. The Japan Meteorological Agency (JMA) has been installing volcano deformation observation station such as GNSS and tiltmeters at volcanoes. In the recent, volcano deformation data that suggest pressure sources near the ground surface have also been obtained at observation stations located around craters. These data were considered to be affected by the topography of the volcano. It is important to consider the effect of topography when analyzing these data. We have been developing a system to numerically calculate volcano deformation considering the topography of volcanoes, and have been studying the influence of volcanic topography on volcano deformation data. We have examined the effect of volcanic topography on the results of shallow pressure source estimation for Nasudake. As a result, when the depth of the pressure source is about the same as the elevation of the observation station, the depth and the magnitude of pressure source was overestimated or underestimated, if volcanic topography was not taken into account (Kawaguchi, 2020, JpGU). In this presentation, we introduce the system we have developed and report on the effect of topography for GNSS data at Izu-Oshima.
The volcano deformation calculation system considering volcanic topography consists of the following programs: making the mesh model of volcano topography, numerical calculation of volcano deformation using the boundary element method, and conversion of the calculation results into observed data for each station. A simple GUI environment for setting parameters to run the program was also created to be used this program in the JMA. The mesh model of the volcano topography was made by using a 10-meter mesh digital elevation model (DEM) of the Geospatial Information Authority of Japan (GSI). For the pressure source, spherical and ellipsoidal pressure sources can be set. The volcano deformation data for each observation station converted from the calculation results were output in the format of the MaGCAP-V developed by the Meteorological Research Institute (MRI).
We calculated the displacements at the GNSS stations of on Izu-Oshima developed by MRI applying this program and compared calculated result with the case not considering the volcanic topography. We set pressure sources at several depth just below the summit of Miharayama, and calculate the displacements at each GNSS station. As a result, when the depth of the pressure source is 1000 m below sea level, there were small differences between the displacement obtained by the calculation and that obtained by assuming an elastic half space. On the other hand, when the elevation of the pressure source is 0 m above sea level, the displacements obtained by the calculations were about twice as large as those obtained assuming elastic half space at some station around the summit area of Miharayama. This suggests that, when estimating the pressure source in the shallow area below the summit, the depth of the pressure source may be shallow or the volume change may be large if the effect of the topography is not taken into account. In the presentation, the results of the pressure source estimation for the observation data of Izu-Oshima volcano will also be presented.
The volcano deformation calculation system considering volcanic topography consists of the following programs: making the mesh model of volcano topography, numerical calculation of volcano deformation using the boundary element method, and conversion of the calculation results into observed data for each station. A simple GUI environment for setting parameters to run the program was also created to be used this program in the JMA. The mesh model of the volcano topography was made by using a 10-meter mesh digital elevation model (DEM) of the Geospatial Information Authority of Japan (GSI). For the pressure source, spherical and ellipsoidal pressure sources can be set. The volcano deformation data for each observation station converted from the calculation results were output in the format of the MaGCAP-V developed by the Meteorological Research Institute (MRI).
We calculated the displacements at the GNSS stations of on Izu-Oshima developed by MRI applying this program and compared calculated result with the case not considering the volcanic topography. We set pressure sources at several depth just below the summit of Miharayama, and calculate the displacements at each GNSS station. As a result, when the depth of the pressure source is 1000 m below sea level, there were small differences between the displacement obtained by the calculation and that obtained by assuming an elastic half space. On the other hand, when the elevation of the pressure source is 0 m above sea level, the displacements obtained by the calculations were about twice as large as those obtained assuming elastic half space at some station around the summit area of Miharayama. This suggests that, when estimating the pressure source in the shallow area below the summit, the depth of the pressure source may be shallow or the volume change may be large if the effect of the topography is not taken into account. In the presentation, the results of the pressure source estimation for the observation data of Izu-Oshima volcano will also be presented.