5:15 PM - 6:45 PM
[SVC26-P15] Estimation of crustal deformation of Miyakejima volcano and its pressure sources by using continuous GNSS data
Keywords:Miyakejima volcano, Mogi source, horizontal plate-shaped sill
1. Introduction
Miyakejima repeatedly erupts with a cycle of about 20 years, and currently, Miyakejima is in the preparatory stage of eruption. Watanabe et al. (2021 JpGU SVC28-P09) estimated a spherical expansion pressure source at a depth of 9.0 km, about 2.5 km southwest of the crater,and a horizontal plate-shaped sill at a depth of 0.3 km, just below the crater, by using high-density GNSS campaign observations and island leveling surveys conducted from 2011 to 2019. In this study, we analyze the recent crustal deformation and estimate the pressure sources on Miyakejima based on continuous GNSS observation data.
2. Research
Currently, the Geospatial Information Authority of Japan (GSI), the Japan Meteorological Agency (JMA), and the National Research Institute for Earth Science and Disaster Prevention (NIED) are conducting continuous GNSS observations of Miyakejima. The National Research Institute for Earth Science and Disaster Prevention (NIED) analyzes the data using Bernese GNSS Software 5.2 and publishes the results on JVGN (https://jvdn.bosai.go.jp). In this study, we used data from January 1, 2013, to December 31, 2023, for the analysis. Data were used for each analysis after removing trends to account for offset periods due to antenna replacement and the effects of seasonal variations. First, we determined the baseline length using the coordinates of each observation point. The first day of observation (January 1, 2013) was used as the base and calculated the change in baseline length from that date to examine the expansion and contraction of the baseline length over time. Next, changes in elevation were examined by plotting the average of elevation for each year at each observation point. Finally, we estimated the pressure sources beneath Miyakejima that could explain the observed displacements. To estimate the pressure sources, we used pydeform (Munekane et al., 2006), a tectonic source estimation software that can relatively accurately estimate changes in pressure sources of finite magnitude in a shallow area.
3. Results and Discussion
The baseline length has increased at all stations over the past 11 years. In addition, the average elevation in each year has increased by a maximum of about 20 cm. Based on these crustal deformation data, we estimated a spherical pressure source and a horizontal plate-shaped sill. This model was consistent with a previous study (Watanabe et al., 2021). We also observed expansion of the spherical pressure source. This indicates that magma has been continuously supplied to Miyakejima basement since the last eruption in 2000.
4. Conclusion
We analyzed continuous GNSS observations data of Miyakejima volcano, which is in the preparatory stage of eruption, for the past 11 years, and estimated crustal deformation and its pressure sources. The results show that there is radial displacement from the center of the island, and pressure source models of spherical and horizontal plate-shaped pressure sources are estimated. This indicates that magma has been continuously supplied to the island since the last eruption in 2000. High-density GNSS campaign observation is scheduled in September 2024, and we plan to use the data to analyze and estimate a more accurate subsurface pressure source model in Miyakejima.
Acknowledgments: In this study, JVGN provided the coordinates of GNSS data, observed by GSI, JMA, and National Research Institute for Earth Science and Disaster Prevention (NIED) and analyzed by NIED.
Crustal source analysis was performed using pydeform developed by Munekane et al.
Miyakejima repeatedly erupts with a cycle of about 20 years, and currently, Miyakejima is in the preparatory stage of eruption. Watanabe et al. (2021 JpGU SVC28-P09) estimated a spherical expansion pressure source at a depth of 9.0 km, about 2.5 km southwest of the crater,and a horizontal plate-shaped sill at a depth of 0.3 km, just below the crater, by using high-density GNSS campaign observations and island leveling surveys conducted from 2011 to 2019. In this study, we analyze the recent crustal deformation and estimate the pressure sources on Miyakejima based on continuous GNSS observation data.
2. Research
Currently, the Geospatial Information Authority of Japan (GSI), the Japan Meteorological Agency (JMA), and the National Research Institute for Earth Science and Disaster Prevention (NIED) are conducting continuous GNSS observations of Miyakejima. The National Research Institute for Earth Science and Disaster Prevention (NIED) analyzes the data using Bernese GNSS Software 5.2 and publishes the results on JVGN (https://jvdn.bosai.go.jp). In this study, we used data from January 1, 2013, to December 31, 2023, for the analysis. Data were used for each analysis after removing trends to account for offset periods due to antenna replacement and the effects of seasonal variations. First, we determined the baseline length using the coordinates of each observation point. The first day of observation (January 1, 2013) was used as the base and calculated the change in baseline length from that date to examine the expansion and contraction of the baseline length over time. Next, changes in elevation were examined by plotting the average of elevation for each year at each observation point. Finally, we estimated the pressure sources beneath Miyakejima that could explain the observed displacements. To estimate the pressure sources, we used pydeform (Munekane et al., 2006), a tectonic source estimation software that can relatively accurately estimate changes in pressure sources of finite magnitude in a shallow area.
3. Results and Discussion
The baseline length has increased at all stations over the past 11 years. In addition, the average elevation in each year has increased by a maximum of about 20 cm. Based on these crustal deformation data, we estimated a spherical pressure source and a horizontal plate-shaped sill. This model was consistent with a previous study (Watanabe et al., 2021). We also observed expansion of the spherical pressure source. This indicates that magma has been continuously supplied to Miyakejima basement since the last eruption in 2000.
4. Conclusion
We analyzed continuous GNSS observations data of Miyakejima volcano, which is in the preparatory stage of eruption, for the past 11 years, and estimated crustal deformation and its pressure sources. The results show that there is radial displacement from the center of the island, and pressure source models of spherical and horizontal plate-shaped pressure sources are estimated. This indicates that magma has been continuously supplied to the island since the last eruption in 2000. High-density GNSS campaign observation is scheduled in September 2024, and we plan to use the data to analyze and estimate a more accurate subsurface pressure source model in Miyakejima.
Acknowledgments: In this study, JVGN provided the coordinates of GNSS data, observed by GSI, JMA, and National Research Institute for Earth Science and Disaster Prevention (NIED) and analyzed by NIED.
Crustal source analysis was performed using pydeform developed by Munekane et al.