2:00 PM - 2:15 PM
[SVC32-02] Modeling of ground deformation associated with the 2015 magma intrusion event of Sakurajima volcano, Japan
Keywords:Ground deformation, GNSS kinematic positioning, Sakurajima volcano, Dike intrusion
Magma transport generates measurable ground deformation if the transported magma is large enough. Ground deformation associated with a magma intrusion of Sakurajima volcano on August 15, 2015, was observed at numerous GNSS sites and tiltmeters. Hotta et al. (2016) modeled a dike east of Minami-dake from the ground deformation. They described the temporal evolution of tilt and strain change at this event. However, they did not describe the temporal evolution of GNSS measurements in detail. Therefore, the evolution of the dike remains unclear. This study aims to understand magma transport through ground deformation. While Kenmochi et al. (VSJ Fall Meeting 2024) described the temporal evolution of GNSS displacements, this study is concerned more with the modeling.
We modeled the GNSS measurements using kinematic positioning and tilt measurements by dike opening, assuming a homogeneous and isotropic medium with topography (Williams and Wedge, 2000).
First, the total horizontal displacement in this study derived from the GNSS kinematic positioning is similar to that of Hotta et al. (2016), who measured the GNSS displacements by static positioning. Therefore, we model the total ground deformation using the parameters estimated by Hotta et al. (2016). However, if topography is considered, their model underestimates the observed displacement to the west of the summit. Subsequently, we model the total ground deformation with a Markov Chain Monte Carlo (MCMC). The dike is estimated ~0.7 km depth below sea level at east of the Minami-dake. This model explains the observed ground deformation well. However, this model has a trade-off between the width and the amount of opening. Indeed, this model does not constrain the width of the dike well.
Finally, we find that the ground deformation's onset time differs at each observation site. This finding suggests magma migration in a horizontal direction. A future study will be devoted to modeling the temporal evolution of the ground deformation to fit the observation.
Acknowledgement: We thank Geospatial Information Authority of Japan for providing GNSS data and Japan Meteorological Agency for providing GNSS data and tilt data.
We modeled the GNSS measurements using kinematic positioning and tilt measurements by dike opening, assuming a homogeneous and isotropic medium with topography (Williams and Wedge, 2000).
First, the total horizontal displacement in this study derived from the GNSS kinematic positioning is similar to that of Hotta et al. (2016), who measured the GNSS displacements by static positioning. Therefore, we model the total ground deformation using the parameters estimated by Hotta et al. (2016). However, if topography is considered, their model underestimates the observed displacement to the west of the summit. Subsequently, we model the total ground deformation with a Markov Chain Monte Carlo (MCMC). The dike is estimated ~0.7 km depth below sea level at east of the Minami-dake. This model explains the observed ground deformation well. However, this model has a trade-off between the width and the amount of opening. Indeed, this model does not constrain the width of the dike well.
Finally, we find that the ground deformation's onset time differs at each observation site. This finding suggests magma migration in a horizontal direction. A future study will be devoted to modeling the temporal evolution of the ground deformation to fit the observation.
Acknowledgement: We thank Geospatial Information Authority of Japan for providing GNSS data and Japan Meteorological Agency for providing GNSS data and tilt data.