Presentation Information
[U15-03]Linking volcano monitoring and volcanic disaster risk reduction★Invited Papers
*Masato Iguchi1 (1.Sakurajima Volcanic Disaster Risk Reduction Research Center, Crisis Management Division, Crisis Management Bureau, Kagoshima city)
Keywords:
Volcano monitoring,Volcanic disaster,Volcanic hazard map
Volcano observation networks have been established with the aim of contributing to the mitigation of volcanic disasters, but the use of observation data for mitigating volcanic disasters has been insufficient. Like other natural disasters, volcanic disasters range from those that directly affect human life to economic damage caused by the destruction of social infrastructure. However, the factors that cause disasters are complex, as volcanic eruptions cause the deposition of highly mobile materials on the ground, such as magma, which is then linked to water. Therefore, disasters are extremely complex.
Hazard assessment is fundamental to volcanic disaster prevention, and this can be achieved through simulations based on numerical models. The most important input parameters in this case are the time function of the eruption rate and its integral, the eruption volume.
Hazard maps are created by assuming eruption rates and durations based on anticipated eruption scenarios, and then assessing the impact area. The MLIT's Real-Time Hazard Map is a system for assessing the flood area by incorporating unexpected crater locations and topographical changes. This system revises hazard areas through rapid correction of topographical information. On the other hand, for tephra, a phenomenon that is advected and dispersed by wind fields, wind fields must be appropriately reflected, and the JMA's mesoscale meteorological model is used.
In a real-time hazard map, understanding the source information is more important than the factors controlling the movement of such ejecta. Temporal changes in eruption rate can be inferred from changes in the deposition distribution of ejecta, but field surveys are often time-consuming. In particular, surveying the tephra that disperses into the atmosphere during large-scale eruptions requires an enormous amount of time due to the wide deposition area. While they do not measure the volume of ejecta itself, remote observation methods such as weather radar and satellite observations are useful for understanding the spatial distribution of ejecta and its evolution over time. Furthermore, because eruption phenomena are accompanied by contractional ground deformation and seismic activity (explosion earthquakes and eruption tremors), they are effective in estimating temporal changes in eruption rate from the perspective of their immediacy and robustness.
In situations where an eruption is imminent, it is important to predict the timing, scale, location, style, and progression of volcanic eruptions, which have traditionally been considered elements of volcanic eruption prediction. Of these, progression is a comprehensive concept that is fundamentally different from the other elements. In other words, the elements necessary for prediction can be thought of as changes in scale, location, and style over time. From the perspective of hazard prediction, this amounts to predicting the time function of the eruption rate for each crater and style. Hazard prediction is possible by inputting the time function of the eruption rate for each crater and style into the corresponding simulator. While the time function of the eruption rate depends on the model, the eruption volume, which is the integrated value of the eruption rate, can be empirically predicted from the ground deformation and seismic activity that precede the eruption. There is a correlation between the total energy of precursory volcanic earthquakes and the volume of ejecta, and an upper limit equation for the volume of ejecta can be empirically determined for the magnitude of volcanic earthquakes. Furthermore, the volume change of the pressure source, which can be determined from ground deformation, is correlated with the volume of ejecta. The eruption style is related to the rate of magma intrusion. If the intrusion rate is high, the eruption will be explosive, and if it is low, the eruption will be mild. At Sakurajima, it has been proposed that the magma intrusion rate, estimated mainly from ground activity preceding past eruptions, will determine the event branching of eruption style and scale.
To predict hazards from observed data, it is necessary to (1) estimate the amount of magma intrusion from seismic activity and ground deformation, (2) construct a model that relates the amount of magma intrusion and the amount of eruption, (3) construct a model for allocating magma to eruption hazard factors (tephra, pyroclastic flow, lava flow) based on the magma intrusion rate, and (4) assess the impact of each hazard factor.
Hazard assessment is fundamental to volcanic disaster prevention, and this can be achieved through simulations based on numerical models. The most important input parameters in this case are the time function of the eruption rate and its integral, the eruption volume.
Hazard maps are created by assuming eruption rates and durations based on anticipated eruption scenarios, and then assessing the impact area. The MLIT's Real-Time Hazard Map is a system for assessing the flood area by incorporating unexpected crater locations and topographical changes. This system revises hazard areas through rapid correction of topographical information. On the other hand, for tephra, a phenomenon that is advected and dispersed by wind fields, wind fields must be appropriately reflected, and the JMA's mesoscale meteorological model is used.
In a real-time hazard map, understanding the source information is more important than the factors controlling the movement of such ejecta. Temporal changes in eruption rate can be inferred from changes in the deposition distribution of ejecta, but field surveys are often time-consuming. In particular, surveying the tephra that disperses into the atmosphere during large-scale eruptions requires an enormous amount of time due to the wide deposition area. While they do not measure the volume of ejecta itself, remote observation methods such as weather radar and satellite observations are useful for understanding the spatial distribution of ejecta and its evolution over time. Furthermore, because eruption phenomena are accompanied by contractional ground deformation and seismic activity (explosion earthquakes and eruption tremors), they are effective in estimating temporal changes in eruption rate from the perspective of their immediacy and robustness.
In situations where an eruption is imminent, it is important to predict the timing, scale, location, style, and progression of volcanic eruptions, which have traditionally been considered elements of volcanic eruption prediction. Of these, progression is a comprehensive concept that is fundamentally different from the other elements. In other words, the elements necessary for prediction can be thought of as changes in scale, location, and style over time. From the perspective of hazard prediction, this amounts to predicting the time function of the eruption rate for each crater and style. Hazard prediction is possible by inputting the time function of the eruption rate for each crater and style into the corresponding simulator. While the time function of the eruption rate depends on the model, the eruption volume, which is the integrated value of the eruption rate, can be empirically predicted from the ground deformation and seismic activity that precede the eruption. There is a correlation between the total energy of precursory volcanic earthquakes and the volume of ejecta, and an upper limit equation for the volume of ejecta can be empirically determined for the magnitude of volcanic earthquakes. Furthermore, the volume change of the pressure source, which can be determined from ground deformation, is correlated with the volume of ejecta. The eruption style is related to the rate of magma intrusion. If the intrusion rate is high, the eruption will be explosive, and if it is low, the eruption will be mild. At Sakurajima, it has been proposed that the magma intrusion rate, estimated mainly from ground activity preceding past eruptions, will determine the event branching of eruption style and scale.
To predict hazards from observed data, it is necessary to (1) estimate the amount of magma intrusion from seismic activity and ground deformation, (2) construct a model that relates the amount of magma intrusion and the amount of eruption, (3) construct a model for allocating magma to eruption hazard factors (tephra, pyroclastic flow, lava flow) based on the magma intrusion rate, and (4) assess the impact of each hazard factor.