Discussions are currently underway for other observation data such as magnetic, electric, and gravity observations to determine the most effective methods for analysis and storage. Experiences in each volcano observatory and historical volcanic eruptions at a singular volcano are not sufficient to judge forthcoming activity. Therefore, the sharing and comparison of such information between observatories worldwide provide more evidence upon which to judge volcanic activity. The JMA sets the threshold for volcanic warning levels.
Geological and petrological studies provide important information about long-term volcanic activity. We obtained many drilling cores during the installation of V-net borehole sensors Nagai et al. Precious core samples have to be preserved physically and archived digitally because they disintegrate easily.
Such cores can be utilized by researchers worldwide, and the database includes information on the locations, geologic and petrologic descriptions, column diagram, photographs, related background, analysis of results, and other information.
Geological data on units such as ashfall deposits provide information about eruption histories, including sequences of eruptions, modes and scales of eruption, and volumes and temporal development of each eruption e. Drilling core and trench section analysis provide us with detailed information about individual historical eruptions, and we can estimate the branching probability based on multiple empirical data Nakagawa et al.
In addition, petrological and laboratory experiment studies provide us with a great deal of information about both the subsurface and surface characteristics of magma behavior. For example, chemical compositions, water content, vesicularity, texture, etc. This information can be stored in the database for comparative study Yoshimoto et al.
FT-IR measurement of water content in a melt Yasuda, is one example of datasets representing magma reservoir characteristics of chemistry, mineralogy, temperature, and water contents for 11 representative active volcanoes that have been archived so far.
These petrological data provide information about the conditions and pressure under which magma was stored and can be converted to depth information. From the geophysical observation point of view, we can detect volcanic earthquakes and volcanic tremors beneath volcanoes, as well as their source depth.
Geophysical and petrological data give us information on source depth individually. Then, we can choose plausible source mechanisms, for example, vaporized fluid flow for shallow regions and super-critical fluid flow for deeper regions. It may be possible to employ more quantitative models.
Not only is the database designed for the analysis of historical eruptions, it is also designed to help evaluation of ongoing volcanic eruptions. One important objective is to identify the type of eruption, whether it is magmatic or non-magmatic, and to evaluate the possibility of a successive larger eruption event.
A quick analysis of volcanic ash, that is, whether it includes juvenile magmatic particles or not, is the key to forecasting the ongoing eruption e. To this end, equipment for automatic ash collection and analysis is under development Miwa et al. This enables the precise sequence of the ashfall deposit to be analyzed with time stamping. In addition, ash particles are automatically analyzed and classified in terms of color and shape through an artificial intelligence AI system, and the equipment automatically reports the result of the component analysis, allowing the existence of magmatic particles to be assessed in real time.
These results will also be uploaded to the JVDN database and will be used for the evaluation of ongoing volcanic activity as well as for countermeasure planning. Numerical simulation is used to evaluate complex volcanic phenomena consisting of both subsurface magmatic processes and surface hazards.
In our project, we are building a volcanic hazard evaluation system that enables parallel evaluation of various volcanic hazards, including lava flow, ashfall, ballistics, and others, based on common input parameters such as flux rate Fujita et al. Each numerical simulation code is being developed, respectively, and the types of input parameters are set for each individual simulation code. Some background data, e.
In many cases, numerical calculation is time-consuming, especially for the simulation of complex phenomena like a volcanic plume and multi-phase lava flow. These outputs should also be stored in the relational SQL database associated with the calculation conditions.
To express probability in volcanic hazard and risk, we conduct multiple sessions of numerical simulation under plausible sets of input parameters and process these results statistically. This database of calculation results will also link volcanic hazard to exposures and vulnerability Fujita et al. The hazard information is expressed as the inundated area, time, velocity, and other characteristic properties for each type of hazard. As both databases are so-called big data, we need high-speed databases.
They can also be visualized by using a Geographical Information System GIS to plot and overlay them on exposures and vulnerabilities, e. Through this visualized information, we can estimate the risk of volcanic hazard quantitatively at the target location, and this information is also useful for countermeasures such as the formulation of evacuation plans by disaster mitigation authorities. Here we introduce some case examples. One of the most widespread and pernicious volcanic hazards is ashfall.
Here, we propose an example of an ashfall due to a Mt. Ashfall distribution is strongly controlled by the height of plume and the local wind profile. We obtain quantitative information of the ashfall deposit for each mesh from the numerical simulation. For risk management, this hazard information can be coupled with the exposure and vulnerability information Figure 4.
In general, the simulation mesh and archived mesh in the database are different from each other, so we need to match these different geometries to estimate the inundation area Figure 4 in Fujita et al.
The building distribution database provided by the Center for Spatial Information Science, The University of Tokyo is an example of static objects, and it has a much higher resolution than those of the numerical simulation. For the combination of hazard simulation and exposure databases, we need to synchronize the size and geometry of the meshes, applying intersection judgment and interpolation.
Our future plan is to provide more quantitative information about the hazard and its risk, for example, using an agent-based model to integrate the ashfall simulation with dynamic information such as dynamic real-time data on humans and transportation.
By doing so, we can propose efficient plans for logistics as part of crisis management. Figure 4. The legend indicates the thickness of ashfall after 6 h from the onset of eruption. Gray makers show the buildings, while dark gray markers show those covered by ashfall. In general, lava flows are less dangerous than the other volcanic hazards, since generally, the flow velocity is not very high, and the damage to human life itself is not very serious.
However, a lava flow destroys the surrounding terrain permanently, so the damage inflicted on properties, public facilities, roads, and other infrastructure can be catastrophic. Most of the important transportation facilities in Japan go through this area, so there would be major economic ramifications if it is damaged by lava flow. We can delineate the impacted area and estimate the available time before the lava flow impacts and formulate a plan for countermeasures.
Figure 5. Japan is famous as one of the volocanic countries in the world. In Japan, there are many "active volcanoes" including famous localities for signtseeing spots or hot springs.
The term of "active volcano" means a volvano which has erupted during last 10, years or continues remarkable fumarolic activity. Volcanoes range in the topographic high places forming the mountains on the land or chains of islands in the ocean. Forecasting the possibility of eruptions for different volcanoes is a difficult task. There is ample accumulated data on Sakurajima, for example, which erupts several hundred times every year, and fairly accurate forecasts can be made on the basis of readily recognized warning signs.
On the other hand, there is little data for volcanoes that have not erupted in decades or hundreds of years, making it difficult to predict when an eruption may occur.
Never assume a volcano is safe because it has not erupted in a long time or because it only has an alert rating of level one. Translated from Japanese.
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