In countries such as Italy, Japan, and Mexico, where active volcanoes are located in highly populated areas, the problem of risk reduction is very important. Actual knowledge about volcanic behavior does not allow deterministic event prediction or the forecasting of eruptions. However, areas exposed to eruptions can be analyzed if eruption characteristics can be inferred or assumed. Models to simulate volcanic eruptions and identify hazardous areas have been developed by collaboration between the IBM Italy Pisa Scientific Center and the Earth Science Department of Pisa University (supported by the Italian National Group of Volcanology of the Italian National Research Council). The input to the models is the set of assumed eruption characteristics: the typology of the phenomenon (ash fall, pyroclastic flow, etc.), vent position, total eruptible mass, wind profile, etc. The output of the models shows volcanic product distribution at ground level. These models are reviewed and their use in hazard estimation (compared with the more traditional techniques currently in use) is outlined. Effective use of these models, by public administrators and planners in preparing plans for the evacuation of hazardous zones, requires the clear and effective display of model results. Techniques to display and visualize such data have been developed by the authors. In particular, a computer program has been implemented on the IBM 7350 Image Processing System to display model outputs, representing both volume (in two dimensions) and distribution of ejected material, and to superimpose the displays upon satellite images that show 3D oblique views of terrain. This form of presentation, realized for various sets of initial conditions and eruption times, represents a very effective visual tool for volcanic hazard zoning and evacuation planning.
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