Probabilistic assessment of tephra fallout hazard at Changbaishan volcano, Northeast China

Tephra fallout is an important type of hazard caused by volcanic eruption, and is also one of the main hazards at Changbaishan volcano, Northeast China. Numerical simulation is an effective approach to assess the dispersion of tephra fallout. According to the theory of dispersion model, we developed a simple and practical diffusion program that can be run on a personal computer. The input parameters for the simulation of tephra fallout from the Millennium Eruption of Changbaishan volcano, such as the size, density and shape of the tephra, the bulk volume and column height, the diffusion parameter P(z), wind direction and intensity, were obtained by field investigation and laboratory analysis. The simulated results in the intermediate scope when the parameter beta > 0.3 are in good agreement with the results from measurement in situ, indicating that the model is reliable and the parameters used in the model are reasonable. We carried out more than 20,000 tephra fallout simulations using a statistical dataset of wind profiles which are obtained from China Meteorological Data Sharing Service System (CMDSSS). Tephra fallout hazard probability maps related to high- and low- magnitude eruption scenarios in Changbaishan volcano, are constructed for several tephra thickness thresholds, such as 70, 20, 10 and 1 cm. The results from this study can give support to the risk mitigation plans in Changbaishan area.