关键词: 火山空降碎屑, 灾害预测, 软件包

Abstract: This paper expatiates on the hazards of volcanic falling tephra, and demonstrates the pratical importance of making program for forecasting the risk of volcanic falling tephra. It describes in detail the main scheme of the program, basic idea of the design, and some considerations about the program. Based on the Visual Basic 6.0 platform, some new programs for various purposes are developed, such as for the calculation of tephra diameter parameters in the light of Sequential Fragmentation Theory by Wohletz;the calculation of magma viscosity by using Magma 3.2 software developed by Wohletz;the calculation of crystallization pressure;the calculation of eruption pressure;the calculation of wind parameters in particular period and region;the calculation of magma dynamic parameters;the calculation of erupted material quantity;the distribution of ballistic trajectories for blocks ejected during volcanic eruptions;the distribution of ballistic trajectories for blocks ejected during plume collapse and the distribution of falling tephra during diffusion. Moreover, the main scheme and functions of each program on the basis of Mapinfor 6.0 platform are introduced in detail, while the basic theory and scientific basis for these programs are provided as well. The St. Helens volcano eruption on May 18, 1980 is taken as an example. The distribution of tephra fallout of this eruption is calculated by using the program introduced in this paper. The obtained result is in good agreement with the observed data, indicating the applicability of this program. Finally, detailed analysis of the shortcomings of the software and the method for further improvement are provided as well.

Key words: volcanic falling tephra, disaster forecast, program