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

摘要： 简述了火山空降碎屑灾害的危害性,指出研制火山空降碎屑灾害预测软件包的实际意义。介绍了软件的主要结构框图、软件设计的基本思路和结构设计时的几点考虑。介绍了在Visual Basic6.0平台下,碎屑粒径参数、岩浆黏度、结晶压力、喷出压力、给定时间段和特定区域的各高度层风参数、岩浆动力学参数、喷出物总量、抛射体分布、坍塌阶段碎屑分布和扩散阶段碎屑分布计算等各程序的主要结构及主要功能。介绍了在Mapinfor6.0平台下软件的主要功能。给出了实现该软件包各项功能的理论基础和科学依据,并展示了1980年5月18日美国圣海伦斯火山喷发的空降碎屑分布计算的实例,同时把计算结果与实际观测数据进行了对比,从而使模型的改进工作和软件的正确性得到了验证。最后,对软件存在的缺陷和需要进一步改进之处进行了细致的分析。

关键词: 火山空降碎屑, 灾害预测, 软件包