Abstract: The volcanic eruption,especially the explosive volcanic eruption,has brought about tremendous disaster to the humanity.Among the types of volcanic disaster,the one produced by falling tephra is the main type regardless of its intensity or its incidence.So,it is of great significance to simulate quantitatively the tephra fallout.The purpose of the contrast research is to test the actual effect of the model,to find out the defects and the commonness and difference of each eruption process.Based on the contrast research,we hope to find out the method to improve our model,and further,to find out the methods of reducing disaster in emergency of volcano eruption.We select three cases for the contrast research,i.e.the eruptions of S.Helens(1980),Pinatubo(1991)and Cerro Negro(1995).The bases for the selection are:first,the dynamic parameters of the three modern eruption cases have been determined by relevant competent agencies;second,the depth of falling tephra was measured before it was changed by wind and rain;and third,the three volcanoes are greatly different in terms of atmosphere factors,landform conditions,and eruptional types,so on.So the three cases can truly test the actual effect of the model.The improved Suzuki mathematic model for tephra dispersion(ZHAO Yi,2003)is adopted in this paper.Based on the depth of falling tephra distribution of S.Helens eruption of 1980(calculated by ZHAO Yi,2003),we calculate the depth of tephra-fall distribution of the Pinatubo eruption in 1991 and Cerro Negro eruption in 1995.Based on the results of numerical simulation,we compared the depth map of tephra-fall distribution with the disaster maps.In the end,the verification and validation of the model are tested.By numerical simulation,the effect factors of the three volcano eruptions are compared,such as,the atmosphere parameters,the eruption intensity,the height of the eruption column and VEI,landform change,eruption type,second deposit thickness.Based on the contrast research,the main future research interests are proposed to be in the areas of:1)the thermal disturbance model over the crater,2)the second deposit thickness model,3)the rainfall-concurrent tephra fallout model,4)the pyroclastic flow model for secondary pyroclastic transport in varied landforms and 5)the mud flow model.

Key words: tephra fall, numerical simulation, diffusion model, contrast research, disaster reduction

摘要： 使用我们改进后的Suzuki二维扩散模型,对菲律宾的Pinatubo火山、美国的St.Helens火山和尼加拉瓜的Cerro Negro火山的喷发碎屑沉降物的分布特征进行了模拟,把计算结果与实际观测数据进行了对比,使模型的正确性得到了验证。同时对上述3座火山的数值模拟结果进行了横向对比,针对不同喷发类型的火山及其喷发的物理过程的多样性,提出了模型的改进方法,从而使数值模拟结果可以作为政府进行火山减灾决策时的一种科学依据。

关键词: 火山碎屑, 数值模拟, 对比研究, 减灾实效