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首页> 外文期刊>Journal of Volcanology and Geothermal Research >A model for the numerical simulation of tephra fall deposits
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A model for the numerical simulation of tephra fall deposits

机译：特菲拉瀑布沉积物数值模拟模型

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A simple semianalytical model to simulate ash dispersion and deposition produced by sustained Plinian and sub-Plinian eruption columns based on the 2D advection-dispersion equation was applied. The eruption column acts as a vertical line source with a given mass distribution and neglects the complex dynamics within the eruption column. Thus, the use of the model is limited to areas far from the vent where the dynamics of the eruption column play a minor role. Vertical wind and diffusion components are considered negligible with respect to the horizontal ones. The dispersion and deposition of particles in the model is only governed by gravitational settling, horizontal eddy diffusion, and wind advection. The model accounts for different types and size classes of a user-defined number of particle classes and changing settling' velocity with altitude. In as much as wind profiles are considered constant on the entire domain, the model validity is limited to medium-range distances (about 30-200 km away from the source). The model was used to reconstruct the tephra fall deposit from the documented Plinian eruption of Mt. Vesuvius, Italy, in 79 A.D. In this case, the model was able to broadly reproduce the characteristic medium-range tephra deposit. The results support the validity of the model, which has the advantage of being simple and fast to compute. It has the potential to serve as a simple tool for predicting the distribution of ash fall of hypothetical or real eruptions of a given magnitude and a given wind profile. Using a statistical set of frequent wind profiles, it also was used to construct air fall hazard maps of the most likely affected areas around active volcanoes where a large eruption is expected to occur.
机译：应用了一个简单的半解析模型，基于二维对流扩散方程，模拟了持续的Plinian和亚Plinian喷发柱产生的灰分扩散和沉积。喷发柱充当具有给定质量分布的垂直线源，并且忽略了喷发柱内的复杂动力学。因此，该模型的使用仅限于远离喷口的区域，在该区域喷发柱的动力学起着较小的作用。垂直风和扩散分量相对于水平风和扩散分量可以忽略不计。模型中粒子的分散和沉积仅受重力沉降，水平涡流扩散和风对流控制。该模型考虑了用户定义数量的粒子类别的不同类型和尺寸类别，并随高度变化了沉降速度。由于在整个域中，只要风廓线被认为是恒定的，模型的有效性就限于中程距离（距源约30-200 km）。该模型被用于从记载的Mt的Plinian喷发中重建Tephra秋季沉积物。意大利维苏威火山（Vesuvius），大约是在公元79年。在这种情况下，该模型能够广泛再现特有的中程特非拉沉积。结果证明了该模型的有效性，其优点是计算简单，快速。它有可能作为一种简单的工具来预测给定幅度和给定风廓线的假想或实际喷发的落灰分布。使用一组频繁的风廓线的统计数据，它还被用于构造活动火山周围最可能受影响的区域的空气坠落危险图，预计该地区将发生大喷发。

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