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首页> 外文期刊>Journal of Volcanology and Geothermal Research >A Monte Carlo methodology for modelling ashfall hazards
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A Monte Carlo methodology for modelling ashfall hazards

机译：蒙特卡洛方法用于模拟粉尘暴危害

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We have developed a methodology for quantifying the probability of particular thicknesses of tephra at any given site, using Monte Carlo methods. This is a part of the development of a probabilistic volcanic hazard model (PVHM) for New Zealand, for hazards planning and insurance purposes.We use an established program (ASHFALL) to model individual eruptions, where the likely thickness of ash deposited at selected sites depends on the location of the volcano, eruptive volume, column height and ash size, and the wind conditions. A Monte Carlo procedure allows us to simulate the variations in eruptive volume and in wind conditions by analysing repeat eruptions, each time allowing the parameters to vary randomly according to known or assumed distributions. Actual wind velocity profiles are used, with randomness included by selection of a starting date. This method can handle the effects of multiple volcanic sources, each source with its own characteristics. We accumulate the tephra thicknesses from all sources to estimate the combined ashfall hazard, expressed as the frequency with which any given depth of tephra is likely to be deposited at selected sites. These numbers are expressed as annual probabilities or as mean return periods. We can also use this method for obtaining an estimate of how often and how large the eruptions from a particular volcano have been. Results from sediment cores in Auckland give useful bounds for the likely total volumes erupted from Egmont Volcano (Mt. Taranaki), 280 km away, during the last 130,000 years.
机译：我们已经开发出一种方法，用于使用蒙特卡洛方法对在任何给定位置的特菲拉特定厚度的概率进行量化。这是新西兰针对概率规划和保险目的开发的概率火山灾害模型（PVHM）的一部分。我们使用已建立的程序（ASHFALL）对单个火山喷发进行建模，其中可能存在的灰分沉积在选定地点取决于火山的位置，喷发量，柱高和灰分大小以及风况。蒙特卡洛程序使我们能够通过分析重复的喷发来模拟喷发量和风况的变化，每次允许参数根据已知或假定的分布随机变化。使用实际风速曲线，并通过选择开始日期来包含随机性。这种方法可以处理多个火山源的影响，每个火山源都有自己的特征。我们从所有来源累积了特菲拉厚度，以估算合并的灰烬危害，表示为任何给定深度的特菲拉可能沉积在选定地点的频率。这些数字表示为年度概率或平均回报期。我们还可以使用此方法来估算特定火山喷发的频率和规模。奥克兰沉积岩心的结果为过去130,000年间280公里外的埃格蒙特火山（塔拉纳基山）喷发的可能总量提供了有用的界限。

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