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Modelling pyroclastic density currents from a subplinian eruption at La Soufrière de Guadeloupe (West Indies, France)
Bulletin of Volcanology ( IF 3.5 ) Pub Date : 2020-11-13 , DOI: 10.1007/s00445-020-01411-6 Tomaso Esposti Ongaro 1 , Jean-Christophe Komorowski 2 , Yoann Legendre 3 , Augusto Neri 1
Bulletin of Volcanology ( IF 3.5 ) Pub Date : 2020-11-13 , DOI: 10.1007/s00445-020-01411-6 Tomaso Esposti Ongaro 1 , Jean-Christophe Komorowski 2 , Yoann Legendre 3 , Augusto Neri 1
Affiliation
We have used a three-dimensional, non-equilibrium multiphase flow numerical model to simulate subplinian eruption scenarios at La Soufrière de Guadeloupe (Lesser Antilles, France). Initial and boundary conditions for computer simulations were set on the basis of independent estimates of eruption source parameters (i.e. mass eruption rate, volatile content, temperature, grain size distribution) from a field reconstruction of the 1530 CE subplinian eruption. This event is here taken as a reference scenario for hazard assessment at La Soufrière de Guadeloupe. A parametric study on eruption source parameters allowed us to quantify their influence on the simulated dynamics and, in particular, the increase of the percentage of column collapse and pyroclastic density current (PDC) intensity, at constant mass eruption rate, with variable vent diameter. Numerical results enabled us to quantify the effects of the proximal morphology on distributing the collapsing mass around the volcano and into deep and long valleys and to estimate the areas invaded by PDCs, their associated temperature and dynamic pressure. Significant impact (temperature > 300 °C and dynamic pressure > 1 kPa) in the inhabited region around the volcano is expected for fully collapsing conditions and mass eruption rates > 2 × 107 kg/s. We thus combine this spatial distribution of temperature and dynamic pressure with an objective consideration of model-related uncertainty to produce preliminary PDC hazard maps for the reference scenario. In such a representation, we identify three areas of varying degree of susceptibility to invasion by PDCs—very likely to be invaded (and highly impacted), susceptible to invasion (and moderately impacted), and unlikely to be invaded (or marginally impacted). The study also raises some key questions about the use of deterministic scenario simulations for hazard assessment, where probability distributions and uncertainties are difficult to estimate. Use of high-performance computing techniques will in part allow us to overcome such difficulties, but the problem remains open in a scientific context where validation of numerical models is still, necessarily, an incomplete and ongoing process. Nevertheless, our findings provide an important contribution to the quantitative assessment of volcanic hazard and risk at La Soufrière de Guadeloupe particularly in the context of the current unrest of the volcano and the need to prepare for a possible future reawakening of the volcano that could culminate in a magmatic explosive eruption.
中文翻译:
模拟 La Soufrière de Guadeloupe(法国西印度群岛)次普林尼喷发的火山碎屑密度流
我们使用三维非平衡多相流数值模型来模拟 La Soufrière de Guadeloupe(法国小安的列斯群岛)的亚普林尼喷发情景。计算机模拟的初始条件和边界条件是根据对 1530 CE 亚普林尼喷发现场重建的喷发源参数(即质量喷发率、挥发物含量、温度、粒度分布)的独立估计设置的。该事件在此被视为在瓜德罗普岛拉苏弗里耶尔进行危害评估的参考情景。对喷发源参数的参数研究使我们能够量化它们对模拟动力学的影响,特别是在恒定质量喷发率和可变喷口直径下,柱塌陷百分比和火山碎屑密度电流 (PDC) 强度的增加。数值结果使我们能够量化近端形态对火山周围塌陷质量分布和深长山谷的影响,并估计 PDC 侵入的区域、相关温度和动态压力。在完全坍塌条件和质量喷发率 > 2 × 107 kg/s 的情况下,预计火山周围有人居住区域会产生重大影响(温度 > 300 °C 和动态压力 > 1 kPa)。因此,我们将这种温度和动态压力的空间分布与对模型相关不确定性的客观考虑相结合,为参考情景生成初步的 PDC 危害图。在这样的表示中,我们确定了三个对 PDC 入侵具有不同程度易感性的区域——很可能被入侵(并且受到高度影响),容易受到入侵(并受到中度影响),不太可能被入侵(或受到轻微影响)。该研究还提出了一些关于使用确定性情景模拟进行危险评估的关键问题,其中概率分布和不确定性难以估计。使用高性能计算技术将部分地使我们能够克服这些困难,但在科学环境中问题仍然存在,数值模型的验证仍然是一个不完整且持续的过程。尽管如此,
更新日期:2020-11-13
中文翻译:
模拟 La Soufrière de Guadeloupe(法国西印度群岛)次普林尼喷发的火山碎屑密度流
我们使用三维非平衡多相流数值模型来模拟 La Soufrière de Guadeloupe(法国小安的列斯群岛)的亚普林尼喷发情景。计算机模拟的初始条件和边界条件是根据对 1530 CE 亚普林尼喷发现场重建的喷发源参数(即质量喷发率、挥发物含量、温度、粒度分布)的独立估计设置的。该事件在此被视为在瓜德罗普岛拉苏弗里耶尔进行危害评估的参考情景。对喷发源参数的参数研究使我们能够量化它们对模拟动力学的影响,特别是在恒定质量喷发率和可变喷口直径下,柱塌陷百分比和火山碎屑密度电流 (PDC) 强度的增加。数值结果使我们能够量化近端形态对火山周围塌陷质量分布和深长山谷的影响,并估计 PDC 侵入的区域、相关温度和动态压力。在完全坍塌条件和质量喷发率 > 2 × 107 kg/s 的情况下,预计火山周围有人居住区域会产生重大影响(温度 > 300 °C 和动态压力 > 1 kPa)。因此,我们将这种温度和动态压力的空间分布与对模型相关不确定性的客观考虑相结合,为参考情景生成初步的 PDC 危害图。在这样的表示中,我们确定了三个对 PDC 入侵具有不同程度易感性的区域——很可能被入侵(并且受到高度影响),容易受到入侵(并受到中度影响),不太可能被入侵(或受到轻微影响)。该研究还提出了一些关于使用确定性情景模拟进行危险评估的关键问题,其中概率分布和不确定性难以估计。使用高性能计算技术将部分地使我们能够克服这些困难,但在科学环境中问题仍然存在,数值模型的验证仍然是一个不完整且持续的过程。尽管如此,