Physical characterization of explosive volcanic eruptions based on tephra deposits: Propagation of uncertainties and sensitivity analysis
Physical characterization of explosive volcanic eruptions based on tephra deposits: Propagation of uncertainties and sensitivity analysis
复制标题
DOI：
10.1016/j.jvolgeores.2015.03.009
复制
发表时间：
2015-04-15
影响因子：
2.9
通讯作者：
Costa, Antonio
中科院分区：
文献类型：
--
作者：
Bonadonna, Costanza;Biass, Sebastien;Costa, Antonio
尽管最近在火山喷发的地球物理监测和实时定量观测方面取得了进展，火山灰沉积物的表征仍然是喷发源参数（ESP）（即羽流高度、喷发体积/质量、质量喷发率 MER、喷发持续时间、总粒度分布 - TGSD）的最大信息来源之一。 ESP 对于火山系统的表征和综合灾害情景的编制至关重要，但自然与传统上无法很好量化的各种程度的不确定性相关。最近的研究强调了与 ESP 估计相关的不确定性，主要与以下方面有关：i）自然系统的内在变异性，ii）观测误差和 iii）用于确定物理参数的策略。在这里，我们回顾了最近关注这些不确定性特征的研究，并提出了确定 ESP 的敏感性分析，以及量化应用于两个案例研究的不确定性传播的系统调查。特别是，我们强调了 ESP 对用作输入参数的特定观测值的依赖性（即最大碎屑的直径、厚度测量值、等厚线面积、沉积物密度、等值线图的顺风和侧风范围，以及用于确定 MER 的经验常数和风速）。最高的不确定性与 MER 和喷发持续时间的估计有关，并且与等值线图侧风范围的确定以及与 MER 和羽流高度相关的经验参数化中使用的经验常数有关。鉴于 MER 和羽流高度之间关系的指数性质，不确定性的传播是不对称的，经验常数的低估和羽流高度的高估对最终结果的影响最大。厚度测量、等厚线面积、幂律拟合积分限制和沉积密度的 +/- 20% 不确定性导致 ESP 不确定性
Regardless of the recent advances in geophysical monitoring and real-time quantitative observations of explosive volcanic eruptions, the characterization of tephra deposits remains one of the largest sources of information on Eruption Source Parameters (ESPs) (i.e. plume height, erupted volume/mass, Mass Eruption Rate MER, eruption duration, Total Grain-Size Distribution - TGSD). ESPs are crucial for the characterization of volcanic systems and for the compilation of comprehensive hazard scenarios but are naturally associated with various degrees of uncertainties that are traditionally not well quantified. Recent studies have highlighted the uncertainties associated with the estimation of ESPs mostly related to: i) the intrinsic variability of the natural system, ii) the observational error and iii) the strategies used to determine physical parameters. Here we review recent studies focused on the characterization of these uncertainties and we present a sensitivity analysis for the determination of ESPs and a systematic investigation to quantify the propagation of uncertainty applied to two case studies. In particular, we highlight the dependence of ESPs on specific observations used as input parameters (i.e. diameter of the largest clasts, thickness measurements, area of isopach contours, deposit density, downwind and crosswind range of isopleth maps, and empirical constants and wind speed for the determination of MER). The highest uncertainty is associated to the estimation of MER and eruption duration and is related to the determination of crosswind range of isopleth maps and the empirical constants used in the empirical parameterization relating MER and plume height Given the exponential nature of the relation between MER and plume height, the propagation of uncertainty is not symmetrical, and both an underestimation of the empirical constant and an overestimation of plume height have the highest impact on the final outcome. A +/- 20% uncertainty on thickness measurements, area of isopach contours, integration limit for the power-law fit and deposit density result in ESP uncertainties