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Field Data, Models and Uncertainty in Hazard Assessment of Pyroclastic Density Currents and Lahars: Global Perspectives

Figure 1
Summary of present and future global perspectives in the field of volcanic hazard assessment of pyroclastic density currents (PDCs) and lahars derived from this Research Topic. (A) Global distribution of countries where volcanic systems have been analyzed in the Research Topic, divided according to whether the main object of study were PDCs or lahars (NB. Two different studies, one for PDCs, Patra et al., and another for lahars, Walsh et al., were presented for Volcán de Colima, Mexico). Map generated using Quantum Geographical Information System (QGIS Development Team, 2021), and Eurostat GISCO Geodata (©EuroGeographics for the administrative boundaries, 1:3 Million Scale. Downloaded January 25, 2021). (B) Interrelationships between three main approaches commonly used in volcanic hazard assessment of PDCs and lahars. One is based on collating fundamental volcanological knowledge for the volcanic system of interest (and/or analogue volcanoes). Both scenario-based as well as probabilistic volcanic hazard assessments (PVHA) build upon this primary volcanological knowledge. Currently, there is a balance between the degree of physical detail and the uncertainty accounted for that can be achieved with scenario-based and PVHA methods. We argue that the three approaches are complementary and mutually beneficial, and that they should be increasingly merged in future hazard assessments. We also stress the key importance of acknowledging the presence of epistemic uncertainty on all three approaches, and of trying to quantify it as best as possible.

Tierz P., A. Bevilacqua, S. Mead, E. Spiller, L. Sandri (2021).
Frontiers in Earth Science, 9,

Pyroclastic density currents (PDCs) and lahars are two of the most destructive volcanic phenomena. They can generate enormous losses of life, as well as extensive structural damage to buildings and infrastructure within tens of kilometers from their source. Hazard assessments of PDCs and lahars represent the foundation for estimating the substantial risk that these volcanic mass flows pose to the human environment.

Unfortunately, these hazard assessments are complicated by the spatio-temporal complexity associated with the processes of triggering, propagation (including flow transitions) and emplacement of PDCs and lahars. This natural variability (or aleatory uncertainty), alongside incomplete and imperfect knowledge (or epistemic uncertainty, should ideally be incorporated into the mass-flow hazard assessment. At the core of any volcanic hazard assessment resides the volcanological knowledge available for the volcano of interest and/or analogous ones, including information about the sources of uncertainty.

In this Research Topic, we have attempted to gather and showcase volcanological expertise from around the globe, related to any component of PDC and lahar hazard assessment: i.e., volcanological field data collection, analysis and interpretation; experimental and/or numerical and/or statistical modeling, including uncertainty quantification. Volcanic systems in 12 countries and 6 continents have been studied.