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8. Probabilistic hazard assessment for pyroclastic density currents at Tungurahua volcano, Ecuador

Author

Aravena, Alvaro, Tadini, Alessandro, Bevilacqua, Andrea, Samaniego, Pablo, Bernard, Benjamin, Hidalgo, Silvana, Le Pennec, Jean-luc, Martínez, Pablo, García, Johnny, Roche, Olivier, Aravena, Alvaro, Tadini, Alessandro, Bevilacqua, Andrea, Samaniego, Pablo, Bernard, Benjamin, Hidalgo, Silvana, Le Pennec, Jean-luc, Martínez, Pablo, García, Johnny, and Roche, Olivier

Abstract

We assess the volcanic hazard derived from pyroclastic density currents (PDCs) at Tungurahua volcano, Ecuador, using a probabilistic approach based on the analysis of calibrated numerical simulations. We address the expected variability of explosive eruptions at Tungurahua volcano by adopting a scenario-based strategy, where we consider three cases: small magnitude violent Strombolian to Vulcanian eruption (VEI 2), intermediate magnitude sub-Plinian eruption (VEI 3), and large magnitude sub-Plinian to Plinian eruption (VEI 4–5). PDCs are modeled using the branching energy cone model and the branching box model, considering reproducible calibration procedures based on the geological record of Tungurahua volcano. The use of different calibration procedures and reference PDC deposits allows us to define uncertainty ranges for the inundation probability of each scenario. Numerical results indicate that PDCs at Tungurahua volcano propagate preferentially toward W and NW, where a series of catchment ravines can be recognized. Two additional valleys of channelization are observed in the N and NE flanks of the volcano, which may affect the city of Baños. The mean inundation probability calculated for Baños is small (6 ± 3%) for PDCs similar to those emplaced during the VEI 2 eruptions of July 2006, February 2008, May 2010, July 2013, February 2014 and February 2016, and on the order of 13 ± 4% for a PDC similar to that produced during the sub-Plinian phase of the August 2006 eruption (VEI 3). The highest energy scenario (VEI 4–5), for which we present and implement a novel calibration procedure based on a few control points, produces inundation areas that nearly always include inhabited centers such as Baños, Puela and Cotaló, among others. This calibration method is well suited for eruptive scenarios that lack detailed field information, and could be replicated for poorly-known active volcanoes around the world.

Published
2024
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19. FLUIDISATION BY PORE PRESSURE OF DENSE GRANULAR FLOWS: NUMERICAL SIMULATIONS VERSUS EXPERIMENTS

Author

Aravena, Alvaro, Chupin, Laurent, Dubois, Thierry, Roche, Olivier, Facultad de Ciencias Básicas, Universidad Catolica Del Maule, Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement et la société-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA), Laboratoire de Mathématiques Blaise Pascal (LMBP), Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA), ANR-10-LABX-0006,CLERVOLC,Clermont-Ferrand centre for research on volcanism(2010), and ECCOMAS, NTNU, SINTEF, NOACM

Subjects
Dense granular flow, Level Set Method, [MATH.MATH-AP]Mathematics [math]/Analysis of PDEs [math.AP], Viscoplastic rheology, Multiphase flow, [MATH.MATH-NA]Mathematics [math]/Numerical Analysis [math.NA]
Abstract

International audience; A model accounting for fluidisation by pore gas pressure in dense granular flows is presented. A viscoplastic rheology, based on the Drucker-Prager criterium, is used to describe the granular medium which is a mixture of air and glass beads. The pore gas pressure, which satisfies an advection-diffusion equation, reduces the friction between the particles and thus the value of the apparent viscosity. As a consequence, dense fluidised granular flows can travel longer distances. In laboratory experiments, the run-out distance reached by dense granular columns when collapsing is almost doubled when fluidisation is applied. This fundamental result, in the context of pyroclastic density currents, is reproduced by numerical simulations performed with the fluidised model.

Published
2022

22. Thematic vent opening probability maps and hazard assessment of small-scale pyroclastic density currents in the San Salvador volcanic complex (El Salvador) and Nejapa-Chiltepe volcanic complex (Nicaragua)

Author

Bevilacqua, Andrea, primary, Aravena, Alvaro, additional, Neri, Augusto, additional, Gutiérrez, Eduardo, additional, Escobar, Demetrio, additional, Schliz, Melida, additional, Aiuppa, Alessandro, additional, and Cioni, Raffaello, additional

Published
2021
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25. Supplementary material to "Thematic vent opening probability maps and hazard assessment of small-scale pyroclastic density currents in the San Salvador Volcanic Complex (El Salvador) and Nejapa-Chiltepe Volcanic Complex (Nicaragua)"

Author

Bevilacqua, Andrea, primary, Aravena, Alvaro, additional, Neri, Augusto, additional, Gutiérrez, Eduardo, additional, Escobar, Demetrio, additional, Schliz, Melida, additional, Aiuppa, Alessandro, additional, and Cioni, Raffaello, additional

Published
2020
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26. Thematic vent opening probability maps and hazard assessment of small-scale pyroclastic density currents in the San Salvador Volcanic Complex (El Salvador) and Nejapa-Chiltepe Volcanic Complex (Nicaragua)

Author

Bevilacqua, Andrea, primary, Aravena, Alvaro, additional, Neri, Augusto, additional, Gutiérrez, Eduardo, additional, Escobar, Demetrio, additional, Schliz, Melida, additional, Aiuppa, Alessandro, additional, and Cioni, Raffaello, additional

Published
2020
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29. Physical constraints for effective magma-water interaction along volcanic conduits during silicic explosive eruptions

Author

Aravena, Alvaro, Vitturi, Mattia de’ Michieli, Cioni, Raffaello, Neri, Augusto, Aravena, Alvaro, Vitturi, Mattia de’ Michieli, Cioni, Raffaello, and Neri, Augusto

Abstract

The entry of groundwater into volcanic conduits has been proposed as a major modifying agent of eruptive dynamics, influencing magma fragmentation and pyroclast dispersion. Although several external water sources and interaction mechanisms have been proposed, the nature and effects of magma-water interaction are still largely unclear, as well as its controlling factors. A common postulate for phreatomagmatic activity to occur is that pressure in a conduit crosscutting a subsurface aquifer should drop below the aquifer pressure, which depends on the properties of the aquifer and the ascending magma. In agreement with most phreatomagmatic eruptions, we show that the injection of large mass fractions of groundwater during silicic explosive eruptions (e.g., >5 wt%) is only physically feasible for low-eruption-rate events; while high-intensity eruptions with evidence of magma-water interaction are probably related to other interaction mechanisms (e.g., the involvement of surface water or the destabilization of aquifer-hosting rocks during collapse phases). Because conditions for access of groundwater to the conduit are preferably reached above the fragmentation level, magma-water interaction seems not to induce dramatic changes to the features of a primary ‘dry’ vesiculation, as commonly claimed. Hence, the low vesicularity indexes often attributed to phreatomagmatic eruptions are difficult to explain by the quenching effect of groundwater on not-fully developed vesicularity. Instead, these indexes may be related to the low eruption rates needed for effective magma-water interaction, generally characterized by significant lateral gradients of vesicularity in narrow conduits.

Published
2018
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30. Thematic vent opening probability maps and hazard assessment of small-scale pyroclastic density currents in the San Salvador Volcanic Complex (El Salvador) and Nejapa-Chiltepe Volcanic Complex (Nicaragua).

Author

Bevilacqua, Andrea, Aravena, Alvaro, Neri, Augusto, Gutiérrez, Eduardo, Escobar, Demetrio, Schliz, Melida, Aiuppa, Alessandro, and Cioni, Raffaello

Subjects
DENSITY currents, RISK assessment, THEMATIC maps, METROPOLITAN areas
Abstract

San Salvador Volcanic Complex (El Salvador) and Nejapa-Chiltepe Volcanic Complex (Nicaragua) have been characterized by a significant variability in eruption style and vent location. Densely inhabited cities are in their surroundings, including the metropolitan areas of San Salvador (~2.4 M people) and Managua (~1.4 M people), respectively. In this study we present novel vent opening probability maps for these volcanic complexes, which are based on a multi-model approach that relies on kernel density estimators. Our volcanological dataset includes: (1) the location of past vents, (2) the mapping of the main fault structures, and (3) the eruption styles of past events, obtained from the critical analysis of literature and/or inferred from volcanic deposits and morphological features observed remotely and in the field. In particular, we present thematic vent opening maps, i.e. we consider different hazardous phenomena separately, including lava emission, small-scale pyroclastic density currents, ejection of ballistic projectiles, and low-intensity pyroclastic fallout. To illustrate the effects of considering the expected eruption style in the construction of vent opening maps, we focus on the analysis of small-scale pyroclastic density currents derived from phreatomagmatic activity or from low-intensity magmatic volcanism. For the numerical simulation of these phenomena we adopted the recently developed branching energy cone model by using the program ECMapProb. Our results show that the implementation of thematic maps of vent opening can produce significantly different hazard levels from those estimated with traditional, non-thematic, maps. [ABSTRACT FROM AUTHOR]

Published
2020
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31. Contributors

Author

Adriana, Agudelo Restrepo, Andrés, Narváez Zuñiga, Aravena, Álvaro, Arturo, Méndez Fajury Ricardo, Bandibas, Joel C., Biass, Sébastien, Bonadonna, Costanza, Calderón, R., Cardona, C., Cioni, Raffaello, de' Michieli Vitturi, Mattia, Del Bello, E., Edmonds, Marie, Flores, F., Gaudin, D., Gregg, Chris E., Iguchi, Masato, Jenkins, Susanna, Johana, Castaño Vasco Leidy, Kendrick, Jackie E., Lallemant, David, Lara, L.E., Lavallée, Yan, Lim, Tian Ning, Lokmer, Ivan, Lucía, Calvache Velasco Marta, Luisa, Monsalve Bustamante María, Marzocchi, Warner, Mauricio, Gómez Martínez Diego, Mauricio, López Vélez Cristián, Menoni, Scira, Miller, C. Dan, Newhall, Christopher G., Pallister, John S., Paola, Narváez Obando, Papale, Paolo, Patricia, Cortés Jiménez Gloria, Pistolesi, Marco, Poland, Michael P., Pompilio, Massimo, Ricci, T., Rouwet, Dmitri, Saccorotti, Gilberto, Sandri, Laura, Scaillet, Bruno, Scarlato, P., Selva, Jacopo, Sigmundsson, Freysteinn, Spina, L., Taddeucci, J., Takarada, Shinji, Tournigand, P-Y, Williams, George, Yun, Sang-Ho, and de Zeeuw-van Dalfsen, Elske

Published
2021
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33. IMEX_SfloW2D 1.0. A depth-averaged numerical flow model for pyroclastic avalanches.

Author

Vitturi, Mattia de' Michieli, Esposti Ongaro, Tomaso, Lari, Giacomo, and Aravena, Alvaro

Subjects
VOLCANIC ash, tuff, etc., AVALANCHES
Abstract

Pyroclastic avalanches are a type of granular flow generated at active volcanoes by different mechanisms, including the collapse of steep pyroclastic deposits (e.g., scoria and ash cones) and fountaining during moderately explosive eruptions. They represent end-members of gravity-driven pyroclastic flows, characterized by relatively small volumes (less than about 1Mm3) and relatively thin (1--10m) layers at high particle concentration (1--50vol.%), manifesting strong topographic control. The simulation of their dynamics and mapping of their hazards pose several different problems to researchers and practitioners, mostly due to the complex and still poorly understood rheology of the polydisperse granular mixture, and to the interaction with the complex natural three-dimensional topography, which often causes rapid rheological changes. In this paper, we present IMEX_SfloW2D, a depth-averaged flow model describing the granular mixture as a single-phase granular fluid. The model is formulated in absolute Cartesian coordinates (where the fluid flow equations are integrated along the direction of gravity) and can be solved over a topography described by a Digital Elevation Model. The numerical discretization and solution algorithms are formulated to allow a robust description of wet-dry conditions (thus allowing to accurately track the front propagation) and to implicitly solve the non-linear friction terms. Owing to these features, the model is able to reproduce steady solutions, such as the triggering and stopping phases of the flow, without the need of empirical conditions. Benchmark cases are discussed to verify the numerical code implementation and to demonstrate the main features of the new model. A preliminary application to the simulation of the February 11th pyroclastic avalanche at Etna volcano (Italy) is finally presented. In the present formulation, a simple semi-empirical friction model (Voellmy-Salm rheology) is implemented. However, the modular structure of the code facilitates the implementation of more specific and calibrated rheological models for pyroclastic avalanches. [ABSTRACT FROM AUTHOR]

Published
2018
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