Manuel Stocchi

University of Bari Aldo Moro

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Silvia Massaro

Istituto Nazionale di Geofisica e Vulcanologia

Antonio Costa

Istituto Nazionale di Geofisica e Vulcanologia

Jacopo Selva

University of Naples Federico II

Laura Sandri

Istituto Nazionale di Geofisica e Vulcanologia

Beatriz Martínez Montesinos

Istituto Nazionale di Geofisica e Vulcanologia

Stefano Caliro

Istituto Nazionale di Geofisica e Vulcanologia

Edoardo Peronace

Institute of Environmental Geology and Geoengineering

Roberto Isaia

Istituto Nazionale di Geofisica e Vulcanologia

Marco Nocentini

Institute of Environmental Geology and Geoengineering

Manuel Títos

Universidad de Granada

Cooperative Institutions

Istituto Nazionale di Geofisica e Vulcanologia

National Research Council

INGV Sezione di Bologna

Institute of Environmental Geology and Geoengineering

Centre National de la Recherche Scientifique

Université Clermont Auvergne

Istituto Nazionale di Fisica Nucleare, Sezione di Bologna

Terra

University of Florence

University of Bari Aldo Moro

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Assessing long-term tephra fallout hazard in southern Italy from Neapolitan volcanoes

Natural hazards and earth system sciences (2023)

Silvia Massaro Manuel Stocchi Beatriz Martínez Montesinos Laura Sandri Jacopo Selva

Abstract. Nowadays, modeling of tephra fallout hazard is coupled with probabilistic analysis that takes into account the natural variability of the volcanic phenomena in terms of eruption probability, eruption sizes, vent position, and meteorological conditions. In this framework, we present a prototypal methodology to carry out the long-term tephra fallout hazard assessment in southern Italy from the active Neapolitan volcanoes: Somma–Vesuvius, Campi Flegrei, and Ischia. The FALL3D model (v.8.0) has been used to run thousands of numerical simulations (1500 per eruption size class), considering the ECMWF ERA5 meteorological dataset over the last 30 years. The output in terms of tephra ground load has been processed within a new workflow for large-scale, high-resolution volcanic hazard assessment, relying on a Bayesian procedure, in order to provide the mean annual frequency with which the tephra load at the ground exceeds given critical thresholds at a target site within a 50-year exposure time. Our results are expressed in terms of absolute mean hazard maps considering different levels of aggregation, from the impact of each volcanic source and eruption size class to the quantification of the total hazard. This work provides, for the first time, a multi-volcano probabilistic hazard assessment posed by tephra fallout, comparable with those used for seismic phenomena and other natural disasters. This methodology can be applied to any other volcanic areas or over different exposure times, allowing researchers to account for the eruptive history of the target volcanoes that, when available, could include the occurrence of less frequent large eruptions, representing critical elements for risk evaluations.

Volcanic hazards

Vulcanian eruption

10.5194/nhess-23-2289-2023

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Quantification of volcanic degassing and analysis of uncertainties using numerical modelling: the case of Stephanos crater (Nisyros Island, Greece)

Research Square (Research Square) (2024)

Silvia Massaro Giancarlo Tamburello Giulio Bini Antonio Costa Manuel Stocchi

Abstract Nisyros Island (Greece) is affected by widespread gas emissions from fumarolic fields located at the bottom of hydrothermal craters in the southern part of its caldera. This morphology and the current low gas fluxes make Nisyros an ideal site for testing the limits of physics-based gas dispersal models in confined and low-emission conditions. Here, we focused our attention on the local scale volcanic gas dispersion from the Stephanos hydrothermal crater. In April 2023, a one-week survey was carried out to measure weather data, CO₂ and H₂S gas fluxes, air concentrations from portable gas stations, chemical composition of fumarolic gases and to acquire thermal images of the crater floor. These data were used as inputs and boundary conditions for numerical simulations using DISGAS-2.6 model in order to quantify the present-day volcanic degassing and its associated uncertainties, accounting for the meteorological variability. Model results are provided in terms of H₂S probabilistic exceedance and persistence maps, showing gas concentrations within the crater that fall below the thresholds indicated for the occurrence of serious respiratory problems. Since DISGAS-2.6 does not account for chemical reactions, this study represents a good opportunity to discuss the methodological limits of simulating the dispersion of H₂S which is challenging due to its rapid degradation and dilution in the atmosphere. In this regard, we also provided an empirical law of the H₂S depletion in low-emission conditions that takes into account the uncertainties related to the field measurements.

10.21203/rs.3.rs-4223998/v1

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Quantification of CO2 degassing and atmospheric dispersion at Caldeiras da Ribeira Grande (São Miguel Island, Azores)

Journal of Volcanology and Geothermal Research (2023)

Fátima Viveiros Eleonora Baldoni Silvia Massaro Manuel Stocchi Antonio Costa

Caldeiras da Ribeira Grande is one of the degassing areas of Fogo, a trachytic central volcano located at São Miguel Island (Azores archipelago). Recently, new steam emissions, soil CO2 and temperature anomalies developed towards the inhabited area, causing high indoor CO2 values and affecting the vegetation and several small animals that were found dead in depressions and low-ventilated zones. During July–August 2021, a soil CO2 flux survey was carried out on the north flank of the volcano, estimating a soil gas release of at least 40 t d−1 (excluding the contribution of the fumaroles) over an area of ∼0.27 km2. Two populations for the CO2 released were found, highlighting the biogenic and volcanic-hydrothermal origins. General NW-SE diffuse degassing structures (DDS) were identified, in agreement with the tectonic lineaments previously recognized in the area. In this regard, we investigated the passive gas dispersion in the atmosphere at Caldeiras da Ribeira Grande performing a model validation aimed to estimate the fumarolic gas flux at source and the potential hazard for human and animal lives posed by CO2. Numerical simulations were carried out with the DISGAS-2.3, a 3D Eulerian advection-diffusion model, and the relative outputs processed through the VIGIL-1.3 workflow able to provide probabilistic long-term CO2 concentration maps, considering a meteorological variability over the last 30 years (1991–2020) taken from the ECMWF ERA5 reanalysis dataset. A best-fit between observed and simulated CO2 concentrations allowed us to estimate the total gas flux of the area (∼209 t d−1) obtained by scaling the soil CO2 gas flux by a factor 30. Such an estimate is composed of ∼174 t d−1 as unknown fumarolic and ∼ 35 td−1 as diffuse contribution, in a good agreement with measurements. Although the present-day CO2 concentration at 0.3 m height cannot be considered to raise serious concerns for human health, we reasonably infer that the death of small animals may be due to local conditions of CO2 accumulation or to the presence of H2S. The current study highlights the relevance of coupling gas flux maps, concentration data, and gas dispersion modeling to obtain robust estimation of gas fluxes, including the fumarolic contribution, and identify zones potentially impacted by dangerous concentrations of volcanic gases, which are relevant for land-use planning and hazard assessment in case of renewed escalations of volcanic activity.

Fumarole

Archipelago

10.1016/j.jvolgeores.2023.107807

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Modelling CO2 dispersion in the air during potential limnic eruption at the lake Pavin (France)

Journal of Volcanology and Geothermal Research (2024)

Victoria Rafflin Guillaume Boudoire Silvia Massaro Manuel Stocchi Antonio Costa

Risk mitigation in long-dormant volcanic provinces is a challenge due to the absence of collective memory of past disasters as well as the scarcity, and subtlety, of unrest signals that can be monitored. In this study, the impact of a potential limnic eruption is assessed at the 92-m-deep lake Pavin (French Massif Central). The lake is hosted in a maar crater formed during the last eruptive event in metropolitan France (~7 ka) and contains dissolved CO2 in the deepest water layer, below 60 m. Carbon dioxide (CO2) emissions measured at the lake surface (0.44 km2) reach up to 10.1 tons/day during the winter. Beyond this (limited) continuous degassing of the lake, the current CO2 budget in the monimolimnion layer (at a depth of 60 m to 92 m) was estimated at 1750 tons, of which about 450 tons are available for release in case of overturn of the lake. Scenarios for CO2 dispersion in the lower atmosphere were simulated with the DISGAS and TWODEE-2 models by varying (i) meteorological conditions, (ii) the amount of CO2 released, (iii) and the mechanisms of degassing during a potential limnic eruption. The simulations allowed identification and delimitation of areas potentially impacted by hazardous CO2 levels in the air down-valley from the lake and directly around the lake. The spatio-temporal evolution of the potential CO2 cloud raises issues regarding the impacts of such a hypothetical event in the close vicinity of the lake and, given the area is populated and highly visited, needs to be considered in future risk mitigation strategies.

Maar

Crater lake

Massif

10.1016/j.jvolgeores.2024.108024

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Assessing long-term tephra fallout hazard in Southern Italy from Neapolitan volcanoes

Silvia Massaro Manuel Stocchi Beatriz Martínez Montesinos Laura Sandri Jacopo Selva

Abstract. Nowadays, tephra fallout hazard is based on coupling the physical modeling of the tephra dispersion processes with a probabilistic analysis that takes into account the natural variability of the volcanic phenomena in terms of eruption probability, eruption sizes, vent position and meteorological conditions. In this framework, we present a prototypal methodology to carry out a multi-volcano long-term tephra fallout hazard assessment in Southern Italy from the active Neapolitan volcanoes: Somma-Vesuvius, Campi Flegrei, and Ischia. FALL3D model (v.8.0) has been used to run thousands of numerical simulations (1,500 per eruption size class), considering the ECMWF ERA5 meteorological dataset over the last 30 years. The output in terms of tephra ground load has been processed within a new workflow for large-scale, high-resolution volcanic hazard assessment, in order to quantify the mean annual frequency with which the tephra load at the ground exceeds given critical thresholds at a target site within a 50-years exposure time, and the relative epistemic uncertainty. This work provides, for the first time, a multi-volcano probabilistic hazard analysis for tephra fallout, fully comparable with those used for seismic phenomena and other natural disasters in which multiple sources are integrated together, and it accounts for potential changes in regimes of each single considered volcano. This allows us to discuss also how the full information can be traced back to provide specific information about the prevalence of different volcanoes and eruptive style in the different target areas, based on hazard disaggregation. The methodology is applicable to any other volcanic areas or over different exposure times.

Volcanic hazards

Hazard map

10.5194/nhess-2023-3

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Citations (8)

Ash fallout long term probabilistic volcanic hazard assessment for Neapolitan volcanoes: an example of what Earth Scientists can do with HPC resources

Manuel Stocchi Silvia Massaro Beatriz Martínez Montesinos Laura Sandri Jacopo Selva

The creation of hazard maps relative to volcanic phenomena requires taking into account the intrinsic complexity and variability of eruptions. Here we present an example of how HPC can allow producing a high resolution multi-source probabilistic hazard assessment due to tephra fallout over a domain covering Southern Italy.&#160;&#160; The three active volcanoes in the Neapolitan area, Somma-Vesuvius, Campi Flegrei and Ischia, were considered as volcanic sources. For each one, we explored&#160; three explosive size classes (Small, Medium and Large) for Somma Vesuvius and Campi Flegrei, and one explosive size class (Large) for Ischia. For each size class, we performed 1500 numerical simulations of ash dispersion (total of 10500) using the&#160; Fall3D (V8.0) model over a computational domain covering&#160; Southern Italy with a 0.03&#176; &#10761; 0.03&#176; (~3 km &#10761; 3 km) resolution. Within each size class, the eruptive parameters have been randomly sampled from well-suited probability distributions and with different meteorological conditions, obtained by randomly sampling a day between 1990 and 2020 and retrieving the relative data from the ECMWF ERA5 database. This allowed exploring the intra-class variability and to quantify aleatoric uncertainty. The results of these simulations have been post-processed with a statistical approach by assigning a weight to each eruption (based on its eruption magnitude) and the annual eruption rate of each size class. For the case of Campi Flegrei, the variability in the eruptive vent position has also been explored by constructing a grid of possible vent locations with different spatial probability. By merging the results obtained for each source and size class we produced a portfolio of hazard maps showing the expected mean annual frequency of overcoming selected thresholds in&#160; ground tephra load. A disaggregation analysis has also been performed in order to understand which particular source and/or size class had the greater impact on a particular area.&#160; The completion of this work, considering both numerical simulations and the statistical elaboration of the results has required a total of more than 5000 core hours and the processing of more than 2TB of data, an effort that wouldn&#8217;t have been possible without the access to high level HPC resources.

10.5194/egusphere-gc11-solidearth-13

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Quantification of volcanic degassing and analysis of uncertainties using numerical modeling: the case of Stephanos crater (Nisyros Island, Greece)

Bulletin of Volcanology (2024)

Silvia Massaro Giancarlo Tamburello Giulio Bini Antonio Costa Manuel Stocchi

Abstract Nisyros Island (Greece) is affected by widespread gas emissions from fumarolic fields located at the bottom of hydrothermal craters in the southern part of its caldera. This morphology and the current low gas fluxes make Nisyros an ideal site for testing the limits of physics-based gas dispersal models in confined and low-emission conditions. Here, we focused our attention on the local scale volcanic gas dispersion from the Stephanos hydrothermal crater. In April 2023, a 1-week survey was carried out to measure weather data, CO 2 and H 2 S gas fluxes, air concentrations from portable gas stations, and chemical composition of fumarolic gases and to acquire thermal images of the crater floor. These data were used as inputs and boundary conditions for numerical simulations using a DISGAS-2.6.0 model in order to quantify the present-day volcanic degassing and its associated uncertainties, accounting for the meteorological variability. Model results are provided in terms of H 2 S probabilistic exceedance and persistence maps, showing gas concentrations within the crater that fall below the thresholds indicated for the occurrence of serious respiratory problems. Since DISGAS-2.6.0 does not account for chemical reactions, this study represents a good opportunity to discuss the methodological limits of simulating the dispersion of H 2 S which is challenging due to its rapid degradation and dilution in the atmosphere. In this regard, we also provided an empirical law of the H 2 S depletion in low-emission conditions that takes into account the uncertainties related to the field measurements.

10.1007/s00445-024-01779-9

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