Garcia, Alexander

Volcanic activity is intrinsically a multi-hazard problem. Different phenomena accompanying volcanic activity, such as seismicity, static deformation, lava flows, gas emission and tephra fallout, can be dangerous to the society and economy with a wide range of impacts. Moreover, the physical parameters representing the intensity measure of such hazards are of different nature and therefore their integration in a single analysis is not straightforward. The most frequent approaches for multi-hazard assessment usually start from considering each hazard as the primary subject of the analysis; afterwards, the multi-hazard analysis is generally based on the integration of multiple volcanic hazards independently assessed, often without any effort of harmonization of the results. Afterwards, the final multi-hazard integration is done using different approaches as e.g., the definition of subjective indexes (for example "Low", "Medium" and "High" hazard zones) or by the spatial overlap of hazard maps representing a specific (sometimes termed "reference") scenario. From a decision-maker point of view, these multi-hazard analyses may not be sufficiently informative, and may be biased by the subjective choices taken by the hazard analysts. In this work, we introduce a target-based approach for multi-hazard assessment in which the target (objective) of the analysis is the starting point of the process. The method is implemented using a fully probabilistic approach that allows also propagating epistemic uncertainties (often quantified while evaluating single hazards separately). The approach is based on a system for the solution of "fault trees" and "event trees" called MERGER [1], and involves: (i) the definition of a clear objective for the analysis (i.e., the "target"), which is probably a more clear task for a decision maker; (ii) the identification of hazardous events that can potentially contribute to the achievement of the "target" objective; and (iii) the definition of possible logical relationships between the events that identify the way in which they can contribute to achieving the target objective. As a demonstrator of our approach, we present some preliminary results obtained in the framework of the PANACEA project (INGV's project "Pianeta Dinamico", funded by the Italian Ministero dell'Università e la Ricerca, MUR) regarding the multi-hazard assessment around Mt Etna volcano. In particular, we identify a few target objectives related to mobility disruption due to Mt Etna activity, and we show how the MERGER model can integrate the probabilistic hazard for seismic events, lava flow inundation and tephra fallout.

Mt. Etna is the largest active volcano in Europe with effusive and explosive eruptions, and intense seismic activity. Its effects on the densely urbanized area located on the Etna flanks were investigated within the PANACEA project (Probabilistic AssessmeNt of volCano-related multi-hazard and multi-risk at Mount EtnA), an innovative and extensive research project aimed to assess the risk consequent to lava flow, tephra fallout, and earthquake hazards. In this work, we illustrate how seismic and volcanic probabilistic hazard scenarios have found their practical application in risk estimation for built-up environment, electric power systems and roads infrastructures. Risk scenarios were assessed at very different scales, from local to sub-regional, and have been done in case of lava flows, tephra fallouts and volcanic earthquakes, leaving out pyroclastic flows as they only affect the summit area of the volcano that is devoid of exposed elements.

The assessment of the spatial probability of future vent opening is one of the key factors in quantifying volcanic hazard, especially for active volcanoes where eruptions can occur at different locations and altitudes over distributed areas. Mount Etna (Italy), one of the most active volcanoes in the world, exhibits such variability, and its flank eruptions can harm people, properties and services over the volcano’s slopes. In this paper, we quantify the spatial probability of future vent opening for Etna’s flank eruptions, adopting a kernel analysis and testing different functions (exponential, Cauchy, uniform and Gaussian). Starting from the assumption that the location of past fissures is indicative of where future events will occur, we consider the flank eruptions of the last 4000 years, thus accounting for a much longer and complete record than in previous studies. The large dataset of eruptive fissures enables splitting the data into training and testing subsets. This allows selecting the best kernel model, testing the completeness of the fissure dataset and investigating a possible migration through time in fissure location. The results show that neither under-recording nor possible migration over time significantly affects the informative value of previous flank fissures in forecasting the location of future ones. The resulting map highlights that the most likely opening area follows a northeast-to-south trend, corresponding to the location of the most active rifts. It also shows that the southern flank of the volcano, which is the most urbanized one, sits downhill of the largest cumulated probability area for flank eruption. We also run sensitivity analyses to test the effect of (i) restricting the data to the most recent 400 years and (ii) including the information on the stress induced on the mapped fissures by sources of deformation proposed in the literature for recent eruptions of Etna. The sensitivity analyses confirm the main features of the proposed map and add information on the epistemic uncertainty attached to it.

The management of multiple hazards simultaneously impacting on a territory is a challenge for effective risk mitigation. This is particularly true on active volcanoes like Mt. Etna, characterized by effusive and explosive eruptions, often coupled with an intense seismic activity. This work aims at presenting the approach of the PANACEA project on the treatment of multi-hazards in terms of risk, which requires a common definition of the exposed elements and their vulnerability. Another aspect emerging from the recent and historical volcanic crises at Etna, is the occurrence of cascading effects and the problem of assessing their short-term interactions. Here we present a risk model taking into account a set of sequences of hazardous events which may result from a volcano unrest to possible impacts to some infrastructural elements. The outcomes of the project are intended to be a significant step towards a more comprehensive resilience to volcanic disasters, leading to a more safe society.

Our ability to estimate surface deformation rates in the Central Mediterranean has considerably enhanced in the last decade thanks to the growth of continuous Global Navigation Satellite System (GNSS) networks. Focusing on the Apennine/Alpine seismogenic belt, this area offers the opportunity to test the use of geodetic strain rates for constraining active tectonic processes and for seismic hazard assessments. Given the importance of geodetic strain rate models in modern hazard estimation approaches, however, one has to consider that different approaches can provide significantly different strain rate maps. Despite the increasing availability of GNSS velocity data, in fact, strain rate models can significantly differ, because of the spatial heterogeneity of GNSS station locations and inherent strategies in computing strain rates. Using a dense GNSS velocity dataset, this study examines three methods for estimating horizontal strain rates, described in the recent literature, and selected to represent approaches of increasing mathematical complexity. The advantages, drawbacks, and optimal settings of each method are discussed. The main result is an ensemble of strain rate models that enable the evaluation of epistemic uncertainties in seismicity rate models constrained by geodetic velocities.

This work presents the first results of the PANACEA project regarding the assessment of different volcano-related hazards at Mt. Etna (lava and pyroclastic flows, tephra fallout and earthquakes) by exploiting data deriving from the volcano’s history with accurate physical–mathematical models. Volcano-related hazards are distributed differently on Etna—from the deserted summit area down to the densely populated flanks—but must be considered together for long-term territorial planning.

Accurate forecasting of volcanic particle (tephra) dispersal and fallout requires a reliable estimation of key Eruption Source Parameters (ESPs) such as the Mass Eruption Rate (Q M). QM is usually estimated from the Top Plume Height (HTP) using empirical and analytical models. For the first time, we combine estimates of HTP and QM derived from the same sensor (radar) with mean wind velocity values (vW) for lava-fountain fed tephra plumes associated with 32 paroxysms of Mt. Etna (Italy) to develop a new statistical model based on a Markov Chain Monte Carlo approach for model parameter estimation. This model is especially designed for application to radar data to quickly infer QM from observed HTP and vW, and estimate the associated uncertainty. It can be easily applied and adjusted to data retrieved by radars worldwide, improving our capacity to quickly estimate QM and related uncertainties required for the tephra dispersal hazard.

Da venerdì 4 novembre a domenica 6 novembre 2022, si è tenuta una esercitazione nazionale denominata “Exe Sisma dello Stretto 2022” in un'area del territorio della Regione Calabria e della Regione Sicilia caratterizzata da una elevatissima pericolosità sismica. L’esercitazione è stata indetta e coordinata dal Dipartimento della Protezione Civile e aveva l’obiettivo di verificare la risposta operativa a un evento sismico significativo del Servizio Nazionale della Protezione Civile, di cui anche l’Istituto Nazionale di Geofisica e Vulcanologia fa parte. Durante le tre giornate, l’INGV ha avuto modo di testare tutte le procedure che l’Istituto ha codificato a partire da quelle del “Protocollo di Ente per le emergenze sismiche e da maremoto”. Dopo che INGV ha dato l’avvio all’intera esercitazione simulando il terremoto di magnitudo MW 6.2 (ML 6.0) alle ore 09:00 UTC in provincia di Reggio Calabria (5 km a SW dal comune di Laganadi), e ha, quindi, inviato il messaggio per il potenziale maremoto con un livello di allerta arancione; inoltre, il Presidente INGV ha prontamente convocato l’Unità di Crisi e attivato tutti Gruppi Operativi. Questi ultimi, nell’ambito dello scenario esercitativo, hanno verificato che i flussi di comunicazione interna e tutte le attività necessarie in emergenza sismica, presenti nei relativi protocolli operativi, risultassero rispettati. L’obiettivo primario dell’esercitazione è stato quindi quello di validare le attività previste e di aggiornare il personale afferente ai Gruppi Operativi stessi. Tra di essi, SISMIKO, che rappresenta il GO dedicato al coordinamento delle reti sismiche mobili INGV in emergenza, nelle settimane precedenti l’esercitazione ha predisposto tutte le attività che intendeva testare, descrivendole brevemente nel Documento d’impianto INGV e con maggior dettaglio in quello del Gruppo Operativo. A pochi giorni dalla chiusura dell’esercitazione, un terremoto di magnitudo ML 5.7 (MW 5.5) registrato alle ore 06:07 UTC del 09 novembre 2022 ha spostato l’attenzione dalla simulazione alla realtà.

Open conduit volcanoes like Stromboli can display elusive changes in activity before major eruptive events. Starting on December 2020, Stromboli volcano displayed an increasing eruptive activity, that on 19 May 2021 led to a crater-rim collapse, with pyroclastic density currents (PDCs) that spread along the barren NWflank, entered the sea and ran across it for more than 1 km. This episode was followed by lava flow output from the crater rim lasting a few hours, followed by another phase of lava flow in June 2021. These episodes are potentially very dangerous on island volcanoes since a landslide of hot material that turns into a pyroclastic density current and spreads on the sea surface can threaten mariners and coastal communities, as happened at Stromboli on 3 July and 28 August 2019. In addition, on entering the sea, if their volume is large enough, landslides may trigger tsunamis, as occurred at Stromboli on 30 December 2002. In this paper, we present an integration of multidisciplinary monitoring data, including thermal and visible camera images, ground deformation data gathered from GNSS, tilt, strainmeter and GBInSAR, seismicity, SO2 plume and CO2 ground fluxes and thermal data from the ground and satellite imagery, together with petrological analyses of the erupted products compared with samples from previous similar events. We aim at characterizing the preparatory phase of the volcano that began on December 2020 and led to the May–June 2021 eruptive activity, distinguishing this small intrusion of magma from the much greater 2019 eruptive phase, which was fed by gas-rich magma responsible for the paroxysmal explosive and effusive phases of July–August 2019. These complex eruption scenarios have important implications for hazard assessment and the lessons learned at Stromboli volcano may prove useful for other open conduit active basaltic volcanoes.

This article describes the IT infrastructure implemented by the Centre for the Monitoring of Subsoil activities to monitor the areas of competence of which, according to the provisions of the Addresses and Guidelines and following the appointment by the Ministry for Economic Development, the INGV is the Structure in charge of seismic and geodetic Monitoring. Particular attention is paid to the hardware and software infrastructure, the data formats used and their installation is described.