Description: Owing to the current lack of reliable pre-eruptive models, often volcanologists rely on the observation of monitoring anomalies to forecast volcanic eruptions. Taking advantage from the work made in the development of Bayesian Event Trees, in this paper we formalize an entropy-based model to translate the observation of anomalies into eruption probabilities. The model has some important features worth being remarked: i) it is rooted in a coherent logic, which gives a physical sense to the heuristic information of volcanologists in terms of entropy; ii) it is fully transparent and it can be established well in advance of a crisis, making the results reproducible and providing a transparent audit trail, which reduces the degree of subjective opinion in volcanological communication with civil authorities; iii) it is embedded in a unified probabilistic framework, which provides an univocal taxonomy of different kinds of uncertainty affecting the forecast and handles these uncertainties in a formal way. For the sake of example, we apply the procedure to the eruption forecasting during the 1982-1984 phase of unrest at Campi Flegrei, Italy.

Description: The emission of volcanic gases can occur during both eruptive and quiescent stages of volcanic activity, affecting air quality when the concentrations exceed species-specific thresholds. Quantitative studies of model validation are essential before applying a simulator for probabilistic volcanic hazard assessment. Here, we provide three examples of model validation aimed at testing the accuracy in providing realistic values of CO〈sub〉2〈/sub〉 concentration, estimating the source gas fluxes using the concentration measurements through resolution of the inverse problem, and identifying potential hazardous gas dispersal scenarios. We selected three case study affected by a persistent diffusive and fumarolic degassing: i) La Solfatara crater, Campi Flegrei caldera, Italy, ii) Caldeiras da Ribeira Grande, São Miguel Island, Azores and iii) Stefanos crater, Nisyros Island, Greece. We used published and original CO〈sub〉2〈/sub〉 flux data as input for numerical simulations run through VIGIL, an open-source workflow for parallel simulations and probabilistic output using two Eulerian models, which account for the passive and gravity-driven gas transport, respectively. Our results provided probabilistic CO〈sub〉2〈/sub〉 concentration maps at 0.5-1.5 m from the ground in order to investigate the potential effects on human and animal health, and statistical tests aimed to infer the best scaling factor for gas flux in reaching hazardous gas concentrations. This kind of methodology has revelad the potential usefulness of the modeling in reproducing the order of magnitude of the observed degassing, therefore, such a testing should be the first logical step to be taken before applying a simulator to assess (gas) hazard in any other volcanic contexts.

Description: Probabilistic Tsunami Hazard and Risk Analysis (PTHA/PTRA) has its roots in the corresponding probabilistic approaches in the seismic sciences. However, there are several substantial differences in the cascading source and effect modeling chain, necessitating for complex workflows, involving still larger gaps in data and knowledge, and requiring different approaches in dealing with uncertainties. The European Cooperation in Science and Technology (COST) Action AGITHAR (Accelerating Global Science in Probabilistic Hazard and Risk Analysis) has run for four years and has since then gathered parts of the scientific community around PTHA/PTRA and made some substantial progress in communicating and unifying the underlying concepts. Additionally, the effort has allowed the European tsunami community to coordinate a number of new research efforts and infrastrucutral developments, which are of benefit for the global science in PTHA/PTRA. In this presentation we will outline the results of AGITHAR's major deliverables, a compilation of research gaps in PTHA/PTRA and uncertainty communication, findings in interdisciplinary tsunami research cooperation, and a collection of current practices in PTHA/PTRA. Ideas and opportunities of sustaining AGITHAR's output into the future will be given.

Description: We present our contribution to the UCIS4EQ (Urgent Computing Integrated Services for EarthQuakes) workflow, where multiple realizations of ground motion fields are required to account for input and model uncertainties under emergency conditions. Our focus is on the initialization and update of an ensemble of scenarios describing the seismic source uncertainty for Urgent Computing (UC) applications. We propose an algorithm to reduce the size of the ensemble for UC usability, such that source uncertainty can be propagated to shaking with numerical simulations of a subset of seismic sources while preserving the key statistical properties of the full ensemble. As target distribution representing the expected shaking variability in the earthquake-hit area, we use the distribution of PGA (Peak Ground Acceleration) values predicted by local GMPEs (Ground Motion Prediction Equations) for the seismic scenarios in the full ensemble. Besides accounting for source uncertainty, our approach estimates the uncertainty associated with the ensemble sampling method and available GMPEs. By sampling an increasing number of seismic scenarios from the full ensemble, the algorithm estimates the total variability of the subsample and assesses its convergence to the target distribution. Besides reducing the time and cost of shaking scenarios simulations, it also enables the retrieval of probabilistic shakemaps, an evolved version of the traditional shakemaps where each POI (Point Of Interest) is assigned a probability distribution of PGA values quantifying both the source and GMPEs uncertainty. Our algorithm is written in Python and makes use of OpenQuake and Shakemap libraries.

Description: The destructive tsunami on 22 December 2018 due to the flank collapse of the Anak Krakatau volcano was a bitter reminder of large tsunami risks and of the shortcomings of the existing tsunami warning systems for atypical (non-seismic) sources. In the Mediterranean, several tsunamis were generated by landslides associated with volcanic systems in the past.The volcanic unrest experienced in 2011-2012 on the Santorini volcanic island in the Southern Aegean Sea pointed out the need to identify and quantify tsunami hazard and risk due to possible flank instability which may be triggered as a result of volcanic unrest or nearby seismotectonic activities. Inspired from this need, in this study we examined three possible landslide scenarios in Santorini Island with tsunamigenic potential. The results show that the scenarios considered in our study are able to generate significant local tsunamis impacting Santorini and the nearby islands, as well as producing significant impact along the coasts of the Southern Aegean Sea. While maximum tsunami amplitudes/arrival time ranges are 1.2m/30-90min for locations in the Greek-Turkish coasts in the far field, they are in the order of ≈60m/1-2min for some locations at the Santorini Island. The extreme tsunami amplitudes and short arrival times for locations inside the Santorini Island is a major challenge in terms of tsunami hazard warning and mitigation. As an effort to address this challenge, a discussion on the requirements for local tsunami warning system addressing atypical sources in the context of multi-hazard disaster risk reduction is also provided.

Description: The Neapolitan volcanoes are some of the most hazardous in the world because capable of large explosive eruptions releasing threatening quantities of ash in the atmosphere that would reasonably reach highly-populated urban areas, even at considerable distances from the sources. This study aims to show a long-term tephra fallout hazard evaluation posed by the Neapolitan volcanoes (Somma-Vesuvius, Campi Flegrei, Ischia) in Southern Italy, and to track future perspectives to combine a multi-hazard assessment to a more local-scale domain. Through a new HPC workflow for volcanic hazard assessment based on a Bayesian procedure, we provided the mean annual frequency with which the tephra load at the ground exceeds given critical thresholds within 50 years. By performing hazard disaggregation, we also got specific information about the prevalence of different volcanoes and eruptive style in the different target areas. Thousands of numerical simulations were run with the FALL3D model to create a large synthetic dataset of tephra ground loads on a 0.03°-resolution gridded domain and a vertical σ-coordinate system with a linear decay. Each simulation took a randomly sampled set of eruptive source parameters within the ranges established by the knowledge of each volcano and meteorological conditions extracted by the ECMWF ERA5 dataset. In particular, results show that the greater tephra load thresholds are exceeded with longer averaged return times (i.e., 100, 500, 1000 years) in the proximity of the Neapolitan area. This pushes us to do a step forward into a more detailed multi-hazard and risk-ranking quantification in the Neapolitan urban area.

Description: Volcanic and non-volcanic gas emission represent a widespread and frequent hazard. In fact, some gas species (e.g., CO2, H2S, SO2) can affect human health and even threaten life at concentrations and doses above species-specific thresholds. Depending on the starting buoyancy relative to the surrounding atmosphere at the emission location, gas emissions can be classified as dilute passive degassing (e.g. fumaroles) and dense gas flow (e.g., cold CO2 accumulation and flows onto the ground). Here we present the latest version of VIGIL (automatic probabilistic VolcanIc Gas dIspersion modeLling), a Python simulation tool capable of handling the complex and time-consuming gas dispersion simulation workflow and interfaced with two dispersion models: a dilute (DISGAS) and a dense gas (TWODEE-2) dispersion model. VIGIL allows exploring the uncertainty of the meteorological conditions and gas emission location and strength. The post-processing script offers the option to create Empirical Cumulative Distribution Functions (ECDF) of the gas concentrations combining the outputs of multiple simulations. The ECDF can be interrogated by the user to produce maps of gas concentration at specified exceedance probabilities. Tracking points can also be used to produce time series of gas concentration at selected locations and hazard curves if ECDF is produced. Furthermore, the new gas persistence calculation capability creates maps of the probability to overcome specified gas specie-specific concentration thresholds over specified durations. We also present results from applications at different volcanically and tectonically active areas showcasing the various capabilities of VIGIL.

Description: Tsunamis constitute a significant hazard for European coastal populations, and the impact of tsunami events worldwide can extend well beyond the coastal regions directly affected. Understanding the complex mechanisms of tsunami generation, propagation, and inundation, as well as managing the tsunami risk, requires multidisciplinary research and infrastructures that cross national boundaries. Recent decades have seen both great advances in tsunami science and consolidation of the European tsunami research community. A recurring theme has been the need for a sustainable platform for coordinated tsunami community activities and a hub for tsunami services. Following about three years of preparation, in July 2021, the European tsunami community attained the status of Candidate Thematic Core Service (cTCS) within the European Plate Observing System (EPOS) Research Infrastructure. Within a transition period of three years, the Tsunami candidate TCS is anticipated to develop into a fully operational EPOS TCS. We here outline the path taken to reach this point, and the envisaged form of the future EPOS TCS Tsunami. Our cTCS is planned to be organised within four thematic pillars: (1) Support to Tsunami Service Providers, (2) Tsunami Data, (3) Numerical Models, and (4) Hazard and Risk Products. We outline how identified needs in tsunami science and tsunami risk mitigation will be addressed within this structure and how participation within EPOS will become an integration point for community development.

Description: The EU Center of Excellence for Exascale in Solid Earth (ChEESE) develops exascale transition capabilities in the domain of Solid Earth, an area of geophysics rich in computational challenges embracing different approaches to exascale (capability, capacity, and urgent computing). The first implementation phase of the project (ChEESE-1P; 2018–2022) addressed scientific and technical computational challenges in seismology, tsunami science, volcanology, and magnetohydrodynamics, in order to understand the phenomena, anticipate the impact of natural disasters, and contribute to risk management. The project initiated the optimisation of 10 community flagship codes for the upcoming exascale systems and implemented 12 Pilot Demonstrators that combine the flagship codes with dedicated workflows in order to address the underlying capability and capacity computational challenges. Pilot Demonstrators reaching more mature Technology Readiness Levels (TRLs) were further enabled in operational service environments on critical aspects of geohazards such as long-term and short-term probabilistic hazard assessment, urgent computing, and early warning and probabilistic forecasting. Partnership and service co-design with members of the project Industry and User Board (IUB) leveraged the uptake of results across multiple research institutions, academia, industry, and public governance bodies (e.g. civil protection agencies). This article summarises the implementation strategy and the results from ChEESE-1P, outlining also the underpinning concepts and the roadmap for the on-going second project implementation phase (ChEESE-2P; 2023–2026).