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  • 1
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    Phreatic eruptions at crater lakes: occurrence statistics and probabilistic hazard forecast (2017)
    SpringerOpen
    In:  Journal of Applied Volcanology, 6 (4).
    Details
    Publication Date: 2020-02-06
    Description: Phreatic eruptions, although posing a serious threat to people in crater proximity, are often underestimated and have been comparatively understudied. The detailed eruption catalogue for Ruapehu Volcano (New Zealand) provides an exceptional opportunity to study the statistics of recurring phreatic explosions at a crater lake volcano. We performed a statistical analysis on this phreatic eruption database, which suggests that phreatic events at Ruapehu do not follow a Poisson process. Instead they tend to cluster, which is possibly linked to an increased heat flow during periods of a more shallow-seated magma column. Larger explosions are more likely to follow shortly after smaller events, as opposed to longer periods of quiescence. The absolute probability for a phreatic explosion to occur at Ruapehu within the next month is about 10%, when averaging over the last 70 years of recording. However, the frequency of phreatic explosions is significantly higher than the background level in years prior to magmatic episodes. Combining clast ejection simulations with a Bayesian event tree tool (PyBetVH) we perform a probabilistic assessment of the hazard due to ballistic ejecta in the summit area of Ruapehu, which is frequently visited by hikers. Resulting hazard maps show that the absolute probability for the summit to be affected by ballistics within the next month is up to 6%. The hazard is especially high on the northern lakeshore, where there is a mountain refuge. Our results contribute to the local hazard assessment as well as the general perception of hazards due to steam-driven explosions.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1186/s13617-016-0053-2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Probabilistic studies with Eject! for Matlab (2019)
    VHub
    In:  VHub.org Resources, 4558 . VHub, 2 pp.
    Details
    Publication Date: 2020-01-15
    Description: The program "Eject!" calculates the trajectories of ballistic projectiles from volcanic eruptions (Mastin, 2001; 2011). The code was originally written in Visual Basic, which we have now translated into an editable Matlab procedure (Strehlow et al., 2017). Input parameters used here are exemplary for the case of Ruapehu volcano, but can be adapted to any specific case. Additionally, we have written a short script that compares the flight trajectory to the topography of the volcano to determine the flight distance.
    Type: Report , NonPeerReviewed
    Format: text
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    OceanRep: Report - other report
  • 3
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    Eject! for Matlab (2019)
    VHub
    In:  VHub.org Resources, 4543 . VHub, 2 pp.
    Details
    Publication Date: 2020-01-15
    Description: The program "Eject!" calculates the trajectories of ballistic projectiles from volcanic eruptions (Mastin, 2001; 2011). The code was originally written in Visual Basic, which we have now translated into an editable Matlab procedure (Strehlow et al., 2017). Input parameters used here are exemplary for the case of Ruapehu volcano, but can be adapted to any specific case. Additionally, we have written a short script that compares the flight trajectory to the topography of the volcano to determine the flight distance.
    Type: Report , NonPeerReviewed
    Format: text
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    OceanRep: Report - other report
  • 4
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    Influence of seismogenic source geometrical accuracy on PTHA: a test case for the Calabrian subduction interface (2017)
    Details
    Publication Date: 2020-10-22
    Description: Exploring different degrees of complexities in the geometry of seismic tsunami sources is a key point to optimize Probabilistc Tsunami Hazard Analyis (PTHA), as fault geometry can have an impact on the generated tsunami. In this regard, one major difficulty is represented by the potentially tsunamigenic offshore faults that are generally poorly constrained and consequently the geometry is often oversimplified as a planar fault. We present compared scenarios of PTHA for ruptures located in the Calabrian subduction interface using different source models. The Calabrian subduction, located in the Mediterranean Sea, has occasionally be blamed to have generated some past large earthquakes and tsunamis, despite it shows no sign of significant seismic activity on the shallow portion of the interface. Significant in-slab seismicity is recorded below 40 km depth and a rate of 1-5 mm/yr characterize the convergence between the two plates involved, Africa and Europe. A 3D model of the subduction interface was obtained from the original interpretation of a grid of ca. 60 (9000 km length) seismic reflection profiles (Spectrum – INGV collaborative framework CA-60) coupled with the detailed analysis of the seismicity, providing a highly detailed 3D surface geometry for the first 100 km depth. This model includes both the first order information on the curvature and changes in strike and an accurate reconstruction of the 3D subduction interface, and can be scaled to different levels of detail. We compare simplified planar vs 3D models with different degrees of geometrical complexities in order to estimate the effect of the source geometry on the tsunami generation and propagation pattern.
    Description: TSUMAPS-NEAM Project, co-financed by the European Union Civil Protection Mechanism, Agreement Number: ECHO/SUB/2015/718568/PREV26; Italian Flagship Project RITMARE
    Description: Unpublished
    Description: Wien
    Description: 5T. Modelli di pericolosità sismica e da maremoto
    Keywords: Tsunami ; PTHA ; Seismogenic source ; 04.06. Seismology ; 05.08. Risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 5
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    Fast evaluation of tsunami scenarios: uncertainty assessment for a Mediterranean Sea database (2018)
    Details
    Publication Date: 2021-03-08
    Description: We present a database of pre-calculated tsunami waveforms for the entire Mediterranean Sea, obtained by numerical propagation of uniformly spaced Gaussian-shaped elementary sources for the sea level elevation. Based on any initial sea surface displacement, the database allows the fast calculation of full waveforms at the 50 m isobath offshore of coastal sites of interest by linear superposition. A computationally inexpensive procedure is set to estimate the coefficients for the linear superposition based on the potential energy of the initial elevation field. The elementary sources size and spacing is fine enough to satisfactorily reproduce the effects of M〉 = 6.0 earthquakes. Tsunami propagation is modelled by using the Tsunami-HySEA code, a GPU finite volume solver for the non-linear shallow water equations. Like other existing methods based on the initial sea level elevation, the database is independent on the faulting geometry and mechanism, which makes it applicable in any tectonic environment. We model a large set of synthetic tsunami test scenarios, selected to explore the uncertainty introduced when approximating tsunami waveforms and their maxima by fast and simplified linear combination. This is the first time to our knowledge that the uncertainty associated to such a procedure is systematically analysed and that relatively small earthquakes are considered, which may be relevant in the near-field of the source in a complex tectonic setting. We find that non-linearity of tsunami evolution affects the reconstruction of the waveforms and of their maxima by introducing an almost unbiased (centred at zero) error distribution of relatively modest extent. The uncertainty introduced by our approximation can be in principle propagated to forecast results. The resulting product then is suitable for different applications such as probabilistic tsunami hazard analysis, tsunami source inversions and tsunami warning systems.
    Description: Published
    Description: 2593–2602
    Description: 5T. Modelli di pericolosità sismica e da maremoto
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
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    The Making of the NEAM Tsunami Hazard Model 2018 (NEAMTHM18) (2021)
    Frontiers
    Details
    Publication Date: 2021-03-08
    Description: The NEAM Tsunami Hazard Model 2018 (NEAMTHM18) is a probabilistic hazard model for tsunamis generated by earthquakes. It covers the coastlines of the North-eastern Atlantic, the Mediterranean, and connected seas (NEAM). NEAMTHM18 was designed as a three-phase project. The first two phases were dedicated to the model development and hazard calculations, following a formalized decision-making process based on a multiple-expert protocol. The third phase was dedicated to documentation and dissemination. The hazard assessment workflow was structured in Steps and Levels. There are four Steps: Step-1) probabilistic earthquake model; Step-2) tsunami generation and modeling in deep water; Step-3) shoaling and inundation; Step-4) hazard aggregation and uncertainty quantification. Each Step includes a different number of Levels. Level-0 always describes the input data; the other Levels describe the intermediate results needed to proceed from one Step to another. Alternative datasets and models were considered in the implementation. The epistemic hazard uncertainty was quantified through an ensemble modeling technique accounting for alternative models’ weights and yielding a distribution of hazard curves represented by the mean and various percentiles. Hazard curves were calculated at 2,343 Points of Interest (POI) distributed at an average spacing of ∼20 km. Precalculated probability maps for five maximum inundation heights (MIH) and hazard intensity maps for five average return periods (ARP) were produced from hazard curves. In the entire NEAM Region, MIHs of several meters are rare but not impossible. Considering a 2% probability of exceedance in 50 years (ARP≈2,475 years), the POIs with MIH 〉5 m are fewer than 1% and are all in the Mediterranean on Libya, Egypt, Cyprus, and Greece coasts. In the North-East Atlantic, POIs with MIH 〉3 m are on the coasts of Mauritania and Gulf of Cadiz. Overall, 30% of the POIs have MIH 〉1 m. NEAMTHM18 results and documentation are available through the TSUMAPS-NEAM project website (http://www.tsumaps-neam.eu/), featuring an interactive web mapper. Although the NEAMTHM18 cannot substitute in-depth analyses at local scales, it represents the first action to start local and more detailed hazard and risk assessments and contributes to designing evacuation maps for tsunami early warning.
    Description: The NEAMTHM18 was prepared in the framework of the European Project TSUMAPS-NEAM (http://www.tsumaps-neam.eu/) funded by the mechanism of the European Civil Protection and Humanitarian Aid Operations with grant no. ECHO/SUB/2015/718568/PREV26 (https://ec.europa.eu/echo/funding-evaluations/financing-civil-protection-europe/selected-projects/probabilistic-tsunami-hazard_en). The work by INGV authors also benefitted from funding by the INGV-DPC Agreement 2012-2021 (Annex B2).
    Description: Published
    Description: 616594
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: 1SR TERREMOTI - Sorveglianza Sismica e Allerta Tsunami
    Description: 2SR TERREMOTI - Gestione delle emergenze sismiche e da maremoto
    Description: 3SR TERREMOTI - Attività dei Centri
    Description: 5SR TERREMOTI - Convenzioni derivanti dall'Accordo Quadro decennale INGV-DPC
    Description: 3IT. Calcolo scientifico
    Description: 4IT. Banche dati
    Description: JCR Journal
    Keywords: probabilistic tsunami hazard assessment ; earthquake-generated tsunami ; hazard uncertainty analysis ; ensemble modeling ; maximum inundation height ; NEAM ; 05.08. Risk ; 03.02. Hydrology ; 04.06. Seismology ; 04.07. Tectonophysics ; 05.01. Computational geophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
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    How much does geometry of seismic sources matter in tsunami modeling? A sensitivity analysis for the Calabrian subduction interface (2018)
    Details
    Publication Date: 2020-10-22
    Description: The geometry of seismogenic sources could be one of the most important factors concurring to control the generation and the propagation of earthquake-generated tsunamis and their effects on the coasts. Since the majority of potentially tsunamigenic earthquakes occur offshore, the corresponding faults are generally poorly constrained and, consequently, their geometry is often oversimplified as a planar fault. The rupture area of mega-thrust earthquakes in subduction zones, where most of the greatest tsunamis have occurred, extends for tens to hundreds of kilometers both down dip and along strike, and generally deviates from the planar geometry. Therefore, the larger the earthquake size is, the weaker the planar fault assumption become. In this work, we present a sensitivity analysis aimed to explore the effects on modeled tsunamis generated by seismic sources with different degrees of geometric complexities. We focused on the Calabrian subduction zone, located in the Mediterranean Sea, which is characterized by the convergence between the African and European plates, with rates of up to 5 mm/yr. This subduction zone has been considered to have generated some past large earthquakes and tsunamis, despite it shows only in-slab significant seismic activity below 40 km depth and no relevant seismicity in the shallower portion of the interface. Our analysis is performed by defining and modeling an exhaustive set of tsunami scenarios located in the Calabrian subduction and using different models of the subduction interface with increasing geometrical complexity, from a planar surface to a highly detailed 3D surface. The latter was obtained from the interpretation of a dense network of seismic reflection profiles coupled with the analysis of the seismicity distribution. The more relevant effects due to the inclusion of 3D complexities in the seismic source geometry are finally highlighted in terms of the resulting tsunami impact.
    Description: Unpublished
    Description: New Orleans
    Description: 1T. Deformazione crostale attiva
    Description: 5T. Modelli di pericolosità sismica e da maremoto
    Keywords: tsunami ; seismic source geometry ; 03.03. Physical ; 04.07. Tectonophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 8
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    The Need to Quantify Hazard Related to Non-magmatic Unrest: From BET_EF to BET_UNREST (2018)
    Details
    Publication Date: 2020-12-14
    Description: Most volcanic hazard studies focus on magmatic eruptions and their accompanying phenomena. However, hazardous volcanic events can also occur during non-magmatic unrest, defined as a state of volcanic unrest in which no migration of magma is recognised. Examples include tectonic unrest, and hydrothermal unrest that may lead to phreatic eruptions. Recent events (e.g. Ontake eruption, September 2014) have demonstrated that the successful forecasting of phreatic eruptions is still very difficult. It is therefore of paramount importance to identify indicators that define the state of non-magmatic unrest. Often, this type of unrest is driven by fluids-on-the-move, requiring alternative monitoring setups, beyond the classical seismic-geodetic-geochemical architectures. Here we present a new version of the probabilistic model BET (Bayesian Event Tree), called BET_UNREST, specifically developed to include the forecasting of non-magmatic unrest and related hazards. The structure of BET_UNREST differs from the previous BET_EF (BET for Eruption Forecasting) by adding a dedicated branch to detail non-magmatic unrest outcomes. Probabilities are calculated at each node by merging prior models and past data with new incoming monitoring data, and the results can be updated any time new data has been collected. Monitoring data are weighted through pre-defined thresholds of anomaly, as in BET_EF. The BET_UNREST model is introduced here, together with its software implementation PyBetUnrest, with the aim of creating a user-friendly, open-access, and straightforward tool to support short-term volcanic forecasting (already available on the VHub platform). The BET_UNREST model and PyBetUnrest tool are tested through three case studies in the frame of the EU VUELCO project.
    Description: Published
    Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 9
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    Shallow slip amplification and enhanced tsunami hazard unravelled by dynamic simulations of mega-thrust earthquakes (2018)
    Details
    Publication Date: 2021-02-10
    Description: The 2011 Tohoku earthquake produced an unexpected large amount of shallow slip greatly contributing to the ensuing tsunami. How frequent are such events? How can they be efficiently modelled for tsunami hazard? Stochastic slip models, which can be computed rapidly, are used to explore the natural slip variability; however, they generally do not deal specifically with shallow slip features. We study the systematic depth-dependence of slip along a thrust fault with a number of 2D dynamic simulations using stochastic shear stress distributions and a geometry based on the cross section of the Tohoku fault. We obtain a probability density for the slip distribution, which varies both with depth, earthquake size and whether the rupture breaks the surface. We propose a method to modify stochastic slip distributions according to this dynamically-derived probability distribution. This method may be efficiently applied to produce large numbers of heterogeneous slip distributions for probabilistic tsunami hazard analysis. Using numerous M9 earthquake scenarios, we demonstrate that incorporating the dynamically-derived probability distribution does enhance the conditional probability of exceedance of maximum estimated tsunami wave heights along the Japanese coast. This technique for integrating dynamic features in stochastic models can be extended to any subduction zone and faulting style.
    Description: Published
    Description: 35007
    Description: 2T. Sorgente Sismica
    Description: 5T. Modelli di pericolosità sismica e da maremoto
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 10
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    Probabilistic hazard analysis for tsunamis generated by subaqueous volcanic explosions in the Campi Flegrei caldera, Italy (2020)
    Details
    Publication Date: 2021-05-12
    Description: A probabilistic hazard analysis of tsunami generated by subaqueous volcanic explosion is applied to the Campi Flegrei caldera (Campania, Italy). An event tree is developed to quantify the tsunami hazard due to the submarine explosions by: i) defining potential size classes of explosion magnitude on the basis of past volcanic activity in the Campi Flegrei caldera and sites in the underwater part of the caldera; ii) simulating the generation and propaga- tion of the consequent tsunami waves able to reach the coasts of the Campania region for all combinations of tsunami-generating vents and sizes; and iii) quantifying the tsunami probability and relative uncertainty, condi- tional upon the occurrence of an underwater eruption at Campi Flegrei. Tsunami hazard generated by subaque- ous volcanic explosions is considered crucial because of its potential high impact on the densely populated coastal areas of the Pozzuoli Bay and Gulf of Naples even if the probability for eruptions in the submarine part of the caldera is certainly low. The tsunami hazard analysis is presented using conditional hazard curves and maps, that is calculating the probability (and relative uncertainties) of exceeding given tsunami intensity thresh- olds (wave amplitudes at the coast), given the occurrence of a subaqueous eruption. The results indicate that a significant tsunami hazard exists in many areas of the Bay of Naples.
    Description: Published
    Description: 106-116
    Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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