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Neri, Augusto
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Neri, Augusto
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145 results
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- PublicationOpen AccessELICIPY 1.0: A Python online tool for expert elicitation(2024)
; ; ; ; ; ; ; Structured expert judgment is crucial when dealing with significant epistemic and aleatoric uncertainties, particularly in probabilistic hazard assessments, where decisions based on uncertain information are often critical. In structured expert elicitations, participants are asked to quantify their uncertainty judgments by providing their percentile estimates of numerical values for a set of questions. More specifically, performance-based elicitations start with ‘‘seed’’ questions for determining experts’ uncertainty quantification skill. The performance scores are thus used to define each expert’s weight to be applied when considering their judgments on ‘‘target’’ questions, i.e., the actual variables of interest for the case study. In this paper we describe ELICIPY, a new Python tool which allows to perform expert elicitation sessions in a framework that covers both the questionnaire collection and the analysis parts, an approach that simplifies the work normally done by the analyst(s). This is achieved through the automatic generation of online webforms to collect the experts’ answers, their check for consistency and, finally, their analysis using different weighting schemes. The tool automatically produces outputs in different formats and creates a pptx presentation file available just after the collection of the answers.76 20 - PublicationOpen AccessScenario-based probabilistic hazard assessment for explosive events at the San Salvador volcanic complex, El Salvador(2023)
; ; ; ; ; ; ; ; ;; ; ; ; ; ;We present a scenario-based, probabilistic hazard assessment for the San Salvador volcanic complex (SSVC), a volcanic field located in the vicinity of San Salvador that includes the El Boquer´on stratovolcano and 25 monogenetic vents. We define a set of likely eruption scenarios for tephra fallout and pyroclastic density currents (PDCs). The eruption scenarios range from violent Strombolian eruptions with a significant uncertainty in source position to sub-Plinian and Plinian activity fed from the central cone. The adopted methodology is mainly based on numerical modeling using Tephra2 (adopting the software TephraProb) to study tephra fallout and the branching box model and the branching energy cone model (adopting the programs BoxMapProb 2.0 and ECMapProb 2.0) to describe inertial and frictional PDCs, respectively. Despite the dominant W-WSW-trending winds, numerical results show that Plinian eruptions at El Boquer´on volcano are able to deposit thick tephra layers in the metropolitan area of San Salvador city, likely reaching mass loads of the order of 100 kg/m2 (conditional probability of 50%). The simulated sub-Plinian events highlight the seasonal influence of wind patterns. In fact, the conditional probability of significant tephra sedimentation in San Salvador city is strongly reduced when eruptions occur during the rainy season. Numerical modeling of violent Strombolian eruptions is performed considering uncertainty in vent position. Results show that the conditional probability of depositing tephra mass loads higher than 10 kg/m2 at a given point reaches a maximum value of ~7% on the NW flank of the volcano, at about 8 km from the central crater. On the other hand, very low conditional probabilities (<1%) are obtained for San Salvador city for any relevant threshold (10 kg/m2 or more) of tephra mass load during violent Strombolian events. Regarding PDCs, results show that those produced during large-scale Plinian eruptions are able to invade significant areas of the volcano surroundings, including San Salvador city. PDCs generated from the partial collapse of a sub-Plinian eruption column exhibit maximum inundation probabilities on the N, W and S flanks of the volcano. Cerro El Picacho exerts a significant shield effect on the propagation of these PDCs, with low inundation probabilities for San Salvador city (<3%). Finally, coupling published vent opening probability maps and numerical modeling of small-scale PDCs yields maximum inundation probabilities on the NW flank of the volcano, reaching maximum conditional probabilities of the order of ~10% and values of about 5% near the village of Nuevo Sitio del Nino.82 18 - PublicationOpen AccessCatalog of major explosions and paroxysms at Stromboli volcano (Italy) from 1970 to 2023(2023)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The catalog consists of the dataset of the major explosions and paroxysms recorded at Stromboli from Jan. 1970 to Oct. 2023, as reconstructed through a detailed review of monitoring bulletins and reports, previous catalogs, and scientific literature of the last ca. 50 years. The catalog includes the calendar date, GMT time and phenomena descriptions for 89 explosive events, of which 4 were paroxysms, 51 were major explosions, and 34 were uncertain major explosions, i.e. explosions of unclear characterization that could have been major explosions or ordinary activity. We detailed the event information content in five columns – (i) seismicity, (ii) sound/air shock, (iii) vents involved, (iv) ash plume/fallout, (v) ballistic projectiles. In addition, we indicated if there were any: (vi) field survey, (vii) pumices erupted, (viii) fires, (ix) map of the products, (x) photo/video of the event, (xi) hot avalanche, (xii) lava flow. The catalog also includes a list of the original literature sources that helped us in the complex characterization of the explosive events. We finally reported if there were people affected by the events, and any previous catalog that comprised them. In our analysis (see also Bevilacqua et al., 2020b), we mostly relied on the detailed characterization of major explosions and paroxysms in Rosi et al. 2013 that provided quantitative constraints on total duration, fallout volume, mass discharge rate, ballistic size, ballistic range and column height of ordinary activity, major explosions, and paroxysms. In several cases, we had to carefully evaluate the original description of the phenomena, due to insufficient quantitative information in the scientific literature. In particular, we considered the hazardous area affected by large ballistic projectiles as the main discriminant factor to distinguish between ordinary activity, major explosions and paroxysms. This area is limited to the Crater Terrace and upper Sciara del Fuoco in case of ordinary activity, to the summit area of the volcano and Sciara del Fuoco during major explosions, and can extend down to low elevations along large part of the island, and sometimes beyond the shoreline, during the paroxysms (Barberi et al., 1993). We also considered several other factors, including the height of the plume, the amount of ash and scoria fallout, the occurrence and strength of any associated shock wave. The occurrence of fires associated with the violent explosive activity was assumed as a good marker for a major explosion too (Rosi et al., 2013). Whilst identifying the paroxysms was relatively straightforward, several possible major explosions were not clearly distinguishable from particularly violent episodes of ordinary Strombolian activity. Thus, our historical record includes the quantification of the main sources of uncertainty, i.e. the possibility of 34 major explosions of uncertain characterization because of insufficient information. We followed a conservative approach and we classified as “uncertain major explosions” all the explosive events for which we could not exclude they were major explosions. This particular case often occurs in the 1970s, 1980s and 1990s, before the installation of surveillance cameras, and, afterwards, when these cameras were not operating for bad weather conditions or temporary malfunctions. In addition, the catalog includes 41 seismic sequences typically associated with higher-than-usual explosive activity but with a size significantly smaller than that of major explosions. These events may have produced a limited ballistic fallout just outside of the crater terrace, i.e. few tens of meters, or short lived effusive activity (e.g. intra-crateric), but they are not associated with the dangerous ballistic fallout of major explosions. About these seismic sequences, we relied on the characterization in Falsaperla & Spampinato, 2003, that is a variable number of explosion quakes in rapid succession (i.e. from tens of seconds to a few minutes), associated with a notable increment in the amplitude of volcanic tremor. This definition relies on the availability of seismic registrations, and therefore a significant under-recording may affect the period before June, 1985, when seismic records started to be acquired continuously at Stromboli. Afterwards, short lapses in the available registrations possibly generated slight underrecording of the seismic sequences in the 1990s and 2000s. Since 2003/2004 the improvement in the seismic network significantly reduced the possible underrecording of seismic sequences. The catalog is accompanied by four supporting files. Supporting Material S1 is a table summary of all the events in the catalog, including a synoptic panel comparing the new catalog to the pre-existing catalogs. Supporting Material S2 is the collection of excerpts from the source documents, including the original figures and descriptions. Supporting Material S3 is the bibliography; a digital version of the literature sources referenced is available from the corresponding author. Supporting Material S4 is an addendum catalog that comprises the descriptions of a number of supplementary explosive events reported as anomalous in literature or monitoring files for various reasons, but not classified by us as paroxysms, major explosions, uncertain major explosions, or seismic sequences. This catalog is complementary to the historical catalog Bevilacqua et al. (2020a), which comprises the years from 1879 to 1960. In the time interval between 1960 and 1970 no major explosions or paroxysms were recorded; however, some under-recording of major explosions might affect that decade. The modeling and estimation of inter-event time and temporal rate of major explosions and paroxysms at Stromboli volcano is detailed in Bevilacqua et al. (2020b) based on the data available at that time. Finally, it is worth mentioning that the present catalog is based on the above reported criteria to characterize the ordinary activity, major explosions and paroxysms which are mostly oriented to the assessment of the hazard associated with the explosive activity of Stromboli. It should also be recognized that a well-defined boundary between these categories may not exist. The catalog is open and dynamic and welcomes contributions from other sources and new information in order to make it more complete and robust.59 15 - PublicationOpen AccessReal-time probabilistic assessment of volcanic hazard for tephra dispersal and fallout at Mt. Etna: the 2021 lava fountain episodes(2023)
; ; ; ; ; ; ; ; ; ; ; Starting from February 2021, Mt. Etna (Italy) experienced a period of intense explosive activity with 17 lava fountain episodes between 16 February and 1 April 2021. During the eruptive cycle, the Istituto Nazionale di Geofisica e Vulcanologia-Osservatorio Etneo (INGV-OE) issued 62 alert notifications known as VONAs (Volcano Observatory Notice for Aviation) to inform the aeronautical authorities about the volcanic activity. We present an automated VONA-based workflow aimed at real-time assessment of the volcanic hazard due to tephra fallout at Mt. Etna. When a VONA reporting tephra emission is issued by INGV-OE, numerical simulations accounting for atmospheric and eruptive uncertainties are automatically initialized to produce probabilistic hazard maps of tephra fallout and atmospheric dispersal. We applied the workflow to three lava fountains that occurred during the 2021 eruptive cycle. To test the modelling results, we compared the simulated ground load with field data, and the extent and position of the simulated volcanic cloud with the observed or estimated volcanic cloud from the Toulouse Volcanic Ash Advisory Center. Overall, we found a good match between simulated and observed quantities (tephra loads and volcanic cloud position), especially when accurate information on eruptive conditions (column height and duration) are supplied by the VONAs. Finally, through a statistical analysis, we found that column height and wind field are fundamental in determining tephra ground accumulation. For this reason, these parameters should be constrained by observational data as accurately as possible when performing numerical simulations, especially in the line of developing operational workflows.327 26 - PublicationOpen AccessData analysis of the unsteadily accelerating GPS and seismic records at Campi Flegrei caldera from 2000 to 2020(2022-11-10)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; Ongoing resurgence affects Campi Flegrei caldera (Italy) via bradyseism, i.e. a series of ground deformation episodes accompanied by increases in shallow seismicity. In this study, we perform a mathematical analysis of the GPS and seismic data in the instrumental catalogs from 2000 to 2020, and a comparison of them to the preceding data from 1983 to 1999. We clearly identify and characterize two overlying trends, i.e. a decennial-like acceleration and cyclic oscillations with various periods. In particular, we show that all the signals have been accelerating since 2005, and 90-97% of their increase has occurred since 2011, 40-80% since 2018. Nevertheless, the seismic and ground deformation signals evolved differently-the seismic count increased faster than the GPS data since 2011, and even more so since 2015, growing faster than an exponential function The ground deformation has a linearized rate slope, i.e. acceleration, of 0.6 cm/yr2 and 0.3 cm/yr2 from 2000 to 2020, respectively for the vertical (RITE GPS) and the horizontal (ACAE GPS) components. In addition, all annual rates show alternating speed-ups and slow-downs, consistent between the signals. We find seven major rate maxima since 2000, one every 2.8-3.5 years, with secondary maxima at fractions of the intervals. A cycle with longer period of 6.5-9 years is also identified. Finally, we apply the probabilistic failure forecast method, a nonlinear regression that calculates the theoretical time limit of the signals going to infinity (interpreted here as a critical state potentially reached by the volcano), conditional on the continuation of the observed nonlinear accelerations. Since 2000, we perform a retrospective analysis of the temporal evolution of these forecasts which highlight the periods of more intense acceleration. The failure forecast method applied on the seismic count from 2001 to 2020 produces upper time limits of [0, 3, 11] years (corresponding to the 5th, 50th and 95th percentiles, respectively), significantly shorter than those based on the GPS data, e.g. [0, 6, 21] years. Such estimates, only valid under the model assumption of continuation of the ongoing decennial-like acceleration, warn to keep the guard up on the future evolution of Campi Flegrei caldera.598 30 - PublicationOpen AccessEruptions and Social Media: Communication and Public Outreach About Volcanoes and Volcanic Activity in Italy(2022-07-07)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Italy is the land of iconic volcanoes, whose activity has been witnessed, described and portrayed for centuries. This legacy has greatly contributed to shaping the public perception of volcanoes and their impact, well beyond the national borders. Stories about famous eruptions overlap and nowadays easily mix up with the impressive footage that is readily available from ongoing eruptions worldwide. As a result, the public discourse may flatten the wide spectrum of possible phenomena into an oversimplified sketch of volcanic eruptions and their impact, where all events seem equally probable and look alike. Actual volcanoes differ in size, eruption magnitude, state of activity, eruptive style, geographical position, and each is located within a specific social and cultural context. All these elements combine in defining the consequences of volcanic activity as well as in determining the severity of the damage and the size of the impacted area. How can we convey such a complexity to the general public? Can social media contribute to raise awareness and build a more resilient society? An effective hazard communication should propose a comprehensible yet realistic description of volcanic settings and provide adequate tools to recognize and understand the specific features of each phenomenon and volcanic area. As we write, two Italian volcanoes display persistent eruptive activity, while other two are going through unrest phases that started in 2012, at Campi Flegrei, and in late summer of 2021, at Vulcano Island. Other active volcanoes (Vesuvius, Ischia, Colli Albani, Lipari, and Pantelleria) have been dormant for tens, hundreds, or thousands of years. Communication in these different contexts also require different approaches that take into account the specific needs of local communities. Social media may provide a unique opportunity to quickly share relevant news and information. Yet, this type of communication has its challenges and volcano observatories can rarely rely on expert social media managers. Sharing experiences and lessons learned is a key to ensure the growth of the volcanological community and improve its ability to connect and engage local residents. Here we discuss the online communication strategies implemented by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) since 2018 to inform Internet and social media users about volcanoes, volcanology, and ongoing volcanic activity, both in Italy and abroad. We describe the internal procedures that we developed and practiced and the experience gathered so far, during both quiet periods and a few volcanic crises. Our experience confirms previous indications about the importance of a steady online presence and suggests that public interest is not always easily predictable.1904 39 - PublicationOpen AccessQuantifying the Statistical Relationships Between Flank Eruptions and Major Earthquakes at Mt. Etna Volcano (Italy)(2022)
; ; ; ; ; ; ; ; ; ; ;At Mt. Etna volcano, flank eruptions are often accompanied by seismic swarms with damaging earthquakes; the most recent case-history is the 2018 flank eruption, associated with a destructive earthquake (Mw 5.0). In this paper, we analyze the earthquake and eruptive catalogs from 1800 to 2018, to produce quantitative estimates of the earthquake rate under the influence of flank eruptions. We quantify that 30% of the flank eruption onsets precede a major (i.e., damaging, Ix ≥ V–VI EMS) earthquake by 30 days or less; 18% of the major earthquakes follow a flank eruption onset in 30 days or less. Thus, we show that the probability of major earthquakes increases 5–10 times after the onset of flank eruptions and this effect lasts for 30–45 days. This is also observed after the end of the eruptions. Results indicate different relationships depending on the location of the volcano-tectonic systems considered individually (eruptive fissures, seismogenic faults). For instance, we describe a 10–20 times increased probability of earthquakes for 65–70 days after eruptions on the northeastern flank, and of new flank eruptions for 45–70 days after earthquakes of the Pernicana fault.1010 27 - PublicationOpen AccessAssessing minimum pyroclastic density current mass to impact critical infrastructures: example from Aso caldera (Japan)(2022)
; ; ; ; ; ; ; ; ; ; ;; ;; ;We describe a method for calculating the probability that a distal geographic location is impacted by a pyroclastic density current (PDC) of a given size, considering the key related uncertainties. Specifically, we evaluate the minimum volume and mass of a PDC generated at the Aso caldera (Japan) that might affect each of five distal infrastructure (marker) sites, with model input parameter uncertainties derived from expert judgement. The five marker sites are all located 115-145 km from the caldera; as these lie in well-separated directions, we can test the effects of the different topographic shielding effects in each case. To inform our probabilistic analysis, we apply alternative kinetic energy assessment approaches, i.e., rock avalanche and density current dynamics. In the latter formulation, the minimum mass needed to reach the markers ranges between median values ~153×10^12 kg and ~465×10^12 kg (M7.2-7.7), depending on the site. Rock avalanche dynamics modelling indicates ~3-times greater mass would be required to reach the marker sites with 50% probability, while the hypothetical scenario of a relatively dilute distal ash-cloud would require ~3-times less mass. We compare our results with the largest recorded Aso eruption, showing that a catastrophic eruption, similar to Aso-4, ≈M8, would present a significant conditional probability of PDCs reaching the marker sites, in the density current formulation and contingent on uncertainty in the erupted mass and on marker site direction.295 14 - PublicationOpen AccessProbabilistic hazard mapping of secondary pyroclastic density currents generated by paroxysm events at Stromboli (Italy)(2022)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; Pyroclastic density currents (PDCs) at Stromboli are typically associated with Strombolian paroxysms. The main mechanisms originating the currents include the eruptive column collapse (i.e. primary PDC), and the remobilization and avalanching of fresh pyroclastic deposits (i.e. secondary PDC). Whereas primary PDCs are commonly confined into the Sciara del Fuoco (SdF), a steep depression on the northwestern side of the island, at least during the paroxysms of 1906, 1930 and 1944 secondary PDCs flowed out of it. These currents were mostly channelized in the valleys on the volcano flanks, and they inundated and buried regions at low elevation, finally reaching the sea and producing temporary deltas of pyroclastic material. The PDCs during the great paroxysm of 1930 reached San Vincenzo village, causing victims and damage to the buildings. In the two paroxysms of 2019 PDCs occurred in the SdF. Although the PDCs were confined inside the depression, they continued to flow over the water for several hundred meters. Moreover, during the paroxysm of July 3, 2019, tephra deposits emplaced on steep slopes right above the village of Ginostra produced small avalanches of incandescent rocks, which fortunately did not get further. Presently, PDCs represent one of the main dangerous manifestation of volcanic activity at Stromboli and therefore need quantitative hazard assessment. In this study we perform new simulations of various 2D depth averaged models of granular flows also considering the effect of some sources of uncertainty. Focusing on secondary PDCs, the source location of the flow was also assumed uncertain, and therefore we adopted a source zonation based on the analysis of topographic slopes and watersheds basins in the upper part of the island, where thick tephra deposits could more likely accumulate during a future paroxysm. Results highlight the areas more exposed to this phenomenon as a function of the model inputs.86 41 - ProductOpen AccessHow does the earthquake probability change after the flank eruptions of Etna?(2022)
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