OA Earth-prints Repository
Not a member yet
16457 research outputs found
Sort by
Geochemical processes in the roots of the Azores magmatic systems
No full textThe Azores archipelago, situated east of the Mid-Atlantic Ridge, comprises volcanic islands arranged along sub-parallel spreading systems and rests on a thick oceanic crust. Magma is supplied directly from the roots of the volcanic systems. Located at or nearby the boundary between the crust and the mantle, they consist of mafic cumulates and mafic mush layers. This work focuses on tephra samples and a submarine lava younger than 40.000 years, collected from both central volcanoes and fissure zones. Our report details a new dataset of major, trace, and volatile elements analysed in glassy melt inclusions trapped in olivine (Fo75.8–85.6) which are extracted from cumulative bodies at the vicinity of the crust-mantle boundary. Their compositions cover a range from subalkaline to mildly alkaline basalt, and trachybasalt, which match those of Azores lavas.
They registered a chemical evolution through fractional crystallisation of olivine alone, as well as olivine and clinopyroxene, as both the FeOt/MgO (1.4–3.1) and CaO/Al2O3 (0.4–1.0) ratios of the melt decrease. Incompatible element ratios of Zr (40–352 ppm), Ba (135–612 ppm), and Rb (5–77 ppm), as compared to Nb (5–82 ppm), exhibit variability within a limited but significant range of values. The ranges in the Nb/Zr, Ba/Nb and Rb/Nb ratios recorded by melt inclusions possibly reveal distinct geochemical sources (at least two), and mixing between partial melts as they move upward. The halogen signature is characteristic of the shallow mantle. The majority of melt inclusions show Cl/K ratio (0.06) similar to E-MORB, although some of them are comparable to N-MORB (Cl/K = 0.03). Their F/Nd ratio may achieve a rather high value (27.8).Published64OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
Tracking flowpaths in a complex karst system through tracer test and hydrogeochemical monitoring: Implications for groundwater protection (Gran Sasso, Italy)
No full textGroundwater in karst aquifers is frequently tapped for drinking purposes, due to frequent huge volumes of resources. Unfortunately, vulnerability of these aquifers can be high, due to possible fast transfer of recharge water on springs by the karst network. On Gran Sasso Mountain regional aquifer, several springs are subjected to drinking withdrawal and an updated evaluation of their potential is now a fundamental issue to be considered, facing climate change effects, which reflect on variation of discharge regimen and values. To distinguish between different contribution of spring recharge, a tracer test has been carried out on the Vitella d'Oro spring, fed both by the regional aquifer and by a local system exposed to karst features developed in the Rigopiano Conglomerates formation. Thanks to hydrogeological, hydrogeochemical and isotopic data, a conceptual model of spring recharge has been proposed and subsequently validated by the tracer test results. All information confirms the superimposition on the regional base flow, by a relevant contribution of the karst network, influencing the spring discharge in recharge periods. In detail, a fast flow component is responsible for discharge peaks and frequently of turbidity events, having a mean velocity ranging from 30 to 70 m/h in the aquifer. Besides of this fast flow, an additional aliquot of the recharge is due to the same local aquifer, but slower flow clearly identifiable by hydrochemistry and isotopic data. Thanks to these findings, a renewed management of the spring has been suggested, considering the different degrees of aquifer vulnerability (turbidity occurrence) directly related to the discharge regimen.Publishede24663JCR Journa
New biostratigraphic and paleoecologic data on the Pliocene-Pleistocene paleogeographic evolution of the northeastern coastal area of the central Tyrrhenian sea (Italy)
No full textIn this work, we present new biostratigraphic and paleoecological data from the Mignone River valley, located in
the central sector of the Tyrrhenian Sea margin and part of the wider Tarquinia basin, and cores in the area of
Rome. By combining the new paleontological information with a review of the extant literature, we re-examine
the stratigraphic architecture of the Pliocene succession in the central sector of the northwestern Tyrrhenian Sea
margin, spanning the Zanclean (MPl1; 5.33–5.08 Ma) through the early Piacenzian (MPl4b; 3.57–3.31 Ma), and
of the following Pleistocene transgressive-regressive sequence, comprising the Gelasian (MPl6; 2.59–1.81 Ma)
through the Santernian (MPl1; 1.81–1.5 Ma).
We propose a revision of the paleogeographic evolution of the central Tyrrhenian Sea basins throughout the
Pliocene-Lower Pleistocene interval, by coherently framing it within the chronology of the volcanic phases that
occurred in this region. In particular, our reconstruction points toward the presence of a single Transgressive-
Regressive (T-R) sequence starting with the Zanclean reflooding of the Mediterranean after the Messinian
Salinity Crisis and ending in the Piacenzian, as opposed to the previously proposed occurrence of two depositional
T-R sequences separated by an erosional phase affecting part of the Globorotalia puncticulata biozone.Published1-20OST2 Deformazione e Hazard sismico e da maremotoOSA2: Evoluzione climatica: effetti e loro mitigazioneOSA4: Ambiente marino, fascia costiera ed Oceanografia operativaJCR Journa
From intensity data to seismic risk assessment in the volcanic area of Mt. Etna
No full textEarthquakes are, by far, the most relevant source of hazard for the densely urbanised areas of Mt. Etna volcano. Local communities continuously suffer social and economic losses due to the high occurrence of damaging earthquakes, which produce intensities up to degree X EMS despite of low magnitude (M < 5.0).
In the framework of the PANACEA project, seismic hazard was performed following the probabilistic approach (PSHA) based on historical macroseismic data. The probability distribution of the expected earthquake damage to residential buildings and the resulting risk effects on population are calculated for exposure times of 30 and 10 years.PublishedCorfu (Greece)OST2 Deformazione e Hazard sismico e da maremot
Dynamics of the Neapolitan Volcanoes Inferred from Tiltmeter and Seismic Data Analysis: A Review
No full textWe discuss some relevant results obtained in recent works on the Neapolitan Volcanoes, i.e., Campi Flegrei, Ischia, and Vesuvius (southern Italy) regarding the coupling between ground deformation detected by tiltmeters and volcano-tectonic seismicity. Great interest is devoted to those volcanoes because of the high level of volcanic risk, to which the inhabitants are exposed. Indeed, continuous and dense monitoring of their activity is provided by the Istituto Nazionale di Geofisica Vulcanologia, which employs different types of instrumentation, among which borehole tiltmeters and seismic networks. The works we consider in the present review focus on the link between seismicity and ground tilt anomalies covering the years 2015–2022. In detail, for the Campi Flegrei caldera, a significant variation in the tiltmeter pattern has been identified. Such anomaly indicates a transition to a different dynamical regime starting since 2020, also supported by some changes in the seismicity, ground temperatures of the fumarolic field, gravimetric and geochemical parameters. Concerning Ischia Island, a variation in the main tilt direction, which switched from NNW to NNE, has been detected in response to the Md 4.0 earthquake that occurred on 21 August 2017. Finally, at Vesuvius the relation among seismicity, ground inclination, and geochemical observables was investigated over the time interval 2012–2020 providing evidence of several simultaneous anomalies as proxies of the dynamical evolution of the volcanic system. Moreover, the comparison of the static displacement induced by seismicity with the measured tilt sheds light on the strict link between these two observables. The joint analyses of the seismic and tiltmeter signals represent a powerful tool for unraveling the volcanic dynamics and separating inner sources from external contributions.In pressJCR Journa
Lahar events in the last 2000 years from Vesuvius eruptions – Part 3: Hazard assessment over the Campanian Plain
No full textIn this study we present a novel general methodology for probabilistic volcanic hazard assessment (PVHA) for lahars. We apply the methodology to perform a probabilistic assessment in the Campanian Plain (southern Italy), focusing on syn-eruptive lahars from a reference size eruption from Somma–Vesuvius. We take advantage of new field data relative to volcaniclastic flow deposits in the target region (Di Vito et al., 2024b) and recent improvements in modelling lahars (de' Michieli Vitturi et al., 2024). The former allowed defining proper probability density functions for the parameters related to the flow initial conditions, and the latter allowed computationally faster model runs. In this way, we are able to explore the effects of uncertainty in the initial flow conditions on the invasion of lahars in the target area by sampling coherent sets of values for the input model parameters and performing a large number of simulations. We also account for the uncertainty in the position of lahar generation by running the analysis on 11 different catchments threatening the Campanian Plain. The post-processing of the simulation outputs led to the production of hazard curves for the maximum flow thickness reached on a grid of points covering the Campanian Plain. By cutting the hazard curves at selected threshold values, we produce a portfolio of hazard maps and probability maps for the maximum flow thickness. We also produce hazard surface and probability maps for the simultaneous exceeding of pairs of thresholds in flow thickness and dynamic pressure. The latter hazard products represent, on one hand, a novel product in PVHA for lahars and, on the other hand, a useful means of impact assessment by assigning a probability to the occurrence of lahars that simultaneously have a relevant flow thickness and large dynamic pressure.Published459-476OSV1: Verso la previsione dei fenomeni vulcanici pericolosiOSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
Completeness and calibration of the Italian Seismological Instrumental and Parametric Database (ISIDe) before 16 April 2005
No full textThe Italian Seismological Instrumental and Parametric Database (ISIDe) is the recipient of earthquake data collected in real-time by the Istituto Nazionale di Geofisica e Vulcanologia (INGV), and used by the studies of earthquake forecasting and seismic hazard assessment in Italy in the last decade. When it went online, following a significant improvement of the seismic acquisition system of INGV, it was including only data since the second fortnight of April 2005. About ten years later, the data since the beginning of 1985 suddenly appeared without any prior notice than the updating of the starting date of the dataset. However, the characteristics of the added data appeared clearly different from the following period both in terms of the numbers of located earthquakes and of types of magnitudes provided. After having analyzed the numerical consistency and the calibration of magnitudes of ISIDe as a function of time from 1985 to 15 April 2005, we can say that such a dataset is incomplete and poorly calibrated compared to other catalogs of Italian seismicity (CSTI, CSI, and HORUS) available for the same period. Hence, we suggest not using it as is for statistical analyses of Italian seismicity. However, it provides some magnitudes that are missed by other catalogs and thus might be used for improving such catalogs.Open access funding provided by Istituto Nazionale di Geofisica e Vulcanologia within the CRUI-CARE Agreement.In pressJCR Journa
Use of deep learning to improve seismic data quality analysis
No full textThe goal is to train a neural network to recognize noise spectra of malfunctioning and functioning stations and separate them into two or more sets (malfunctioning and functioning). In the first part, the reader is provided with criteria for classifying spectra (with example diagrams).Seismic data are influenced by various types of noise, which are typically categorized into two primary classes: anthropogenic and environmental. However, the detection of instrumental noise or malfunctioning stations also plays a crucial role in ensuring the data quality and the efficiency of a seismic network. The visual inspection of seismic spectral diagrams (e.g. power spectral density) enables us to identify issues that could potentially compromise data quality, thereby affecting subsequent calculations such as Magnitude or Peak Ground Acceleration (PGA). However, this process is time-consuming and demands significant human expertise due to the complexity of the diagrams, compounded by the sheer number of stations requiring examination. Therefore, in this paper, we explore the feasibility of transferring human expertise into an artificial intelligence system to create an automated system capable of rapidly performing such detection. More specifically, in the first part of this paper, we use Probability Density Function (PDF) diagrams, enabling an initial assessment of station performance via visual inspection. We describe this plot type and provide examples that reveal whether a station is functioning correctly or if technical issues exist. A table containing the main evaluation criteria is provided. In the second part of this paper, we demonstrate that these plots can serve as input for a neural network, allowing the development of the aforementioned automated system. Through extensive testing under various conditions, we have observed that the trained network consistently achieves an accuracy rate exceeding 85% across all four conducted tests. In the latest and most significant test, the achieved accuracy is approximately 87%.Istituto Nazionale di Geofisica e VulcanologiaPublishedSE320OST5 Verso un nuovo MonitoraggioJCR Journa
Quantification of volcanic degassing and analysis of uncertainties using numerical modeling: the case of Stephanos crater (Nisyros Island, Greece)
No full textNisyros 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.Published95JCR Journa
▪ Origin and significance of hydrocarbons in CO 2 -rich gases from Central Italy seismic areas
No full textTectonically active areas of Central Italy are marked by intense CO 2 degassing, whose origin and role in earthquake processes are fundamental questions in geoscience. This study investigates the origin and geological controls on the geochemistry of light hydrocarbons from CO 2-dominated gas emissions located in the inner sector of the Umbria-Marche Apennines (Central Italy), aiming to better understand the sources and migration pathways of geogenic fluids in the region. Our findings indicate that light hydrocarbons are predominantly thermogenic, with negligible abiotic contributions. We demonstrate that Mesozoic carbonate rocks are the primary source across the study area, though conditions of hydrocarbon formation and migration vary. Specifically, higher temperatures and open-system conditions prevail in the southern regions, likely due to thermal stress associated with Quaternary magmatism. We propose that light hydrocarbons form at crustal depths (≤5-6 km) and are transported to the surface by ascending CO 2 from deeper sources. Finally, this work highlights that hydrocarbon geochemistry, combined with helium isotopes, can provide insights for reconstructing the circulation and origin of fluids in crustal reservoirs and assessing the thermal regime in tectonically active areas.Published20–26JCR Journa