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Imaging the Plumbing System of the Asymmetric Vavilov Spreading Ridge (Tyrrhenian Sea Back‐Arc Basin) From Combined Bathymetry and Magnetic Data
No full textBack-arc basins (BABs) are associated with plate margins where crustal shortening, seafloor spreading, and volcanism coexist. The Vavilov basin (Tyrrhenian Sea) is a Pliocene BAB associated with the Apennine-Tyrrhenian Sea subduction system and characterized by mantle exhumation. The NNE-SSW elongated Vavilov seamount represents the easternmost and younger spreading ridge of the Vavilov basin. Here we present results of a morphological and magnetic study of the Vavilov seamount. Our results show that the seamount represents the last stage of the eastward asymmetric opening of the BAB. Its plumbing system consists of a dike swarm emplaced during the reversed Matuyama epoch and a younger shallow reservoir feeding the central and eastern sectors during the normal Brunhes epoch. This evolution is associated with the progressive loading of the edifice due to lava flow emplacement. The asymmetry of the seamount mirrors the asymmetric opening of the Vavilov back-arc basin.Publishede2023GL105196OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
Tracking air quality trends and vehicle traffic dynamics at urban scale using satellite and ground data before and after the COVID-19 outbreak
No full textThe implications of the COVID-19 outbreak are subjected to an increasing number of studies. So far, air quality trends related to the lockdown due to the pandemic have been analysed in large cities or entire regions. In this work, the region studied is the metropolitan area of Cagliari, which is the main city on the island of Sardinia (Italy) and can be representative of a coastal city that includes industrial settlements. The purpose of the study is to evaluate the effect of restrictions related to the COVID-19 outbreak on air quality levels and the traffic dynamics in this type of urban area. Nitrogen Dioxide (NO₂) levels before, during and after COVID-19 lockdown have been investigated using data acquired from the Sentinel-5P/TROPOMI satellite combined with on-site measurements. Both TROPOMI detected and ground-based data have revealed higher levels of NO₂ before and after the lockdown, compared to those during the period of COVID-related restrictions, in particular in the urban area of Cagliari. On the other hand, NO2 registered in the oil refinery area did not show significant differences associated with lockdown. The correlation of TROPOMI NO₂ tropospheric column with ground data (surface NO2) on a monthly mean basis showed different values based on the background and the highest Pearson's coefficient was of about 0.78 near to the city centre, where traffic can be considered a significant source of emission. In addition, a comparison of the air pollution level with the dynamics of vehicle traffic was investigated. The study highlighted a remarkable correlation between the reduction of the number of vehicles and the corresponding tropospheric NO₂ values that decreased on a weekly mean basis.Published165464OSA2: Evoluzione climatica: effetti e loro mitigazioneJCR Journa
One-Year Seismic Survey of the Tectonic CO2-Rich Site of Mefite d'Ansanto (Southern Italy): Preliminary Insights in the Seismic Noise Wavefield
No full textA passive seismic experiment is carried out at the non-volcanic highly degassing site of Mefite d'Ansanto located at the northern tip of the Irpinia region (southern Italy), where the 1980 MS 6.9 destructive earthquake occurred. Between 2020 and 2021, background seismic noise was recorded by deploying a broadband seismic station and a seismic array composed of seven 1 Hz three-component sensors. Using two different array configurations, we were allowed to explore in detail the 1-20 Hz frequency band of the seismic noise wavefield as well as Rayleigh wave phase velocities in the 400-800 m/s range. Spectral analyses and array techniques were applied to one year of data showing that the frequency content of the signal is very stable in time. High frequency peaks are likely linked to the emission source, whereas at low frequencies seismic noise is clearly correlated to meteorological parameters. The results of this study show that small aperture seismic arrays probe the subsurface of tectonic CO2-rich emission areas and contribute to the understanding of the link between fluid circulation and seismogenesis in seismically active regions.Published16301T. Struttura della TerraJCR Journa
Polar Cap Patches Scaling Properties: Insights from Swarm Data
No full textAmong the effects of space weather, the degradation of air traffic communications and satellite-based navigation systems are the most notable. For this reason, it is of uttermost importance to understand the nature and origin of ionospheric irregularities that are at the base of the observed communication outages. Here we focus on polar cap patches (PCPs) that constitute a special class of ionospheric irregularities observed at very high latitudes in the F region. To this purpose we use the so-called PCP flag, a Swarm Level 2 product, that allows for identifying PCPs. We relate the presence of PCPs to the values of the first- and second-order scaling exponents and intermittency estimated from Swarm A electron density fluctuations and to the values of the Rate Of change of electron Density Index (RODI) for two different levels of geomagnetic activity, over a time span of approximately 3.5 years starting on 16 July 2014. Our findings show that values of RODI, first- and second-order scaling exponents and intermittency corresponding to measurements taken inside PCPs differ from those corresponding to measurements taken outside PCPs. Additionally, the values of the first- and second-order scaling exponents and of intermittency indicate that PCPs are in a turbulent state. Investigation of the coincidence of loss of lock (LoL) events with PCPs displayed that approximately 57.4% of LoLs in the Northern hemisphere and 45.7% in the Southern hemisphere occur in coincidence of PCPs when disturbed geomagnetic activity is considered. During quiet geomagnetic conditions these percentages decrease to 51.4% in the Northern hemisphere and to 20.1% in the Southern hemisphere.Published4320OSA3: Climatologia e meteorologia spazialeJCR Journa
Volcanic Early Warning Using Shannon Entropy: Multiple Cases of Study
No full textThe search for pre-eruptive observables that can be used for short-term volcanic forecast remains a scientific challenge. Pre-eruptive patterns in seismic data are usually identified by analyzing seismic catalogs (e.g., the number and types of recorded seismic events), the evolution of seismic energy, or changes in the tensional state of the volcanic medium as a consequence of changes in the volume of the volcano. However, although successful volcanic predictions have been achieved, there is still no generally valid model suitable for a large range of eruptive scenarios. In this study, we evaluate the potential use of Shannon entropy as short-term volcanic eruption forecasting extracted from seismic signals at five well studied volcanoes (Etna, Mount St. Helens, Kilauea, Augustine, and Bezymianny). We identified temporal patterns that can be monitored as short-term eruptive precursors. We quantified the decay of Shannon entropy prior to eruptions, noting that changes appear between 4 days and 12 hr before. When Shannon entropy is combined with the temporal evolution of other features (i.e., energy, kurtosis, and the frequency index), we can elaborate physical models according to the occurring volcanic processes. Our results show that pre-eruptive variation in Shannon entropy is a confident short-term volcanic eruption monitoring tool.Publishede2023JB026684OSV3: Sviluppo di nuovi sistemi osservazionali e di analisi ad alta sensibilitàJCR Journa
A review of plagioclase growth rate and compositional evolution in mafic alkaline magmas: Guidelines for thermometry, hygrometry, and timescales of magma dynamics at Stromboli and Mt. Etna
No full textMafic alkaline magmas, such as those feeding the persistent eruptive activity of Stromboli and Mt. Etna volcanoes in Italy, are dominated by the crystallization of plagioclase via cooling and degassing phenomena related to the dynamics of shallow crustal reservoirs and eruptive conduits. Because plagioclase textures and compositions are extremely sensitive to the changes of intensive variables in subvolcanic plumbing systems, the phenomenological variability of erupted crystals preserves detailed evidence of complex growth histories. From this point of view, we reappraise the textural maturation and compositional complexity of plagioclase by allying thermodynamic and kinetic principles to natural and experimental observations, with the purpose of drawing up guidelines for reconstructing magma dynamics in mafic alkaline volcanic settings. A multifaceted statistical method is adopted to parameterize the decay of crystal growth rate with increasing crystallization time, as relaxation kinetics prevails over melt supersaturation effects. This model parameterization is combined with the textural analysis of natural plagioclase crystals to quantify the residence time of phenocrysts in equilibrium with magmas at Stromboli and Mt. Etna and/or the timescale of rapid microlite growth during disequilibrium ascent of magmas within the conduit. The role played by temperature and melt-water content on plagioclase components and major cation substitution mechanisms is also evaluated under both isobaric-isothermal and decompression conditions. The emerging paradigm is that the influence of dissolved water on anorthite-albite exchange between plagioclase and melt is overwhelmingly mitigated by changes in temperature at conditions of P = 30–300 MPa, T = 1050–1150 °C, fO2 = NNO + 1.9-NNO + 2.3, and melt-H2O = 0.6–4.4 wt%. As a corollary, anorthite and albite melt activities are almost fully encapsulated in the variation of anhydrous melt components as the crystallization of plagioclase proceeds during magma cooling. Following this line of reasoning, we propose an integrated modeling approach to decipher complex zoning patterns in natural plagioclase phenocrysts from mafic alkaline eruptions. Key findings from our re-assessment of equilibrium, thermometric, and hygrometric models indicate that temperature and dissolved water can be iteratively estimated for different plagioclase textural patterns if crystals are sufficiently strongly zoned and probability-based criteria are applied to determine the maximum probability distribution from kernel density analysis.Natural Environment research Council UK grant NE/T009292/1;
INGV Progetti Ricerca Libera 2019 Grant #52/2020;
INGV Departmental Strategic Project UNO;
PRIN MIUR Grant #2017J277S9_004.Published104399OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
Ice Sheet and Sea Ice Ultrawideband Microwave radiometric Airborne eXperiment (ISSIUMAX) in Antarctica: first results from Terra Nova Bay
No full textAn airborne microwave wide-band radiometer (500–2000 MHz) was operated for the first time in Antarctica
to better understand the emission properties of sea ice, outlet glaciers and the interior ice sheet from Terra Nova Bay to Dome C. The different glaciological regimes were revealed to exhibit unique spectral signatures in this portion of the microwave spectrum. Generally, the brightness temperatures over a vertically homogeneous ice sheet are warmest at the lowest frequencies, consistent with models that predict that those channels sensed the deeper, warmer parts of the ice sheet. Vertical heterogeneities in the ice property profiles can alter this basic interpretation of the signal. Spectra along the lengths of outlet glaciers were modulated by the deposition and erosion of snow, driven by strong katabatic winds. Similar to previous experiments in Greenland,
the brightness temperatures across the frequency band were low in crevasse areas. Variations in brightness temperature were consistent with spatial changes in sea ice type identified in satellite imagery and in situ ground-penetrating radar data. The results contribute to a better understanding of the utility of microwave wide-band radiometry for cryospheric studies and also advance knowledge of the important physics underlying existing L-band radiometers operating in space.Published255–278OSA2: Evoluzione climatica: effetti e loro mitigazioneJCR Journa
Middle-late Pleistocene chronology of palaeoshorelines and uplift history in the low-rising to stable Apulian foreland: Overprinting and reoccupation
No full textTo refine knowledge about terrace phases and uplift history for a tectonically poor deformed region, we apply the synchronous correlation method to reconstruct the chronology of a poorly constrained sequence of raised palaeoshorelines on the Apulian foreland, southern Italy. This work uses new chronological constraints obtained by amino acid racemisation (AAR) and isoleucine/alloisoleucine epimerisation (IE) on Patella spp., Thetystrombus latus (Gmelin), Glycymeris sp., and ostracods and U-series dating on corals Hoplangia durotrix Gosse and Cladocora caespitosa Linneo. This procedure provides a quantitative estimate of the vertical movements and associated rates within a region of the Apulian foreland. The synchronous correlation method uses sea-level highstands and uplift rate(s) as inputs; in particular, for sea-level highstands, the inputs are the age of the highstands and the sea-level elevation of the highstands relative to the present-day sea level. The output is a set of currently expected elevations of each sea-level highstand (the present elevations of palaeoshorelines). We then used regression analysis to assess the robustness between our observed palaeoshorelines and expected elevations of sea-level highstands. Our results show that the best fitting scenario is obtained using the sea-level curves of (i) Waelbroeck et al. (2002) from present to 410 ky BP and (ii) Rohling et al. (2014) from 410 to 590 ky BP as inputs for our synchronous correlation method, with uplift rates ranging from 0.09 mm/y to 0.07 mm/y with a mean value of 0.08 mm/y from 590 ky BP onwards.
We recognised palaeoshorelines in the field belonging to the following highstands: 120 ky BP (MIS 5.5, second peak), 127 ky BP (MIS 5.5, first peak), 212 ky BP (MIS 7.3), 330 ky BP (MIS 9.3), 410 (MIS 11), 525 ky BP (MIS 13.3), and 590 ky BP (MIS 15). Our results show field observations of the reoccupation effect of younger palaeoshorelines over older ones due to the relatively slow uplift rates measured in the investigated area as predicted by our synchronous correlation method. In particular, we show a well-mapped and described reoccupation of the MIS 5.5 palaeoshoreline over the MIS 7.3 palaeoshoreline, constrained by new absolute dating.
In addition, the data from the Apulian foreland suggest an MIS 7.3 highstand close to the present sea level.Published1085302T. Deformazione crostale attivaJCR Journa
Ground displacement assessment on Pico Volcano, Azores, by multitemporal InSAR data
No full textInterpreting the signal deriving from interferometric synthetic aperture radar (InSAR) analyses in volcanic islands, characterized by strong regional deformations and recurrent seismicity, is a complex and challenging issue. In these zones, the secondary effects connected to the SAR acquisition system cannot be neglected, and it is important to consider that delay phenomena of the electromagnetic waves, due to the propagation in the tropospheric layer and loss of SAR coherence because of dense vegetation, could affect the interferometric phase. This work focuses on Pico, the second largest and the youngest island of the Azores Archipelago (North Atlantic Ocean). This island consists of a central volcano and a fissure zone. These systems are inactive but recurrent microseismicity occurs in a rock volume host- ing a partially crystallized magma storage system, which fed the recent activity of the central volcano. In the same area affected by microseismicity, the main volcanic edifice shows flank instability. All these elements support the hypothesis of possible reactivation of the shallow magmatic system. Aiming to check potential active ground displacements and to define their source, we collected two datasets of C-band Sentinel-1 SAR data, both in descending and ascending acquisition geometry, from January, 2017, to December, 2020. The application of the small baseline subset method of differential InSAR allowed drawing the mean ground velocity maps over the island and the displacement time series, useful to understand the defor- mation evolution. InSAR data only evidence areas affected by small-scale subsidence at the cinder cones of the fissure zone and along the southeastern slope of Pico volcano, where local debris flows activate during rainy periods.Published032402OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
Evidence of “Lake Nyos-type” behavior in the geological record: A review
No full textIn this article, volcanic lakes that have shown sedimentological evidence of limnic eruptions (i.e., Nyos-type gas bursts) are reviewed. Indeed, to better assess “Nyos-type lakes” related hazards, paleolimnology offers a
promising tool to trace the evidence of potential ancient Nyos-type gas explosions. After gas bursts from Lakes Monoun and Nyos in 1984 and 1986, respectively, multiple paleolimnological approaches have been applied to several lakes assumed to be Nyos-type Around the world,. Only 3 lakes in Europe (i.e. lakes Pavin in France, Albano and Monticchio in Italy and one in Africa (i.e. Lake Kivu in D.R. Congo) evidenced markers of limnic eruptions in their sedimentary archives. These features include reworked sediments with reversed ages, brown colors of sedimentary deposits, gas-rich sediments, iron hydroxide-rich sediments, strong Ti and Fe enrichments, sedimentary hiatuses, absence of seismic evidence in the sedimentary record, and significant change in geochemical signature. The dating of these sedimentary deposits has made it possible to determine the ages of the events and their recurrence. This has led to associating these markers with evidence of limnic eruptions, eventhough some lakes are in temperate climates that favor seasonal overturning of lake waters and thus gradual release of accumulated gas. There is still no agreement on the dynamics and causes, and the scientific debate remains open since there is no concrete reference event in historical time. Lakes Monoun and Nyos, the first and only lakes exploded in recent history, could therefore be considered as natural laboratories to better understand limnic eruptions in lakes around the world. Unfortunately, the well-studied aspects of these Cameroonian “killer lakes” are based more on the dynamics of the explosions, hazard assessment based on water chemistry, and gas releases, rather than on the possible similar behavior in the recent geologic past by applying a combination of old and new limnological approaches. In addition, as the first natural laboratory, Lake Monoun features several advantages, including smaller surface area, shallower depth favorable for coring, easy access, and negligible gas content after artificial degassing since the early 2000s.Published104603OSV1: Verso la previsione dei fenomeni vulcanici pericolosiJCR Journa