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3D study of dyke-induced asymmetric graben: The 1971 Mt. Etna (Italy) case by structural data and numerical modelling
No full textIn this work, we have integrated field data and numerical models to characterise a unique dyke-induced graben system, exposed both in section and plan view, with an unexpected asymmetric fault geometry. This volcanotectonic feature is related to the 1971 eruption of Mt. Etna (southern Italy) and is located near the northern wall of the Valle del Bove, a huge depression carved into the eastern flank of the edifice. A new structural map and quantitative data were obtained from the analysis of aerial stereophotos collected before the onset of the 1971 eruption and after, high-resolution drone-derived models and field surveys carried out in the summer of 2022. In plan view, the graben is 2-km-long and its width ranges 27-143 m from the bottom to the upper part of the section view, with about 82 m of difference in elevation from top to bottom. Graben faults clearly show an asymmetric setting in terms of attitude, with one fault that dips 70 • to the south, and the other one that dips 50 • to the north. Vertical offset values are greater at higher elevations. We also ran a set of numerical models, aimed at investigating the distribution and orientation of stresses around the inferred dyke tip and in the host rock. The comparison between field data and numerical models suggests a key role of the inclined topography, as shown in section view, in determining the orientation of dyke-induced σ 1 and σ 3 in the host rock. This, in turn, controls the geometry of the graben faults, resulting in the observed asymmetric setting. Additionally, dyke-induced stress concentrations and vertical offset values support the hypothesis of a downward propagation of the graben faults, from the surface down to the dyke tip.This work was carried out under the framework of the CRUST - Interuniversity
Centre for 3D Seismotectonics with Territorial Applications, and under
the aegis of the International Lithosphere Program, Task Force II. This
paper is also an outcome of the Virtual Reality lab for Earth Sciences -
GeoVires (https://geovires.unimib.it/), University of Milano-Bicocca.
Agisoft Metashape is acknowledged for photogrammetry processing.
Our work was also supported by funding from the convention “All. A
INGV-DPC” and by PRL 2019 Developing a semi-automatic method for
data collection and volcanic hazard assessment in volcano failure-prone
areas using UAV-derived dense cloudsPublished105231OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
Assessment of the performance of the TOPGNSS and ANN-MB antennas for ionospheric measurements using low-cost u-blox GNSS receivers
No full textLow-cost GNSS receivers have recently been gaining reliability as good candidates for ionospheric studies. In line with these gains are genuine concerns about improving the performance of these receivers. In this work, we present a comprehensive investigation of the performances of two antennas (the u-blox ANN-MB and the TOPGNSS TOP-106) used on a low-cost GNSS receiver known as the u-blox ZED-F9P. The two antennas were installed on two identical and co-located u-blox receivers. Data used from both receivers cover the period from January to June 2022. Results from the study indicate that the signal strengths are dominantly greater for the receiver with the TOPGNSS antenna than for the receiver with the ANN-MB antenna, implying that the TOPGNSS antenna is better than the ANN-MB antenna in terms of providing greater signal strengths. Summarily, the TOPGNSS antenna also performed better in minimizing the occurrence of cycle slips on phase TEC measurements. There are no conspicuous differences between the variances (computed as 5-min standard deviations) of phase TEC measurements for the two antennas, except for a period around MayeJune when the TOPGNSS gave a better performance in terms of minimizing the variances in phase TEC. Remarkably, the ANN-MB antenna gave a better performance than the TOPGNSS antenna in terms of minimizing the variances in pseudorange TEC for some satellite observations. For precise horizontal (North and East) positioning, the receiver with the TOPGNSS antenna gave better results, while the receiver with the ANN-MB antenna gave better vertical (Up) positioning. The errors for the receivers of both antennas are typically within about 5 m (the monthly mean was usually smaller than 1 m) in the horizontal direction and within about 10 m (the monthly mean was usually smaller than 4 m) in the vertical direction.PublishedJCR Journa
Multi-Layer Approach to Detect and Analyze Coastal Aggregation of Macro-Plastic Litter
No full textThis study is to describe the activities carried on in the frame of the research project Multi-layEr approaCh to detect and analyze cOastal aggregation of MAcRo-plastic littEr (ECO-MARE). The research activity, funded by the Italian Ministry of Research (MUR), is to observe aggregation of macroplastic at sea using measurements remotely sensed by a suite of sensors equipped onboard of tower-, drone-, and satellite platforms. In this study, the design of the research activity is described and a preliminary experimental campaign will be presented.Publishe
The kinetic effect induced by variable cooling rate on the crystal-chemistry of spinel in basaltic systems revealed by EPMA mapping
No full textThe crystal-chemical variations of spinels grown as a function of cooling rate (ΔT/Δt) were analyzed via X-ray electron-microprobe (EPMA) maps. Maps were collected serially by using a fixed distance. Spinels solidified from a tholeiitic MOR basaltic liquid (B100) cooled at cooling rates (ΔT/Δt) of 1, 7, 60, and 180 °C/h, between 1300 and 800 °C and at ambient P and fO2. As ΔT/Δt increases, the amount of spinel is invariably <5 area% and its size decreases. Compared to the previous data set collected by common single and selected EPMA analytical points (112 analyses), the kinetic effects induced by ΔT/Δt are here quantitatively captured by a large number of analyses (2052).
The TiO2, Al2O3, MgO, and FeOtot show large compositional variations at low cooling rates (from 1 to 60 °C/h), and only the average TiO2 concentration shows a well-defined trend as a function of ΔT/Δt. However, calculated average cation amounts (apfu) unveil quantitative kinetic effects. When ΔT/Δt increases (from 1 to 180 °C/h), only Ti4+ shows a linear decreasing trend, whereas the other major Al3+, Fe3+, Fe2+, and Mg2+ cations alone are scattered. Conversely, the sums of trivalent (Al3++Fe3+) and divalent (Mg2++Fe2+) cations quantitatively capture the effect of the ΔT/Δt. These new outcomes could be the base of novel geospeedometers with significant implications in volcanology, geophysics, and material sciences in regard to silicate melt rheology on Earth. They should be extended to high-pressure, hydrated, and low oxygen fugacity conditions. Furthermore, the analytical approach used here to capture kinetic effects on spinel growth and compositions can be also applied to other crystalline phases grown from silicate liquids.Published1171–1180JCR Journa
Analyzing the 222Rn/220Rn Ratio in a Seismic Area: A Reliable Method to Understand the Development of Active Structural Discontinuities in Earthquake Surveillance and Sustainability
No full textPublishedJCR Journa
New constraints on the Middle-Late Pleistocene Campi Flegrei explosive activity and Mediterranean tephrostratigraphy (~160 ka and 110-90 ka)
No full textThe Campi Flegrei (CF) caldera, in southern Italy, is the source of some of the most powerful Late Pleistocene
eruptions of the European sub-continent (e.g., Campanian Ignimbrite, Neapolitan Yellow Tuff eruptions).
Although the CF caldera has been continuously and intensively investigated for decades, relatively little is known
regarding its earliest volcanic activity. In this work, integrating existing and new tephrostratigraphic data, we
provide a comprehensive and updated framework for the CF volcanic activity which has occurred at ~160 ka and
between ~110 ka and ~90 ka. The new tephrostratigraphic, geochemical (EMPA +LA-ICP-MS), chronological
(40Ar/39Ar dating) and grain-size distribution data relate to CF tephra deposits preserved in mid-proximal
(Campanian Plain), distal (Tyrrhenian Sea) and ultra-distal (Lower Danube area) sedimentary archives. Our
results allowed us to recognize the presence of at least 13 CF eruptions covering the investigated time frame, with
12 eruptions occurring between 110 and 90 ka. Our high-resolution stratigraphic and chronological investigation
also allowed us to recognize that the Triflisco/C-22 tephra, previously considered as a single marker layer, can be
actually separated into three different events, sourced from within the CF area in the short time interval of ~93-
90 ka, suggesting a more complex and intense volcanic history than previously thought. Moreover, a Bayesian
age-depth model, constrained by previous and new high precision 40Ar/39Ar ages, has led to a reliable estimate of
the ages of those undated CF eruptions. Overall, the updated framework on the stratigraphy, chronology,
dispersion, and geochemistry of the CF tephra of ~160 ka and between 110 ka and 90 ka consolidates the notion
that the Middle-Late Pleistocene activity in theCF area represents a significant stage of its volcanic evolution,
characterised by intense and frequent explosive eruptions.Published108623OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
Bollettino Sismico Italiano gennaio – aprile 2023
No full textLa revisione da parte degli analisti del BSI della sismicità registrata in Italia dal 1 gennaio al 30 aprile 2023 ha riguardato tutti i terremoti di magnitudo M≥1.5, mentre i parametri dei terremoti di magnitudo inferiore a tale soglia sono quelli calcolati in tempo reale, nella SALA DI SORVEGLIANZA SISMICA DI ROMA.
I terremoti più forti (M≥3.5) e pochi altri di particolare interesse [vedi Marchetti et al., 2016, DOI: 10.4401/ag- 6116], sono stati revisionati dagli analisti del BSI, mediamente nelle 24 ore successive al loro accadimento.Istituto Nazionale di Geofisica e Vulcanologia - Dipartimento di Protezione CivilePublishedOST5 Verso un nuovo Monitoraggi
A Multidisciplinary Study for the Recognition of Fault-Induced Instability Conditions on Cultural Heritage: The Case of Paternò (Sicily, Italy)
No full textThe 16th century AD St. Barbara’s Church in Paternò, a town located at the SW foot of Mt. Etna volcano (Sicily, Italy), has since 2009 showed evident signs of structural instability and collapse. This is causing great concern among the local population and poses a growing hazard to the attendees to the masses. After precautionary closure of the church, we carried out geological, seismic, geophysical and geochemical surveys in order to shed light on the possible causes of the phenomenon. From the results of all surveys above, the presence of a hidden fault was hypothesized. The fault would prove to cross the west side of the church, parallel to its front portal, and continue both to the north and to the south of the edifice. It is part of a more complex system of faults that crosses the whole town of Paternò and is likely a result of the complex dynamics of Mt. Etna. This fault seems to also be a pathway for the upward flow of saline hydrothermal fluids, similar in composition to those emitted in nearby areas and whose corrosive action possibly contributed to the weakening of the rocks beneath the church. Temporal monitoring of several hydrological parameters (water temperature, water level and CO2 content) in some sites in and around the church allowed a better understanding both of the fault dynamics and of the extent of hydrothermal influence in the studied area.Published5007-5031JCR Journa
Extremely deuterium depleted methane revealed in high-temperature volcanic gases
No full textActive volcanoes often discharge hot (T ≫ 100 °C) magmatic gases whose original composition has been modified through partial interaction with an externally fed hydrothermal system. The study of methane (CH4) in these volcanic discharges may provide useful information on the interplay between deep magmatic gases and shallow circulation of hydrothermal fluids. However, the origin of CH4 in high-temperature volcanic gases and the factors exerting control on its abundance and stable isotope composition are still largely unknown. Here, we present the abundances and stable isotopic composition of CH4 in hot (99–387 °C) volcanic gases from the La Fossa volcanic crater of Vulcano Island (Southern Italy).
Our investigation revealed low (<1.5 μmol/mol) CH4 concentrations and an extraordinarily large variability in CH4 stable isotopic composition, with δ13C and δ2H values being positively correlated and varying from −35 to −9.2 ‰ and −670 to −102 ‰, respectively. Notably, CH4 isotopes measured at Vulcano almost encompasses the global-scale variability observed in natural fluids, with δ2H values ≤ −500 ‰ being the first ever reported in nature. Gases showing extremely negative δ13C-CH4 and δ2H-CH4 values systematically display higher CH4 abundances.
We propose two possible scenarios in order to explain the observed huge variation in δ13C and δ2H: (1) mixing of 13C- and 2H-depleted CH4 with 13C- and 2H-enriched CH4 of thermogenic origin formed under hydrothermal conditions; (2) post-genetic removal and isotopic alteration of 13C- and 2H-depleted CH4 occurring during the ascent of volcanic gases. Comparing our dataset with available isotopic data from naturally occurring and artificially produced CH4, a thermogenic origin for the isotopically light CH4 seems unlikely. We postulate that the 13C- and 2H-depleted CH4 may have formed via kinetically-controlled abiotic synthesis through CO (or CO2) hydrogenation reactions in the hot ascending gas phase, possibly at temperatures intermediate between those typical of magmatic and hydrothermal conditions. Further investigations of methane in high-temperature volcanic gases are necessary to test this hypothesis.Published148-165OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
Reconstructing the Belbaşhanı Pumice Plinian eruption, Hasandağ Volcano, Turkey
No full textHasandağ volcano (Central Anatolia, Turkey) has recently underwent an increase in local seismicity and fumarolic activity since 2013. In the past, this volcano has produced multiple large explosive eruptions during the last million years. The Belbaşhanı Pumice is the product of a sub-Plinian to Plinian eruption dated at ~ 417 ± 20.5 ka (40 Ar/ 39 Ar). Here, we present a complete volcanological study including stratigraphy, glass chemistry, pumice morphology, geochronology, and eruption source parameters with the associated uncertainties, to characterize the Belbaşhanı Pumice eruption. The eruption involved a column of 18-29 km in height, with the main dispersal axis towards the northeast. A pumice layer up to ~ 17-m-thick accumulated in proximal deposits along the Belbaşhanı path, and up to 2-m-thick in medial-distal areas (~ 18 km northeast from the vent). The high and tubular vesicularity of the pumice clasts indicates that the Belbaşhanı eruption was predominantly magmatic. The bulk volume of the Belbaşhanı Pumice fallout deposit has been estimated as 0.5 and 8 km 3 (with ~ 2 km 3 being the mean value), which corresponds to Volcanic Explosivity Index (VEI) of at least 4 and up to 6. Both isopach and isopleth maps indicate that the volcanic vent may have been located at the intersection of the Tuz Gölü fault and Ulukışla caldera, within the Hasandağ volcanic complex. The glass composition of Belbaşhanı Pumice confirms that the eruption belongs to the Hasandağ magmatic system. The reconstruction of the Belbaşhanı Pumice eruption represents an essential baseline in providing volcanological constraints for further investigations of tephra fallout hazard assessment in Central Anatolia, especially considering that a new Plinian eruption cannot be ruled out at Hasandağ volcano in the future. The chemical and geochronological datasets presented here could aid in refining tephrochronological correlations, with the goal of synchronizing paleoenvironmental and paleoclimatic records alongside archaeological sites.Published61OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa