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Multiple Seismic Slip‐Rate Pulses and Mechanical and Textural Evolution of Calcite‐Bearing Fault Gouges
No full textAbstractNatural fault zones are complex, spatially heterogeneous systems. Rock deformation experimental studies simplify the complexity of natural fault zones either as a surface discontinuity between intact rocks (bare‐rock surfaces) or as a few mm‐thick gouge layer. However, depending on the simplified fault type and its slip history, the response to applied deformation can vary. In this work, we conduct laboratory experiments for investigating the evolution of mechanical parameters of simulated faults made of calcite gouge subjected to multiple (four) identical seismic slip‐rate pulses. We observed that, as the number of applied slip‐rate pulses increased, (a) initial friction and steady‐state friction remained approximatively constant, (b) peak friction and normalized strength excess increased and, (c) the slip distances to achieve peak and steady‐state friction, Da and Dc, decreased. The greatest changes occurred between the first and the second slip‐rate pulse. From this pulse onward, the dissipated energy of the calcite gouge fault was similar to those obtained in bare‐rock surfaces experiments. Microstructural analysis showed that, strain is localized in up to two (recrystallized) principal slip zones (PSZ) with sub‐micrometric grain size, surrounded by low porosity sintered and non‐sintered comminuted gouge domains. We conclude that previous seismic slip episodes impact on both the structure and the strain localization processes within a fault, contributing to its shear fabric evolution. We highlight that the strain localization process identifies the PSZ, dissipating the least amount of energy within the entire experimental fault zone.This study has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant agreement 856559). MC participated in this work as Principal Investigator of the ERC project FEAR (Grant agreement 856559) under the European Community's Horizon 2020 Framework Programme. SA, CC, and ES participated in this work in the framework of the ERC project FEAR (Grant agreement 856559) under the European Community's Horizon 2020 Framework Programme. This work was also supported by Project FSE+ 2021–2027, Contributi premiali per i ricercatori e assegnisti di ricerca per rafforzarne la condizione professionale e potenziare il sistema della ricerca del Lazio (Atto n. G05411 del 05/05/2022) attributed to SA, ES and CC. GDT acknowledges the ERC CoG project 614705 NOFEAR and Progetto PRIN 2022 Di Toro - 2022WE2JY9. CC acknowledges Christopher Harbord for the technical development of the gouge sample holder, Stefano Castelli for the optical scans of the polished samples, and Giacomo Pozzi and Manuela Nazzari for assistance with the FEG-SEM at INGV, and Jacopo Nava and Leonardo Tauro for assistance with the FEG-SEM at University of Padua.
Open access publishing facilitated by Istituto Nazionale di Geofisica e Vulcanologia, as part of the Wiley - CRUI-CARE agreement.Publishede2024JB029099OST3 Vicino alla fagliaJCR Journa
Verification of parameterizations for clear sky downwelling longwave irradiance in the Arctic
No full textGround-based high resolution observations of downward longwave irradiance (DLI), surface air temperature, water vapour surface partial pressure and column amount, zenith sky infrared (IR) radiance in the atmospheric window, and all-sky camera images are regularly obtained at the Thule High Arctic Atmospheric Observatory (THAAO, 76.5° N, 68.8° W), North-West Greenland. The datasets for the years 2017 and 2018 have been used to assess the performance of different empirical formulas to infer clear sky DLI. An algorithm to identify clear sky observations has been developed, based on value, variability, and persistence of zenith sky IR radiance. Seventeen different formulas to estimate DLI have been tested against the THAAO dataset, using the originally determined coefficients. The formulas which combine information on total column water vapour and surface air temperature appear to perform better than others, with a mean bias with respect to the measured DLI smaller than 1 W/m2 and a root mean squared error (RMSE) around 6 W/m2. Some formulas, specifically developed for the Arctic, are found to produce poor statistical results; this is attributed partly to limitations in the originally used dataset, which does not cover a whole year, or is relative to very specific conditions (i.e., the ice sheet). The bias displays a significant improvement when the coefficients of the different formulas are calculated using the THAAO dataset. The presence of two full years of data allows the investigation of the inter-annual variability, and the use of different years for the determination of the coefficients and the evaluation of results. The smallest values of the bias and RMSE reach 0.1 W/m2 and 5 W/m2, respectively. Overall, best results are found for formulas which use both surface parameters and total water vapour column, and have been developed from global datasets. Conversely, formulas which express the atmospheric emissivity as a linear function of the logarithm of the column integrated water vapour appear to poorly reproduce the observations at THAAO.Published1617–1632OSA2: Evoluzione climatica: effetti e loro mitigazioneJCR Journa
PLANET EARTH, SUSTAINABILITY AND CLIMATE CHANGE FROM ITALIAN ELEMENTARY SCHOOL DRAWINGS
No full texthe Istituto Nazionale di Geofisica e Vulcanologia (INGV) stands as a prominent international research institution in the field of geophysics. Its focus extends beyond scientific exploration, placing significant emphasis on the dissemination of scientific culture and the enhancement of awareness regarding risks and prevention. The overarching goal is to address the community's needs and inquiries related to our planet while engaging society through clear, direct, and efficient communication on scientific research and technological innovations.
In a world where citizens need to be well-informed, conscious, and capable of making critical decisions concerning their health and safety, knowledge plays a pivotal role in dispelling doubts and enabling informed choices. Educational initiatives are tailored to raise awareness about Earth sciences and research, fostering an interest in scientific culture. The INGV's calendar project serves as a valuable complement to its dissemination activities with schools. Each year, schools eagerly contribute to this initiative by submitting drawings from pupils, each centered around specific themes within Earth science subjects [1]. Drawing, being a crucial activity for children, not only stimulates their imagination but also serves as an incredible means of expressing emotions. For example, artwork has been used to investigate learning strategies [2], and to analyze children's volcanic risk awareness [3], and their perceptions of the environment [4,5]. The graphic designs of the calendars are developed and realized by the INGV Laboratorio Grafica e Immagini, the Graphics and Images Laboratory [6]. Each project draws inspiration from the competition's theme, considering the diversity of drawings and employing various techniques, colors, and subjects, all while maintaining a focus on the children's contributions. This extensive and unique dataset is being analyzed with a focus on drawings related to competitions that share similar and comparable main topics, beginning with children's perceptions of science and scientists [7]. The current study presents a preliminary analysis of children's perspectives on the climate change, the Planet Earth, its sustainability, and its future.The 2021-2022 edition of the INGV calendar benefited from the contribution of the NET 2021 Project, funded by the European Commission to promote the European Researchers’ Night (GA n. 955459).Published2029-2036OS: Terza missioneN/A or not JC
Calibration of Swarm Plasma Densities Overestimation Using Neural Networks
No full textRecent studies have shown that the measurements of Langmuir Probes (LPs) onboard ESA's Swarm mission overestimate ion densities on the nightside by up to 50%. The overestimation is due to the assumption of oxygen‐only plasma for ion density calculations, which is often violated at mid‐latitudes on the nightside. In this study, we present a calibration model that resolves the nighttime overestimation by Swarm LPs. Using observations by Swarm FacePlate (FP) as a reference, we develop a neural network (NN) model that adjusts LP data to the FP measurements. The model incorporates dependence on solar and geomagnetic conditions, parameterized by the P10.7 and Hp30 indices, location, day of the year and local time. Our model reveals a distinct double‐crest pattern in nighttime density overestimation by LPs, centered at ∼30° quasi‐dipole latitude in both hemispheres. This overestimation intensifies during low solar activity and shows strong seasonal dependence. During solstices, the crests are more pronounced in the local winter hemispheres, while during equinoxes the crests are weaker and exhibit hemispheric symmetry. This morphology aligns with the presence of light ions diffusing downward from the plasmasphere. Validating the LP data in conjunctions with Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) observations showed a much stronger agreement after applying the developed correction: for Swarm B, nighttime correlation with COSMIC increased from 0.74 to 0.93. The NN‐calibrated LP data set has numerous applications in ionospheric research, and the developed model can provide useful insights into the ion composition in the topside ionosphere.Publishede2024SW003925OSA3: Climatologia e meteorologia spazialeJCR Journa
Search for anomalies in Stromboli's pre-paroxysm activity through an automatic hybrid method of time series analysis
No full textStromboli (Italy) is an open-vent volcano with persistent explosive activity producing up to five hundred mild explosions per day. Fluctuations in explosion intensity, varying even by orders of magnitude in terms of emitted volume and their subsequent impact on the surrounding regions, sometimes occur abruptly. Consequently, identifying precursors of larger eruptive activities, particularly for more intense (paroxysmal) explosions, is challenging. In order to search for anomalies in the pre-paroxysm activity related to the summer 2019 eruption, we applied a hybrid method to the automatic analysis of geophysical and geochemical time series. This approach is based on the combination of two methods: 1. the Empirical Mode Decomposition (EMD) and 2. the Support Vector Regression (SVR). The aggregation of these two methods allowed us to identify anomalies in the patterns of the geophysical and geochemical parameters measured on Stromboli in a ten-month period including the July–August 2019 eruption. The results of this study are encouraging for an improvement of the monitoring systems and for volcano early warning applications.This work has been supported by the INGV project Pianeta Dinamico 2023-2025 - ObseRvation, Measurement and modelling of Eruptive processes (ORME), and partially supported by the Progetto Strategico Dipartimentale INGV 2019 “Forecasting eruptive activity at Stromboli volcano: timing, eruptive style, size, intensity and duration” (FIRST, Delibera n. 144/2020; Scientific Responsibility: S.C.). Furthermore, this research has benefited from the support of Convenzione B2 DPC-INGV 2022-2024, Stromboli, Task 1.3 “Development of a unique activity index and estimation of the probability of the transition between ‘ordinary’ and ‘extraordinary’ eruptive activity”, and of the INGV project “Reti Multiparametriche”, Task A2 “Development of methods for the identification of precursors of Stromboli's paroxysms and major explosions based on multiparametric data analysis and study of possible early warning techniques”.Published108131OSV1: Verso la previsione dei fenomeni vulcanici pericolosiJCR Journa
Gravitational and elastic energies stored in crustal volumes activate normal versus strike-slip and thrust seismogenic faults
No full textShallow crustal faults are passive features mobilized by the dissipation of the potential energy and the shear stress accumulated in the brittle volume surrounding them. However, the stored energy in the vol- ume differs from the tectonic setting, i.e., it is mainly gravitational in extensional tectonic settings, whereas it is elastic in strike-slip and contractional tectonic environments. In extensional settings, below about 1 km, the horizontal tensile stress is overwhelmed by the confining pressure of the lithostatic load, and it becomes positive, i.e. compressive. Therefore, there is no horizontal tension in extensional tectonic settings and the pro-gravity motion of the crustal volume is provided by the lithostatic load, which is the vertical maximum principal stress. The elastic energy is rather accumulated by the maximum horizontal principal stresses, i.e., iso-gravity in transcurrent settings and counter-gravity in contractional tectonic settings. The different relation with the gravitational force in the different tectonic settings generates sev- eral relevant differences in the three main tectonic environments. The extensional tectonic settings, both in continental and oceanic rift zones generate normal fault-related earthquakes, i.e., pro-gravity move- ments, or graviquakes. They differ from the other tectonic setting because are marked by (i) lower energy and lower differential stress to activate faults with respect to strike-slip and contractional tectonics; (ii) lower maximum earthquake magnitude; (iii) a larger number of low magnitude earthquakes in exten- sional settings because the crust moves downward as soon as it can move, whereas contractional settings require larger accumulation of energy to move counter-gravity; (iv) consequently, the b-value of the Gutenberg-Richter is higher than 1 and the aftershocks are more numerous and last longer in extensional settings; (v) the downward motion of the hangingwall determines more diffuse cataclastic deformation with respect to the other tectonic settings because the lithostatic load works everywhere, whereas in the other tectonic settings is concentrated where the elastic energy accumulates; (vi) in extensional settings the volume dimension is determined by thickness of the brittle layer, and its length is in average three times the seismogenic thickness; in strike-slip and contractional settings dominates the elastic energy (elastoquakes), and the mobilized volume may be ten to thirty times longer in a single seismic sequence, being its size proportional both to the brittle thickness and the relative speed of plates. These differences characterize the seismic cycle of graviquakes with respect to the elastoquakes. The bigger the volume, the wider the seismogenic fault in all tectonic settings. The interplay between the horizontal tectonic forces and the lithostatic load, which is ubiquitous, varies in the three main tectonic settings, generating differ- ent seismotectonic styles and an increase of magnitude as the effect of the vertical gravitational force becomes a minority relative to the elastic storage and coseismic rebound.Published101894OST2 Deformazione e Hazard sismico e da maremotoJCR Journa
Crustal Deformation and Seismic Velocity Perturbations in the Alto Tiberina Fault Zone (Northern Apennines, Italy)
No full textCrustal perturbations related to seismic activity can generally be observed with the occurrence of a large magnitude event. For less energetic seismic sequences though, the associated transient crustal variations are questionably measurable, and their observation gets easily obscured by relatively stronger perturbations such as the ones related to hydrological processes. In this study we reveal the significant role that terrestrial water‐storage variations play in governing temporal crustal changes in the tectonically active Northern Apennines of Italy, and discuss the potential of accounting for its correction in order to monitor the relatively weaker transient perturbations caused by local seismic swarms. This area is characterized by an extensive level of low‐energetic seismic activity, typically clustered in time and space, of which three main seismic swarms outstand during the 12 year period of study (2010–2021). Our analysis compares independent observations and processing methods of Global Navigation Satellite System measurements and ambient seismic noise recordings. We adopt a multivariate statistical approach to discriminate between independent sources of ground deformation, and seismic noise cross‐correlation analysis to monitor relative seismic‐velocity variations. The result shows how the perturbation effects produced by variations in total water content are dominant in both time series of ground deformations and seismic‐velocity variations. After correcting for the water‐related variation effects, our monitoring results reveal perturbations in the crustal properties whose activation time and depth range correlate with the occurrences of the seismic swarms.Publishede2024JB029023OST3 Vicino alla fagliaJCR Journa
A Potential Link between Space Weather and Atmospheric Parameters Variations: A Case Study of November 2021 Geomagnetic Storm
No full textOn 4 November 2021, during the rising phase of solar cycle 25, an intense geomagnetic storm (Kp = 8−) occurred. The effects of this storm on the outer magnetospheric region up to the ionospheric heights have already been examined in previous investigations. This work is focused on the analysis of the solar wind conditions before and during the geomagnetic storm, the high-latitude electrodynamics conditions, estimated through empirical models, and the response of the atmosphere in both hemispheres, based on parameters from the ECMWF ERA5 atmospheric reanalysis dataset. Our investigations are also supported by counter-test analysis and Monte Carlo tests. We find, for both hemispheres, a significant correspondence, within 1–2 days, between high-latitude electrodynamics variations and changes in the temperature, specific humidity, and meridional and zonal winds, in both the troposphere and stratosphere. The results indicate that, in the complex solar wind–atmosphere relationship, a significant role might be played by the intensification of the polar cap potential. We also study the reciprocal relation between the ionospheric Joule heating, calculated from a model, and two adiabatic invariants used in the analysis of solar wind turbulence.Published3318OSA3: Climatologia e meteorologia spazialeJCR Journa
Crustal Structure of Etna Volcano (Italy) From P‐Wave Anisotropic Tomography
No full textSeveral seismic tomographic studies have been carried out to outline the intricate interplay between tectonics and magma uprising at Etna volcano. Most of these studies assume a seismically isotropic crust. Here we employ a novel methodology that accounts for the anisotropic structure of the crust. Anisotropy patterns are consistent with the Etna structural trends, unveiling the depth extent of fault segments. A high-velocity volume, deepening toward the northwest, identifies the subducting foreland units that appear to confine a low‐velocity anomaly, interpreted as the expression of magmatic fluids within the crust. A discontinuity, likely tectonic in origin, affects the subducting units and allows magma transfer from depth to the surface. This structural configuration may explain the presence of such a very active basaltic strato‐volcano within an atypical collisional geodynamic context.Publishede2024GL108733OSV3: Sviluppo di nuovi sistemi osservazionali e di analisi ad alta sensibilitàJCR Journa
A novel view of the destruction of Pompeii during the 79 CE eruption of Vesuvius (Italy): syn-eruptive earthquakes as an additional cause of building collapse and deaths
No full textThe ancient city of Pompeii, destroyed by the 79 CE Plinian eruption of Vesuvius, is one of the most famous archaeological sites worldwide and an open-air laboratory for many disciplines. The destruction of Pompeii has so far been reconstructed in terms of a succession of volcanic phenomena and related effects, identified as the accumulation of pumice lapilli on roofs and dynamic pressure exerted by pyroclastic currents on buildings, and neglecting the potential effects of the syn-eruptive seismicity, the occurrence of which is beautifully described by an erudite eyewitness to the catastrophe, Pliny the Younger. During a recent excavation in the Insula dei Casti Amanti, in the central part of Pompeii, the peculiar evidence of building collapses, that overwhelmed two individuals, has been uncovered. The multidisciplinary investigation, involving archaeology, volcanology, and anthropology, gathered information on the construction technique of the masonry structures, the volcanological stratigraphy, the traumatic pattern of bone fractures of the skeletons, along with the detection of the wall displacements, that led to archaeoseismological considerations. The merging of the data has highlighted the need of an updated perspective in the assessment of the damage at Pompeii during the 79 CE eruption, by considering the syn-eruptive seismicity as a factor contributing to the destruction of the city and death of the inhabitants. By comparing the attitude and characteristics of different types of damage, and after ruling out any other possible damaging event, our conclusions point to the occurrence of syn-eruptive earthquake-induced failures of masonry structures. The structural collapses, based on our stratigraphic and volcanological data, are chronologically consistent with the beginning of the caldera-forming phase of the eruption which was accompanied by strong seismic shocks. The crush injuries of the skeletons of the two individuals are consistent with severe compression traumas and analogous to those shown by individuals involved in modern earthquakes testifying that, apart from other volcanic phenomena, the effects of syn-eruptive seismicity may be relevant. These outcomes lay the foundation for a more extensive study concerning the assessment of the contribution of the syn-eruptive seismic destruction at Pompeii and open new perspectives for volcanological, archaeoseismological and paleopathological studies.Published1386960JCR Journa