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Linking the Langevin equation to scaling properties of space plasma turbulence at sub-ion scales
No full textCurrent understanding of the kinetic-scale turbulence in weakly collisional plasmas still remains elusive. We employ a general framework in which the turbulent energy transfer is envisioned as a scale-to-scale Langevin process. Fluctuations in the sub-ion range show a global scale invariance, thus suggesting a homogeneous energy repartition. In this Letter, we interpret such a feature by linking the drift term of the Langevin equation to scaling properties of fluctuations. Theoretical expectations are verified on solar wind observations and numerical simulations, thus giving relevance to the proposed framework for understanding kinetic-scale turbulence in space plasmas.PublishedL042014OSA3: Climatologia e meteorologia spazialeJCR Journa
Paleoseismological Constraints on the Anghiari Normal Fault (Northern Apennines, Italy) and Potential Implications for the Activity of the Altotiberina Low‐Angle Normal Fault
No full textThe NE-dipping Anghiari normal fault, bounding to the west the Sansepolcro basin in the Upper Tiber Valley (northern Apennines), is thought to be a synthetic splay of the Altotiberina low-angle normal fault (LANF), an active ENE-dipping extensional detachment whose seismogenic behavior is debated. In order to assess the Anghiari fault capability to break the surface during strong earthquakes and be the source of historical earthquakes, we acquired high resolution topographic data, performed field survey and geophysical investigations (Seismic reflection, Ground Penetrating Radar, Electrical Resistivity Tomography) and dug
three paleoseismological trenches across different fault sections of the Anghiari fault. The acquired data reveal for the first time the Late Pleistocene to historical activity of the Anghiari fault, constraining the age of seven paleo-earthquakes over the last 25 ka, the youngest of which is comparable with one of the poorly constrained historical earthquakes of the Sansepolcro basin. The yielded slip rate is >0.2 mm/yr averaged over the last 25 ka and the recurrence interval is about 2,500–3,200 years. An analysis of the anisotropy of the magnetic susceptibility performed in one of the paleoseismological trenches revealed an extensional stress field, continuously acting during the sedimentation of the entire trenched stratigraphy. Our results confirm the ability of the Anghiari fault to generate surface faulting earthquakes. In addition, if the Anghiari fault does sole at depth into the Altotiberina low-angle normal fault, this LANF could also be seismogenic and generate M > 6Publishede2023TC007798OST3 Vicino alla fagliaJCR Journa
A semi-empirical model for magnetic storm dynamics
No full textThe near-Earth electromagnetic environment represents a far-from-equilibrium system characterized by sudden irregular energy relaxation events. For a broad class of complex systems, time series can be interpreted in terms of a superposition of stochastic and deterministic components occurring at different time scales. In this work we use the generalization of the SYM-H index provided by the SuperMAG collaboration (SMR), which is meant for monitoring the global variation of the horizontal component of the Earth’s magnetic field in the near-equatorial regions. The aim of this work is to model the SMR dynamics via stochastic differential equations thus providing a semi-empirical model whose parameters are retained from data. As a first step we test the Markov condition on the SMR data sample, which represents the basic condition for our stochastic modeling, and we show that such a requirement is accurately satisfied by SMR time series. This allows us to infer the model parameters for the SMR index through the Kramers–Moyal analysis. Finally, we give evidence that a purely diffusive process is not representative of the observed dynamics and then a model based on jump-diffusion processes must be considered to correctly reproduce the dynamical features of the SMR index.PublishedGM325OSA1: Variazioni del campo magnetico terrestre, imaging crostale e sicurezza del territorioJCR Journa
Aseismic creep and gravitational sliding on the lower eastern flank of Mt. Etna: Insights from the 2002 and 2022 fault rupture events between Santa Venerina and Santa Tecla
No full textFault creep along the lower eastern flank of Mt. Etna volcano has been documented since the end of the 19th
century and significantly contributes to the surface faulting hazard in the area. On 29 October 2002, during a
seismic swarm related to dyke intrusions, two earthquakes caused extensive damage and surface faulting in an
area between the Santa Venerina and Santa Tecla villages. On the same day after the two earthquakes, an
episodic aseismic creep occurred along the Scalo Pennisi Fault close to the Santa Tecla coastline. On 8 February
2022, during another aseismic creep event along the Scalo Pennisi Fault, we observed the reopening of the pre existing 2002 ground ruptures mostly as pure dilational fractures. We mapped the 2002 and 2022 surface
ruptures, and collected data on displacement, length, and pattern of ground breaks. Ground ruptures affected
structures located along the activated fault segments, including roads, walls and buildings. The 2002 surface
faulting propagation can be ascribed to a sliding of the Mt. Etna eastern flank toward the SE, as also suggested by
the related shallow seismicity, and InSAR and geodetic data between 2002 and 2005. For the 2022 event, dif ferential InSAR data, acquired in both descending and ascending views, allowed us to decompose Line of Sight
(LOS) displacement into horizontal and vertical components. We detect a ~ 700 m long and ~ 500 m wide
deformation zone with a downward and eastward motion (max displacement ~1,5 cm) consistent with a normal
fault. We inverted the InSAR–detected surface deformation using a uniform-slip fault model and obtained a
shallow detachment for the causative fault, located at ~300 m depth, within the volcanic pile. This is the first in depth study along the Scalo Pennisi Fault to suggest a shallow faulting that accommodates Mt. Etna E flank
gravitational sliding.Published229829JCR Journa
Micro-meteoroids impact vaporization as source for Ca and CaO exosphere along Mercury's orbit
No full textThe study of the micro-meteoroid environment is relevant to planetary science and space weathering of airless bodies, as the Moon or Mercury. In fact, the meteoroids hit directly the surfaces producing impact debris and vapor, thus contributing to shape the exosphere of the planet. This work is focused on the study and modelling of the Mercury's Ca exosphere formation through the process of Micro-Meteoroids Impact Vaporization (MMIV). The MESSENGER/NASA mission provided measurements of Mercury's Ca exosphere, allowing the study of its configuration and its seasonal variations. The observed Ca exhibited very high energies, with a scale height consistent with a temperature > 50,000 K, originated mainly on the dawn-side of the planet. It was suggested that the originating process is due to MMIV, but previous estimations were not able to justify the observed intensity and energy. We investigate the possible pathways to produce the high energy observed in the Ca exosphere and discuss about the generating mechanism. The most likely origin may be a combination of different processes involving the release of atomic and molecular surface particles. We use the exospheric Monte Carlo model by Mura et al. (2007) to simulate the 3-D spatial distribution of the Ca-bearing molecule and atomic Ca exospheres generated through the MMIV process, and we show that their morphology and intensity are consistent with the available MESSENGER observations if we consider a cloud quenching temperature < 3750 K. The results presented in this paper can be useful in the exospheric studies and in the interpretation of active surface release processes, as well as in the exosphere observations planning for the ESA-JAXA BepiColombo mission that will start its nominal mission phase in 2026.Published115616OSA3: Climatologia e meteorologia spazialeJCR Journa
Dove nascono i terremoti: la sismogenesi dell’Italia centrale e settentrionale
No full textÈ tracciato qui un sintetico percorso per descrivere la sismotettonica
dell’Italia centrale e settentrionale, attraverso l’analisi delle
deformazioni e delle dislocazioni oggi in atto nella litosfera, la
porzione più esterna e fredda del pianeta.
Usualmente non siamo non grado di renderci conto delle deformazioni
crostali attualmente in corso - oggetto di studio della
cosiddetta tettonica attiva - ma sappiamo che sono sempre presenti
e che da queste si originano i terremoti.
Descriveremo pertanto i principali sistemi di faglie ritenuti
in grado di generare forti terremoti nell’Italia centrale e settentrionale.
La completa parametrizzazione della geometria e della
cinematica di una faglia attiva e in grado di generare terremoti
viene definita sorgente sismogenetica; ci concentreremo sulle
sorgenti ritenute responsabili dei terremoti più forti, in particolare
dei terremoti di magnitudo superiore a 5.5. Precisiamo che
la magnitudo di 5.5 è ritenuta discriminante per due principali
motivi: 1. è usualmente considerata il valore “di soglia” oltre il
quale la faglia assume dimensioni tali da poter – in taluni casi
– essere identificata attraverso le metodologie geologiche; 2. in
Italia, per via delle tipologie costruttive prevalenti, lo scuotimento
generato da terremoti crostali con magnitudo superiore a 5.5 può
creare danni significativi alle opere antropichePublished17-224T. Sismicità dell'Itali
S wave Splitting in Central Apennines (Italy): anisotropic parameters in the crust during seismic sequences
No full textIn this work, we reviewed the main anisotropic results obtained in the last two decades along the Central Apennines. Moreover, we improved this database, with new results coming from the seismicity that occurred in the Montereale area, between 2009 and 2017, which corresponds to a spatio-temporal gap in the previously analyzed datasets. The examined papers concerned both seismic sequences (as Colfiorito in 1997, Pietralunga in 2010, L’Aquila in 2009, Amatrice in 2016) and background seismicity (as the 2000-2001 Città di Castello experiment). The whole of the collected results shows a general NW-SE fast shear wave direction consistent with both the orientation of the extensional active Quaternary and inherited compressive fault systems, focal mechanisms and local stress field. Also, we observed a more intense anisotropy strength (normalized delay time > 0.006 s/km) nearby the strongest events (M > 5), all concentrated in the hanging-wall of the activated fault systems. In fact, this area is deeply affected by the surrounding rock volume perturbations that, in turn, have altered both the local stress field and crustal fracturing network. The most common anisotropic interpretative models that could explain our results are 1) the stress-induced anisotropy according to the Extensive-Dilatancy Anisotropy (EDA) model where the anisotropic pattern is related to the local stress variation and most of the variability is visible in time; 2) the tectonic-controlled anisotropy according to the Structural-Induced Anisotropy (SIA) model where the anisotropic pattern is related to the major structural features and most of the variability is visible only in space. As reported by the examined studies in Central Apennines the possibility to discriminate between stress and structural anisotropy is quite complex in a region where the directions of the extensional regime, the in situ horizontal maximum stress, the strike of major faults, both active and inherited coincide. Generally, in this review, we noted an overlap and mixture of the two aforementioned mechanisms and, just through a temporal analysis, made in the Montereale area, we supposed a predominant stressinduced anisotropy only in rock volumes where anisotropic parameter variations have been detected.PublishedSE211OST3 Vicino alla fagliaJCR Journa
Lava Flow Hazard and Its Implication in Geopark Development for the Active Harrat Khaybar Intracontinental Monogenetic Volcanic Field, Saudi Arabia
No full textHarrat Khaybar is an active monogenetic volcanic field in western Saudi Arabia that hosts
spectacular monogenetic volcanoes and a Holocene volcanic cone with extensive lava fields. The
volcanic region is a subject of intensive land use development, especially along tourism ventures,
where the volcanic features are the key elements to utilize for increasing visitation rates to the region.
The youngest eruption is suspected to be Holocene and occurred fewer than 5000 years ago based
on the cross-cutting relationship between the youngest lava flows and archaeological sites. Lava
flows are typical, from p¯ahoehoe to ‘a‘¯a types with great diversity of transitional textural forms.
Here, we recorded typical transitional lava flow surface textures from the youngest flows identified
by digital-elevation-model-based terrain analysis, satellite imagery, and direct field observations.
We performed lava flow simulations using the Q-LavHA plug-in within the QGIS environment.
Lava flow simulations yielded satisfactory results if we applied eruptions along fissures, long
simulation distances, and ~5 m lava flow thickness. In these simulations, the upper flow regimes
were reconstructed well, but long individual lava flows were not possible to simulate, suggesting
that morphological steps likely promoted lava ponding, inflation, and sudden deflation by releasing
melts further along shallow syneruptive valley networks.Published705OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
The 1908 Messina Straits Earthquake: Cornerstones and the Need to Step Forward
No full textNo abstractPublished557-561JCR Journa
Discriminating carbon dioxide sources during volcanic unrest: The case of Campi Flegrei caldera (Italy)
No full textLarge calderas are among the main emitters of volcanic CO2, which is mainly supplied by the deep degassing of magmatic fluids. However, other sources of non-magmatic CO2 can also occur due to the intense interaction among magmatic fluids, wide hydrothermal systems, and their host rocks. In particular, massive amounts of CO2 are released by calderas during unrest phases and have been often detected before eruptions. An accurate assessment of CO2 sources is thus fundamental to properly understand gas monitoring signals during volcanic crises. We focused on the restless Campi Flegrei caldera, in southern Italy, where CO2 fluxes at the Solfatara-Pisciarelli hydrothermal site have been progressively increasing up to 4000–5000 t/d during the ongoing unrest that started in 2005. Theoretical models of magma degassing have been able to reproduce the CO2-N2-He variations at the Solfatara fumaroles. However, a time-dependent deviation between measured and modeled N2/CO2 and He/CO2, well correlated with the temporal evolution of ground uplift and temperature of the hydrothermal system, has been observed since 2005. We show that these variations are controlled by intense physical-chemical perturbation of the hydrothermal system, which is driving the decarbonation of hydrothermal calcite stored in reservoir rocks. This process is providing large volumes of non-magmatic CO2 during the current unrest, contributing up to 20%–40% of the total fumarolic CO2.Published397-4012V. Struttura e sistema di alimentazione dei vulcaniJCR Journa