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Structural characterization of fault damage zones in carbonates (Central Apennines, Italy)
Full text linkThe Italian Central Apennines are one of the most seismically active areas in the Mediterranean, hit in the last few centuries by several destructive earthquakes (i.e. L’Aquila 2009, Mw 6.3 e L’Aquila 1703, Mw 6.7; Avezzano 1915, Mw 7.1; Maiella 1706, Mw 6.8). The mainshocks and the aftershocks of these earthquake sequences propagate and often nucleate in normal fault zones NNW-SSE oriented, cutting km-thick limestones and dolostones formations Jurassic - Cretaceous in age. These normal faults, expression of the extensional tectonics that developed since late Pliocene on the previous compressive structures, present at their footwall few meters to hundreds of meters thick damage zones, characterized by a dense network of fractures and secondary faults. Despite their peculiarity and their geological interest:
1. the mechanism of formation of these damage zones,
2. their role in the seismic cycle,
3. their relationship during nucleation and propagation of individual seismic ruptures,
4. factors controlling their thickness,
are still unknown. From these open questions and due to the absence of detailed studies about fault damage zones in carbonates, the necessity to investigate their structure arose.
Previous high-resolution field structural surveys were performed in the last few years on the Vado di Corno fault zone (Campo Imperatore, L’Aquila) and Monte Marine fault zone (Aterno Valley, L’Aquila).
Here we describe two minor carbonate-hosted faults located in the same area (Central Apennines): the Subequana Valley fault (Middle Aterno Valley, L’Aquila) and the Capo di Serre fault (Gran Sasso Massif, L’Aquila), both with the typical Apennine trend, and length (8-10 km) and displacement (200-300 m) smaller than the previous investigated cases (14-20 km in length, 1700-2000 m in displacement).
For the structural characterization of these two faults, I performed two weeks of fieldwork to map the fault zones at scale 1:1000, collecting:
- data relative to the main fault plane;
- data relative to secondary faults in the damage zone;
- joint sets in different structural stations;
- samples for the description of the structural domains.
I defined a fault zone rocks legend based on field observations and calibrated on the previous works (i.e. Vado di Corno and Monte Marine fault zone). From the collected data of each fault, a structural map and related geological cross-sections were realized. The description of the structural domains in the field was supported by the observations of polished hand-samples and thin sections at the optical microscope.
Based on these preliminary observations, faults with similar length and displacement have different damage zones (i.e., thickness, presence/absence of a high strain damage zone): the Subequana Valley damage zone is at least 230 m thick in the point of maximum thickness along strike and has extended high strain and a low strain damage zones; the Capo di Serre damage zone has a maximum thickness of 120 m, with a prevalent low strain damage zone.
The most relevant observations regard the damage zone thickness variations along strike; these variations, in terms of intensity and thickness of damage, are related to the presence of secondary structures and stepover zones between different segments of the main fault. As a consequence, the main factor controlling the thickness of damage zones is the presence of geometrical complexities such as inherited or secondary structures, rather than the depth of exhumation, the hosting lithology, and the accumulated displacement of the fault.
Possible other factors having a key role in the development of these volumes of intensely deformed rock can be:
- barrier effect on the rupture propagation in correspondence of the step-over zone;
- interference between secondary structures and seismic waves.
Data about damage zone thickness, length, and displacement of the two faults are finally compared to the previous investigated faults in the Apennines and to the other cases in the literature, with the aim to define possible scaling-relations
Estimate of earthquake source parameters from an exhumed ancient seismogenic fault (Gole Larghe Fault Zone, Italy)
Full text linkSeismological inversion methods are extremely useful to understand the mechanics of earthquakes. However, some earthquake source parameters such as fault strength evolution (τ f ) and frictional dissipated power (Q̇ = σN μss u̇ in MW/m2, where σN is the normal stress, μss is the friction coefficient at steady state and u̇ is the slip rate) cannot be derived by the inversion of seismic waves. Nevertheless, τ f andQ̇ are extremely important to improve knowledge about earthquakes, since they control the moment release rate, the temperature increase in the slip zone and therefore the activation of coseismic fault dynamic weakening mechanisms.
The study of frictional melts, preserved in the geological record as pseudotachylytes and exhumed by orogenic activity, allows the observation of entire fault segments from few to hundreds meters that can be studied to retrieve τ f (Sibson, 1975; Di Toro et al., 2006). In a previous study (Nielsen et al., 2010), the authors proposed a theoretical model that linkedQ̇ to the pseudotachylyte-host rock boundary micro-roughness. Frictional dissipated power, indeed, is proportional to shear heating: increasingQ̇ increases the temperature gradient perpendicular to the fault during coseismic slip.
Since rocks are usually composed by different minerals with different melting temperatures, a high thermal gradient (highQ̇) will cause the minerals to melt uniformly near the sliding surface (i.e., independently of their melting points), resulting in a relatively smooth pseudotachylyte-wall rock boundary. On the other hand, a gentle temperature gradient (lowQ̇) with widely-spaced isotherms will mainly melt those minerals with low melting points, generating a rough boundary.
A first attempt at estimating frictional dissipated power using pseudotachylyte microroughness was performed in the M.Sci. thesis of Castagna (2012), where the author proved that artificial pseudotachylytes produced with SHIVA (a powerful rotary shear apparatus designed to reproduce in the laboratory deformation conditions typical of natural seismic fault slip; Di Toro et al., 2010) become smoother with increasingQ̇. However, this relationship (pseudotachylyte-wall rock smoothing with increasingQ̇) was not well-established in natural pseudotachylytes and it was not possible to estimate frictional dissipated power in natural faults. Moreover, micro-roughness on natural pseudotachylytes was found to be considerably higher than the one found in experimental pseudotachylytes, making a direct comparison between natural and experimental faults very challenging.
In this thesis, I try to refine the relationship between micro-roughness and frictional dissipated power in natural pseudotachylytes to get an estimate ofQ̇. In order to do so, I collect five new samples from the Gole Larghe fault zone (GLFZ, Adamello batholith, Southern Alps) and perform a detailed microstructural analysis of 22 carefully selected samples from the large collection of pseudotachylytes from the GLFZ produced in the years by the research group of Prof. Di Toro. One of the main goals was also to identify the physical processes acting on the pseudotachylyte-host rock boundary during seismic rupture propagation and slip. I also revise and improve a MATLAB®script used to quantitatively describe the micro-roughness (expressed as the characteristic asperities height, ω0, and the average asperities radius, λave).
The microstructural analysis, together with the refinement of the micro-roughness measurement methodology, lead to a robust relationship between the micro-roughness and frictional dissipated power in natural faults, though a precise estimate ofQ̇ using the experimental data for the calibration is still not possible. In fact, micro-roughness of natural pseudotachylytes is also related to (1) the wall-rock damage induced by the propagation of the seismic rupture, which is not reproduced in the laboratory experiments simulating seismic slip and (2) the initial roughness of the natural faults, which are rougher than the experimental ones (the latter are well-polished for experimental issues).
However, for natural near-ideal faults which, as discussed in this thesis, satisfy the assumptions for the theoretical model proposed by Nielsen et al. (2010), I estimated for the GLFZ ancient earthquakes frictional dissipated power values of 156±90 MW m2 . This estimate, which is the first field-based frictional dissipated power estimate for an earthquake ever produced, is slightly larger than theQ̇ predicted (10-100 MW m2) from simplified earthquake models (e.g., Sibson, 1980)
Passaggio a industria 4.0: rilevamento automatico dell'OEE
No full textIl presente elaborato di tesi è stato sviluppato presso la Bertagni 1882 S.p.A., azienda alimentare che fonda il suo core business nella produzione di pasta ripiena. L'obbiettivo del progetto riguarda il passaggio da un sistema di rilevamento dell'OEE manuale ad uno semi-automatico dove le macchine, connesse in rete, raccolgono automaticamente dei dati di produzione
Studio e progettazione di un intervento di rinnovo tecnologico di sottostazione elettrica (SSE) ferroviaria di conversione
Full text linkL'elaborato fornisce lo studio di una ignota sottostazione elettrica ferroviaria di conversione per la trazione elettrica alla tensione di 3 kVcc, sottoposta ad un intervento di rinnovo tecnologico con finalità di risolvere i problemi emersi durante il suo esercizio attraverso un'analisi e una progettazione secondo le normative vigenti
Age and kinematics of very metal-poor stars in the Galactic disk.
Full text linkAn investigation of 253 very metal-poor stars ([Fe/H] < -1.5) from Barklem (2005) was done to
determine the age and origin of the data set. All stars are located in the Galactic halo (|b| > 20 o). To
derive the age, two photometric systems were used for analysis: Johnson as the main and Gaia EDR3 as
the testing one. From the isochrone fitting technique, the best fit was derived by eye-balling the star
distribution in the CMD. For this purpose, two different packs of isochrones were used: Padova
isochrones and a suite of Stellar Tracks and Isochrones (BaSTI). They used the most modern stellar
models taking into account low metallicities. Kinematics were derived by numerical calculation of orbit
in two different potentials: with and without bar. For the calculation of orbits and orbital parameters
parallaxes, proper motion and radial velocities from Gaia EDR3 were employed. As a result, we found
that our data set consists of three metallicity groups: Fe/H ≈ -2.0, Fe/H ≈ -2.2 - -2.5, Fe/H ≈ -3.2 with age
14 Gyr, 11 Gyr, 14 Gyr respectively (where the last result is not accurate due to the lack of stars in turnoff
point region). This result is consistent with the previous derived age for individual metal-poor stars
Bond (2013), VandeBerg (2014) and the age of the Universe (13.77 ± 0.06 Gyr) based on data on the
cosmic microwave background (CMB), baryon acoustic oscillations, and Hubble constant (Bennett
(2013), although, it tells us that these stars should be born recently after the Big Bang. The youngest
population is located in the upper Galactic halo, instead, two others are coming from the lower Galactic
halo. The presence of not carbon depleted Blue Strugglers is found. From a dynamical point of view,
stars are separated into disk and halo stars according to their kinematics. Part of both groups is found to
be affected by the bulge potential. However, stars with different metallicity present in all dynamical
groups. But on average the stars following halo kinematics are more metal-poor. From chemical
composition the stars under consideration show correlation between [Al/Fe] and [Fe/H] and anticorrelation
for [Mg/Fe] and [Fe/H]
Strumenti di pianificazione economico-finanziaria nelle PMI
No full textNegli ultimi anni, l'evoluzione del contesto normativo ha richiesto a grandi e piccole aziende in Italia, un cambiamento sostanziale delle procedure e dei metodi utilizzati nella conduzione d'impresa. Nello specifico, il nuovo codice della crisi d'impresa e le nuove regole in materia bancaria hanno indotto le imprese a sviluppare o perfezionare un sistema di pianificazione e controllo, che permetta all'imprenditore o al management di avere una visione corretta dell'andamento della propria attività
Il concetto di terreno edificabile ai fini Irpef (con particolare riguardo alla categoria dei redditi diversi)
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A first attempt at using machine learning for the classification of vegetation habitats in the French Alps
No full textMonitoring the flora is key to maintain an equilibrium among the
transformations of our planet. In order to be efficient in this process,
several tools of different nature are applied and here, in this thesis, we
present a first approach involving machine learning techniques applied to
the vegetation data collected by the National Alpine Botanical Conservatory
located in Gap (France). A research project was carried out to build a
system capable of predicting the different habitats present in the French
Alps. The study was mainly composed of several experimentations and
comparisons based on the state-of-the-art classification methods developed in machine learning, with considerations to the botanical field of study. We founded different solutions in the prediction of the habitats,
the various models and options that we developed are usable in different
frameworks of the process of territory management. Our results are finally discussed not only to have a clear vision of what we built and how to take advantage of it, but also as a starting point for further developments, as these were the firsts attempts in this specific context of research