Combining gravimetry, passive seismology and rock physical properties to constrain intra-crustal structures : the Ivrea Geophysical Body and the Gotthard Base Tunnel

The structure of the Alpine orogen is complex, and many areas present an imaging gap between regional geophysical and local geological information. In the frame of this thesis, I have performed joint investigations, collecting new gravity and passive seismic data and combining them with surface geological observations and rock sample laboratory analysis, to provide higher-resolution images and models of an intra-crustal and a shallow Alpine structure. I targeted the Ivrea Geophysical Body (IGB) and the Gotthard Base Tunnel (GBT), as they provide ideal areas for testing the resolution limits of passive geophysical investigations and addressing pending structural questions as well. The IGB, considered as a sliver of Adriatic lower lithosphere, located at unusually shallow depths along the inner arc of the Western Alps, is associated with well-known density and seismic velocity anomalies. Aiming at refining the IGB structure and its relationship with the geological Ivrea-Verbano Zone (IVZ) outcropping at the surface, I collected 207 new relative gravity data and I installed 10 broadband seismic stations which operated for 27 months. In a first, 3D gravity study, I compiled a surface rock- density map and used it to define a density-corrected gravity anomaly named Niggli anomaly. Modelling the Niggli anomaly allowed to address more properly the IGB structure at depth, the latter being modelled as a 3D, single density-contrast interface beneath the entire IVZ. From this, I obtained 400 ± 100 kg · m−3 as optimal density contrast, and a ∼ 20 km-wide protruding structure reaching as shallow as 1 ± 1 km depth below sea level. Petrological considerations allow to suggest ultramafic and mantle peridotite rocks as most likely components for the IGB. In a second, refined 2D study, the seismic data was also included to constrain the IGB model along the Val Sesia cross-section. A joint inversion was designed, exploiting seismic receiver functions and gravity anomalies, following an iterative inversion scheme to constrain the geometry and physical properties of the IGB. An optimal density contrast between 200 and 400 kg · m−3 was obtained, with shallow segments 1-3 km depth below sea level, and in agreement with rock physical properties indicated by previous studies. For the final study, along the GBT, I acquired 80 new relative gravity data points at the surface and used 77 points measured in the tunnel to test and constrain the geological model established during tunnel construction. To this end, I developed an iterative scheme with fully 3D, density-dependent gravity terrain-adaptation corrections, to then consistently compare the observations with the synthetics from the 2D geology-based density model. Density data models for various lithologies were compiled from the SAPHYR rock physics database. The results show that in situ rock densities provide a better fit to the observed gravity data, and that the geological structure of GBT proposed earlier can be reasonably fit with surface and tunnel geophysical data. -- La structure de la chaîne alpine est complexe, et de nombreuses zones présentent une lacune de résolution entre les informations géophysiques à l’échelle régionale et les informations géologiques à l’échelle locale. Dans le cadre de cette thèse, j’ai récolté et analysé de nouvelles données gravimétriques et de sismique passive. Les données ont été analysées en combinaison avec des observations géologiques de surface et des analyses de laboratoire d’échantillons de roches, pour fournir des images et des modèles à plus haute résolution de la croûte terrestre alpine, à faible et moyenne profondeur. Je me suis concentré sur le Corps d’Ivrée (IGB) et sur le Tunnel de Base du Saint-Gothard (GBT), car ils représentent des zones idéales pour tester les limites de résolution de la géophysique passive, et pour répondre à des questions structurales d’intérêt. L’IGB, considéré comme une écaille de lithosphère inférieure de la plaque Adriatique situé à faible profondeur le long de l’arc intérieur des Alpes occidentales, est associé à des fortes anomalies de densité et de vitesse sismique. Dans le but d’affiner la structure de l’IGB et sa relation avec la zone géologique d’Ivrea-Verbano (IVZ), j’ai mesuré 207 nouveaux points gravimétriques, et j’ai installé 10 stations sismologiques large-bande pour 27 mois. Dans une première étude gravimétrique 3D, j’ai compilé une carte de densité de roches de surface, pour ensuite l’utiliser à définir une anomalie gravimétrique corrigée, nommé anomalie gravimétrique de Niggli. La modélisation de cette anomalie a permis de mieux décrire la structure de l’IGB en profondeur, cette dernière étant modélisée comme une interface de contraste de densité en 3D sous l’IVZ. A l’issue de cette modélisation, j’ai obtenu un contraste de densité optimal de 400 ± 100 kg ·m−3, et une structure incrustée de ∼ 20 km de large, à une profondeur aussi faible que 1 ± 1 km sous le niveau de la mer. Des considérations pétrologiques permettent de suggérer des roches ultra-mafiques et de péridotite du manteau comme les composantes les plus probables de l’IGB. Dans une deuxième étude en 2D, les données sismiques ont été incluses pour affiner le modèle de l’IGB le long du profil Val Sesia. Une inversion conjointe des données sismiques et gravimétriques a été conçue, suivant une approche itérative pour contraindre la géométrie et les propriétés physiques de l’IGB. Un contraste de densité optimal entre 200 et 400 kg · m−3 a été obtenu, avec des segments à faible profondeur atteignant 1 à 3 km sous le niveau de la mer, et en accord avec les propriétés physiques des roches indiquées par des études précédentes. Pour l’étude finale, le long du GBT, j’ai collecté 80 nouveaux points gravimétriques, et utilisé 77 points mesurés dans le tunnel pour tester et contraindre le modèle géologique établi lors de la construction du tunnel. À cette fin, j’ai développé un schéma itératif avec des corrections et adaptations gravimétrique de terrain entièrement en 3D et en fonction de la densité, pour ensuite comparer de manière cohérente les observations avec les résultats provenant du modèle de densité 2D basé sur la géologie. Des modèles de densité pour diverses lithologies ont été compilés à partir du catalogue de physique de roches SAPHYR. Les résultats montrent que les densités de roche in situ expliquent mieux les données gravimétriques, et que la structure du modèle géologique du GBT proposé précédemment peut être raisonnablement décrite avec des données géophysique de surface et du tunnel

Analysis of existing tsunami scenario databases for optimal design and efficient real-time event matching

Pre-computed tsunami scenario databases constitute a traditional basis to the production of tsunami forecasts in real time, achieved through a combination of properly selected Green’s functions-like objects. The considered case-study database contains water elevation fields and waveform signals produced by an arrangement of evenly-spaced elementary seismic sources, covering fault areas relevant in determining the Portuguese tsunami hazard. This work proposes a novel real-time processing for the tsunami forecast production, aiming at the accuracy given by traditional methods but with less time cost. The study has been conducted on the Gorringe Bank fault (GBF), but has a general validity. First, the GBF database is analysed in detail, seeking for remarkable properties of the seismic sources, in terms of frequency content, cross-correlation and relative differences of the fields and waveform signals. Then, a reference forecast for a seismic event placed on the GBF is given, by using all the traditionally available subfaults. Furthermore, a novel processing algorithm is defined to produce approximate forecasts, through a strategic exploitation of the information obtainable by each of the seismic sources, taken in minor number. A further focus on sensible locations is provided. Remarkable results are obtained in terms of physical properties of the seismic sources and time-gain for the forecast production. Seismic sources at depth produce longwave dominated signals, allowing for an optimisation of the database content, in terms of sources required to properly represent seismogenic areas at certain depths. In terms of time cost, an overall improvement is obtained concerning the forecast production, since the proposed strategy gives highly accurate forecasts, using half of the seismic sources used by traditional forecasting methods, which reduces the required accesses to the database

New eco-sustainable feed in aquaculture: influence of insect-based diets on the content of potentially toxic elements in the experimental model zebrafish (Danio rerio).

According to the concept of circular economy, insects represent good candidates as aquafeed ingredients. Nevertheless, there are some potential chemical risks linked with insect consumption. In this study, we reared the teleost Danio rerio, used as an experimental model, with five experimental diets characterized by increasing levels (0%, 25%, 50%, 75%, and 100%) of full-fat Hermetia illucens (Hi) prepupae, substituting for fish meal (FM) and fish oil (FO). We investigated the presence of potentially toxic elements (PTEs) Cd, Pb, Ni, As, and Hg in larval (20 days), juvenile (2 months), and adult (6 months) fish. Quantitative determinations of Cd, Pb, Ni, and As were made with an atomic absorption spectrometer; the total mercury content was determined by a direct mercury analyzer. The substitution of FM and FO with Hermetia illucens meal led to a reduction in the content of some PTEs, such as Pb, As, and Ni, in fishfeed, leading to concentrations below the legal limit of undesirable substances in animal feed. By increasing the Hi meal dietary content, we observed in the Danio rerio specimens an increase in Cd, Pb, and Ni content and a reduction in As content for all life stages. Moreover, a general increase in the content of Cd, Pb, Hg, and Ni from larvae to juvenile was measured, while the shift of Danio rerio from the juvenile to the adult stage involved a significant increase in the content of Pb, Hg, and Ni. Larvae had a reduced ability to bioaccumulate metal(loid)s compared to juveniles and adults. In conclusion, the content of PTEs in Danio rerio is influenced both by the type of diet administered and by the life stage of the animal itself. This research demonstrates the possibility of using Hi prepupae as an aquafeed ingredient without exposing fish to a chemical risk and, in perspective, allows applying these eco-sustainable diets for the breeding of edible fish species, without endangering human healt

Moho depths beneath the European Alps: a homogeneously processed map and receiver functions database

We use seismic waveform data from the AlpArray Seismic Network and three other temporary seismic networks, to perform receiver function (RF) calculations and time-to-depth migration to update the knowledge of the Moho discontinuity beneath the broader European Alps. In particular, we set up a homogeneous processing scheme to compute RFs using the time-domain iterative deconvolution method and apply consistent quality control to yield 112 205 high-quality RFs. We then perform time-to-depth migration in a newly implemented 3D spherical coordinate system using a European-scale reference P and S wave velocity model. This approach, together with the dense data coverage, provide us with a 3D migrated volume, from which we present migrated profiles that reflect the first-order crustal thickness structure. We create a detailed Moho map by manually picking the discontinuity in a set of orthogonal profiles covering the entire area. We make the RF dataset, the software for the entire processing workflow, as well as the Moho map, openly available; these open-access datasets and results will allow other researchers to build on the current study

Report on an open dataset to constrain the Balmuccia peridotite body (Ivrea-Verbano Zone, Italy) through a participative gravity-modelling challenge

The Balmuccia peridotite exposes relatively fresh mantle rocks at the Earth’s surface, and as such it is of interest for geologists and geophysicists. The outcrop is a kilometre-scale feature, yet its extent at depth is insufficiently imaged. Our aim is to provide new constraints on the shape of the density anomaly this body represents, through 3D gravity modelling. In an effort to avoid personal or methodology bias, we hereby launch an invitation and call for participative modelling. We openly provide all the necessary input data: pre-processed gravity data, geological map, in situ rock densities, and digital elevation model. The expected inversion results will be compared and jointly analysed with all participants. This approach should allow us to conclude on the shape of the Balmuccia peridotite body and the associated uncertainty. This crowd effort will contribute to the site surveys preparing a scientific borehole in the area in frame of project DIVE

Risk prediction of clinical adverse outcomes with machine learning in a cohort of critically ill patients with atrial fibrillation

Critically ill patients affected by atrial fibrillation are at high risk of adverse events: however, the actual risk stratification models for haemorrhagic and thrombotic events are not validated in a critical care setting. With this paper we aimed to identify, adopting topological data analysis, the risk factors for therapeutic failure (in-hospital death or intensive care unit transfer), the in-hospital occurrence of stroke/TIA and major bleeding in a cohort of critically ill patients with pre-existing atrial fibrillation admitted to a stepdown unit; to engineer newer prediction models based on machine learning in the same cohort. We selected all medical patients admitted for critical illness and a history of pre-existing atrial fibrillation in the timeframe 01/01/2002-03/08/2007. All data regarding patients' medical history, comorbidities, drugs adopted, vital parameters and outcomes (therapeutic failure, stroke/TIA and major bleeding) were acquired from electronic medical records. Risk factors for each outcome were analyzed adopting topological data analysis. Machine learning was used to generate three different predictive models. We were able to identify specific risk factors and to engineer dedicated clinical prediction models for therapeutic failure (AUC: 0.974, 95%CI: 0.934-0.975), stroke/TIA (AUC: 0.931, 95%CI: 0.896-0.940; Brier score: 0.13) and major bleeding (AUC: 0.930:0.911-0.939; Brier score: 0.09) in critically-ill patients, which were able to predict accurately their respective clinical outcomes. Topological data analysis and machine learning techniques represent a concrete viewpoint for the physician to predict the risk at the patients' level, aiding the selection of the best therapeutic strategy in critically ill patients affected by pre-existing atrial fibrillation

The impact of alternative delivery strategies for novel tuberculosis vaccines in low-income and middle-income countries: a modelling study

BackgroundTuberculosis is a leading infectious cause of death worldwide. Novel vaccines will be required to reach global targets and reverse setbacks resulting from the COVID-19 pandemic. We estimated the impact of novel tuberculosis vaccines in low-income and middle-income countries (LMICs) in several delivery scenarios.MethodsWe calibrated a tuberculosis model to 105 LMICs (accounting for 93% of global incidence). Vaccine scenarios were implemented as the base-case (routine vaccination of those aged 9 years and one-off vaccination for those aged 10 years and older, with country-specific introduction between 2028 and 2047, and 5-year scale-up to target coverage); accelerated scale-up similar to the base-case, but with all countries introducing vaccines in 2025, with instant scale-up; and routine-only (similar to the base-case, but including routine vaccination only). Vaccines were assumed to protect against disease for 10 years, with 50% efficacy.FindingsThe base-case scenario would prevent 44·0 million (95% uncertainty range 37·2–51·6) tuberculosis cases and 5·0 million (4·6–5·4) tuberculosis deaths before 2050, compared with equivalent estimates of cases and deaths that would be predicted to occur before 2050 with no new vaccine introduction (the baseline scenario). The accelerated scale-up scenario would prevent 65·5 million (55·6–76·0) cases and 7·9 million (7·3–8·5) deaths before 2050, relative to baseline. The routine-only scenario would prevent 8·8 million (95% uncertainty range 7·6–10·1) cases and 1·1 million (0·9–1·2) deaths before 2050, relative to baseline.InterpretationOur results suggest novel tuberculosis vaccines could have substantial impact, which will vary depending on delivery strategy. Including a one-off vaccination campaign will be crucial for rapid impact. Accelerated introduction—at a pace similar to that seen for COVID-19 vaccines—would increase the number of lives saved before 2050 by around 60%. Investment is required to support vaccine development, manufacturing, prompt introduction, and scale-up

Lifting line method for modelling covering and blanketing effects for yacht fleet race simulation

An approach is presented that can be used to enhance the realism of yacht fleet race simulations. The wake of an upwind sailing yacht is represented as a single heeled horseshoe vortex (and image) system. At each time step changes in vortex strength are convected into the wake as a pair of vortex line elements. These subsequently move in accordance with the local wind, self-induced velocity and velocity induced by the presence of the wakes of other yachts. An empirical based decay factor is used to eventually remove the far wake. A synthesis of sail yacht wake representations based on detailed 3D Reynolds Averaged Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) calculations with wind tunnel test results are used to capture the initial strength of the combined main-jib vortex system and its vertical height. These were based on a typical upwind sail arrangement for a range of heel angles and in-line calculations for a pair of yachts separated by three boat lengths. This paper details the basis of the validated CFD results for a yacht at heel and the analysis of the CFD results to provide an approximate single line vortex method for the yacht. The developed algorithm will eventually run within the Robo-Race which is a real-time yacht race strategy analysis tool based on MATLAB®-Simulink® developed at the University of Southampton

Criterio energetico per determinare l'orientazione di una faglia trasforme

In questa tesi si affronta la problematica di determinare l'orientazione della superficie di faglia che sarà interessata da scorrimento relativo, assegnato un certo sforzo tettonico Sigma in base ad un criterio di massima energia rilasciata. Dapprima, introdotte le nozioni di base della meccanica dei continui, si studia il criterio di fagliazione dato dalla teoria di Anderson. In seguito, una volta acquisito questo primo risultato, si applica la teoria delle dislocazioni elastiche, per studiare dal punto di vista energetico la stessa faglia, situata in un semispazio elastico. Assumendo che la faglia massimizzante l'energia rilasciata in seguito alla frattura del mezzo continuo, assegnati i dati del problema, sia quella che più probabilmente sarà soggetta ad attivazione e scorrimento, si confronta quanto ottenuto con i risultati della teoria della fagliazione di Anderson. Entrambi gli approcci presentano conclusioni simili, gli angoli di orientamento infatti sono compresi tra 1/2atan1/f e pi/4 con l'orientazione che tende a pi/4 diminuendo l'influenza dell'attrito o viceversa aumentando lo sforzo applicato sulla superficie di faglia. Tuttavia i due approcci presentano significative differenze quando l'energia rilasciata è molto maggiore di zero