Nanoseismic monitoring for detection of rockfalls. Experiments in quarry areas

Le frane per crollo da ammassi rocciosi fratturati sono tra i processi di instabilità gravitativa che più frequentemente interessano opere antropiche quali tagli su versanti naturali o artificiali, pareti di cava, trincee stradali, autostradali o ferroviarie, sia per ciò che attiene le aree di distacco che per quelle di accumulo. Nell’ambito dell’applicazione di sistemi di early warning per la gestione del rischio geologico legato a queste tipologie di frana, una sperimentazione della tecnica del monitoraggio nanosismometrico è stata effettuata presso due siti estrattivi non più in attività: le “Pirrere” della Baia di Cala Rossa sull’isola di Favignana (Trapani), in Sicilia, e la cava dismessa di Acuto (Frosinone), in Italia Centrale. Il monitoraggio nanosismometrico è una tecnica di indagine che consente di individuare e localizzare deboli eventi sismici, fino a magnitudo locale (ML) nell’ordine di -3, attraverso l’impiego di quattro sensori sismometrici disposti secondo una specifica geometria di array detta SNS (Seismic Navigation System). Nel presente lavoro, mediante il software NanoseismicSuite sono stati analizzati 73 eventi di crollo indotti artificialmente attraverso la caduta controllata di blocchi di roccia nei due siti estrattivi abbandonati; sono stati lanciati, simulando fenomeni di rockfalls, rispettivamente 47 blocchi di roccia nella cava di Acuto e 26 eventi in quattro diverse cave a cielo aperto presenti nel settore occidentale di Cala Rossa. Tali eventi, avendo punto epicentrale noto, hanno permesso di determinare il miglior modello di sottosuolo in termini di valori di velocità delle onde P ed S attraverso un’operazione di back analysis. L’analisi è stata, infatti, effettuata variando i valori di velocità e scegliendo quelli relativi all’epicentro teorico ottenuto dall’analisi dell’evento che fosse il più vicino possibile al punto reale di impatto del blocco di roccia. Al fine di valutare la sensibilità della geometria dell’array SNS e l’influenza del sito di installazione sulla capacità di individuare e localizzare gli eventi, le sperimentazioni sono state condotte sia variando il raggio di apertura che la zona di installazione degli array: presso Acuto le acquisizioni di segnale sono state condotte prima con un array SNS con apertura di 20 m e successivamente con un array di apertura 10 m, mentre presso Cala Rossa l’array è stato installato alternativamente all’aperto in un’area di plateau roccioso ed in una galleria facente parte dell’area di cava abbandonata. Analizzando i dati si è ottenuta una precisione dell’ubicazione epicentrale compresa tra il 10 ed il 22% della distanza che intercorre tra la sorgente e l’array nanosismometrico. Il miglior modello di sottosuolo ottenuto per entrambi i casi di studio è risultato avere una velocità delle onde P pari a 900 m/s ed un rapporto VP/VS pari a 1.73, valori in accordo con le condizioni di intenso stato di fratturazione delle rocce carbonatiche affioranti nelle due zone di cava. Per gli eventi di crollo indotti la magnitudo ML è risultata essere compresa tra -2.8 e -1.3; considerando l’energia sviluppata dall’impatto, legata alla massa del blocco ed all’altezza e alla velocità di caduta, non è stato possibile definire una relazione tra magnitudo ed energia, probabilmente a causa delle differenti caratteristiche del punto di impatto dei diversi blocchi. In generale, si è osservato che la precisione di ubicazione degli eventi, in termini di azimuth e distanza dal reale epicentro, è risultata paragonabile sia variando l’apertura dell’array che variando il sito di installazione. Per il sito sperimentale di Acuto, il processo di picking manuale del tempo di primo arrivo delle onde P è risultato essere più affidabile nel caso di array con apertura pari a 10 m. La sperimentazione effettuata a Cala Rossa ha permesso, invece, di osservare una migliore capacità di individuazione degli eventi nelle tracce relative all’array posizionato in galleria a causa della minore rumorosità di base del sito di installazione. Tra le registrazioni sismometriche sono state identificate varie tipologie di segnali, oltre a quelli generati dal lancio dei blocchi, alcune riconducibili ad eventi naturali di crollo altre a deboli terremoti. L’analisi dei segnali riferibili alla prima tipologia di eventi naturali, effettuata tenendo in considerazione i modelli di sottosuolo precedentemente calibrati, ha portato all’identificazione in ambedue i siti di aree aventi maggiore suscettibilità a frane per crollo. In definitiva, si può ritenere che i risultati ottenuti in questo studio siano incoraggianti rispetto all’efficacia della tecnica di monitoraggio nanosismometrico nell’individuazione e nell’ubicazione di fenomeni di crollo in roccia e portano a ritenere questa tecnica potenzialmente applicabile in aree in cui tali eventi possono interferire con infrastrutture antropiche.In the frame of early warning and risk mitigation studies for landslide processes involving rock masses, two quarry areas (Cala Rossa Bay in Sicily and Acuto in Central Italy) were monitored with SNS (Seismic Navigation System) arrays. In this study, 73 rockfalls were simulated by launches of rock blocks. This allowed to perform a back analysis for defining the best seismic velocity model of the subsoil half-space; the records related to each impact caused by the rock block launch were managed by the nanoseismic monitoring approach, varying the velocity model to obtain a theoretical epicentre as close as possible to the actual location of the impact point. In order to evaluate the sensibility of the SNS array, the results obtained by different array apertures and positions were compared in terms of azimuth and distance error with respect to the real epicentres. On the other hand, several natural rockfalls were detected; their analysis allowed to identify areas having higher susceptibility to rockfalls by using the previously calibrated subsoil half-space model. Further studies are required to better define the areas prone to rockfall generation in the considered test sites; nevertheless, the here obtained results show an encouraging perspective about the application of the nanoseismic monitoring with respect to vulnerable infrastructures in rockfall prone areas

Analysis of the seismic site effects along the ancient Via Laurentina (Rome)

This paper presents an evaluation of the Local Seismic Response (LSR) along the route of the ancient Roman road Via Laurentina, which has been exposed in several areas of southwest Rome over the last decade during the construction of new buildings and infrastructures. It is an example of LSR analysis applied to ancient and archaeological sites located in alluvial valleys with some methodological inferences for the design of infrastructure and urban planning. Since the ancient road does not cross the alluvial valley (namely the Fosso di Vallerano Valley) normal to its sides, it was not possible to directly perform 2D numerical modelling to evaluate the LSR along the road route. Therefore, outputs of 2D numerical models, obtained along three cross sections that were normal oriented respect to the valley, were projected along the route of the Via Laurentina within a reliable buffer attributed according to an available high-resolution geological model of the local subsoil. The modelled amplification functions consider physical effects due to both the 2D shape of the valley and the heterogeneities of the alluvial deposits. The 1D and 2D amplification functions were compared to output that non-negligible effects are related to the narrow shape of the fluvial valley and the lateral contacts between the lithotecnical units composing the alluvial fill. The here experienced methodology is suitable for applications to the numerical modelling of seismic response in case of linear infrastructures (i.e., roads, bridges, railways) that do not cross the natural system along physically characteristic directions (i.e. longitudinally or transversally)

A critical analysis of happiness and well-being. Where we stand now, where we need to go

This paper aims to critically analyse happiness and well-being to find novel ways for theorizing and promoting better life conditions for individuals and societies. The necessity to shift from a subjective view of individual well-being to a more social and contextual version of these constructs is the common thread running throughout the whole work. To this end, the first part introduces the reader into the complexity of the happiness and well-being scholarship by outlining some of the most relevant approaches developed by the psychological and economic literature. After highlighting the limitations of both disciplines, the second part of the paper presents some alternative models, namely the Feminist Economics, the Capabilities Approach, and the model of Four Qualities of Life. In addition to these, we will draw attention, in the last section, to the Critical Community Psychology approach to happiness and well-being. Our main argument is that this emerging discipline bears the potential to frame the pursuit of the good life in a whole new fashion that takes into account a) contextual features, in particular the recourses that a given environment offers and the opportunity to access them, b) the role of power, justice, and liberation, and c) the value of participation, reciprocity, and ethics of care. Current limitations of CCP are also discussed and future directions outlined

Rashba spin-orbit coupling and spin precession in carbon nanotubes

The Rashba spin-orbit coupling in carbon nanotubes and its effect on spin-dependent transport properties are analyzed theoretically. We focus on clean non-interacting nanotubes with tunable number of subbands $N$. The peculiar band structure is shown to allow in principle for Datta-Das oscillatory behavior in the tunneling magnetoresistance as a function of gate voltage, despite the presence of multiple bands. We discuss the conditions for observing Datta-Das oscillations in carbon nanotubes.Comment: 12 pages, published versio

From "Gomorrah Domain" to "Don Peppe Diana Lands". A Southern Italian Experience of Work-Based Liberation, Community Networking, and Well Being

The article describes working experiences in relation to empowering activities, which have been carried out in a local community in the province of Caserta (in Southern Italy), a place characterized by the widespread presence of organized criminal groups. In this study, workplace is intended as a community network aimed at the promotion of coscientization, liberation, and well-being. Specifically, this paper features initiatives and projects aimed at establishing new community values through a re-construction of a work-based social system standing against criminal clans, which tend to dominate not only economical transactions but also civil life

Self-sustained oscillator as a model for explosion quakes at Stromboli Volcano

International audienceWe analyze seismic signals produced by explosion-quakes at Stromboli Volcano. We use standard nonlinear procedures to search a low-order effective dynam-ics. The dimension of the reconstructed phase space depends on the number of samples. Namely larger time lengths cor-respond to dynamical systems of different complexity. If we restrict the analysis to the signal associated directly to the source (Chouet et al., 1997), we obtain a phase space dimen-sion equal to two. We reproduce this part of the signal with a simple single self-sustained oscillator

A2163: Merger events in the hottest Abell galaxy cluster II. Subcluster accretion with galaxy-gas separation

Located at z = 0.203, A2163 is a rich galaxy cluster with an intra-cluster medium (ICM) that exhibits extraordinary properties, including an exceptionally high X-ray luminosity, average temperature, and a powerful and extended radio halo. The irregular and complex morphology of its gas and galaxy structure suggests that this cluster has recently undergone major merger events that involve two or more cluster components. In this paper, we study the gas structure and dynamics by means of spectral-imaging analysis of X-ray data obtained from XMM-Newton and Chandra observations. From the evidence of a cold front, we infer the westward motion of a cool core across the E-W elongated atmosphere of the main cluster A2163-A. Located close to a galaxy over-density, this gas 'bullet' appears to have been spatially separated from its galaxy (and presumably dark matter component) as a result of high-velocity accretion. From gas brightness and temperature profile analysis performed in two opposite regions of the main cluster, we show that the ICM has been adiabatically compressed behind the crossing 'bullet' possibly because of shock heating, leading to a strong departure of the ICM from hydrostatic equilibrium in this region. Assuming that the mass estimated from the Yx proxy best indicates the overall mass of the system and that the western cluster sector is in approximate hydrostatic equilibrium before subcluster accretion, we infer a merger scenario between two subunits of mass ratio 1:4, leading to a present total system mass of M500 $\propto 1.9 \times 1015 M_{\odot}$. The exceptional properties of A2163 present various similarities with those of 1E0657-56, the so-called 'bullet-cluster'. These similarities are likely to be related to a comparable merger scenario.Comment: A&A, in pres

The Cerebellar Fastigial Nucleus Contributes to CO\u3csub\u3e2\u3c/sub\u3e-H\u3csup\u3e+\u3c/sup\u3e Ventilatory Sensitivity in Awake Goats

The purpose of this study was to test the hypothesis that an intact cerebellar fastigial nucleus (CFN) is an important determinant of CO2-H+ sensitivity during wakefulness. Bilateral, stainless steel microtubules were implanted into the CFN (N = 9) for injection (0.5–10 μl) of the neurotoxin ibotenic acid. Two or more weeks after implantation of the microtubules, eupneic breathing and CO2-H+ sensitivity did not differ significantly (P \u3e 0.10) from pre-implantation conditions. Injection of ibotenic acid (50 mM) did not significantly alter eupneic PaCO2 (P \u3e 0.10). The coefficient of variation of eupneic PaCO2 was 4.0 ± 0.6 and 3.7 ± 0.4% over the 2 weeks before and after the lesion, respectively. CO2-H+ sensitivity expressed as inspired ventilation/PaCO2 decreased from 2.15 ± 0.17 pre-lesion to 1.58 ± 0.26 l/(min mmHg) 3–6 days post-lesion (P \u3c 0.02, −27%). There was no significant (P \u3e 0.10) recovery of sensitivity between 7 and 10 days post-lesion. The lesion also increased (P \u3c 0.05) the day-to-day variability of this index by nearly 100%. When CO2 sensitivity was expressed as elevated inspired CO2/room air VI, values at 7%, but not 3 and 5% inspired CO2, were reduced and more variable (P \u3c 0.05) after the ibotenic acid injections. We conclude that during wakefulness, the CFN contributes relatively more to overall ventilatory drive at high relative to low levels of hypercapnia

Stationary states of a spherical Minority Game with ergodicity breaking

Using generating functional and replica techniques, respectively, we study the dynamics and statics of a spherical Minority Game (MG), which in contrast with a spherical MG previously presented in J.Phys A: Math. Gen. 36 11159 (2003) displays a phase with broken ergodicity and dependence of the macroscopic stationary state on initial conditions. The model thus bears more similarity with the original MG. Still, all order parameters including the volatility can computed in the ergodic phases without making any approximations. We also study the effects of market impact correction on the phase diagram. Finally we discuss a continuous-time version of the model as well as the differences between on-line and batch update rules. Our analytical results are confirmed convincingly by comparison with numerical simulations. In an appendix we extend the analysis of the earlier spherical MG to a model with general time-step, and compare the dynamics and statics of the two spherical models.Comment: 26 pages, 8 figures; typo correcte