3,762 research outputs found
Integrated passive and active geophysical prospections for seismic sites characterization
No full textThe seismic monitoring of the territory is extremely important in a seismic area as Italy, in order to determine the strong ground motion parameters, as peak ground acceleration and velocity, and develop risk management strategies for earthquake hazards. For a correct definition of strong ground motion parameter, the knowledge of site effects is determinant. In fact, the seismic motion is strongly affected by the materials through which seismic waves travel especially within the shallowest part of the subsurface. Local geological (lithology) and geomorphological conditions may produce strong modifications in the amplitude level, spectral content and time duration of earthquake ground motion. Furthermore, the knowledge of local site conditions (geology, topography, shear wave velocity, soil deposit thickness and resonant frequency) is fundamental for the definition of the EC8 site class (CEN, 2003) for each seismic station. Geological surveys are not enough for a detailed seismic site characterization and must be integrated by other investigation such as dedicated geophysical surveys. Among these, the most commons are the passive and active seismic investigations: seismic refraction and reflection, multichannel analysis of surface waves, H/V spectral ratio, spatially averaged coherency spectrum and frequency-wavenumber methods. This contribution shows the results obtained from the integration of some geophysical methods for the characterization of some RAF sites in Friuli Venezia Giulia (Maselli, 2007): two are seismic noise techniques (H/V spectral ratio and frequency–wavenumber (F-K) methods) while the other is an active seismic method (seismic refraction) including both P and S waves analysis.
H/V spectral ratio (Nakamura, 1989) is a single-station method used to evaluate the resonance frequency of soft sediment over hard bedrock. This method calculates the ratio between the horizontal and the vertical Fourier spectra of ambient noise recorded at a single site by a three-component sensor. F-K method (Lacoss et al. 1969; Horike 1985) is an array-based method used to evaluate Vs profiles of soft, low velocity, sedimentary layers overlying hard bedrock. It extracts surface wave dispersion curves from ambient noise recordings. Vs profiles are estimated inverting the dispersion curves. Seismic refraction method measures the travel time of the seismic wave between the seismic source and the receivers to measure the velocity and the depth of the refracting surface. Four sites were investigated through these methods, one in correspondence with a borehole in Gemona del Friuli (GEMO) and the other three in correspondence with three RAF seismic stations: Gemona del Friuli (GESC), Polcenigo (POLC) and Monte Pala (PALA). Due to the presence pf a 120 meters long borehole reaching the basement, GEMO was selected as a reference site to compare the results obtained with the other methods and also to have a calibration site for the analysis
Man Made Deltas
No full textThe review of geochronological and historical data documents that the largest southern European deltas formed almost synchronously during two short intervals of enhanced anthropic pressure on landscapes, respectively during the Roman Empire and the Little Ice Age. These growth phases, that occurred under contrasting climatic regimes, were both followed by generalized delta retreat, driven by two markedly different reasons: after the Romans, the fall of the population and new afforestation let soil erosion in river catchments return to natural background levels; since the industrial revolution, instead, flow regulation through river dams overkill a still increasing sediment production in catchment basins. In this second case, furthermore, the effect of a reduced sediment flux to the coasts is amplified by the sinking of modern deltas, due to land subsidence and sea level rise, that hampers delta outbuilding and increases the vulnerability of coastal zone to marine erosion and flooding
Data is the new sex. Forme di data intimacy nel design dell’informazione
No full textLa moderna emancipazione della sessualità verso una condizione di desiderio sospeso, consapevole, non istintuale, che rifiuta la subitaneità e l’orgasmocentrismo, suggerisce un rinnovato utilizzo del concetto di eros nella società post digitale e nella viscerale sete di conoscenza che la permea. Il rapporto erotico che culmina con il momento di massimo raggiungimento del piacere, cioè, oggi rivede le sue priorità e l’identità dell’ipotetico ’altro’ con cui entriamo in contatto in questa permanente ricerca di piacere diventa olistica, multidimensionale, inorganica e spesso immateriale. Se secondo le teorie post umaniste alla condizione relazionale di erotismo – neutrale – verso il divino e l’animale si affianca il rapporto di desiderio verso l’oggetto, nello specifico la macchina , oggi il rapporto con l’altro si complica e il significato di ’altro’ supera l’entità ontologica degli esseri viventi e delle macchine: anche il dato diventa una ‘instance’ e un’entità separata con la quale interagire intimamente e che manifesta qualità diverse dalle categorie citate. Il dato in quest’ottica è protagonista di operazioni di scoperta, affezione, desiderio che si verificano in sistemi autopoietici fondati su una nuova dimensione relazionale. L’erotismo del dato supera l’idea di abbattimento delle barriere tra gli esseri umani attraverso le media technologies e le stimolazioni sensoriali sinestetiche poiché vaglia nuovi approcci costruttivi del rapporto tra il soggetto umano e la creazione di informazioni. Questo rapporto erotico più consapevole, maturo, talvolta indiretto con il dato, trova una possibile definizione nel concetto di ‘intimità’ indagato dalla psicologia per descrivere il rapporto tra organico e non organico. Secondo Jacques Lacan il termine intimità descrive una condizione relazionale non necessariamente associata ai desideri e alle passioni fisiche e sessuali ma più propriamente una connessione emotiva, sensoriale, spirituale o fisica profonda e stretta tra due entità. Applicato al rapporto con il dato, il concetto di intimità ammette la possibilità di costruire connessioni che superano i costrutti sociali e culturali e che proiettano l’essere umano verso una condizione di trascendenza dalla stessa natura umana e ontologia materiale, demistificando la centralità dell’uomo e individuando nuove forme di relazione con il non-umano. Nel presente saggio si indagheranno queste forme di erotismo che vedono interagire il dato – o meglio le sue visualizzazioni – e l’essere umano, protagonisti di una pletora di relazioni intime che nascono da un lato dall’imperante e pervasiva società dei dati e dei processi di dataficazione, dall’altro da una continua ricerca di conoscenza e di relazione che in uno scenario postumano coinvolge anche elementi intangibili informativi, con cui si crea un’entropia spontanea, e una relazione dinamica e dalle configurazioni eterogenee. L’analisi di questa eterogeneità condurrà all’identificazione di rapporti intimi con il dato, ad una data intimacy olistica descritta attraverso parallelismi con le parafilie e ispirata dalle riflessioni condotte in psicanalisi da Sigmund Freud e Jacques Lacan e alle teorie sociali di filosofi come e alle teorie sociali di filosofi come Friedrich Nietzsche e Ferdinand Tonnies che, come si vedrà, saranno alla base del tipo di relazione intima tra persona e dato
Large-scale single incised valley from a small catchment basin on the western Adriatic margin (central Mediterranean Sea)
No full textThe Manfredonia Incised Valley (MIV) is a huge erosional feature buried below the Apulian shelf, on the western side of the Adriatic margin. The incision extends more than 60 km eastward, from the Tavoliere Plain to the outer shelf, not reaching the shelf edge. High-resolution chirp sonar profiles allow reconstruction of the morphology of the incision and its correlation at regional scale. The MIV records a single episode of incision, induced by the last glacial–interglacial sea level fall that forced the rivers draining the Tavoliere Plain to advance basinward, reaching their maximum extent at the peak of the Last Glacial Maximum. The valley was filled during a relatively short interval of about 10,000 yr during the Late Pleistocene–Holocene sea level rise and almost leveled-off at the time of maximum marine ingression, possibly recording the short-term climatic fluctuations that occurred. The accommodation space generated by the lowstand incision was exploited during the following interval of sea level rise by very high rates of sediment supply that allowed the preservation of up to 45 m of valley fill. High-resolution chirp sonar profiles highlight stratal geometries that are consistent with a typical transgressive valley fill of an estuary environment, including bay-head deltas, central basin and distal barrier-island deposits, organized in a backstepping configuration. The highest complexity of the valley fill is reached in the shallowest and most proximal area, where a kilometric prograding wedge formed during a period dominated by riverine input, possibly connected to high precipitation rates. Based on the depth of the valley margins during this interval, the fill was likely isochronous with the formation of sapropel S1 in the Mediterranean region and may have recorded significant fluctuations within the hydrological cycle
Local marine reservoir age (δr) reconstructed based on the tsunami deposit from Pangani bay (Tanzania)
No full textQuantifying the local marine reservoir age (ΔR) and its change over time is critical for precise radiocarbon calibration of marine samples and for the study of the ocean carbon cycle. ΔR values are scarce for the African coast facing the Indian Ocean, and the few values available were obtained from pre-bomb shells collected during the 19th century. Here, the ΔR value for calibrated year 1110 ± 25 (1σ) CE was reconstructed from radiocarbon dating and Bayesian analysis of marine and terrestrial materials coexisting in a tsunami deposit discovered in Pangani Bay (Tanzania, western Indian Ocean coast). The reconstructed ΔR of –8 ± 40 (1σ, n = 3) is similar to pre-bomb regional estimates and provides new information to investigate regional ΔR change over time. The Bayesian analysis of the dated samples revises the age of the tsunami event found in Pangani Bay to 1064–1157 cal CE (95.4% confidence level) or 1110 ± 25 (1σ) cal CE, about one century younger compared to the previous estimate. Our results indicate that the new ΔR value and the proposed calibration approach can be used to refine existing chronologies in the region, with implications for paleo-environmental reconstructions and archaeological studies of Early Swahili societies
Bottom currents, submarine mass failures and halokinesis at the toe of the Sigsbee Escarpment (Gulf of Mexico) : Contrasting regimes during lowstand and highstand conditions?
No full textWe are grateful to BP for the provision of both sea-floor and subsurface data. We thank the journal editor Michele Rebesco for his continuous support, and Lorena Moscardelli, Daniele Casalbore and an anonymous reviewer for their detailed and constructive comments, which have allowed us to considerably improve the manuscript.Peer reviewe
Gravitational waves in massive gravity theories: waveforms, fluxes and constraints from extreme-mass-ratio mergers
No full textIs the graviton massless? This problem was addressed in the literature at a phenomenological level, using modified dispersion relations for gravitational waves, in linearized calculations around flat space. Here, we perform a detailed analysis of the gravitational waveform produced when a small particle plunges or inspirals into a large nonspinning black hole. Our results should presumably also describe the gravitational collapse to black holes and explosive events such as supernovae. In the context of a theory with massive gravitons and screening, merging objects up to 1 Gpc away or collapsing stars in the nearby galaxy may be used to constrain the mass of the graviton to be smaller than ∼10-23 eV, with low-frequency detectors. Our results suggest that the absence of dipolar gravitational waves from black hole binaries may be used to rule out entirely such theories.Is the graviton massless? This problem was addressed in the literature at a phenomenological level, using modified dispersion relations for gravitational waves, in linearized calculations around flat space. Here, we perform a detailed analysis of the gravitational waveform produced when a small particle plunges or inspirals into a large non-spinning black hole. Our results should presumably also describe the gravitational collapse to black holes and explosive events such as supernovae. In the context of a theory with massive gravitons and screening, merging objects up to away or collapsing stars in the nearby galaxy may be used to constrain the mass of the graviton to be smaller than , with low-frequency detectors. Our results suggest that the absence of dipolar gravitational waves from black hole binaries may be used to rule out entirely such theories
Le Voyage d’Orient (selezione critica)
No full textIn occasione dei 50 anni trascorsi dalla morte di Le Corbusier, nel Dipartimento di Pianificazione Design Tecnologia dell'Architettura (DPTA), è stato avviato un viaggio critico e interdisciplinare nelle sue opere scritte e l'incontro ravvicinato con 15 di queste. Sono stati scelti quei volumi la cui filiera temporale potesse restituire una sorta di percorso lungo il quale incrociare le sue teorie su progresso urbano e civile. Questo contributo ha lavorato sul testo Maison de l'homme, coinvolgendo due docenti del Dipartimento DPTA, i professori Cecilia Cecchini e Luciano Cupelloni come autori/tutor e i seguenti dottorandi come co-autori: Vincenzo Maselli, Emanuele Montereale e Yota Nicolarea.Marking the occasion of the 50th anniversary of Le Corbusier’s death, the Department of Planning, Design and Technology of Architecture at Sapienza University of Rome embarked upon a critical and interdisciplinary journey to his work, focusing on 15 amongst his written works. The selection of his works has been made on a temporal basis which could offer a sequence of path-connected theories of Le Corbusier on urban and social development
Oceanographic exchanges between the Southern and Northern Atlantic during the Cenozoic inferred from mixed contourite-turbidite systems in the Brazilian Equatorial Margin
No full textThe Equatorial Atlantic Ocean is a key region to study the oceanographic and climatic changes that occurred during the Cenozoic. Using of 2D and 3D seismic reflection data and boreholes from the Ceará Basin in the Brazilian Equatorial Margin, this work reconstructs how deep-water oceanographic currents in the Equatorial Atlantic Ocean changed during the Cenozoic by investigating the evolution of contourite depositional systems (CDS) and mixed contourite-turbidite system (mCTS). Seismic data interpretation indicates a southward-flowing proto-North Brazil Current (Proto-NBC) was already established in the Eocene and inverted direction in the late Miocene. During most of the Cenozoic, the Ceará Basin went through an alternation of CDS and mCTS, which evolved in response to different sea level and oceanographic regimes. We propose a six-phase evolutionary model for the Brazilian Equatorial Margin to summarize such changes: (1) Paleocene and early Eocene, formation of the CDS under the influence of a southeast-flowing, low intensity, proto-NBC; (2) early Oligocene, still dominance of southeast-flowing currents and further development of the CDS; (3) late Oligocene, initial deposition the m-CTS with prevalence of down-slope processes in proximal regions and bottom-current (still southeast-flowing) reworking in distal regions; (4) early Miocene, the previous late Oligocene conditions are sustained until the (5) middle Miocene, when the proto-NBC becomes weaker and start to invert its direction from southeast to northwest; finally, from the late Miocene (6), the onset of the northwest flow of NBC is established and the mCTS further develops. By documenting the evolution of Cenozoic contourite and mixed contourite-turbidite systems in the Brazilian Equatorial Margin, our study contributes to the understanding of the Atlantic Meridional Overturning Circulation in the Equatorial Atlantic, providing a baseline for future investigations.
Introduction
Sediment deposition and erosion along continental margins may occur under the influence of several processes acting with down-slope or along-slope directions (Faugères et al., 1999; Rebesco and Camerlenghi, 2008; Meiburg and Kneller, 2010). Gravity-driven processes, such as turbidity currents or landslides, relate with the first group, while bottom-current processes, with the latter (Rebesco et al., 2014). The relation between down- and along-slope processes is influenced by the oceanic circulation, and the resulting sedimentary deposits have been characterized using seismic reflection data, both 2D and 3D (Faugères et al., 1999; Viana, 2002; Rebesco and Stow, 2002; Hernández-Molina et al., 2009; Rebesco, 2016). Sediments accumulated under the sole action of bottom currents form contourite depositional systems (CDS; see Hernández-Molina et al., 2006), whereas when bottom currents interact, synchronously or asynchronously, with gravity-driven flows, the resulting deposits are named mixed contourite-turbidite systems (mCTS; see Faugères et al., 1999; Rebesco et al., 2014, Rodrigues et al., 2022). CDS and mCTS have been documented in many continental margin settings across the world (Llave et al., 2007; Hernández-Molina et al., 2010; Rebesco et al., 2014; Gruetzner et al., 2016; Sansom, 2018; Miramontes et al., 2016, Miramontes et al., 2019; Pandolpho et al., 2021), particularly in the Atlantic Ocean, with examples from the North Atlantic (Heezen et al., 1966; Hollister and Heezen, 1972; Rebesco et al., 2013), Nova Scotia margin (Campbell and Mosher, 2016; Rodrigues et al., 2022), Iberian margin (Alves et al., 2003), Brazil margin (Gomes and Viana, 2002; Viana, 2002; Maselli et al., 2019; Maestrelli et al., 2020), Southern São Paulo Plateau (Borisov et al., 2013), Uruguayan Basin (Hernández-Molina et al., 2016), Argentine Basin (Von Lom-Keil et al., 2002; Hernández-Molina et al., 2009, Hernández-Molina et al., 2010), Vema Channel (Faugères et al., 1998, Faugères et al., 2002) and Scotia Sea (García et al., 2016). Problematically, modern and ancient contourite and mixed contourite-turbidite systems along the Brazilian Equatorial Margin (BEM) are still poorly known (Tallobre et al., 2016; Almeida et al., 2019).
The recent availability of 2D and 3D seismic reflection data acquired for hydrocarbon exploration has made possible to better understand the sedimentary processes governing the evolution of the BEM (De Almeida et al., 2015; Almeida et al., 2019; Jovane et al., 2016; Maestrelli et al., 2020). Here, the recognition and characterization of CDS and mCTS systems are of critical importance as they may help to understand the palaeoceanographic evolution of the basin during the Cenozoic, and shed light on the oceanographic connections between the Northern and Southern hemispheres. In detail, the North Brazil Current (NBC) and the Deep Western Boundary Current (DWBC) contribute to the Atlantic Meridional Overturning Circulation (AMOC) in the Equatorial Atlantic and have influenced the evolution of the BEM since its formation (da Silveira et al., 1994; Wilson et al., 2011; Zhang et al., 2011). The AMOC is essential for the Earth's climate and is related to several climatic, depositional and oceanographic changes around the world (Guihou et al., 2011; Zhang et al., 2015; Mulitza et al., 2017; Lynch-Stieglitz, 2017). Consequently, quantifying the onset and evolution of deep-water depositional systems influenced by the NBC and the DWBC may shed light in longer-term changes in the AMOC, and thus provide new insights on Earth's climate history.
In this study, we mapped and characterized the contourite deposits and associated turbidite channels in the Ceará Basin, Brazil Equatorial Margin, through multiple high-resolution seismic reflection datasets tied to boreholes. The BEM has been developing since the early stages of the Cenozoic, and could provide a better comprehension of equatorial paleoceanography, including the onset and evolution of the deep-water bottom-current circulation in the BEM. Our study documents new contourite and mixed contourite-turbidite systems in the Equatorial Atlantic and emphasizes the importance of the BEM in recording the oceanographic changes occurred during the Cenozoic whilst contributing to the comprehension of how those systems may change and evolve through time
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