Mantle degassing on a near shore volcano,SE Tyrrhenian Sea          下载免费PDF全文

Maria F. Loreto  Francesco Italiano  Davide Deponte  Lorenzo Facchin  Fabrizio Zgur 《地学学报》2015,27(3):195-205

The presence of a seamount‐like structure, located a few nautical miles offshore the Capo Vaticano Promontory (western Calabria, S Italy), was revealed by combined geophysical and geochemical investigation. The edifice covers ~55 km², with a top located at a depth of about 70 m below sea level, and consists mainly of a NW‐trending structure orthogonally interrupted by minor ridges, the largest of which is affected by extensional faults. The top of the edifice hosts active vents, injected fluids that have been investigated for dissolved volatiles. Gas analyses revealed high CO₂ and CH₄ contents, several orders of magnitude above the atmospheric‐type values expected for shallow, coastal marine waters, and a noteworthy enrichment in mantle‐derived ³He, which is an unambiguous indicator of the mantle origin of the fluids. Our results, combined with available data from the literature, suggest that the edifice is a tectonically controlled volcanic system, which presence near the Calabria region changes the role played by faults in the frame of the subduction process.  相似文献   

The Role of Wake Production on the Scaling Laws of Scalar Concentration Fluctuation Spectra Inside Dense Canopies     

D. Poggi  G. G. Katul  B. Vidakovic 《Boundary-Layer Meteorology》2011,139(1):83-95

The scalar concentration fluctuations within a plane parallel-to-the-ground surface were measured inside a model canopy composed of densely arrayed rods using the laser-induced fluorescence technique. Two-dimensional scalar concentration spectra were computed and were shown to exhibit an approximate ?3 power-law scaling at wavenumbers larger than those associated with wake production during quiescent instances when von Karman vortex streets dominated the flow. However, during instances when sweeps disrupted the flow, the spectral exponents increased above ?3. The ?3 power-law for these concentration fluctuation spectra measurements was shown to be consistent with a simplified spectral budget for locally homogeneous and isotropic turbulence augmented with a relaxation time scale similarity argument that assumed a constant enstrophy injection rate and wake generation mechanism. Hence, the origin of this ?3 power-law scaling here differs from the well-known ?3 power-law result for the so-called inertial diffusive range derived for the scalar concentration spectrum at small Prandtl numbers.  相似文献   

Predictive assessment of the asbestos content in the Western Italian Alps: an essential tool for an effective approach to risk analysis and management in tunneling operations and muck reuse     

Davide Labagnara  Mario Patrucco  Piergiorgio Rossetti  Valeria Pellegrino 《Environmental Earth Sciences》2013,70(2):857-868

The modern approach to the design and management of tunnel excavation, and muck reuse, can be influenced to a great extent by the possible presence of rock formations containing asbestos minerals. This situation creates problems concerning the protection of the workers’ health and the expectable environmental criticalities, while a drastic re-consideration of the muck destination is necessary. Since, in the case of carcinogens, corrective action following exposure or dispersion is not acceptable, detailed knowledge of the characteristics of the material to be excavated is all the more essential. Only on this basis it is possible to design the tunneling operations in a prevention through design approach, so that the tunnel driving techniques, fittings and technologies, and special equipment and modus operandi, can grant, where necessary, minimized risk conditions, and make a correct decision on whether, how and when these measures must be fully activated, since such an approach involves a remarkable impact on costs and work organization. In the Western Alps a detailed identification and quantification of the asbestos content in rocks is a difficult task, due to the fact that the asbestos in the host rocks, mainly serpentinite, shows a highly variable distribution, typical of ophiolitic belts throughout the world, as it is mostly associated with joints and shear zones. The possibilities of a predictive assessment of the asbestos content in the formations to be excavated are here discussed, with special reference to the reliability of the achievable results.  相似文献   

Discussion on sea level fluctuations along the Adriatic coasts coupling to climate indices forced by solar activity: Insights into the future of Venice     

Davide Zanchettin  Pietro Traverso  Mario Tomasino   《Global and Planetary Change》2006,50(3-4):226-234

The North Atlantic Oscillation (NAO), which is a dominant circulation pattern in Northern Hemisphere winter, is known to affect sea-level variability in the Mediterranean Sea mainly through the hydrostatic response of water masses to pressure anomalies and changes in evaporation/precipitation budgets. In this study the influence of the NAO on sea levels along the Adriatic coasts is re-assessed in the attempt to uncover the potential causes of the observed high sensitivity of the northern basin to NAO fluctuations. The investigation is focused on the role of the NAO as forcing factor of the winds blowing in the area and of the freshwaters input from the Po River, both of which influence the hydrodynamics of the Northern Adriatic. In addition, some insights into the future of Venice are discussed on the basis of the hypothesis that NAO phases are modulated by the varying solar activity through the intensity of the Earth's geomagnetic activity.  相似文献   

Time-resolved spectroscopy of GRB 021004 reveals a clumpy extended wind     

Davide Lazzati  Rosalba Perna  Joseph Flasher  Vikram V. Dwarkadas  Fabrizio Fiore 《Monthly notices of the Royal Astronomical Society》2006,372(4):1791-1798

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Internal shocks in the jets of radio-loud quasars     

Maddalena Spada  Gabriele Ghisellini  Davide Lazzati †  Annalisa Celotti 《Monthly notices of the Royal Astronomical Society》2001,325(4):1559-1570

The central engine causing the production of jets in radio sources may work intermittently, accelerating shells of plasma with different mass, energy and velocity. Faster but later shells can then catch up slower earlier ones. In the resulting collisions shocks develop, converting some of the ordered bulk kinetic energy into magnetic field and random energy of the electrons which then radiate. We propose that this internal shock scenario , which is the scenario generally thought to explain the observed gamma-ray burst radiation, can also work for radio sources in general, and for blazars in particular. We investigate in detail this idea, simulating the birth, propagation and collision of shells, calculating the spectrum produced in each collision, and summing the locally produced spectra from those regions of the jet which are simultaneously active in the observer's frame. We can thus construct snapshots of the overall spectral energy distribution, time-dependent spectra and light curves. This allows us to characterize the predicted variability at any frequency, study correlations between the emission at different frequencies, specify the contribution of each region of the jet to the total emission, and find correlations between flares at high energies and the birth of superluminal radio knots and/or radio flares. The model has been applied to reproduce qualitatively the observed properties of 3C 279. Global agreement in terms of both spectra and temporal evolution is found. In a forthcoming work, we will explore the constraints that this scenario sets on the initial conditions of the plasma injected in the jet and the shock dissipation for different classes of blazars.  相似文献   

A Combined Remote Sensing–Numerical Modelling Approach to the Stability Analysis of Delabole Slate Quarry,Cornwall, UK     

Mohsen Havaej  John Coggan  Doug Stead  Davide Elmo 《Rock Mechanics and Rock Engineering》2016,49(4):1227-1245

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Using historical climate observations to understand future climate change crop yield impacts in the Southeastern US     

Davide Cammarano  David Zierden  Lydia Stefanova  Senthold Asseng  James J. O’Brien  James W. Jones 《Climatic change》2016,134(1-2):311-326

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The onset of the Messinian salinity crisis in the deep Eastern Mediterranean basin   总被引：1，自引：0，他引：1       下载免费PDF全文

Vinicio Manzi  Rocco Gennari  Stefano Lugli  Davide Persico  Matteo Reghizzi  Marco Roveri  B. Charlotte Schreiber  Ran Calvo  Ittai Gavrieli  Zohar Gvirtzman 《地学学报》2018,30(3):189-198

Astronomical tuning of the Messinian pre‐salt succession in the Levant Basin allows for the first time the reconstruction of a detailed chronology of the Messinian salinity crisis (MSC) events in deep setting and their correlation with marginal records that supports the CIESM ( 2008 ) 3‐stage model. Our main conclusions are (1) MSC events were synchronous across marginal and deep basins, (2) MSC onset in deep basins occurred at 5.97 Ma, (3) only foraminifera‐barren, evaporite‐free shales accumulated in deep settings between 5.97 and 5.60 Ma, (4) deep evaporites (anhydrite and halite) deposition started later, at 5.60 Ma and (5) new and published ⁸⁷Sr/⁸⁶Sr data indicate that during all stages, evaporites precipitated from the same water body in all the Mediterranean sub‐basins. The wide synchrony of events and ⁸⁷Sr/⁸⁶Sr homogeneity implies inter‐sub‐basin connection during the whole MSC and is not compatible with large sea‐level fall and desiccation of the Mediterranean.  相似文献   

Structure and properties of the Adriatic crust in the central‐eastern Southern Alps (Italy) from local earthquake tomography     

Alfio Viganò  Davide Scafidi  Silvana Martin  Daniele Spallarossa 《地学学报》2013,25(6):504-512

Structure and properties of the Adriatic crust were determined from local earthquake tomography around the Giudicarie fault zone (central‐eastern Southern Alps, Italy). Tomographic results, based on well‐suited 436 revised earthquakes (period 1994–2007), have a resolution comparable to the scale of regional geological domains and tectonic structures. The observed strong velocity anomalies correlate well with lithological variations corresponding to different geological domains (particularly magmatic complexes at depth) and with high fracturing and/or presence of fluids along active fault systems (South Giudicarie and Valsugana–Bassano del Grappa–Montello thrusts).  相似文献