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371.
Michel Pichavant Ida Di Carlo Silvio G. Rotolo Bruno Scaillet Alain Burgisser Nolwenn Le Gall Caroline Martel 《Contributions to Mineralogy and Petrology》2013,166(2):545-561
To test mechanisms of basaltic magma degassing, continuous decompressions of volatile-bearing (2.7–3.8 wt% H2O, 600–1,300 ppm CO2) Stromboli melts were performed from 250–200 to 50–25 MPa at 1,180–1,140 °C. Ascent rates were varied from 0.25 to ~1.5 m/s. Glasses after decompression show a wide range of textures, from totally bubble-free to bubble-rich, the latter with bubble number densities from 104 to 106 cm?3, similar to Stromboli pumices. Vesicularities range from 0 to ~20 vol%. Final melt H2O concentrations are homogeneous and always close to solubilities. In contrast, the rate of vesiculation controls the final melt CO2 concentration. High vesicularity charges have glass CO2 concentrations that follow theoretical equilibrium degassing paths, whereas glasses from low vesicularity charges show marked deviations from equilibrium, with CO2 concentrations up to one order of magnitude higher than solubilities. FTIR profiles and maps reveal glass CO2 concentration gradients near the gas–melt interface. Our results stress the importance of bubble nucleation and growth, and of volatile diffusivities, for basaltic melt degassing. Two characteristic distances, the gas interface distance (distance either between bubbles or to gas–melt interfaces) and the volatile diffusion distance, control the degassing process. Melts containing numerous and large bubbles have gas interface distances shorter than volatile diffusion distances, and degassing proceeds by equilibrium partitioning of CO2 and H2O between melt and gas bubbles. For melts where either bubble nucleation is inhibited or bubble growth is limited, gas interface distances are longer than volatile diffusion distances. Degassing proceeds by diffusive volatile transfer at the gas–melt interface and is kinetically limited by the diffusivities of volatiles in the melt. Our experiments show that CO2-oversaturated melts can be generated as a result of magma decompression. They provide a new explanation for the occurrence of CO2-rich natural basaltic glasses and open new perspectives for understanding explosive basaltic volcanism. 相似文献
372.
A representation of seismic hazard is proposed for Italy based on the zone-free approach developed by Woo (BSSA 86(2):353–362, 1996a), which is based on a kernel estimation method governed by concepts of fractal geometry and self-organized seismicity, not requiring the definition of seismogenic zoning. The purpose is to assess the influence of seismogenic zoning on the results obtained for the probabilistic seismic hazard analysis (PSHA) of Italy using the standard Cornell’s method. The hazard has been estimated for outcropping rock site conditions in terms of maps and uniform hazard spectra for a selected site, with 10 % probability of exceedance in 50 years. Both spectral acceleration and spectral displacement have been considered as ground motion parameters. Differences in the results of PSHA between the two methods are compared and discussed. The analysis shows that, in areas such as Italy, characterized by a reliable earthquake catalog and in which faults are generally not easily identifiable, a zone-free approach can be considered a valuable tool to address epistemic uncertainty within a logic tree framework. 相似文献
373.
Michele Palermo Stefano Silvestri Tomaso Trombetti Luca Landi 《Bulletin of Earthquake Engineering》2013,11(5):1661-1681
This research work focuses on the analysis of the hysteretic seismic behaviour of inelastic SDOF systems equipped with viscous dampers. In detail, it is aimed at obtaining a practical tool useful for the seismic design of building structures with added dampers, within the framework of the traditional seismic design based on ductility. The objective is to evaluate the appropriate force reduction factor for highly damped (i.e. damping ratio greater than 5 %) SDOF systems able to guarantee a prescribed level of structural safety. 相似文献
374.
On the dimensioning of viscous dampers for the mitigation of the earthquake-induced effects in moment-resisting frame structures 总被引:1,自引:1,他引:0
Michele Palermo Saverio Muscio Stefano Silvestri Luca Landi Tomaso Trombetti 《Bulletin of Earthquake Engineering》2013,11(6):2429-2446
The effectiveness of viscous dampers in mitigating the seismic excitation impacts upon building structures has been widely proved. Recently, with reference to the specific case of equal mass, equal stiffness, shear-type structures, the authors developed a direct practical procedure which gives the mechanical characteristics of the manufactured viscous dampers capable of providing the frame structure with a prescribed value of the first damping ratio. In this paper, a comprehensive rational framework is presented, which allows to formally extend the validity of the proposed procedure to the more realistic case of a generic moment-resisting frame structure. Also the influence of various lateral stiffness distributions is investigated. 相似文献
375.
Stephen Serjeant † Alberto Carramiñana † Eduardo Gonzáles-Solares Phillipe Héraudeau Raúl Mújica † Ismael Perez-Fournon Nicola Sedgwick † Michael Rowan-Robinson Alberto Franceschini Thomas Babbedge Carlos del Burgo Paolo Ciliegi reas Efstathiou Fabio La Franca Carlotta Gruppioni David Hughes Carlo Lari Seb Oliver Francesca Pozzi Manfred Stickel Mattia Vaccari 《Monthly notices of the Royal Astronomical Society》2004,355(3):813-818
376.
377.
Massimiliano Ferronato Giuseppe Gambolati Carlo Janna Pietro Teatini 《国际地质力学数值与分析法杂志》2008,32(6):633-657
The stress variation induced by gas/oil production may activate pre‐existing regional faults. This may enhance the expected land subsidence due to the generation of mechanically weak points close to the producing field. A class of elasto‐plastic interface elements (IE), specifically designed to address the mechanical behaviour of faults over a regional scale, is integrated into a finite element (FE) geomechanical model and used to investigate the role exerted by active faults in anthropogenic land subsidence. The importance of regional faults depends on a variety of factors including depth of the depleted reservoir, fault number, orientation and size, geomechanical properties of porous medium, pore pressure drawdown induced by fluid production, etc. With the aid of some representative examples, a useful indication is provided as to where and how fault activation may influence both magnitude and extent of the land subsidence bowl above producing gas/oil reservoirs, pointing to a generally limited impact on the ground surface. The simulation of a real faulted gas reservoir in a complex 3‐D setting shows that the proposed IE can be simply and efficiently incorporated into a FE geomechanical model, thus improving the quality of the stress and displacement prediction. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
378.
Climate change and warm‐water species at the north‐western boundary of the Mediterranean Sea 下载免费PDF全文
Valeriano Parravicini Luisa Mangialajo Laure Mousseau Andrea Peirano Carla Morri Monica Montefalcone Patrice Francour Michel Kulbicki Carlo Nike Bianchi 《Marine Ecology》2015,36(4):897-909
The effects of global change are particularly serious in areas where range shifts of species are physically constrained such as the Ligurian Sea, which is one of the coldest sectors of the Mediterranean. In this basin, historical information on water temperature (from the sea surface down to 75 m depth) dates back to the 1950s. Early studies also recorded warm‐water species occurrence. Thanks to these data we provide the first detailed characterization of water temperature variation from 1958 up to 2010 in the layer 0–75 m depth. We coupled this analysis with the available information on rocky reef epibenthic communities (literature review from 1955 to 1964 and field data from 1980 to 2010). The analysis of water temperature revealed several patterns of variation: a cooling phase from 1958 to 1980, a phase of rapid warming from 1980 to 1990 and a phase of slower warming from 1990 to 2010. Inter‐annual variation in temperature increased over the entire period for the water layer down to 20 m. Warm‐water native and alien species richness increased during the warming phases. Literature estimates suggest a decrease in warm‐water native species richness during the cooling phase. The analysis of quantitative data collected in the early 1990s and late 2000s indicated a decrease in the cover of warm‐water native species on shallow rocky reefs and an increase in deeper waters. We argue that increased inter‐annual variation in water temperature may disadvantage native warm‐water species in shallow waters. Our results indicate that the effect of temperature rises in cold, constrained basins may be more complex than the simple prediction of species changing their geographical range according to their thermal limits. 相似文献
379.
Cintolesi Carlo Pulvirenti Beatrice Sabatino Silvana Di 《Boundary-Layer Meteorology》2021,180(1):79-104
Boundary-Layer Meteorology - Techniques for improving the removal of pollution from urban canyons are crucial for air quality control in cities. The removal mainly occurs at the building roof... 相似文献
380.
Manzini Carlo Filippo Ottonelli Daria Degli Abbati Stefania Marano Corrado Cordasco Emilia Angela 《Bulletin of Earthquake Engineering》2022,20(4):2045-2084
Bulletin of Earthquake Engineering - The paper presents the comparison of the results of non-linear static analyses performed with different software based on the equivalent frame (EF) modelling... 相似文献