Ground deformations in collapsed caldera structures     

Giuseppe De Natale  Folco Pingue 《Journal of Volcanology and Geothermal Research》1993,57(1-2)

A method is presented to analyze the effect of stress-strain discontinuities on the ground deformations generated by a pressure source. This is meant to simulate the effects due to caldera structures, likely to present fractured zones at the borders of the collapsed area. A method originally developed by Crouch (1976) to solve plane-strain problems has been used to simulate deformation curves for several source and discontinuity geometries. The main result is that the location of the discontinuities controls the extension of the deformed zone, and always reduces it with respect to a continuous medium. With respect to a homogeneous medium the presence of lateral discontinuities also acts towards lowering the overpressure required to produce a given amount of deformation. These results indicate that, when analyzing ground deformations in calderas, the use of classical methods involving continuous media should be avoided, or at least taken with caution. These methods, in fact, assume that the extension of the deformed zone is only linked to the source depth.Some examples of ground deformations in active calderas have been analyzed in the framework of the results obtained from theoretical modeling. Four calderas recently affected by ground deformations have been considered: Rabaul (New Guinea), Campi Flegrei (Italy), Long Valley and Yellowstone (U.S.A.). The effects of collapsed structures on the deformation field are possibly evidenced for all the four calderas. At Rabaul and Campi Flegrei, the fracture systems mainly affecting the ground deformations probably represent younger, innermost collapses and are well evidenced by seismicity studies. Ground deformations are here concentrated in an area much smaller than the one enclosed by geologically visible caldera rims. In particular, at Rabaul, the effect of the innermost collapse can explain the high concentration of the uplift in the period 1971–1985, previously modeled by a very shallow source (1–3 km) in terms of overpressure in the main magma chamber, probably located at 4–5 km of depth.  相似文献   

Crystal-chemistry of a unique jadeite-rich acmite-poor omphacite from the Nybø eclogite pod,Sørpollen,Nordfjord, Norway     

David C. Smith  Annibale Mottana  Giuseppe Rossi 《Lithos》1980,13(3):227-236

An omphacite from the Nybø eclogite pod, Norway, has a chemical composition which plots within the gap, often regarded as a miscibility gap, which is evident in all previous compilations of natural jadeite-rich acmite-poor omphacite compositions. Its cation site populations determined by crystal structure refinement accord well with its chemical composition analysed by electron microprobe. Its disordered space group C2/c symmetry extends the known compositional range of C2/c pyroxene. The postulated miscibility gap is regarded as real and wide at low temperatures, but it appears to narrow with increasing temperature or ultimately with increasing acmite proportion. The adjacent primitive symmetry field appears to initially widen with increasing temperature or increasing acmite proportion, at the expense of the diminishing miscibility gap, before finally closing with further increase.  相似文献   

Trace elements in tentacles from the jellyfish Pelagia noctiluca     

Giuseppe Cimino  Maria Alfa  Giuseppina La Spada 《Marine pollution bulletin》1983,14(5):197-198

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The gravitational field of a homogeneous hemisphere     

Giuseppe E. Ratti 《Pure and Applied Geophysics》1967,68(1):5-10

Summary After remarking that the homogeneous hemisphere might be adopted as a model to represent various geological bodies in the quantitative interpretation of gravity anomalies, a finite expression for its gravitational potential is derived.

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Riassunto Dopo aver rilevato che la semisfera omogenea potrebbe essere adottata quale modello per rappresentare var corpi geologici nell'interpretazione quantitativa di anomalie di gravità, si deriva una espressione finita per il potenziale gravitazionale di tale figura.

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This work has been presented at the XIV General Meeting of the Italian Society of Geophysics and Meteorology (Genova, April 14–15, 1966).  相似文献   

Polychlorinated biphenyl and organochlorine pesticide residues in Lophius budegassa from the Mediterranean Sea (Italy)     

Storelli MM  Storelli A  Barone G  Marcotrigiano GO 《Marine pollution bulletin》2004,48(7-8):743-748

Persistent organochlorines, such as polychlorinated biphenyls, including coplanar congeners and DDT compounds, were measured in the liver of a teleost species: namely, Lophius budegassa. The mean concentrations of PCBs (1249 ng/g wet wt) were comparable with DDTs mean levels (1459 ng/g wet wt). Among DDTs the compound found at the highest concentration was p,p'-DDE representing 76% of the total DDT burden. The PCB profiles were dominated by congeners 153, 180, and 138 accounting for 49.8%, 16.0% and 13.7% of the total PCBs. The total 2,3,7,8-TCDD toxic equivalent (TEQs) of six coplanar PCBs, including mono- and non-ortho congeners, was 0.98 pg/g wet wt. The congeners with highest TEQs values were non-ortho-congeners followed by mono-ortho ones.  相似文献   

3-D Modelling of Campi Flegrei Ground Deformations: Role of Caldera Boundary Discontinuities     

Fran?ois?Beauducel  Giuseppe De?Natale  Franco?Obrizzo  Folco?PingueEmail author 《Pure and Applied Geophysics》2004,161(7):1329-1344

Campi Flegrei is a caldera complex located west of Naples, Italy. The last eruption occurred in 1538, although the volcano has produced unrest episodes since then, involving rapid and large ground movements (up to 2 m vertical in two years), accompanied by intense seismic activity. Surface ground displacements detected by various techniques (mainly InSAR and levelling) for the 1970 to 1996 period can be modelled by a shallow point source in an elastic half-space, however the source depth is not compatible with seismic and drill hole observations, which suggest a magma chamber just below 4 km depth. This apparent paradox has been explained by the presence of boundary fractures marking the caldera collapse. We present here the first full 3-D modelling for the unrest of 1982–1985 including the effect of caldera bordering fractures and the topography. To model the presence of topography and of the complex caldera rim discontinuities, we used a mixed boundary elements method. The a priori caldera geometry is determined initially from gravimetric modelling results and refined by inversion. The presence of the caldera discontinuities allows a fit to the 1982–1985 levelling data as good as, or better than, in the continuous half-space case, with quite a different source depth which fits the actual magma chamber position as seen from seismic waves. These results show the importance of volcanic structures, and mainly of caldera collapses, in ground deformation episodes.  相似文献   

Non-integrability of a Weakly Integrable Hamiltonian System     

Giuseppe Pucacco  Kjell Rosquist 《Celestial Mechanics and Dynamical Astronomy》2004,88(2):185-207

The geometric approach to mechanics based on the Jacobi metric allows to easily construct natural mechanical systems which are integrable (actually separable) at a fixed value of the energy. The aim of the present paper is to investigate the dynamics of a simple prototype system outside the zero-energy hypersurface. We find that the general situation is that in which integrability is not preserved at arbitrary values of the energy. The structure of the Hamiltonian in the separating coordinates at zero energy allows a perturbation treatment of this system at energies slightly different from zero, by which we obtain an analytical proof of non-integrability.This revised version was published online in October 2005 with corrections to the Cover Date.  相似文献   

Magma ascent and eruptive processes from textural and compositional features of Monte Nuovo pyroclastic products, Campi Flegrei, Italy     

Monica Piochi  Giuseppe Mastrolorenzo  Lucia Pappalardo 《Bulletin of Volcanology》2006,68(5):496-496

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Field investigations and monitoring as tools for modelling the Rossena castle landslide (Northern Appennines, Italy)     

Alessandro Chelli  Giuseppe Mandrone  Giovanni Truffelli 《Landslides》2006,3(3):252-259

In the evening of February 28, 2004, a landslide took place in the village of Rossena (Northern Apennines, Italy), built at the base of a crag shaped in a basalt mass and wrapped in highly deformed formation of clay and shale with blocks. The failure damaged some houses, roads and fields but, fortunately, the medieval Rossena Castle, lying on the crag, was not involved at all. The goal of the study was to attain a technical and geological model of the slope to generate a landslide risk zonation, for regularity and development planning, so that the most correct action plans could be proposed. A detailed geological and geomorphological survey allowed for distinguishing the different gravitative landform of this area. It was very helpful to plan direct and indirect investigation, including borehole drillings, samplings, seismic (tomography), and electrical surveys. A monitoring system was built up immediately after the event (three wire extensometers and one inclinometer), then progressively substituted by a more complete one (two tiltmeters, two jointmeters, four inclinometers, two incremental extensometers, and two piezometers). The phenomenon can be divided in different parts. The central sector of the slope is interested by compound slides likely affecting the bedrock and can be considered, at present, the ‘engine’ of the whole instability framework. Indeed, as a consequence, in the upper portion of the slope the huge blocks in which the outer part of the crag is disjointed experienced vertical displacements and, locally, topplings. Finally, the lowest sector is affected by slow movements, probably connected to bedrock creep or rock flow, while the toe, really at the foot of the slope, by shallow landslides. This instability framework is the result of a complex evolution, starting almost more than 9,000 years ago, as testified from a radiocarbon dating. In more recent time (19th century), the Rossena landslide was also triggered by an earthquake that induced the partially breaking up of the crag, causing rock falls and cracks in the ground.  相似文献   

Use of Plume Mapping Data to Estimate Chlorinated Solvent Mass Loss     

Jeffrey R. Barbaro  Pradumna P. Neupane 《Ground Water Monitoring & Remediation》2006,26(4):115-127

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