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11.
12.
Prof. Dr. Klaus -J. Reutter Marlies Teichmüller Rolf Teichmüller Giorgio Zanzucchi 《International Journal of Earth Sciences》1983,72(3):861-893
The rocks of the Northern Apennines predominantly consist of non-metamorphic terrigeneous deposits (flysches and molasses) some of which are preorogenic, some synorogenic and others postorogenic with respect to the nappe tectonics (Miocene). As plant fragments frequently occur in these sediments, a study of coal rank based on reflectance measurements on vitrinites (% Rm = mean value of the random reflectance in non polarized light) contributes to the clarification of the relation between the orogenic and the palaeogeothermal development. The determination of the Rm values of more than 180 samples from outcrops and three deep drillings revealed some important features. Within the pile of Liguride and Tuscanide nappes, the coal rank increases from the uppermost nappe to the lower nappes until lowgrade metamorphism is reached in the Lower Tuscanides. In the single nappes the rank decreases from the Tyrrhenian coast (internal zone) towards the Po Plain (external zone). This regional trend is disturbed only locally by young post-coalification tectonics. In the uppermost Liguride nappe (M. Antola Unit) a pre-Oligocene (i. e. pre-Apenninic) thermal event was detected. Postorogenic heating is connected with the magmatic activity of Late Miocene to Pleistocene age in Tuscany. Except for these preorogenic and postorogenic thermal events, the main coalification is generally younger than the emplacement of the nappes in the nappe pile during the Apenninic orogeny in the Miocene, but it is older than the last thrust movements and the final tensional tectonics in the internal zones of the chain. For these reasons, the main regional thermal event has to be considered as synorogenic or, more precisely, as late-synorogenic. 相似文献
13.
Coupling of oceanic and continental crust during Eocene eclogite-facies metamorphism: evidence from the Monte Rosa nappe,western Alps 总被引:1,自引:0,他引:1
Thomas J. Lapen Clark M. Johnson Lukas P. Baumgartner Giorgio V. Dal Piaz Susanne Skora Brian L. Beard 《Contributions to Mineralogy and Petrology》2007,153(2):139-157
High precision U–Pb geochronology of rutile from quartz–carbonate–white mica–rutile veins that are hosted within eclogite
and schist of the Monte Rosa nappe, western Alps, Italy, indicate that the Monte Rosa nappe was at eclogite-facies metamorphic
conditions at 42.6 ± 0.6 Ma. The sample area [Indren glacier, Furgg zone; Dal Piaz (2001) Geology of the Monte Rosa massif: historical review and personal comments. SMPM] consists of eclogite boudins that are exposed
inside a south-plunging overturned synform within micaceous schist. Associated with the eclogite and schist are quartz–carbonate–white
mica–rutile veins that formed in tension cracks in the eclogite and along the contact between eclogite and surrounding schist.
Intrusion of the veins at about 42.6 Ma occurred at eclogite-facies metamorphic conditions (480–570°C, >1.3–1.4 GPa) based
on textural relations, oxygen isotope thermometry, and geothermobarometry. The timing of eclogite-facies metamorphism in the
Monte Rosa nappe determined in this study is identical to that of the Gran Paradiso nappe [Meffan-Main et al. (2004) J Metamorphic Geol 22:261–281], confirming that these two units have shared the same Alpine metamorphic history. Furthermore,
the Gran Paradiso and Monte Rosa nappes underwent eclogite-facies metamorphism within the same time interval as the structurally
overlying Zermatt-Saas ophiolite [∼50–40 Ma; e.g., Amato et al. (1999) Earth Planet Sci Lett 171:425–438; Mayer et al. (1999) Eur Union Geosci 10:809 (abstract); Lapen et al. (2003) Earth Planet Sci Lett 215:57–72]. The nearly identical P–T–t histories of the Gran Paradiso, Monte Rosa, and Zermatt-Saas units suggest that these units shared a common Alpine tectonic
and metamorphic history. The close spatial and temporal associations between high pressure (HP) ophiolite and continental
crust during Alpine orogeny indicates that the HP internal basement nappes in the western Alps may have played a key role
in exhumation and preservation of the ophiolitic rocks through buoyancy-driven uplift. Coupling of oceanic and continental
crust may therefore be critical in preventing permanent loss of oceanic crust to the mantle. 相似文献
14.
Earthquake early warning systems (EEWS) seem to have potential as tools for real‐time seismic risk management and mitigation. In fact, although the evacuation of buildings requires warning time not available in many urbanized areas threatened by seismic hazard, they may still be used for the real‐time protection of critical facilities using automatic systems in order to reduce the losses subsequent to a catastrophic event. This is possible due to the real‐time seismology, which consists of methods and procedures for the rapid estimation of earthquake features, as magnitude and location, based on measurements made on the first seconds of the P‐waves. An earthquake engineering application of earthquake early warning (EEW) may be intended as a system able to issue the alarm, if some recorded parameter exceeds a given threshold, to activate risk mitigation actions before the quake strikes at a site of interest. Feasibility analysis and design of such EEWS require the assessment of the expected loss reduction due to the security action and set of the alarm threshold. In this paper a procedure to carry out these tasks in the performance‐based earthquake engineering probabilistic framework is proposed. A merely illustrative example refers to a simple structure assumed to be a classroom. Structural damage and non‐structural collapses are considered; the security action is to shelter occupants below the desks. The cost due to a false alarm is assumed to be related to the interruption of didactic activities. Results show how the comparison of the expected losses, for the alarm‐issuance and non‐issuance cases, allows setting the alarm threshold on a quantitative and consistent basis, and how it may be a tool for the design of engineering applications of EEW. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
15.
Geologic remote sensing (Ninth Thematic Conference) 相似文献
16.
Giorgio Ranalli 《Pure and Applied Geophysics》1973,104(1):507-512
Summary The seismic strength (resistance to sudden failure) of the seismically active regions of the crust and upper mantle is estimated and is found to be maximum at depths of 50 to 125 km. The pattern of strength versus depth can be explained in terms of lithospheric plate sinking beneath an ocean trench. The lack of earthquakes at depths larger than 700 km is probably due to decreasing shear stress rather than vanishing seismic strength.
Résumé Dans cette communication on évalue la résistance à la rupture séismique des matériaux constituant l'écorce et le manteau supérieur de la Terre. Les résultats indiquent la présence d'un maximum à la profondeur de 50–125 km. La distribution de la résistance avec la profondeur peut être expliquée par la résorption de la lithosphère au-dessous d'un fossé océanique. L'absence de séismes dans les zones plus profondes (z>700 km) n'est pas due à la réduction de la résistance séismique, mais très probablement à l'insuffisance des tensions internes dans les matériaux.相似文献
17.
Carmela Freda Mario Gaeta Daniel B. Karner Fabrizio Marra Paul R. Renne Jacopo Taddeucci Piergiorgio Scarlato John N. Christensen Luigi Dallai 《Bulletin of Volcanology》2006,68(6):567-591
A comprehensive volcanological study of the Albano multiple maar (Alban Hills, Italy) using (i) 40Ar/39Ar geochronology of the most complete stratigraphic section and other proximal and distal outcrops and (ii) petrographic observations,
phase analyses of major and trace elements, and Sr and O isotopic analyses of the pyroclastic deposits shows that volcanic
activity at Albano was strongly discontinuous, with a first eruptive cycle at 69±1 ka producing at least two eruptions, and
a second cycle with two peaks at 39±1 and 36±1 ka producing at least four eruptions. Contrary to previous studies, we did
not find evidence of magmatic or hydromagmatic eruptions younger than 36±1 ka. The activity of Albano was fed by a new batch
of primary magma compositionally different from that of the older activity of the Alban Hills; moreover, the REE and 87Sr/86Sr data indicate that the Albano magma originated from an enriched metasomatized mantle. According to the modeled liquid line
of descent, this magma differentiated under the influence of magma/limestone wall rock interaction. Our detailed eruptive
and petrologic reconstruction of the Albano Maar evolution substantiates the dormant state of the Alban Hills Volcanic District.
Electronic Supplementary Material Supplementary material is available for this article at
Editorial responsibility: J. Donnelly-Nolan
An erratum to this article can be found at 相似文献
18.
The availability of reliable constitutive models linking the bulk electric properties of porous media to their inner structure is a key requirement for useful quantitative applications of noninvasive methods. This study focuses on the use of dielectric measurements to monitor fluid saturation changes in porous materials. A number of empirical, semi-empirical and theoretical relationships currently exists that link the bulk dielectric constant with volumetric water content. One such relationship, named complex refractive index model or Lichteneker-Rother model has been extensively applied in recent years. Here we first analyse the characteristics of this Lichteneker-Rother model by means of theoretical considerations. This theoretical analysis indicates that the Lichteneker-Rother exponent is dependent upon the geometrical properties of the porous structure, as well as the permittivity contrast between the different phases. Pore-scale modelling and experimental data further support this result. The parameter estimation robustness in presence of synthetic data error is also assessed. This demonstrates that Lichteneker-Rother parameters cannot, in general, be independently identified on the basis of bulk dielectric constant versus moisture content data. 相似文献
19.
A structural and geophysical approach to the study of fractured aquifers in the Scansano-Magliano in Toscana Ridge, southern Tuscany, Italy 总被引:1,自引:0,他引:1
Roberto Francese Francesco Mazzarini Andrea Bistacchi Gianfranco Morelli Giorgio Pasquarè Nicola Praticelli Henry Robain Nigel Wardell Annalisa Zaja 《Hydrogeology Journal》2009,17(5):1233-1246
Fresh water availability has recently become a serious concern in the Italian Apennines, as various activities rely on a predictable supply. Along the ridge between Scansano and Magliano in Toscana, in southern Tuscany, the situation is further complicated by contamination of the nearby alluvial aquifers. Aquifers locally consist of thin fractured reservoirs, generally within low-permeability formations, and it can be difficult to plan the exploitation of resources based on conventional techniques. An integrated study based on geological data investigated the link between tectonics and groundwater circulation, to better define the hydrological model. After the regional identification of fault and fracture patterns, a major structure was investigated in detail to accurately map its spatial position and to understand the geometry and properties of the associated aquifer and assess its exploitation potential. The subsurface around the fault zone was clearly imaged using ground probing radar, two-dimensional and three-dimensional resistivity tomography, and three-dimensional shallow seismic surveys. The vertical and horizontal contacts between the different geological units of the Ligurian and Tuscan series were resolved with a high degree of spatial accuracy. Three-dimensional high-resolution geophysical imaging proved to be a very effective means of characterising small-scale fractured reservoirs. 相似文献
20.
Pieralberto Maianti Marco Rusmini Riccardo Tortini Giorgio Dalla Via Federico Frassy Andrea Marchesi Francesco Rota Nodari Marco Gianinetto 《Natural Hazards》2014,73(2):473-492
Accidental release of crude oil into the sea due to human activity causes water pollution and heavy damages to natural ecosystems killing birds, fish, mammals and other organisms. A number of monitoring systems are used for tracking the spills and their effects on the marine environment, as well as for collecting data for feeding models. Among them, Earth observation technologies play a crucial role and moderate spatial resolution satellite systems are able to collect images with a very short revisit time or even daily. This paper describes the use of Moderate-Resolution Imaging Spectroradiometer data for monitoring large oil slicks with the fluorescence/emissivity index and object-based image analysis. Two case studies are presented: the Deepwater Horizon (2010) and the Campos Basin (2011) oil spill accidents. Results show that it is possible to track the dynamics of the slick both for massive and long-lasting accidents and for smaller and very quick accidents. The main advantages of the method proposed are a straightforward implementation, a fast and semi-automated data processing and the capability of integration of daytime and nighttime acquisitions, as well as its adaptability to different sensors. 相似文献