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91.
Isotope analyses of lavas from the Hyblean Plateau (SE Sicily) provided first order constraints for the characterization of the relative magma sources, contributing to a better understanding of the tectono-magmatic evolution of the northernmost part of the African plate. To integrate this research, we are currently studying ultramafic xenoliths of mantle provenance exhumed by the Hyblean alkaline volcanics. These mainly consist of anhydrous spinel-facies peridotites and subordinate pyroxenites/websterites. The paragenesis of the latter is extremely variable in terms of modal proportions and mineral composition, with clinopyroxene composition ranging from Cr-diopside to Al-augite, and variable amount of spinel ± garnet. New Sr-Nd isotopic analyses carried out on hand-picked (and leached) clinopyroxenes indicate that peridotites have 87Sr/86Sr ranging from 0.70288 to 0.70309, and 143Nd/144Nd from 0.51287 to 0.51292. This Sr-Nd isotopic fingerprint approaches that of the HIMU mantle end-member, regionally referred as EAR (European Astenospheric Reservoir) to emphasize a connection with a sub-lithospheric metasomatic component ubiquitous throughout Europe, the Mediterranean area and North Africa. The Sr-Nd analyses of pyroxenites also reveal an EAR affinity, but are slightly distinct from those of peridotites. They display 87Sr/86Sr ranging between 0.70305–0.70326 and 143Nd/144Nd between 0.51292–0.51299, overlapping the composition typical of the Hyblean alkaline lavas. This possibly implies that pyroxene-rich domain significantly contributed to the genesis of the Hyblean magmas. Therefore, the presented Sr-Nd isotopic ratios suggest that the role of the pyroxene-rich mantle portions was more important than commonly considered in the petrogenetic models of Hyblean magmas. This scenario would be coherent with recent evidences highlighting the importance of pyroxenites (together with peridotites) as contributing sources to basalt generation. 相似文献
92.
Federico Rossetti Mohsen Nasrabady Gianluca Vignaroli Thomas Theye Axel Gerdes Mohammad Hossein Razavi Hosein Moin Vaziri 《地学学报》2010,22(1):26-34
The ophiolitic mélange of the Sabzevar Range (northern Iran) is a remnant of the Mesozoic oceanic basins on the northern margin of the Neotethys that were consumed during the Arabia–Eurasia convergence history. Occurrence of km-scale, dismembered mafic HP granulitic slices is reported in this study. Granulites record an episode of amphibole-dehydratation melting and felsic (tonalite/throndhjemite) melt segregation at c. 1.1 GPa and 800 °C. In situ U(-Th)–Pb geochronology of zircon and titanite grains hosted in melt segregations points to an Early Cretaceous (Albian) age for the metamorphic climax. Results of this study (i) impose reconsideration of the current palaeotectonic models of the Neothetyan convergent margin during the Early Cretaceous and (ii) argue that punctuated events of subduction of short-lived back-arc oceanic basins accompanied the long-lasting history of the Neotethyan subduction in the region. 相似文献
93.
The paper presents the results of a major assessment of Code adoption and implementation in nine fishing countries in Asia (China, Thailand, Vietnam), Africa (Senegal, Guinea Bissau and Guinea) and in the Caribbean (Jamaica, Dominican Republic and Trinidad & Tobago), which are part of the international research project ECOST. The main findings are that the Code as an international policy instrument remains relevant and adaptable to the current international fisheries context, and that its guiding principles and provisions have been endorsed and adopted in almost unanimous fashion by the countries covered, and integrated into fisheries policy letters and legal frameworks. However, results also suggest that tackling the truly difficult issues in fisheries, such as combating illegal, unreported and unregulated (IUU) fishing or adjusting fishing overcapacity has been a lot less successful. The design and implementation of necessary measures often remains very weak in domains with important economic and political dimensions. The causes for this are attributed to a mix of administrative inertia, lack of political will and stamina, and short-sighted economic considerations. 相似文献
94.
Roberto Tonini Alberto Armigliato Gianluca Pagnoni Stefano Tinti 《Natural Hazards》2014,70(2):1507-1525
The M w = 9.1 mega-thrust Sumatra–Andaman earthquake that occurred on December 26, 2004, was followed by a devastating tsunami that killed hundreds of thousands of people and caused catastrophic effects on human settlements and environments along many coasts of the Indian Ocean, where even countries very far from the source were affected. One of these cases is represented by the Republic of Seychelles, where the tsunami reached the region about 7 h after the earthquake and produced relevant damages, despite the country was more than 4,500 km far from the seismic source. In the present work, we present and discuss a study of the 2004 Sumatra tsunami by means of numerical simulations with the attention focused on the effects observed at the Seychelles Archipelago, a region never previously investigated with this approach. The case is interesting since these islands lay on a very shallow oceanic platform with steep slopes so as the ocean depth changes from thousands to few tens of meters over short distances, with significant effects on the tsunami propagation features: the waves are strongly refracted by the oceanic platform and the tsunami signal is modified by the introduction of additional frequencies. The study is used also to validate the UBO-TSUFD numerical code on a real tsunami event in the far field, and the results are compared with the available observations, i.e., the sea level time series recorded at the Pointe La Rue station, Mahé Island, and run-up measurements and inundation lines surveyed few weeks after the tsunami at Praslin Island, where the tsunami hit during low tide. Synthetic results are found in good agreement with observations, even though some of the observations remain not fully solved. Moreover, simulations have been run in high-tide condition since the 2004 Sumatra tsunami hitting at high tide can be taken as the worst-case scenario for the Seychelles islands and used for tsunami hazard and risk assessments. 相似文献
95.
Alessandro Pisa Filippo Frontera Gianluca Loffredo Damiano Pellicciotta Natalia Auricchio 《Experimental Astronomy》2005,20(1-3):219-228
We report on preliminary results obtained with a Monte Carlo (MC) code developed to study the optical properties of Laue lenses for astro-physical observations. The MC code is written in the Python programming language and uses open source libraries. Among the physical quantities which can be investigated with the MC code, we paid our attention mainly to the estimation of the effective area, field of view (FOV) and point spread function (PSF) of the lens for observation of sources on-axis and off-axis. 相似文献
96.
97.
Paul Eccleston Bruce Swinyard Marcel Tessenyi Giovanna Tinetti Ingo Waldmann Marc Ferlet Ranah Irshad Tanya Lim Kevin Middleton Tom Bradshaw Martin Crook Tom Hunt Berend Winter Ian Bryson Naidu Bezawada William Taylor Neil Bowles Enzo Pascale Gianluca Morgante Emanuele Pace Alberto Adriani Jean-Michel Reess Marc Ollivier Roland Ottensamer Mirek Rataj Gonzalo Ramos Zapata Jan-Rutger Schrader Avri Selig Kate Isaak Martin Linder Ludovic Puig 《Experimental Astronomy》2015,40(2-3):427-447
98.
How to assess landslide activity and intensity with Persistent Scatterer Interferometry (PSI): the PSI-based matrix approach 总被引:5,自引:4,他引:1
We provide a step-by-step analysis and discussion of the ‘PSI-based matrix approach’, a methodology employing ground deformation velocities derived through Persistent Scatterer Interferometry (PSI) for the assessment of the state of activity and intensity of extremely to very slow landslides. Two matrices based on PSI data are designed respectively for landslides already mapped in preexisting inventories and for newly identified phenomena. Conversely, a unique intensity scale is proposed indiscriminately for both. Major influencing factors of the approach are brought to light by the application in the 14 km2 area of Verbicaro, in Northern Calabria (Italy). These include lack of PSI data within the landslide boundaries, temporal coverage of the available estimates, and need of field checks as well as the operative procedures to set the activity and intensity thresholds. For the area of Verbicaro, we exploit 1992–2011 PSI data from ERS1/2 and RADARSAT1/2 satellites, projecting them along the maximum slope directions. An activity threshold of ±5 mm/year is determined by applying the average projection factor of local slopes to the PSI data precision. The intensity threshold between extremely and very slow phenomena (16 mm/year) is reduced by ~20 % to account for temporal and spatial averages being applied to attribute representative velocities to each landslide. The methodology allows assessing the state of activity and the intensity for 13 of the 24 landslides premapped in the 2007 inventory and for two newly identified phenomena. Current limitations due to characteristics and spatial coverage of PSI data are critically tackled within the discussion, jointly with respective implications. 相似文献
99.
Giuseppe Maddaloni Nicola Caterino Gianluca Nestovito Antonio Occhiuzzi 《Bulletin of Earthquake Engineering》2013,11(6):2407-2428
The seismic events occurred in recent years highlighted the extreme vulnerability of large part of the existing constructed facilities and the need to adopt innovative solutions to improve their seismic performance. With this purpose, the possible exploitation of a seismic early warning system (SEWS) in the framework of semi-active structural control using magnetorheological (MR) dampers is herein investigated. The main idea consists in the use of these time-varying properties devices to control an hosting structure by changing their behaviour according to an anticipate estimate, provided by the SEWS, of the peak ground acceleration (PGA) of the incoming earthquake. In this way, the dampers are able to adapt their mechanical characteristics to the specific earthquake obtaining the optimal seismic response. The present paper describes the application of this protection technique to a case-study problem, a highway bridge located in Southern California. The seismic response of the benchmark bridge is investigated by nonlinear time-history analyses by adopting 16 real earthquake ground excitations. These accelerograms cover a wide variety of magnitudes, distances to fault and soil types. Possible errors on estimation of PGA provided by SEWS and their effects on the proposed control system are also considered. The results obtained confirm that unavoidable errors in the PGA estimates provided by the SEWS do not propagate to the seismic response. Conversely, the proposed strategy turns out to damp these errors, resulting in a robust seismic behaviour of the protected structure. 相似文献
100.
Gianluca Sottili Danilo M. Palladino Biagio Giaccio Paolo Messina 《Mathematical Geosciences》2012,44(5):619-634
Benford’s analysis is applied to the recurrence times of approximately 17,000 seismic events in different geological contexts
of Italy over the last 6 years, including the Mt. Etna volcanic area and the seismic series associated with the destructive
M
w 6.3, 2009 L’Aquila earthquake. A close conformity to Benford’s law and a power-law probability distribution for the recurrence
times of consecutive events is found, as typical of random multiplicative processes. The application of Benford’s law to the
recurrence event times in seismic series of specific seismogenic regions represents a novel approach, which enlarges the occurrence
and relevance of Benford-like asymmetries, with implications on the physics of natural systems approaching a power law behaviour.
Moreover, we propose that the shift from a close conformity of Benford’s law to Brownian dynamics, observed for time separations
among non-consecutive events in the study seismic series, may be ruled by a periodical noise factor, such as the effects of
Earth tides on seismicity tuning. 相似文献