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121.
Pierre Bouilhol Urs Schaltegger Massimo Chiaradia Maria Ovtcharova Andreas Stracke Jean-Pierre Burg Hamid Dawood 《Chemical Geology》2011,280(3-4):243-256
The combination of age determination and geochemical tracers allows understanding the source evolution during magmatism. We studied the Sapat Complex, in the exhumed Cretaceous Kohistan Paleo-Island Arc, to reconstruct the formation of the juvenile lower arc crust and the evolution of the mantle source during arc magmatism. High precision ID-TIMS U/Pb dating on zircon, shows that a protracted period of magmatic accretion formed the Sapat Complex between 105 and 99 Ma. Since continued melt percolation processes that formed the lower crust obscured the original bulk rock Nd–Pb–Sr isotopic composition, we rely on the Hf isotopic composition of zircons of different ages to unravel the source evolution. Nd and Pb bulk isotopic compositions coupled with Hf isotopic composition on zircons allow reconstructing a geodynamical scenario for the Sapat Complex, and the Cretaceous history of the Arc. We suggest that trenchward migration of the hot mantle source at 105 Ma explains the small heterogeneous εHf signal between + 14 and + 16. This heterogeneity vanished within ca. 2 million years, and the εHf of the source evolved from + 16 to + 14 at 99 Ma. Integrated to the Kohistan Cretaceous history, which has a baseline of εHf ≈ 14, these data pinpoint two geodynamical events, with slab retreat and the formation of the Sapat Complex followed by splitting of the Kohistan island arc at 85 Ma. 相似文献
122.
Geomorphology and GIS analysis for mapping gully erosion susceptibility in the Turbolo stream catchment (Northern Calabria, Italy) 总被引:8,自引:0,他引:8
Massimo Conforti Pietro P. C. Aucelli Gaetano Robustelli Fabio Scarciglia 《Natural Hazards》2011,56(3):881-898
This work summarizes the results of a geomorphological and bivariate statistical approach to gully erosion susceptibility
mapping in the Turbolo stream catchment (northern Calabria, Italy). An inventory map of gully erosion landforms of the area
has been obtained by detailed field survey and air photograph interpretation. Lithology, land use, slope, aspect, plan curvature,
stream power index, topographical wetness index and length-slope factor were assumed as gully erosion predisposing factors.
In order to estimate and validate gully erosion susceptibility, the mapped gully areas were divided in two groups using a
random partitions strategy. One group (training set) was used to prepare the susceptibility map, using a bivariate statistical
analysis (Information Value method) in GIS environment, while the second group (validation set) to validate the susceptibility
map, using the success and prediction rate curves. The validation results showed satisfactory agreement between the susceptibility map and the existing data on gully areas
locations; therefore, over 88% of the gullies of the validation set are correctly classified falling in high and very high
susceptibility areas. The susceptibility map, produced using a methodology that is easy to apply and to update, represents
a useful tool for sustainable planning, conservation and protection of land from gully processes. Therefore, this methodology
can be used to assess gully erosion susceptibility in other areas of Calabria, as well as in other regions, especially in
the Mediterranean area, that have similar morphoclimatic features and sensitivity to concentrated erosion. 相似文献
123.
Sebastiano Imposa Francesco Barone Domenico Bella Massimo Cristaldi Stefano Gresta 《Environmental Earth Sciences》2011,64(7):1777-1786
A “standard procedure” to characterize the seismic hazard of a given area was proposed. It is based on a multidisciplinary
approach implying: (1) the knowledge of the seismic history of the area; (2) detailed geological surveys; (3)seismic noise
measurements; (4) simulations of earthquake scenarios. The downtown of Acireale, a typical baroque town located on Eastern
Sicily, was chosen as the “test area”. A catalog of the local seismogenic faults (able to generate earthquakes in historical
times) has been compiled, as well as a seismic catalog for the effects of both local and regional earthquakes. The analysis
of both catalogs allowed us to make the following conclusions: (1) the most important seismogenic faults affecting the Acireale
municipality do not affect the downtown, while the related local earthquakes attenuate their energy (and intensity) in short
(few km) distances; (2) the highest seismic intensity (degree X) experienced in Acireale downtown was caused by the 1693 regional earthquake; (3) over the last 140 years, the downtown has
experienced the highest intensity value of VII only once, while six times the intensity was VI. On the whole, this implies
a moderate seismic hazard. The estimation of the seismic hazard has been also approached by the experimental method of recording
seismic noise. Measurements have been performed at seven different sites, where drills gave detailed information on the shallow
subsurface geology to obtain HV (horizontal/vertical) spectral ratios. On the whole, the highest site amplification factor
was moderate (about 7). A further investigation based on synthetic seismograms (and spectra) produced by simulating two given
earthquake scenarios was also performed. The two scenarios are, respectively, representative of the largest expected earthquake
in the area (the 1693 shock) and of a moderate (magnitude ca. 5.5) local earthquake (as the 1818 one). Moderate to strong
locally expected accelerations were evidenced. 相似文献
124.
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126.
Daniele Spiga Gianpiero Tagliaferri Paolo Soffitta Oberto Citterio Stefano Basso Ronaldo Bellazzini Alessandro Brez Wolfgang Burkert Vadim Burwitz Enrico Costa Luca de Ruvo Ettore Del Monte Sergio Fabiani Gisela Hartner Benedikt Menz Massimo Minuti Fabio Muleri Giovanni Pareschi Michele Pinchera Alda Rubini Carmelo Sgrò Gloria Spandre 《Experimental Astronomy》2014,37(1):37-53
The Joint European X-ray Telescope (JET-X) was the core instrument of the Russian Spectrum-X- γ space observatory. It consisted of two identical soft X-ray (0.3–10 keV) telescopes with focusing optical modules having a measured angular resolution of nearly 15 arcsec. Soon after the payload completion, the mission was cancelled and the two optical flight modules (FM) were brought to the Brera Astronomical Observatory where they had been manufactured. After 16 years of storage, we have utilized the JET-X FM2 to test at the PANTER X-ray facility a prototype of a novel X-ray polarimetric telescope, using a Gas Pixel Detector (GPD) with polarimetric capabilities in the focal plane of the FM2. The GPD was developed by a collaboration between INFN-Pisa and INAF-IAPS. In the first phase of the test campaign, we have re-tested the FM2 at PANTER to have an up-to-date characterization in terms of angular resolution and effective area, while in the second part of the test the GPD has been placed in the focal plane of the FM2. In this paper we report the results of the tests of the sole FM2, using an unpolarized X-ray source, comparing the results with the calibration done in 1996. 相似文献
127.
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129.
An analytical solution in terms of elliptic integrals is found for the problem connected to the isolthermal collapse of a gaseous sphere. In this way the time-dependence of spatial density distribution is promptly obtained in each point inside the sphere itself. An application for interstellar clouds is given. 相似文献
130.
Antonio Bianchini † Brian Alford ‡ Ronald Canterna Massimo Della Valle ‡ 《Monthly notices of the Royal Astronomical Society》2001,321(4):625-628
Low-resolution spectra, taken at La Silla (ESO), identify the old nova RS Car (1895) as a ∼18 mag star located 7 arcsec southwest from the previous published position. This suggests a much brighter absolute magnitude of the old nova, M v ∼5.4, than previously suspected. The spectrum reveals a continuum energy distribution typical of optically thick accretion discs and quite a high excitation state of the gas. The possible detection of the AlO λ 4843 emission band is discussed. 相似文献