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11.
Miguel Angelo Stipp Basei Benjamim Bley Brito Neves Oswaldo Siga Junior Marly Babinski Marcio Martins Pimentel Colombo Celso Gaeta Tassinari Maria Helena Bezerra Hollanda Allen Nutman Umberto Giuseppe Cordani 《Precambrian Research》2010
The South-American continent is constituted of three major geologic–geotectonic entities: the homonym platform (consolidated at the end of the Cambrian), the Andean chain (essentially Meso-Cenozoic) and the Patagonian terrains, affected by tectonism and magmatism through almost all of the Phanerozoic. The platform is constituted by a series of cratonic nuclei (pre-Tonian, fragments of the Rodinia fission) surrounded by a complex fabric of Neoproterozoic structural provinces. 相似文献
12.
The relation between karst spring discharge and rainfall by cross-correlation analysis (Campania, southern Italy) 总被引:4,自引:2,他引:2
The relation between rainfall and the discharge from two springs, located at the base of different karst massifs in southern Italy, is investigated by cross-correlation analyses. Data are derived from a continuous time window of 13 years. The input signal involves multiple rainfall time series (cumulative rainfall over varying time windows), while the time series of daily spring discharges are used as the output signal. Analyses were first conducted on the unprocessed data and then on data for which linear trends and seasonal components had been removed, the latter by a spectral analysis. Analyses contributed to the investigation of the time required for water to flow through the karst aquifers at the two sites. Long time intervals of the cumulative rainfall (>60 days) appear to be the main component affecting the spring discharge hydrographs; shorter time intervals seem to be related to quick-flow paths. Some statistics about the linear regression and the meaning of the cross-correlation analysis are discussed. Cross-correlation analysis can provide strong support for identification of the main rainfall contribution and the travel time through the main infiltration pathways in aquifers. 相似文献
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14.
Alejandra L. Cameselle Roger Urgeles Ben De Mol Angelo Camerlenghi Jason C. Canning 《International Journal of Earth Sciences》2014,103(2):423-440
The Messinian Salinity Crisis (MSC) resulted from a significant multi-phase drop and subsequent reflooding of the Mediterranean Sea from 5.96 to 5.33 Ma. Well-developed drainage networks, characterized by step-like profiles and abrasion platforms, are associated to this event. The Ebro Continental Margin (Western Mediterranean) presents an additional complexity since the capture of the drainage of the adjacent subaerial Ebro Basin took place sometime prior to the Messinian stage. Using 3D seismic reflection data, this work provides new insights into the origin of the step-like profile of the Messinian erosional surface (MES) and timing of the capture of the subaerial Ebro Basin. The results obtained indicate a sedimentary-active continental slope and delta progradation during Middle-Late Miocene, in a normal regressive context associated to a pre-Messinian proto-Ebro River. The mature development attained by the Messinian Ebro River network during the MSC corroborates that the capture of the Ebro Basin occurred prior to the MSC. The configuration of the clinoforms below the MES suggests that deltaic sediments of the Messinian Paleo-Ebro River deposited during the Tortonian and initial Messinian sea-level drawdown. The MES formed at the top of the Tortonian Highstand, where a fluvial network was deeply carved, and in the topset region of the Messinian Falling Stage Systems Tract, where minor erosion occurred. Fluvial deposits are outstandingly preserved on the main valleys of the MES. Therefore, the step-like profile of the MES was not created during Zanclean inundation, but during the latest stages of the main Messinian sea-level fall and lowstand. 相似文献
15.
This work presents a geomorphometric approach for outlining anomalies of the topographic surface that may be related to geological structures or to geomorphological phenomena. It is based on 2D discrete wavelet transform of digital elevation models. This transform is used to extract singularities of a series of data. This is specifically applied to a digital elevation model, in order to get its detail coefficients and to have evidence about their variations and values. In particular, this approach can be helpful for the delineation and identification of landforms singularities, like landslides and geological structures. The potential and effectiveness of this approach is shown by an application to a case study about a large deep-seated landslide, located at the central-south front of the Apennine in South Italy. 相似文献
16.
Abstract— We propose the Sirente crater field to be the first discovered impact craters in Italy. They are located in the Sirente plain within the mountains of the Abruzzo region, central Italy. The craters are distributed in a field 450 m long and 400 m wide. This field consists of ?17 smaller craters close to a larger main crater. The main crater is located in the southern end of the crater field and is 140 m long and 115 m wide, measured rim‐to‐rim. It has a well‐developed, saddle‐shaped rim that rises at a maximum 2.2 m above the surrounding plain. Radiocarbon dating of the target surface preserved below the rim gave a calibrated age of formation at about a.d. 412 (1650 ± 40 radiocarbon years b.p.). This young age is consistent with the apparent little modification of the rim. The morphology of the main crater and its relation to a crater field strongly points to its origin by impact from a projectile that broke up during its passage through the atmosphere. Quartz is very rare in the target and no planar deformation features have been found so far. The rim material and the upper 4 m of the main crater infill are impregnated with ferric oxides, which gives a more reddish colour compared to the other sediments of the plain. Rusty crusts with high Fe and Mn content occur in the rim material, but have not been found in the plain's sediments. Some of these crusts can be separated by magnet, and have sporadic micron‐sized Ni‐rich granules. The main crater is in the size range of the craters with explosive dispersion of the projectile and has many features comparable to both large experimental and meteoritic impact craters formed in loose sediments. We suggest that this crater represents a rare example of well‐preserved, small impact crater formed in unconsolidated target materials. 相似文献
17.
Angelo J. Skalafuris 《Astrophysics and Space Science》1969,3(2):234-257
We examine the problem of a shock wave propagating in a gravitational field in the presence of pressure and density gradients by attacking the non-linear equations of fluid flow. Our approach is analytical rather than numerical, and we analyze the characteristic equations of a fluid in the presence of gravity with radiative dissipation. Because the radiation field enters the fluid equations in the form of an integral, radiative dissipation may be considered an inhomogeneity which does not affect the characteristic directions. The fluid equations remain hyperbolic and thus are amenable to solution by the standard techniques of gas analysis.We give an equation of path for a shock wave and we enumerate the physical conditions which lead to stability or instability. We find that shock waves are generally unstable in most stellar atmospheres unless they are very weak. The form of the instability is that of a spicule deformation similar to that observed in the upper solar chromosphere.This work was carried out at the Smithsonian-Harvard Astrophysical Observatory and was presented in a thesis to Brandeis University, May 1963. 相似文献
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19.
On the seismic performances of rigid block‐like structures coupled with an oscillating mass working as a TMD
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Giorgia Simoneschi Alessandro Geniola Andrea M. de Leo Angelo Di Egidio 《地震工程与结构动力学》2017,46(9):1453-1469
In this paper, the effects of a mass damper on the rocking motion of a non‐symmetric rigid block‐like structure, subject to different seismic excitation, are investigated. The damper is modelled as a single degree of freedom oscillating mass, running at the top of the block and connected to it by a linear visco‐elastic device. The equations of rocking motion, the uplift and the impact conditions are derived. A nondimensionalisation of the governing equations is performed with the aim to obtain an extensive parametric analysis. The results are achieved by numerical integration of these equations. The slenderness and the base of the rigid block, and the eccentricity of the centre of mass are taken as variable parameters in the analyses. The main objective of the study is to check the performance of the damper versus the spectral characteristics of the seismic input. Three earthquake registrations with different frequency contents are used in the analyses. The results show that the presence of the mass damper leads to different levels of improvement of the response of the system, depending on the spectral characteristics of the seismic input. Curves providing the overturning slenderness of blocks of specific sizes versus the characteristics of the TMD are obtained. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
20.
Angelo Forestieri Elisa Arnone Stephen Blenkinsop Angela Candela Hayley Fowler Leonardo V. Noto 《水文研究》2018,32(3):332-348
Increasing precipitation extremes are one of the possible consequences of a warmer climate. These may exceed the capacity of urban drainage systems, and thus impact the urban environment. Because short‐duration precipitation events are primarily responsible for flooding in urban systems, it is important to assess the response of extreme precipitation at hourly (or sub‐hourly) scales to a warming climate. This study aims to evaluate the projected changes in extreme rainfall events across the region of Sicily (Italy) and, for two urban areas, to assess possible changes in Depth‐Duration‐Frequency (DDF) curves. We used Regional Climate Model outputs from Coordinated Regional Climate Downscaling Experiment for Europe area ensemble simulations at a ~12 km spatial resolution, for the current period and 2 future horizons under the Representative Concentration Pathways 8.5 scenario. Extreme events at the daily scale were first investigated by comparing the quantiles estimated from rain gauge observations and Regional Climate Model outputs. Second, we implemented a temporal downscaling approach to estimate rainfall for sub‐daily durations from the modelled daily precipitation, and, lastly, we analysed future projections at daily and sub‐daily scales. A frequency distribution was fitted to annual maxima time series for the sub‐daily durations to derive the DDF curves for 2 future time horizons and the 2 urban areas. The overall results showed a raising of the growth curves for the future horizons, indicating an increase in the intensity of extreme precipitation, especially for the shortest durations. The DDF curves highlight a general increase of extreme quantiles for the 2 urban areas, thus underlining the risk of failure of the existing urban drainage systems under more severe events. 相似文献