Seismic and field evidence for selective inversion of Cretaceous normal faults, Salta rift, northwest Argentina   总被引：1，自引：0，他引：1  

Jonas Kley  Eduardo A. Rossello  Csar R. Monaldi  Bjrn Habighorst 《Tectonophysics》2005,399(1-4):155

Northwestern Argentina was the site of the continental Salta rift in Cretaceous to Paleogene time. The Salta rift had a complex geometry with several subbasins of different trends and subsidence patterns surrounding a central high. Fault trends in the rift were extremely variable. There is evidence of normal and/or transfer faults trending N, NE, E and SE. It is not clear if all these faults were active at the same time, indicating a poorly defined extension direction, or if they formed in different, non-coaxial extension phases. In either case, their trends were very likely influenced by preexisting fault systems. Beginning in early Eocene time, the rift basins were superseded by Andean foreland basins and later became caught in the Andean thrust deformation propagating eastward, resulting in the inversion of rift faults. Due to their different orientations, not all faults were equally prone to reactivation as thrusts. N to NNE trending faults were apparently most strongly inverted, probably often to a degree where the traces of their normal fault origin have become obliterated. We present seismic evidence of moderately inverted N trending faults in the Tres Cruces basin and field examples of preserved E trending normal faults. However, reactivation sometimes also affects faults trending approximately parallel to the main Neogene shortening direction, indicating short-term deviations from the general pattern of Neogene thrust deformation. These pulses of orogen-parallel contraction may be linked to the intermittent activity of oblique transfer zones.  相似文献   

Sediment hosted lead–zinc deposits of the Neoproterozoic Bambuí Group and correlative sequences, São Francisco Craton, Brazil: A review and a possible metallogenic evolution model   总被引：3，自引：0，他引：3  

Aroldo Misi  Sundaram S.S. Iyer  Carlos Eduardo S. Coelho  Colombo C.G. Tassinari  Washington J.S. Franca-Rocha  Ion de Abreu Cunha  Adriana S. Rocha Gomes  Tolentino Flvio de Oliveira  Joo Batista G. Teixeira  Valter Mnaco C. Filho 《Ore Geology Reviews》2005,26(3-4):263-304

The Proterozoic sediment-hosted Zn–(Pb) sulfide and non-sulfide deposits of the São Francisco Craton, Brazil, are partially syn-diagenetic and epigenetic and were probably formed during extensional events. The majority of the deposits occur within shallow water dolomites. The Pb isotopic data of sulfides are relatively homogeneous for individual deposits and plot above the upper crust evolution curve of the Plumbotectonic model. Some of the deposits are characterized by highly radiogenic lead (²⁰⁶Pb/²⁰⁴Pb ≥ 21) originating from the highly radioactive crust of the São Francisco Craton. Pb and S isotopic data suggest the sources of metal and sulfur for the deposits to be the basement rocks and seawater sulfates in the sediments, respectively. The relatively high temperatures of formation (100 to 250 °C) and moderate salinity (3% to 20% NaCl equiv.) of the primary fluid inclusions in the sphalerite crystals suggest the participation of basinal mineralizing fluids in ore formation. The steep paleo-geothermal gradient generated by the radioactively enriched basement rocks probably assisted in heating up the circulating mineralizing fluids.  相似文献   

Calibration of Four Species of Tillandsia as Air Pollution Biomonitors   总被引：1，自引：0，他引：1  

Eduardo D. Wannaz  María L. Pignata 《Journal of Atmospheric Chemistry》2006,53(3):185-209

Many organisms have been used as bioindicators of atmospheric contamination, with moss and lichen species being the most common. However, studies using epiphytic vascular species of Tillandsia have shown a good correlation between the presence of pollutants and the bioindicator's response. Therefore, the aim of our investigation was to calibrate and compare the response of four Tillandsia species of Argentina to ascertain whether they could be used as atmospheric contamination biomonitors. For this, we analysed the correlation between the levels of heavy metals in total atmospheric deposition samples and: a) their rate of enrichment; b) the physiological response of the plant samples. Tillandsia samples collected from a non contaminated area in the province of Córdoba were transplanted to four areas in the capital city with different sources of pollution (industrial or traffic emissions). They were exposed for a period of 3 to 6 months after which the concentrations of Pb, Ni, Fe, Zn, Cu and S as well as the physiological parameters of foliar damage were determined. Simultaneously samples of total atmospheric deposition were also taken.The highest level of metal enrichment was found in T. capillaris followed by T. tricholepis, T. permutata and T. retorta. Also, the use of a foliar damage index proved to be effective and could be a useful tool to evaluate different levels of atmospheric quality in these species. The rate of heavy metal deposition was higher in the industrial area for all metals except for Zn whose values were higher in areas with high levels of traffic.  相似文献   

Evaluation of residual drift demands in regular multi‐storey frames for performance‐based seismic assessment     

Jorge Ruiz‐García  Eduardo Miranda 《地震工程与结构动力学》2006,35(13):1609-1629

This paper summarizes results of a comprehensive analytical study aimed at evaluating the amplitude and heightwise distribution of residual drift demands in multi‐storey moment‐resisting frames after earthquake excitation. For that purpose, a family of 12 one‐bay two‐dimensional generic frame models was subjected to an ensemble of 40 ground motions scaled to different intensities. In this investigation, an inelastic ground motion intensity measure was employed to scale each record, which allowed reducing the record‐to‐record variability in the estimation of residual drift demands. The results were statistically processed in order to evaluate the influence of ground motion intensity, number of stories, period of vibration, frame mechanism, system overstrength, and hysteretic behaviour on central tendency of residual drift demands. In addition, a special emphasis was given to evaluate the uncertainty in the estimation of residual drift demands. Results of incremental dynamic analyses indicate that the amplitude and heightwise distribution of residual drift demands strongly depends on the frame mechanism, the heightwise system structural overstrength and the component hysteretic behaviour. An important conclusion for performance‐based assessment is that the evaluation of residual drift demands involves significantly larger levels of uncertainty (i.e. record‐to‐record variability) than that of maximum drift demands, which suggests that this variability and corresponding uncertainty should be explicitly taken into account when estimating residual drift demands during performance‐based seismic assessment of frame buildings. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Three-Dimensional Interpolation and Lithofacies Analysis of Granular Composition Data for Earthquake-Engineering Characterization of Shallow Soil     

Katsuaki Koike  Yoshihiro Shiraishi  Eduardo Verdeja  Kenji Fujimura 《Mathematical Geology》1998,30(6):733-759

In Japan, many major cities are located on tectonic basins which are surrounded by faults and underlain by soft alluvial materials. Because these areas are subject to earthquake damages, it is important to determine their seismic engineering characteristics. Geotechnical databases which contain many borehole logs are useful information sources for this type of analysis. Each datum stored in the database has a value or an attribute, and its location is irregular in both horizontal and vertical directions. A new interpolation method based on the optimization principle is proposed here to deal with such three-dimensionally distributed data. Susceptibility of unconsolidated ground to liquefaction is known to be related to the content of loose and saturated sand. The mixture ratio of several soil types in a deposit, i.e., granular composition, is strongly influenced by the sedimentary environment. There are two numerical methods: the optimization principle method (OPM) used to determine three-dimensional distribution of granular composition and the model used to evaluate liquefaction. The application of the proposed methods to two locations in Japan indicated that the zones with high susceptibility to liquefaction were indeed those that had suffered from liquefaction during past earthquakes.  相似文献   

Coupling of boundary and finite elements for soil-structure interaction problems     

Otto von Estorff  Eduardo Kausel 《地震工程与结构动力学》1989,18(7):1065-1075

The investigation of complex soil-structure interaction problems is usually carried out with numerical solution procedures such as the finite element or the boundary element method. It must be noted, however, that the choice of one or the other of these approaches is not just a matter of preferences; depending on the type of the problem under consideration, either boundary or finite elements may be more advantageous. A considerable expansion in the computational power can be obtained, on the other hand, if one resorts to hybrid schemes which retain the main advantages of the two methods and eliminate their respective disadvantages. This paper presents results obtained with a boundary element-finite element coupling procedure, and discusses its applicability to some representative soil-structure interaction problems. The structures considered are elastic systems, such as foundations, tunnels and filled trenches (modelled by finite elements), which are coupled with homogeneous elastic halfspaces (modelled by boundary elements). The examples demonstrate the importance of using a model that includes wave radiation effects. The coupling approach is formulated entirely in the time domain so that an extension of the algorithm to non-linear analyses seems to present no further difficulties.  相似文献   

Natural analogues for the transuranic actinide elements: An investigation in Minas Gerais,Brazil     

Merril Eisenbud  Konrad Krauskopf  Eduardo Penna Franca  Wayne Lei  Robert Ballad  Paul Linsalata  Kenkichi Fujimori 《Environmental Geology》1984,6(1):1-9

A highly weathered deposit of thorium and rare earth elements located near the summit of a hill in the state of Minas Gerais, Brazil, is being studied as an analogue for a radioactive waste repository that sometime in the distant future may be eroded to the surface or intruded by groundwater Thorium serves as an analogue for Pu⁴⁺, and La³⁺ as an analogue for Cm³⁺ and Am³⁺ The mobilization rate constants of the analogue elements by groundwater are so slow (of the order of 10⁻⁹ per year) as to suggest that essentially complete radioactive decay of the transuranic actinides would occur in place even under the relatively unfavorable conditions that exist at a site such as this  相似文献   

Early Paleozoic Structural and Metamorphic Evolution of Western Sierra de San Luis (Argentina), in Relation to Cuyania Accretion     

Pablo Diego GonzAlez  Ana Maria Sato  Eduardo Jorge Llambias  Miguel A.S. Basei  Silvio R.F. Vlach 《Gondwana Research》2004,7(4):1157-1170

Structural, metamorphic and isotopic data obtained from the Nogoli Metamorphic Complex of western Sierra de San Luis indicate that the Early Paleozoic Famatinian Orogeny overprinted an already structured and metamorphosed older basement. The older geological features are relict NW trending fabric associated with high-grade (amphibolite facies) regional metamorphism preserved within thin strips of schists and paragneisses and in the core of mafic to ultramafic lenses. Arc magmatism, medium P (Barrovian type)/high T (amphibolite to granulite facies) regional metamorphism and penetrative NNE to NE trending foliation are related to the building of the Famatinian orogenic belt. The P-T conditions of the Famatinian prograde metamorphism reached a pressure peak of ca. 8 kb, with a thermal peak from -750°C up to -820°C. U-Pb conventional and chemical dating and Ar-Ar plateau ages constrain the peak of the main orogenic phase related to the Famatinian belt to 470–457 Ma (Early to Mid-Ordovician). Greenschist facies retrograde metamorphism closely associated with shear zones and secondary Ar-Ar plateau and Sm-Nd ages suggest that a late to post-orogenic phase of the Famatinian belt was active at least since -445 Ma. This phase continued during the Silurian to Late Devonian times through multiple reactivation of early shear zones. The Famatinian Orogeny reset a previous thermal history and therefore, the timing of the relict fabric could not be constrained conclusively with radiometric dates. Despite this difficulty, a range of 520 to 490 Ma suggests some inheritance from Pampean events registered by the older NW-SE fabric. The Early to Mid-Ordovician regional metamorphism and ductile deformation of the western Sierra de San Luis is interpreted as the orogenic effects of the collision of the allochthonous Cuyania terrane with the autochthonous proto-Pacific margin of Gondwana during the Famatinian Orogeny.  相似文献   

The Age of Sustainable Development     

Eduardo Medeiros 《The Journal of geography》2019,118(1):49-50

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Groundwater Level Prediction/Forecasting and Assessment of Uncertainty Using SGS and ARIMA Models: A Case Study in the Bauru Aquifer System (Brazil)     

Takafuji  Eduardo Henrique de Moraes  Rocha  Marcelo Monteiro da  Manzione  Rodrigo Lilla 《Natural Resources Research》2019,28(2):487-503

Natural Resources Research - Best water management practices should involve the prediction of the availability of groundwater resources. To predict/forecast and consequently manage these water...  相似文献