Modelling a torrential event in a river confluence     

M. Roca  J.P. Martín-Vide  P.J.M. Moreta 《Journal of Hydrology》2009,364(3-4):207-215

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Implications of long-term land-use change for the hydrology and solute budgets of small catchments in Amazonia     

Sonja Germer  Christopher Neill  Tobias Vetter  Joaquín Chaves  Alex V. Krusche  Helmut Elsenbeer 《Journal of Hydrology》2009,364(3-4):349-363

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Petrogenesis of the mafic igneous rocks of the Betic Cordilleras: A field, petrological and geochemical study     

Maria Teresa Gómez-Pugnaire  Peter Ulmer  Vicente López-Sánchez-Vizcaíno 《Contributions to Mineralogy and Petrology》2000,139(4):436-457

Mafic igneous rocks are widespread in the Nevado-Filábride Complex, the lowermost metamorphic unit of the internal zones of the Betic Cordilleras. They form intrusive, small, discontinuous bodies, predominantly dikes with subordinate small lava flows. The entire complex underwent alpine compressional metamorphism during the Paleogene continental collision, resulting in eclogites and blueschists in the mafic bodies and high-pressure assemblages in the intruded metasediments. Locally, weakly metamorphosed or completely unmetamorphosed igneous rocks with the same textural features occur as patches surrounded by eclogitized igneous rocks. The bulk rock chemistry of unmetamorphosed and completely metamorphosed mafic igneous rocks is consistent with an alkaline to transitional tholeiitic magmatism with typical within-plate geochemical characteristics. All but a few samples are nepheline normative and display REE and trace element characteristics typical of continental, rift-related magmatism. This conclusion is strongly supported by the mineral chemistry of the major constituents, in particular the calcic Ti-rich character of clinopyroxene, the lack of orthopyroxene, and the occurrence of kaersutitic amphibole. Incompatible trace element abundances and Sr and Nd isotopes support the provenance of these magmas from a variably metasomatized previously depleted sub-continental lithospheric mantle source. Received: 5 July 1999 / Accepted: 28 February 2000  相似文献   

CO2-rich thermomineral groundwater in the Betic Cordilleras, southeastern Spain: Genesis and tectonic implications     

J. C. Cerón  M. Martín-Vallejo  L. García-Rossell 《Hydrogeology Journal》2000,8(2):209-217

The CO₂-rich thermal groundwater in the Betic Cordilleras in Spain has been studied with regard to the geological and hydrogeological setting, physical and chemical characteristics, and ¹³C-isotope content. The study area is about 60 km northeast of Almería city, in southeastern Spain. The thermomineral waters are plentiful and are related to regional geothermal anomalies. Temperatures of 20 −41°C, high bicarbonate concentrations (183–1824 mg/L), and high amounts of PCO₂ (<1.1 bar) characterize the groundwater. CO₂ spatial variations are related to proximity to the Carboneras, Palomares, and Guadalentín fault systems, which may be the surface representation of the zone of crustal thinning and magmatism. δ ¹³C values probably indicate a deep source for the CO₂, either the mantle or perhaps carbonate rocks in the metamorphic substratum. The high amount of CO₂ in the groundwater causes problems in wells and severely restricts water usage. The hydrothermal features of this area are probably related to neotectonic activity. Received, September 1998/Revised, June 1999, September 1999/Accepted, December 1999  相似文献   

Interplay of orbital forcing and tectonic pulses in the Cambrian Iberian platform, NE Spain     

J. J. Álvaro  E. Vennin  A. Muñoz  B. Sánchez-Valverde  J. L. Ojeda 《International Journal of Earth Sciences》2000,89(2):366-376

The stratigraphy of carbonate/shale couplets, cycles and cycle-stacking patterns in a Cambrian shallow water platform (Iberian Chains, NE Spain) are related to sea-level changes driven by orbital forcing and by tectonic pulses. The interplay of both effects can be discriminated in the Iberian fault-controlled platform, in which the tectonic activity can be analysed by accurate and detailed biostratigraphic correlations based on trilobite zonation. The stratigraphic hierarchy of rhythmically interbedded limestones and shales, in two coeval but structurally separated geodynamic settings, yields cycle ratios of 1.44 :1. This ratio is supported by time thickness and spectral analysis, which is based on a graphic method of analysis: the Map of Grey Lines. The cycle ratio seems to be evidence for orbital forcing by obliquity and precession cycles predicted for early Paleozoic time. Carbonate/shale couplets, the smallest rhythmic units recognisable in the field, represent short-term, periodic fluctuations in supply of terrigenous sediments and carbonate productivity of uncertain origin, which could be associated with one of several harmonics of the former orbital cycles. The pulsating tectonic activity was approximated by using a quantitative analysis of tectonically induced subsidence (Shaw method). Recurrence frequencies of tectonic pulses were estimated and dated by biostratigraphy. As a result, tectonic disturbances in the Cambrian Iberian platform show an episodic periodicity comparable to that of orbital eccentricity cycles, which could mask their recognition. Received: 15 November 1999 / Accepted: 9 February 2000  相似文献   

Complex site effects and building codes: Making the leap   总被引：1，自引：0，他引：1  

Francisco J. Chávez-García  Ezio Faccioli 《Journal of Seismology》2000,4(1):23-40

The engineering community is aware of the importance of site effects, but it lags behind seismological studies when it comes to incorporating site effect considerations in design spectra for seismic norms. This lag is reflected in the conspicuous fact that current building codes make allowance for 1D site effects but ignore complex site effects. The purpose of this paper is to explore a way for including complex site effects in a building code environment. We take as example Eurocode 8, which is a modern code that exemplifies the current approach to site effect consideration. We examine the restrictions that we have imposed to make the problem of a feasible size and discuss the approach we have taken. We propose a strategy to incorporate a class of complex site effects in a design elastic spectrum.  相似文献   

About the Efficiency of Numerical 1-D and 2-D Modelling of Site Effects in Basin Structures     

J. Riepl  J. Zahradník  V. Plicka  P.-Y. Bard 《Pure and Applied Geophysics》2000,157(3):319-342

—In the present study we compare results obtained from experimental estimates of local site amplification effects with those from numerical modelling using four different techniques. We benefit from an extremely precise knowledge of the near-surface structure and experimental estimates of the local amplification factors which are determined from seismic weak-motion data recorded by a dense array across a sedimentary basin at a European test-site in Northern Greece. The possibilities and limitations of the different modelling techniques (a 1-D technique, and three 2-D techniques) to model the effects of local amplification effects are tested. Amplifications calculated by the numerical techniques are only qualitatively compared with observed data from experimental studies in the time domain and directly in the frequency domain.¶As a result we conclude that, in the case of a complex subsurface geometry, 1-D modelling underestimates the amplification patterns in terms of absolute amplification level, and cannot correctly account for resonant frequencies, at least for modes higher than the fundamental mode. If a more realistic incident wave field than just a plane wave is taken into account, 2-D modelling reveals the fundamental frequency and shows adequate amplifications not only at the fundamental frequency but also at higher frequencies. The general trend of the amplifications at the lowest frequencies is well determined by the 2-D numerical modelling, and can therefore supply information for seismic risk analysis.  相似文献   

Recent Climate Warming: Surface Air Temperature Series and Geothermal Evidence     

Čermák  Vladimír  Šafanda  Jan  Krešl  Milan  Dědeček  Petr  Bodri  Louise 《Studia Geophysica et Geodaetica》2000,44(3):430-441

Long-term (1961 – 1996) meteorological air temperature series together with the reconstructed ground surface temperature histories, obtained by inverting borehole temperature-depth profiles, were used to project regional patterns of the recent (climate) warming rate on the territory of the Czech Republic. The characteristic magnitude of the warming rate of 0.02 –0.03 K/yr was confirmed by the results of several years of monitoring the temperature in two experimental boreholes. The monitoring of shallow temperatures at depths of about 30 –40 m, i.e. below the reach of the seasonal surface temperature variations, can serve as an alternative tool of direct quantitative assessment of the present warming rate. The data also seem to sustain a potential man-made component contributing to the more pronounced recent warming rate observed in the areas of large agglomeration.  相似文献   

Contribution of Local Seismic Networks To The Regional Velocity Model of The Bohemian Massif     

Růžek  Bohuslav  Zedník  Jan  Klíma  Karel  Ruprechtová  Libuše 《Studia Geophysica et Geodaetica》2000,44(2):175-187

The routine location of regional seismic events using data from the Czech National Seismological Network (CNSN) is based on Pn, Pg, Sn, Sg phases. A simple velocity model derived from Kárník's (1953) interpretation of an earthquake in Northern Hungary in 1951 has hitherto been used. At present, numerous local seismic networks record and locate local events, which are occasionally recorded at regional distances as well. Due to the relatively small dimensions of local networks, hypocenters (and origin times) determined by a local network might be considered as nearly exact from the point of view of regional-scale CNSN. The comparison of common locations performed by CNSN and by a local network enables us to estimate the accuracy of CNSN locations, as well as to optimize a simple velocity model. The joint interpretation of the CNSN bulletin and the catalogues of four local seismic networks WEBNET, OSTRAVA, KLADNO and LUBIN produced a new ID velocity model. The most frequent epicentral error in this model is less than 5 km, and most foci lie up to 15 km from the true position. The performed analysis indicates bimodal distribution of Sn residuals.  相似文献   

Quiet-time periods observed by EPHIN/SOHO during the minimum of the 22nd solar cycle     

Gómez-Herrero  Raúl  RodrÍguez-FrÍas  M. Dolores  del Peral  Luis  Sequeiros  Juan  Müller-Mellin  Reinhold  Kunow  Horst  Sierks  Holger 《Solar physics》2000,194(2):405-413

An analysis of the hydrogen and helium isotopic composition from EPHIN data, during the quiet-time period from January 1 to June 1, 1996, is presented. An isotopic discrimination and background rejection have been applied and relationships between the abundances of ²H/¹H, ³He/⁴He, and ⁴He/¹H have been calculated. The energy spectra in the 4–50 MeV nucl^–1 range have been obtained and the contribution of the different spectral components have been analysed in this energy range. We conclude that the main contribution to the ⁴He spectrum is of anomalous origin, while the proton and ³He spectra have contributions mainly from particles of solar origin at low energies and from the galactic cosmic radiation modulated by the heliosphere at high energies. The deuterium spectrum is mainly of galactic origin.  相似文献