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Vyacheslav?V.?AkininEmail author Alexander?V.?Sobolev Theodoros?Ntaflos Wolfram.?Richter 《Contributions to Mineralogy and Petrology》2005,150(1):85-101
Clinopyroxene megacrysts from young melanephelinitic lavas were divided into Cr-rich and Cr-poor suites. Sr, Nd, and Pb isotopic
ratios of leached megacrysts and host lava are indistinguishable from each other and indicate a depleted source. Host lavas
do not display chemical evidence for significant fractional crystallization, which is required to explain the compositional
range of the megacrysts. This rules out a simple cognate genetic relationship between the two, and strictly defines megacrysts
as xenocrysts. The well-defined correlations of trace elements with the Mg-numbers in the megacrysts are interpreted as the
result of extensive fractional/equilibrium crystallization of magma over a large temperature range at near isobaric condition
in the upper mantle. Trace element variations in megacrysts are consistent with fractional crystallization of clinopyroxene
alone for the Cr-rich suite, and clinopyroxene + garnet for the Cr-poor suite from at least two bathes of related melts. Megacrysts
parent magma might represent mantle melts, which were never erupted in their initial composition. 相似文献
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Pinios (Peneus) River (Central Greece): Hydrological — Geomorphological elements and changes during the quaternary 总被引:1,自引:0,他引:1
George Migiros George D. Bathrellos Hariklia D. Skilodimou Theodoros Karamousalis 《Central European Journal of Geosciences》2011,3(2):215-228
The Pinios River is the third longest river of Greece. It drains the entire drainage basin of Thessaly (eastern part of Central Greece), part of which is the largest plain of the country. In this research the hydrological, geomorphological and geological characteristics of the riverine area of Pinios were studied. Classification and grouping of these characteristics were then carried out, which led to the segmentation of the Pinios River into seven sections, each one with its own set of thematic data. These sets assign separate functions and evolutions of the river system during the Quaternary. Specifically, the basin of the present Pinios River, before its evolution into a river basin, comprised three separate and independent systems. The present Pinios River emerged as a river system from the merging of the lacustrine paleoenvironments along with the major tributaries that drained large parts of the present hydrological basin and as soon as the karstic openings of the central hill valley and the Tempi valley took place during the Quaternary. The followed methodology for the segmentation of the river can be used for the study of heterogeneous river systems. 相似文献
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Christos Makris Panagiota Galiatsatou Konstantia Tolika Christina Anagnostopoulou Katerina Kombiadou Panayotis Prinos Kondylia Velikou Zacharias Kapelonis Elina Tragou Yannis Androulidakis Gerasimos Athanassoulis Christos Vagenas Ioannis Tegoulias Vassilis Baltikas Yannis Krestenitis Theodoros Gerostathis Kostantinos Belibassakis Eugen Rusu 《Ocean Dynamics》2016,66(12):1603-1635
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Theodoros M. Tsapanos 《Geophysical Journal International》2003,153(2):403-408
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A probabilistic procedure was applied to assess seismic hazard for the sites of five Greek cities (Athens, Heraklion, Patras, Thessaloniki and Volos) using peak ground acceleration as the hazard parameter. The methodology allows the use of either historical or instrumental data, or a combination of both. It has been developed specifically for the estimation of seismic hazard at a given site and does not require any specification of seismic sources or/and seismic zones. A new relation for the attenuation of peak ground acceleration was employed for the shallow seismicity in Greece. The computations involved the area- and site-specific parts. When assessing magnitude recurrence for the areas surrounding the five cities, the maximum magnitude, mmax, was estimated using a recently derived equation. The site-specific results were expressed as probabilities that a given peak ground acceleration value will be exceeded at least once during a time interval of 1, 50 and 100 years at the sites of the cities. They were based on the maximum peak ground acceleration values computed by assuming the occurrence of the strongest possible earthquake (of magnitude mmax) at a very short distance from the site and using the mean value obtained with the help of the attenuation law. This gave 0.24 g for Athens, 0.53 g for Heraklion (shallow) and 0.39 g Heraklion (intermediate-depth seismicity), 0.30 g for Patras, 0.35 g for Thessaloniki and 0.30 g for Volos. In addition, the probabilities of exceedance of the estimated maximum peak ground acceleration values were calculated for the sites. The standard deviation of the new Greek attenuation law demonstrates the uncertainty and large variation of predicted peak ground acceleration values. 相似文献
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b-Values of two tectonic parts in the circum-pacific belt 总被引:1,自引:0,他引:1
Theodoros M. Tsapanos 《Pure and Applied Geophysics》1990,134(2):229-242
Two different data sets have been applied to compute theb-parameter of the magnitude-frequency relation for two different areas in the circum-Pacific belt. These areas are: a) South America, Middle America and Mexico, b) all the remaining island arcs of the circum-Pacific belt, starting from Alaska and the Aleutian islands and proceeding southeastwards. The first data set spreads over 77 years, while the second one covers a 90-year period. In both cases the results clearly showed that theb-values are lower in the first of the above-mentioned areas, while respectively higher in the second. This is due to the tectonic conditions in these areas as estimated during the present work. 相似文献
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This paper introduces a new way of estimating the inelastic response of first‐mode dominated structures with behaviour that can be approximated with the elastoplastic idealization. The proposed approach emerges from formal dimensional analysis and is liberated from the response of the elastic system. The application of the proposed method hinges upon the existence of a distinct time scale and a length scale that characterize the most energetic component of the ground shaking. Such time and length scales emerge naturally from the distinguishable pulses which dominate a wide class of strong earthquake records; they are directly related with the rise time and slip velocity of faulting, and can be formally extracted with validated mathematical models published in the literature. The most decisive feature of this work is that the inelastic response curves that result with the proposed approach assume similar shapes for different values of the normalized yield displacement. Because of this similarity the paper proposes a single inelastic response curve which offers directly the maximum inelastic displacement of the structure given the energetic pulse period and pulse amplitude of the ground shaking. When the proposed method is applied to MDOF structures it is not capable to estimate interstorey drifts nor is capable to capture the effects of negative stiffness which may result due to P‐delta effect. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献