Biogeographical affinities of marine algae in the Saronikos Gulf,Athens, Greece   总被引：1，自引：0，他引：1  

Aristidis Diapoulis Dr.  Theodoros Koussouris Dr.  Haritonidis Savas 《GeoJournal》1988,17(1):85-89

Hard substrate photophilius marine algae species of the Saronikos Gulf amount to 197. Of them, 42 were Atlantic subtropical, 36 Atlantic tropical, and just 19 Atlantic boreal and 11 Boreal. The R/P ratio was 3.22. This shows the Atlantic subtropical character of the marine flora.  相似文献   

Probable evidence for periodicities in global seismic energy release     

Ioannis Liritzis  Theodoros M. Tsapanos 《Earth, Moon, and Planets》1993,60(2):93-108

A complete data set of globally distributed shallow (h , 60 Km) earthquakes have been used for first time to test the possible existence of periodicities in the seismic energy release. Only main shocks of magnitude,M 7.0 were considered, which occurred in the whole Earth during 1898–1985. These magnitudes are converted in seismic energy, which is released during the occurrence of earthquakes, through Bath's formula. The detection of such kind of periodicities is important in seismology, because these patterns may lead to the prediction of large earthquakes. Statistical techniques, such as Maximum Entropy (ME), and two Fourier approaches, the Fast Fourier Transform (FFT) and Power Spectrum (PS) of truncated subrecords of the whole time series have been applied to examine the possible existence of such periodicities in seismic energy release. Furthermore, the even-spacing technique is used to validate our results and a type-curve has been constructed for the data set.The results exhibit a network of periodicities with predominant periods at 3(±0.5), 4.5, 6.5, 8–9, 14–20, and 31–34 years. Some periods were occasionally interrupted. The latter implies that our time-series is not stationary, in that, the spectral peaks drift when the data are viewed through different time windows. The fact that the signal is weak and embedded in less accurate older data could contribute to this effect. The question of stability/validity of the apparently cyclic behaviour of the annual global seismic energy release, is one which requires further investigation.  相似文献   

A Probabilistic Estimation of Strong Earthquakes'''' Occurrence in Aeghion Area, Central Greece     

Theodoros M.Tsapanos  Odysseus Ch.Galanis 《中国地震研究》2003,17(3):286-296

INTRODUCTIONTheexaminedareaislocatedintheGulfofCorinthandhasbeenrecognizedasoneofthemostactiveriftsinthewholeAegeanSea .Itsquaternarynormalfaulting (Sebriere ,1 977)anditshighseismicity (PapazachosandPapazachou ,1 997;AmbraseysandJackson ,1 990 )makeitaphysicallaboratorywithintheMediterraneanarea ,wherethephysicalprocessrelatedtotheseismiccyclecouldbestudied .ThecityofAeghionexperiencedastrong (MW =6 4 )earthquakeinJune 1 995,whichcausedseveredamage (Tselentis ,etal.,1 996 ) .Twent…  相似文献   

Large Scale Tests on Jointed and Bedded Rocks Under Multi-Stage Triaxial Compression and Direct Shear     

Maximiliano R. Vergara  Peter Kudella  Theodoros Triantafyllidis 《Rock Mechanics and Rock Engineering》2015,48(1):75-92

  相似文献   

Subcontinental lithospheric mantle beneath Central Europe     

Jacek Puziewicz  Magdalena Matusiak-Małek  Theodoros Ntaflos  Michel Grégoire  Anna Kukuła 《International Journal of Earth Sciences》2015,104(8):1913-1924

  相似文献   

Monotonic and cyclic tests on kaolin: a database for the development,calibration and verification of constitutive models for cohesive soils with focus to cyclic loading     

Torsten Wichtmann  Theodoros Triantafyllidis 《Acta Geotechnica》2018,13(5):1103-1128

A database with about 60 undrained monotonic and cyclic triaxial tests on kaolin is presented. In the monotonic tests, the influences of consolidation pressure, overconsolidation ratio, displacement rate and sample cutting direction have been studied. In the cyclic tests, the stress amplitude, the initial stress ratio and the control (stress vs. strain cycles) have been additionally varied. Isotropic consolidation leads to a failure due to large strain amplitudes with eight-shaped effective stress paths in the final phase of the cyclic tests, while a failure due to an excessive accumulation of axial strain and lens-shaped effective stress paths was observed in the case of anisotropic consolidation with \(q^{\text{ ampl }}< |q^{\text{ av }}|\). The rate of pore pressure accumulation grew with increasing amplitude and void ratio (i.e. decreasing consolidation pressure and overconsolidation ratio). The “cyclic flow rule” well known for sand has been confirmed also for kaolin: With increasing value of the average stress ratio \(|\eta ^{\text{ av }}| = |q^{\text{ av }}|/p^{\text{ av }}, \) the accumulation of deviatoric strain becomes predominant over the accumulation of pore water pressure. The tests on the samples cut out either horizontally or vertically revealed a significant effect of anisotropy. In the cyclic tests, the two kinds of samples exhibited an opposite inclination of the effective stress path. Furthermore, the horizontal samples showed a higher stiffness and could sustain a much larger number of cycles to failure. All data of the present study are available from the homepage of the first author. They may serve for the examination, calibration or improvement in constitutive models dedicated to cohesive soils under cyclic loading, or for the development of new models.  相似文献   

Regularities and mechanism of formation of the mantle lithosphere structure beneath the Siberian Craton in comparison with other cratons     

I.V. Ashchepkov  N.V. Vladykin  T. Ntaflos  H. Downes  R. Mitchell  A.P. Smelov  N.V. Alymova  S.I. Kostrovitsky  A. Ya Rotman  G.P. Smarov  I.V. Makovchuk  Yu.B. Stegnitsky  E.N. Nigmatulina  O.S. Khmelnikova 《Gondwana Research》2013,23(1):4-24

Regularities of the mantle structure beneath the Siberian Craton were determined using the monomineral thermobarometry and common Opx-Gar methods. Samples were taken from 80 pipes from the Siberian Craton and in comparison 70 pipes from worldwide kimberlites. The largest pipes contain several dunite layers in the lower part of lithospheric mantle which are responsible for the diamond grade. The lithospheric mantle consists of two major parts divided at a depth of 4.0 GPa by a pyroxenite layer. Major intervals determined for the mantle beneath Udachnaya and Mir are: 1) 8.0–6.5 GPa harzburgites, eclogites and dunitic veins; 2) 6.5–5.5 GPa sheared peridotites, low-Cr pyroxenites, dunites; 3)in 5.5–4.0 GPa interval there are 4–6 layers of harzburgitic paleoslabs; 4) 4.0–3.5 GPa the pyroxenites lens; 5) upper layered Sp-Gar peridotite sequence including a trap of basaltic and other silicate melt cumulates at 3.0–2.0 GPa. The lithospheric mantle beneath seven different tectonic terrains in Siberia is characterized by TRE geochemistry and major elements of peridotitic clinopyroxenes. The mantle in Magan terrain contains more fertile peridotites in the South (Mir pipe) than in North (Alakit) which were metasomatized by subduction-related melts producing Phl and Cpx about 500–800 Ma ago. Daldyn terrain is essentially harzburgitic in the west part (abyssal peridotite) but in the east in Upper Muna (East Daldyn terrain) the mantle is more differentiated and in general more oxidized. The Markha terrain (Nakyn) contains depleted but partly refertilized harzburgites, subducted pelitic material and abundant eclogites. Circum-Anabar mantle is ultradepleted in the lower part but in the upper regions it has been fertilized by fluid-rich melts very enriched in incompatible elements. The P-Fe# diagrams (and other components) reveal different structure of mantle columns in each terrain. They are subvertical for the mantle sampled by Devonian pipes. Beneath Mesozoic pipes the mantle has been affected by melt percolation caused by the Siberian Superplume which created continuous Fe-enrichment in the upper part. The models of continent growth and evolution are briefly discussed. In general the geothermal regime and mantle heating is negatively correlated with the thickness of lithosphere. The sheared peridotites under Udachnaya and other kimberlite pipe are likely to have formed after the intrusion of protokimberlite volatile rich (hydrous) melts and hydraulic fracturing. This mechanism is responsible for the origin of asthenospheric lenses.Progressive melting especially in the pervasive zones may be responsible for the creation of 3-4 upper asthenospheric lens near mostly before 4.0 GPa which may be accompanied by mantle diapirism. Such a lens is the trap for the kimberlites in Siberia in Mesozoic time and in rifted intracontinental areas and margins.  相似文献   

Clinopyroxene megacrysts from Enmelen melanephelinitic volcanoes (Chukchi Peninsula,Russia): application to composition and evolution of mantle melts     

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   

Shearing of Materials with Intermittent Joints     

Eleni Gerolymatou  Theodoros Triantafyllidis 《Rock Mechanics and Rock Engineering》2016,49(7):2689-2700

  相似文献   

Constraints of the formation of carbonatites in the Chernigovka Massif,Azov Region,Ukraine     

I. D. Ryabchikov  L. N. Kogarko  S. G. Krivdik  T. Ntaflos 《Geology of Ore Deposits》2008,50(6):423-432

Data on compositions of coexisting minerals in the graphite-bearing carbonatites of the Chernigovka massif are reported. Thermodynamic analysis of these results made it possible to establish that the temperature of equilibrium between graphite, dolomite, calcite, magnetite, and olivine for silica activity buffered by the (zircon + baddeleyite) assemblage is approximately 600°C. The minimal pressure of formation of these mineral assemblages is approximately 0.2 GPa, which is consistent with estimates of the erosion depth for the Chernigovka massif. The oxygen fugacity typical of the graphite-bearing carbonatite is 0.6–0.8 log units below the quartz-magnetite-fayalite buffer. Such values are typical of magmatic systems, e.g., basalts of the mid-ocean ridges (MORB). At 600°C, the gas phase in the C-H-O system equilibrated with the mineral assemblage of the carbonatite studied is dominated by CO₂ and H₂O, whereas methane-rich fluids appear at lower temperatures.  相似文献