P and S velocity structures of the Santorini–Coloumbo volcanic system (Aegean Sea,Greece) obtained by non-linear inversion of travel times and its tectonic implications     

I. Dimitriadis  C. Papazachos  D. Panagiotopoulos  P. Hatzidimitriou  M. Bohnhoff  M. Rische  T. Meier 《Journal of Volcanology and Geothermal Research》2010

One of the most prominent tectonic features of the Eastern Mediterranean region is the Hellenic volcanic arc in the Southern Aegean Sea, with the Santorini Island being one of the most active volcanic centers. Recent seismic studies show that the main seismic activity of the Santorini volcanic center is strongly associated with the volcanic processes, as well as with the seismo-tectonic regime of the broader Southern Aegean Sea area. The main cluster of local seismicity is located near the northeastern edge of the Santorini Island, beneath the Coloumbo Reef, which is a submarine volcanic seamount of the Santorini Island volcanic system.  相似文献   

Biological Test for the Detection of Low Concentrations of Infectious Cryptosporidium parvum Oocysts in Water     

Panagiotis Karanis  Dirk Schoenen 《洁净——土壤、空气、水》2001,29(4):242-245

An in vivo SCID mouse infectivity assay was used to determine its capacity to detect the infectivity of low concentrations of Cryptosporidium parvum oocysts in water. This biological test can be applied to demonstrate oocysts infectivity in water samples derived from drinking water supply and/or environmental sources.  相似文献   

Determination of source,path and site parameters based on non-linear inversion of accelerometric data in Greece     

I. Grendas  N. Theodoulidis  P. Hatzidimitriou  B. Margaris  S. Drouet 《Bulletin of Earthquake Engineering》2018,16(11):5061-5094

Source, propagation path and site conditions are the factors affecting seismic ground motion. Consequently, recordings acquired at a seismic station are formed by the convolution of these three factors. In this work S-wave acceleration Fourier spectra of earthquakes recorded at local and regional scale, by the ITSAK accelerometric network for the period 2010–2016, are modeled as a product of source, propagation path (including geometric and anelastic attenuation) and site effects. The data set consists of 136 crustal earthquakes occurred in the broader Aegean area, with magnitudes 4.2?≤?M_w?≤?6.5 and epicentral distances 20 km?≤?R?≤?350 km, recorded at 112 broadband accelerometric stations installed at sites with various geologic conditions. Based on this data set, an iterative Gauss–Newton inversion method to solve the non-linear problem and retrieve the different terms of source, propagation path and site, is applied. This method uses an initial input model trying to find the best and at the same time a stable solution for the inverted parameters, which are, moment magnitude (M_w), corner frequency (f_c), attenuation quality factor (Q_s?=?Q_of^α), slope of the geometric attenuation (1/R^γ) and site transfer function (S(f)). The initial values of the starting model can be either known from other studies or inferred within a reasonable range. Depending on the level of knowledge on these input parameters, the associated standard deviation can be adjusted (large values for unknown parameters or small values for parameters which are well constrained). Results of the analyses exhibit satisfactory agreement of estimated source parameters with those proposed by seismological centers in Greece and propagation path properties similar to the ones determined in relevant previous studies for the same region. In addition, the site transfer functions obtained by the non-linear inversion are comparable with those calculated for the same sites using either standard spectral ratio or horizontal-to-vertical spectral ration (HVSR—receiver function) techniques. The aforementioned results are encouraging for reliable earthquake source parameters, propagation path properties and site effect assessment, in areas of intermediate to high seismicity.  相似文献   

Optimum seismic design of reinforced concrete frames according to Eurocode 8 and fib Model Code 2010          下载免费PDF全文

Panagiotis E. Mergos 《地震工程与结构动力学》2017,46(7):1181-1201

Traditional seismic design, like the one adopted in Eurocode 8 (EC8), is force‐based and examining a single level of seismic action. In order to provide improved control of structural damage for different levels of seismic action, the new fib Model Code 2010 (MC2010) includes a fully fledged displacement‐based and performance‐based seismic design methodology. However, the level of complexity and computational effort of the MC2010 methodology is significantly increased. Hence, the use of automated optimization techniques for obtaining cost‐effective design solutions becomes appealing if not necessary. This study employs genetic algorithms to derive and compare optimum seismic design solutions of reinforced concrete frames according to EC8 and MC2010. This is important because MC2010 is meant to serve as a basis for future seismic design codes. It is found that MC2010 drives to more cost‐effective solutions than EC8 for regions of low seismicity and better or similar costs for regions of moderate seismicity. For high‐seismicity regions, MC2010 may yield similar or increased structural costs. This depends strongly on the provisions adopted for selecting the set of ground motions. In all cases, MC2010 provides enhanced control of structural damage. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Electrical resistivity tomography mapping of beachrocks: application to the island of Thassos (N. Greece)   总被引：1，自引：0，他引：1  

Psomiadis David  Tsourlos Panagiotis  Albanakis Konstantinos 《Environmental Earth Sciences》2009,59(1):233-240

Electrical resistivity tomography (ERT) technique is widely used in mapping subsurface electrical properties. In this study, ERT was used to map a beachrock outcrop, extended both inland, under beach sediments, and seawards, on and under seafloor sediments. Mapping of beachrock is considered important because it can help evaluate the lateral and vertical extend of the formation. Fast and reliable mapping of beachrocks may contribute in several applications like engineering and construction, coastal management, recreational reformation as well as scientific approaches like coastal evolution research, and palaeo-environmental studies. The outcome of the survey was the mapping of the formation with centimeter precision, especially towards the sea. Special processing was applied to the data in order to constrain the inversion procedure to include the known sea water layer.  相似文献   

A Timoshenko finite element straight beam with internal degrees of freedom          下载免费PDF全文

Denis Caillerie  Panagiotis Kotronis  Robert Cybulski 《国际地质力学数值与分析法杂志》2015,39(16):1753-1773

We present hereafter the formulation of a Timoshenko finite element straight beam with internal degrees of freedom, suitable for nonlinear material problems in geomechanics (e.g., beam type structures and deep pile foundations). Cubic shape functions are used for the transverse displacements and quadratic for the rotations. The element is free of shear locking, and we prove that one element is able to predict the exact tip displacements for any complex distributed loadings and any suitable boundary conditions. After the presentation of the virtual power and the weak form formulations, the construction of the elementary stiffness matrix is detailed. The analytical results of the static condensation method are provided. It is also proven that the element introduced by Friedman and Kosmatka in 1 , with shape functions depending on material properties, is derived from the new beam element. Validation is provided using linear and material nonlinear applications (reinforced concrete column under cyclic loading) in the context of a multifiber beam formulation. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Development of the SAR TT-OSL procedure for dating Middle Pleistocene dune and shallow marine deposits along the southern Cape coast of South Africa   总被引：1，自引：0，他引：1  

Zenobia Jacobs  Richard G. Roberts  Terry J. Lachlan  Panagiotis Karkanas  Curtis W. Marean  David L. Roberts 《Quaternary Geochronology》2011,6(5):491-513

Optically stimulated luminescence (OSL) dating is now commonly used to estimate the depositional age of Quaternary landforms along the southern Cape coast of South Africa. Due to the early onset of dose saturation in the quartz-rich sediments from this region, determining the age of deposits much older than the last three glacio-eustatic sea-level high stands has been a challenge. In this study, we explored the feasibility of using the thermally-transferred OSL (TT-OSL) dating method to obtain ages for aeolian and shallow marine deposits at three different localities that hold promise to further illuminate the long and complex Late Quaternary sea-level history of this region. The bleachability and behaviour of both the recuperated OSL (ReOSL) and the basic-transferred OSL (BT-OSL) signals were investigated, and used as independent chronometers to infer (a) the degree of bleaching of the sediments and (b) the stability of the ReOSL signal for dating of older samples. We examined the sensitivity of both signals to varying preheat temperatures and further developed the single-aliquot regenerative-dose procedure for TT-OSL dating of our samples. To verify our procedures, and to understand some of the underlying mechanisms responsible for the problems we observed, modern analogues and known-age Marine Isotope Sub-stage (MIS) 5e samples from the same localities were also measured. The Middle Pleistocene deposits investigated in this study produced statistically consistent ReOSL and BT-OSL ages compatible with sea-level high stands during Marine Isotope Stage 11. This result is of considerable significance, as it may yield new insights into maximum sea-level heights during this period, which is widely considered an appropriate analogue for future environmental conditions.  相似文献   

Mineralogy and geochemical environment of formation of the Perama Hill high-sulfidation epithermal Au-Ag-Te-Se deposit, Petrota Graben, NE Greece   总被引：1，自引：0，他引：1  

Panagiotis Christos Voudouris  Vasilios Melfos  Paul G. Spry  Robert Moritz  Constantinos Papavassiliou  George Falalakis 《Mineralogy and Petrology》2011,103(1-4):79-100

  相似文献   

Provenance analysis of Eocene–Oligocene turbidite deposits in Pindos Foreland Basin, fold and thrust belt of SW Greece: constraints from framework petrography and bulk-rock geochemistry     

Panagiotis A. Konstantopoulos  Avraam Zelilidis 《Arabian Journal of Geosciences》2013,6(12):4671-4700

The provenance of Eocene–Oligocene turbidites from the Pindos Foreland Basin, SW Greece, has been constrained using petrographical and geochemical techniques. Modal petrographic analysis of the studied sandstones shows that the source area comprises sedimentary, metamorphic, and plutonic igneous rocks deposited in a recycled orogenic environment and in magmatic arc province. The relative proportions of the detrital components indicate that the Late Eocene–Early Oligocene sandstones of West Peloponnesus are quartz-rich and were primarily derived from granitic and metamorphic basement rocks typically of a tectonically active area. Major, trace, and rare earth element (REE) concentrations in both sandstones and mudstones complement the petrographical data indicating an active continental margin/continental island arc signature. All the samples are light REE, enriched relative to heavy REE (HREE), with flat HREE pattern and positive Eu anomalies, suggesting that the processes of intra-crustal differentiation (involving plagioclase fractionation) were not of great importance. The results derived from the multi-element diagrams also suggest an active margin character and a mafic/ultramafic source rock composition.  相似文献   

J-type carbon stars in the Large Magellanic Cloud     

D. H. Morgan  R. D. Cannon  D. Hatzidimitriou  B. F. W. Croke 《Monthly notices of the Royal Astronomical Society》2003,341(2):534-550

A sample of 1497 carbon stars in the Large Magellanic Cloud (LMC) has been observed in the red part of the spectrum with the 2dF facility on the Anglo-Australian Telescope. Of these, 156 have been identified as J-type (i.e. ¹³C-rich) carbon stars using a technique which provides a clear distinction between J stars and the normal N-type carbon stars that comprise the bulk of the sample, and yields few borderline cases. A simple two-dimensional classification of the spectra, based on their spectral slopes in different wavelength regions, has been constructed and found to be related to the more conventional c and j indices, modified to suit the spectral regions observed. Most of the J stars form a photometric sequence in the   K − ( J − K )  colour–magnitude diagram, parallel to and 0.6 mag fainter than the N-star sequence. A subset of the J stars (about 13 per cent) are brighter than this J-star sequence; most of these are spectroscopically different from the other J stars. The bright J stars have stronger CN bands than the other J stars and are found strongly concentrated in the central regions of the LMC. Most of the rather few stars in common with Hartwick and Cowley's sample of suspected CH stars are J stars. Overall, the proportion of carbon stars identified as J stars is somewhat lower than has been found in the Galaxy. The Na D lines are weaker in the LMC J stars than in either the Galactic J stars or the LMC N stars, and do not seem to depend on temperature.  相似文献