Structural identification of Egnatia Odos bridges based on ambient and earthquake induced vibrations     

Evaggelos Ntotsios  Christos Karakostas  Vasilios Lekidis  Panagiotis Panetsos  Ioannis Nikolaou  Costas Papadimitriou  Thomas Salonikos 《Bulletin of Earthquake Engineering》2009,7(2):485-501

The dynamic characteristics of two representative R/C bridges on Egnatia Odos motorway in Greece are estimated based on low amplitude ambient and earthquake-induced vibrations. The present work outlines the instrumentation details, algorithms for computing modal characteristics (modal frequencies, damping ratios and modeshapes), modal-based finite element model (FEM) updating methods for estimating structural parameters, and numerical results for the modal and structural dynamic characteristics of the two bridges based on ambient and earthquake induced vibrations. Transverse, bending and longitudinal modes are reliably identified and stiffness-related properties of the piers, deck and elastomeric bearings of the FEMs of the two bridges are estimated. Results provide qualitative and quantitative information on the dynamic behavior of the bridge systems and their components under low-amplitude vibrations. Modeling assumptions are discussed based on the differences in the characteristics identified from ambient and earthquake vibration measurements. The sources of the differences observed between the identified modal and structural characteristics of the bridges and those predicted by FEMs used for design are investigated and properly justified.  相似文献   

Production of high-resolution remote sensing images for navigation information infrastructures     

WANGZhijun DjemelZiou CostasArmenakis 《地球空间信息科学学报》2004,7(2):129-134

This paper introduces the image fusion approach of multi-resolution analysis-based intensity modulation (MRAIM) to produce the high-resolution multi-spectral images from high-resolution panchromatic image and low-resolution multi-spectral images for navigation information infrastructure. The mathematical model of image fusion is derived according to the principle of remote sensing image formation. It shows that the pixel values of a high-resolution multi-spectral images are determined by the pixel values of the approximation of a high-resolution panchromatic image at the resolution level of low-resolution multi-spectral images, and in the pixel valae computation the M-band wavelet theory and the d trous algorithm are then used. In order to evaluate the MRAIM approach, an experiment has been carried out on the basis of the IKONOS 1 m panchromatic image and 4 m multi-spectral images. The result demonstrates that MRAIM image fusion approach gives promising fusion results and it can be used to produce the high-resolution remote sensing images required for navigation information infrastructures.  相似文献   

Radio VHF Precursors of Earthquakes     

Yuri Ruzhin  Costas Nomicos 《Natural Hazards》2007,40(3):573-583

On the basis of our analysis of a number of continuous observations made by the monitoring network on Crete, we assume that electrically active clouds are produced in an atmosphere above the sea on the eve of earthquake. These electrically active clouds, which occur at heights of 0.1–10 km, create the conditions for electrical discharges in an atmosphere that may be the source of the very high frequency (VHF) radio-emissions registered on Crete. We further suggest possible mechanisms of thunder electricity generation. We present the model of convection transport in which the first condition in the generation of thunder electricity is an atmosphere with a horizontal gradient of temperature. Base on this model, the occurrence of electrical charges on the surface of the sea and their transportation further upwards to heights of up to 10 km is due to pollution energy allocated within the bottom of the sea as gases and heat injection. The average flux density and power estimations of the VHF precursors were made for the Crete net situation to compare with published VHF data and radio star sources.  相似文献   

Source discriminants for near-field tsunamis   总被引：3，自引：0，他引：3  

Emile A. Okal  Costas E. Synolakis 《Geophysical Journal International》2004,158(3):899-912

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Laboratory experiments of tsunami runup on a circular island   总被引：2，自引：0，他引：2  

Michael J. Briggs  Costas E. Synolakis  Gordon S. Harkins  Debra R. Green 《Pure and Applied Geophysics》1995,144(3-4):569-593

Laboratory experiments of a 7.2-m-diameter conical island were conducted to study three-dimensional tsunami runup. The 62.5-cm tall island had 1 on 4 side slopes and was positioned in the center of a 30-m-wide by 25-m-long flat-bottom basin. Solitary waves with height-to-depth ratios ranging from 0.05 to 0.20 and source lengths ranging from 0.30 to 7.14 island diameters were tested in water depths of 32 and 42 cm. Twenty-seven capacitance wave gages were used to measure surface wave elevations at incident and four radial transects on the island slope. Maximum vertical runup measurements were made at 20 locations around the perimeter of the island using rod and transit. A new runup gage was located on the back or lee side of the island to record runup time series.  相似文献   

Far-field tsunami hazard from mega-thrust earthquakes in the Indian Ocean   总被引：2，自引：0，他引：2  

Emile A. Okal  Costas E. Synolakis 《Geophysical Journal International》2008,172(3):995-1015

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Modelling macroseismic observations for historical earthquakes: the cases of the M = 7.0, 1954 Sofades and M = 6.8, 1957 Velestino events (central Greece)   总被引：1，自引：0，他引：1  

Giannis Papazachos  Costas Papazachos  Andreas Skarlatoudis  Harris Kkallas  Efthimios Lekkas 《Journal of Seismology》2016,20(1):151-165

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Tsunami Generation Above a Sill   总被引：1，自引：0，他引：1  

Themistoklis S. Stefanakis  Frédéric Dias  Costas Synolakis 《Pure and Applied Geophysics》2015,172(3-4):985-1002

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Seasonal abundance of non-commercial demersal fish in the eastern Mediterranean Sea in relation to hydrographic and sediment characteristics     

Dimitrios Damalas  Christos D. Maravelias  Stelios Katsanevakis  Aristomenis P. Karageorgis  Costas Papaconstantinou 《Estuarine, Coastal and Shelf Science》2010

Fish-habitat associations were investigated for twenty-five non-commercial demersal species in the Aegean Sea (eastern Mediterranean) using Generalized Additive Modeling techniques. Fishery related abundance indices, derived from experimental bottom trawl surveys, were linked to various habitat variables: substrate characteristics, area, season, depth, temperature and salinity. Depth was the most important factor for all species. Eleven species showed decreasing abundance with depth, while the remaining species were more abundant in specific depth zones either on the continental shelf or in the upper continental slope. Most species were associated with specific substratum characteristics such as the dry weight percentage of sand-gravel and the carbonate content. The dry weight percentage of sand-gravel in the sediments was selected as a predictor of the relative abundance of most (twenty three) species. Seasonal patterns in the relative abundance of species were observed, related in most cases to the seasonal differentiation of temperature. The effect of temperature was more pronounced in summer and autumn, when a marked thermocline is observed, while it was much less intense in winter. For most of the species, the preferable habitat was identified, that contributes valuable information for the successful implementation of an ecosystem approach to fisheries management.  相似文献   

On the variability of the surface environment response to synoptic forcing over complex terrain: a multivariate data analysis approach     

Christos H. Halios  Costas G. Helmis  Helena A. Flocas  Stephan Nyeki  Dimosthenis N. Assimakopoulos 《Meteorology and Atmospheric Physics》2012,118(3-4):107-115

Synoptic climatology relates the atmospheric circulation with the surface environment. The aim of this study is to examine the variability of the surface meteorological patterns, which are developing under different synoptic scale categories over a suburban area with complex topography. Multivariate Data Analysis techniques were performed to a data set with surface meteorological elements. Three principal components related to the thermodynamic status of the surface environment and the two components of the wind speed were found. The variability of the surface flows was related with atmospheric circulation categories by applying Correspondence Analysis. Similar surface thermodynamic fields develop under cyclonic categories, which are contrasted with the anti-cyclonic category. A strong, steady wind flow characterized by high shear values develops under the cyclonic Closed Low and the anticyclonic H–L categories, in contrast to the variable weak flow under the anticyclonic Open Anticyclone category.  相似文献