Partial pressure and air–sea CO2 flux in the Aegean Sea during February 2006     

Evangelia Krasakopoulou  Spyridon Rapsomanikis  Anastasios Papadopoulos  Evangelos Papathanassiou 《Continental Shelf Research》2009,29(11-12):1477-1488

Data on the distribution of fCO₂ were obtained during a cruise in the Aegean Sea during February 2006. The fCO₂ of surface water (fCO₂^sw) was lower than the atmospheric fCO₂ (fCO₂^atm) throughout the area surveyed and ΔfCO₂ values varied from ?34 to ?61 μatm. The observed under-saturation suggests that surface waters in the Aegean represent a sink for atmospheric CO₂ during the winter of 2006. Higher fCO₂^sw values were recorded in the ‘less warm’ and ‘less saline’ shallow northernmost part of the Aegean Sea implying that the lower seawater temperature and salinity in this area play a crucial role in the spatial distribution of fCO₂^sw.A first estimate of the magnitude of the air–sea CO₂ exchange and the potential role of the Aegean Sea in the transfer of atmospheric CO₂ was also obtained. The air–sea CO₂ fluxes calculated using different gas transfer formulations showed that during February 2006, the Aegean Sea absorbs atmospheric CO₂ at a rate ranging from ?6.2 to ?11.8 mmol m^?2 d^?1 with the shipboard recorded wind speeds and at almost half rate (?3.5 to ?5.5 mmol m^?2 d^?1) with the monthly mean model-derived wind speed. Compared to recent observations from other temperate continental shelves during winter period, the Aegean Sea acts as a moderate to rather strong sink for atmospheric CO₂.Further investigations, including intensive spatial and temporal high-resolution observations, are necessary to elucidate the role of the Aegean Sea in the process of transfer of atmospheric CO₂ into the deep horizons of the Eastern Mediterranean.  相似文献   

Complex Site Effects in Thessaloniki (Greece): II. 2D SH Modelling and Engineering Insights     

Dimitrios?RaptakisEmail author  Konstantia?Makra  Anastasios?Anastasiadis  Kyriazis?Pitilakis 《Bulletin of Earthquake Engineering》2004,2(3):301-327

This paper presents results of numerical modelling of site response for Thessaloniki, obtained with two different 2D methods; a finite difference and a finite element method. Ground motion across a 2D model of the subsoil of the city has been simulated for vertically incident SH waves. The predominance of locally generated surface waves is very clear in the synthetic seismograms of a weak event and of stronger ones. These results are then compared with the observations in time domain and frequency domain. The role of the soil formations with high attenuation in the lateral propagation and the effect of the differential motion close to the lateral variations are also pinpointed. The stronger events were finally used to compute strong ground motion in order to reveal and to discuss practical engineering aspects such as peak ground acceleration value, the most familiar indicator in seismic norms, the soil to rock spectral coefficients for the period bandwidth of interest, and the aggravation factor in terms of 2D to 1D response spectra as a useful ruler to account for complex site effects.  相似文献   

Tsunami Hazard in the Eastern Mediterranean: Strong Earthquakes and Tsunamis in the Corinth Gulf,Central Greece     

Papadopoulos  Gerassimos A. 《Natural Hazards》2003,29(3):437-464

The exhaustive review of a long number of historical documents, books, reports,scientific and press reports, instrumental recordings, previous catalogues andpersonal field observations, concluded with the production of a completely newtsunami catalogue for the Corinth Gulf, Central Greece, which is arranged in theformat adopted by the GITEC group for the new European Tsunami Catalogue.The catalogue is presented in three sections: the Quick-Look Table, the Quick-LookAccounts File and the References File. An Appendix explains why some particularsea disturbances were not included in the new catalogue although they were consideredas tsunami events by previous researchers. Past history clearly shows that most tsunamis in the Corinth Gulf are produced by strong (Ms 5.5) offshore and near shore earthquakes. However, seismic or aseismic sliding of coastal and submarine sediments is a significant factor in tsunamigenesis. Calculations based on the random model indicate that the probability for at least one tsunami occurrence of intensity TI 2 TI 3 and TI 4 within 50 years equals 0.851, 0.747 and 0.606, respectively. From the intensity–frequency relationship the mean return period of tsunami intensity TI 2, TI 3 and TI 4 equals to 16, 40 and 103 years. The tsunami geographicaldistribution, however, is non-random with a clear trend for the tsunamigenesis todecrease drastically from west to east within the Corinth Gulf. In fact, the probabilityfor a strong earthquake to cause a tsunami of TI 3 in the Corinth Gulf consideredas an entity is 0.35, while in the western part of the Gulf it goes up to 0.55. Therefore, the rapid and accurate determination of the earthquake focal parameters is of great importance in an algorithm of a real-time tsunami warning system in the Corinth Gulf.  相似文献   

Empirical relationships between aftershock area dimensions and magnitude for earthquakes in the Mediterranean Sea region     

Konstantinos I. Konstantinou  Gerassimos A. Papadopoulos  Anna Fokaefs  Katerina Orphanogiannaki 《Tectonophysics》2005,403(1-4):95-115

Fault dimension estimates derived from the aftershock area extent of 36 shallow depth (≤ 31 km) earthquakes that occurred in the Mediterranean Sea region have been used in order to establish empirical relationships between length, width, area and surface-wave/moment magnitude. This dataset consists of events whose aftershock sequence was recorded by a dense local or regional network and the reported location errors did not exceed on average 3–5 km. Surface-wave magnitudes for these events were obtained from the NEIC database and/or published reports, while moment magnitudes as well as focal mechanisms were available from the Harvard/USGS catalogues. Contrary to the results of some previously published studies we found no evidence in our dataset that faulting type may have an effect on the fault dimension estimates and therefore we derived relationships for the whole of the dataset. Comparisons, by means of statistical F-tests, of our relationships with other previously published regional and global relationships were performed in order to check possible similarities or differences. Most such comparisons showed relatively low significance levels (< 95%), since the differences in source dimension estimates were large mainly for magnitudes lower than 6.5, becoming smaller with increasing magnitude. Some degree of similarity, however, could be observed between our fault length relationship and the one derived from aftershock area lengths of events in Greece, while a difference was found between our regional and global fault length relationships. A calculation of the ratio defined as the fault length, derived from our relationships, to the length estimated from regional empirical relationships involving surface ruptures showed that it can take a maximum value of about 7 for small magnitudes while it approaches unity at Ms 7.2. When calculating the same ratio using instead global empirical relationships we see the maximum value not exceeding 1.8, while unity is reached at Mw 7.8, indicating the existence of a strong regional variation in the fault lengths of earthquakes occurring in the Mediterranean Sea region. Also, a relationship between the logarithms of the rupture area and seismic moment is established and it is inferred that there is some variation of stress drop as a function of seismic moment. In particular, it is observed that for magnitudes lower than 6.6 the stress drop fluctuates around 10 bar, while for larger magnitudes the stress drop reaches a value as high as 60 bar.  相似文献   

Altersbeziehungen zwischen Metamorphose und Deformation im zentralen Teil des Serbomazedonischen Massivs (Vertiskos Gebirge,Nord-Griechenland)     

Dr. C. Papadopoulos  Dr. A. Kilias 《International Journal of Earth Sciences》1985,74(1):77-85

The relations between metamorphism and deformation of the crystalline rocks in the central part of the Serbomacedonian mass (mountain Vertiskos), are studied. It is found a syntectonic — amphibolitic metamorphic phase (Kr₁) in reference to a folding phase (T₁), characterized by almost vertical isoclinal shear-folds. This main metamorphism was followed by a syntectonic metamorphism of green schist facies (Kr₂) in relation to a folding phase (T₂), characterized by slightly inclined fractured folds, directied NNW-SSE to NNE-SSW. Finally, a very low grade metamorphic event (Diaphthorese, Kr₃) influenced the whole rocks of the area. It can be regarded either as the final stage of the Kr₂ phase or as a younger and distinct metamorphic event. The K/Ar and Rb/Sr datation of the white micas, biotites and hornblends showed that the Kr₂ phase is of Cretaceous age and so the Kr₁ phase must be older than Cretaceous.  相似文献   

Evidence for periodic seismicity in the inner Aegean seismic zone     

G. A. Papadopoulos  Ph. Voidomatis 《Pure and Applied Geophysics》1987,125(4):613-628

The most complete and reliable data of strong (M _s6.5), shallow (h<70 km) earthquakes which occurred in the inner Aegean seismic zone have been utilized to describe its seismicity time variation during 1800–1986 by two independent statistical models. The first is a sequentially stationary model of seismicity rates which shows that intervals of low seismicity rate, lasting for some 37 years, alternate with high rate intervals of 8–12 years duration. The second model is a statistical model according which seismic energy released within 5-year time windows approximates a harmonic curve within a period of about 50 years. This model is in agreement with the notion that the time series of strong earthquake occurrences in the inner Aegean seismic zone consists of a random (shocks withM _s=6.5–6.8) and a nonrandom component (M _s6.9). Maxima and minima of the harmonic curve coincide with the high and low rate intervals, respectively. A model of regional stationary accumulation of thermal stresses along certain seismic belts and their cyclic relaxation may explain this periodicity.  相似文献   

Newtonian tidal theory and PPN metric theory. Variable G and earthquakes,II   总被引：1，自引：0，他引：1  

D. D. Dionysiou  G. A. Papadopoulos  E. N. Sarris  P. G. Tsikouras 《Earth, Moon, and Planets》1994,64(1):1-29

The tidal accelerations due to the Moon and the Sun can be computed at the same time and place of the earthquake events. The search for an earthquake-tide correlation has been referred to small Greek regions and in certain magnitude range. The events correlating with the tides are functions of the angles of the place with respect to the sublunar and subsolar points. A significant correlation has been obtained between the earthquake events and the gravity tide which means that tides are one of the most important triggering mechanism, or in other words, triggering appears as function of Newtonian or Post-Newtonian gravity. Any tidal correlation of earthquakes, which has been examined in this paper, is explicitly given by Tables and Figures as a function of Newtonian and Post-Newtonian gravity.The present paper completes the previous one.This work has been supported by the Greek General Secretariat of Research and Technology under Grant No. 89E160.  相似文献   

Rocking amplification and strong‐motion duration          下载免费PDF全文

Anastasios I. Giouvanidis  Elias G. Dimitrakopoulos 《地震工程与结构动力学》2018,47(10):2094-2116

This paper characterizes the ability of natural ground motions to induce rocking demands on rigid structures. In particular, focusing on rocking blocks of different size and slenderness subjected to a large number of historic earthquake records, the study unveils the predominant importance of the strong‐motion duration to rocking amplification (ie, peak rocking response without overturning). It proposes original dimensionless intensity measures (IMs), which capture the total duration (or total impulse accordingly) of the time intervals during which the ground motion is capable of triggering rocking motion. The results show that the proposed duration‐based IMs outperform all other examined (intensity, frequency, duration, and/or energy‐based) scalar IMs in terms of both “efficiency” and “sufficiency.” Further, the pertinent probabilistic seismic demand models offer a prediction of the peak rocking demand, which is adequately “universal” and of satisfactory accuracy. Lastly, the analysis shows that an IM that “efficiently” captures rocking amplification is not necessarily an “efficient” IM for predicting rocking overturning, which is dominated by the velocity characteristics (eg, peak velocity) of the ground motion.  相似文献   

A frequency‐dependent and intensity‐dependent macroelement for reduced order seismic analysis of soil‐structure interacting systems          下载免费PDF全文

Nikolaos Lesgidis  Anastasios Sextos  Oh‐Sung Kwon 《地震工程与结构动力学》2018,47(11):2172-2194

The computational demand of the soil‐structure interaction analysis for the design and assessment of structures, as well as for the evaluation of their life‐cycle cost and risk exposure, has led the civil engineering community to the development of a variety of methods toward the model order reduction of the coupled soil‐structure dynamic system in earthquake regions. Different approaches have been proposed in the past as computationally efficient alternatives to the conventional finite element model simulation of the complete soil‐structure domain, such as the nonlinear lumped spring, the macroelement method, and the substructure partition method. Yet no approach was capable of capturing simultaneously the frequency‐dependent dynamic properties along with the nonlinear behavior of the condensed segment of the overall soil‐structure system under strong earthquake ground motion, thus generating an imbalance between the modeling refinement achieved for the soil and the structure. To this end, a dual frequency‐dependent and intensity‐dependent expansion of the lumped parameter modeling method is proposed in the current paper, materialized through a multiobjective algorithm, capable of closely approximating the behavior of the nonlinear dynamic system of the condensed segment. This is essentially the extension of an established methodology, also developed by the authors, in the inelastic domain. The efficiency of the proposed methodology is validated for the case of a bridge foundation system, wherein the seismic response is comparatively assessed for both the proposed method and the detailed finite element model. The above expansion is deemed a computationally efficient and reliable method for simultaneously considering the frequency and amplitude dependence of soil‐foundation systems in the framework of nonlinear seismic analysis of soil‐structure interaction systems.  相似文献   

Mainshock-consistent ground motion record selection for aftershock sequences     

Athanasios N. Papadopoulos  Mohsen Kohrangi  Paolo Bazzurro 《地震工程与结构动力学》2020,49(8):754-771

In recent years, the additional risk posed to the built environment due to aftershock sequences and triggered events has been brought to attention, and several efforts have been directed towards developing fragility functions for structures in damaged conditions. Despite this rise of interest, a rather fundamental component for such tasks, namely that of aftershock ground motion record selection, has remained under-scrutinized. Herein, we propose a pragmatic procedure that can be applied for the selection of mainshock-aftershock ground motion pairs using consistent causal parameters and accounting for the correlation between their spectral accelerations. In addition, a structural analysis strategy that can be employed for the analytical derivation of damage-dependent fragility functions is outlined and presented through a case study. A more conventional back-to-back IDA analysis is also carried out in order to compare the derived damage-dependent fragility functions with the ones obtained with the proposed procedure. The results indicate that record selection remains a crucial factor even when assessing the structural vulnerability of damaged buildings, and should thus be treated cautiously.  相似文献