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31.
Athanassios Ganas Kostas Chousianitis Evaggelia Batsi Maria Kolligri Apostolos Agalos Gerassimos Chouliaras Kostas Makropoulos 《Journal of Seismology》2013,17(2):465-484
On 18 January 2010, 15:56 UTC, a M w ?=?5.1 (National Observatory of Athens; NOA) earthquake occurred near the town of Efpalion (western Gulf of Corinth, Greece), about 10 km to the east of Nafpaktos, along the north coast of the Gulf. Another strong event occurred on 22 January 2010, 00:46 UTC with M w ?=?5.1 (NOA) approximately 3 km to the NE of the first event. We processed the seismological and geodetic data to examine fault plane geometry, dip direction, and earthquake interactions at the western tip of the Corinth rift. Our data include relocated epicenters of 1,760 events for the period January–June 2010 and daily global positioning system observations from the Efpalio station for the period 1 December 2009–1 March 2010. We suggest that the first event ruptured a blind, north-dipping fault, accommodating north–south extension of the Western Gulf of Corinth. The dip direction of the second event is rather unclear, although a south dip plane is weakly imaged in the post-22 January 2010 aftershock distribution. A Coulomb stress model based on homogeneous slip distribution of the first event showed static stress triggering of the second event of the order of 22–34 KPa that was transferred along the plane of failure. We also point out the existence of north dipping, high-angle faults at 10–15 km depths, which were reactivated because of Coulomb stress transfer, to the west and south of Efpalion. The January 2010 earthquakes ended a 15-year-old quiescence in that area of the Gulf. The crustal volume near Efpalion was also characterized by b values in the range 0.6–0.8 (1970–2010 period). 相似文献
32.
Kostas Philippopoulos Despina Deligiorgi Thaleia Mavrakou John Cheliotis 《Meteorology and Atmospheric Physics》2014,124(3-4):195-204
This study presents an analysis of the relationship between winter large-scale circulation and surface meteorological conditions over Greece for the period 1979–2009. The adopted methodology involves the application of an automated atmospheric circulation classification scheme based on the self-organizing map approach. The impact of each of the identified relevant 19 winter atmospheric circulation patterns on local meteorological condition is examined at seven sites by calculating the corresponding differences from the mean meteorological conditions. The conditional transition probabilities of circulation patterns indicate the existence of increased 1-day persistence, especially for the anticyclonic and the pattern related to Genoa depressions. Positive temperature anomalies are observed for the cyclonic patterns, while negative anomalies are attributed to the effect of anticyclonic circulation. 相似文献
33.
The feeding habits of the deep-sea blue–red shrimp Aristeus antennatus were determined based on the analysis of 1047 stomach contents, sampled in the Greek Ionian Sea (E. Mediterranean). The diet of this economically and biologically important decapod was studied in relation to the season, size class and sex. The diet of A. antennatus consisted of 54 different prey categories, and belonged mainly to smaller crustaceans (e.g. natantian decapods, euphausiids, tanaidaceans), molluscs, polychaetes, chaetognaths and, to a lesser extent, fishes. The above prey categories consisted of 71–82% of the relative abundance and total occurrence for males and 61–81% for females. Females seemed to be better fed than males (stomach fullness, food quality). A. antennatus displayed a highly diversified diet and the different feeding patterns were discussed. Diet composition showed slight seasonal fluctuations. The observed slight differences on A. antennatus diet among the western, central and eastern Mediterranean could be attributed to the more oligotrophic character of the eastern part of the basin. The principal factors driving the changes in the feeding strategy of this decapod among the seasons are the increased energy demands related to sexual requirements and the food availability in the marine environment. The ontogenetic changes in the shrimp's diet were relatively clear. Larger individuals exhibited selecting prey with a good swimming capacity (e.g. fishes), while the smaller individuals consumed prey with low mobility (e.g. copepods, ostracods). 相似文献
34.
Small-Strain Shear Modulus and Damping Ratio of Sand-Rubber and Gravel-Rubber Mixtures 总被引：2，自引：0，他引：2
Anastasios Anastasiadis Kostas Senetakis Kyriazis Pitilakis 《Geotechnical and Geological Engineering》2012,30(2):363-382
This study examines the small-strain dynamic properties of mixtures composed of sandy and gravelly soils with granulated tire
rubber in terms of shear modulus (GO), and damping ratio in shear (Dmin). Torsional resonant column tests are performed on dry, dense specimens of soil-rubber mixtures in a range of soil to rubber
particles size 5:1–1:10 and rubber content from 0 to 35% by mixture weight. The experimental results indicate that the response
of the mixtures is significantly affected by the content of rubber and the relative size of rubber to soil particles. Concering
the small-strain shear modulus, an equivalent void ratio is introduced that considers the volume of rubber particles as part
of the total volume of voids. Based on a comprehensive set of test results a series of equations were developed that can be
used to evaluate the shear modulus and damping ratio at small shear strain levels if the confining pressure, the content of
rubber by mixture weight, the grain size of soil and rubber particles, and the dynamic and physical properties of the intact
soil are known. 相似文献
35.
Identifying wildland fire ignition factors through sensitivity analysis of a neural network 总被引：6，自引：2，他引：4
Christos Vasilakos Kostas Kalabokidis John Hatzopoulos Ioannis Matsinos 《Natural Hazards》2009,50(1):125-143
Artificial neural networks (ANNs) show a significant ability to discover patterns in data that are too obscure to go through
standard statistical methods. Data of natural phenomena usually exhibit significantly unpredictable non-linearity, but the
robust behavior of a neural network makes it perfectly adaptable to environmental models such as a wildland fire danger rating
system. These systems have been adopted by many developed countries that have invested in wildland fire prevention, and thus
civil protection agencies are able to identify areas with high probabilities of fire ignition and resort to necessary actions.
Since one of the drawbacks of ANNs is the interpretation of the final model in terms of the importance of variables, this
article presents the results of sensitivity analysis performed in a back-propagation neural network (BPN) to distinguish the
influence of each variable in a fire ignition risk scheme developed for Lesvos Island in Greece. Four different methods were
utilized to evaluate the three fire danger indices developed within the above scheme; three of the methods are based on network’s
weights after the training procedure (i.e., the percentage of influence—PI, the weight product—WP, and the partial derivatives—PD
methods), and one is based on the logistic regression (LR) model between BPN inputs and observed outputs. Results showed that
the occurrence of rainfall, the 10-h fuel moisture content, and the month of the year parameter are the most significant variables
of the Fire Weather, Fire Hazard, and Fire Risk Indices, respectively. Relative humidity, elevation, and day of the week have
a small contribution to fire ignitions in the study area. The PD method showed the best performance in ranking variables’
importance, while performance of the rest of the methods was influenced by the number of input parameters and the magnitude
of their importance. The results can be used by local forest managers and other decision makers dealing with wildland fires
to take the appropriate preventive measures by emphasizing on the important factors of fire occurrence. 相似文献
36.
Multivariate analysis of landscape wildfire dynamics in a Mediterranean ecosystem of Greece 总被引：5，自引：0，他引：5
Kostas D Kalabokidis Nikos Koutsias Pavlos Konstantinidis† Christos Vasilakos‡ 《Area》2007,39(3):392-402
This paper focuses on spatial distribution of long-term fire patterns versus physical and anthropogenic elements of the environment that determine wildfire dynamics in Greece. Logistic regression and correspondence analysis were applied in a spatial database that had been developed and managed within a Geographic Information System. Cartographic fire data were statistically correlated with basic physical and human geography factors (geomorphology, climate, land use and human activities) to estimate the degree of their influence at landscape scale. Land cover types of natural and agricultural vegetation were the most influential factors for explaining landscape wildfire dynamics in conjunction with topography and grazing. 相似文献
37.
In a previous paper (Makropoulos and Burton, 1985) the seismic hazard in Greece was examined in terms of magnitude recurrence using Gumbel's third asymptotic distribution of extreme values and concepts of the physical process of strain energy release. The present study extends the seismic hazard methods beyond magnitude to the estimation of expectations of levels of peak ground acceleration exceedance thus allowing for a direct comparison between these two methodologies as well as establishing information relevant to design and planning criteria.The limited number of strong motion records do not permit regional study of attenuation of ground vibration in Greece. An average formula is derived from eight well known formulae which resulted from worldwide studies, this is: a = 2164 e0.70m (r+20)−1.80 cm s−2 where a is peak ground acceleration, m is earthquake magnitude and r is hypocentral distance in kilometres. This formula agrees with the observed values of peak ground acceleration values recorded in Greece.Acceleration seismic hazard is calculated at each of six chosen cities. Values of maximum acceleration with probability 70% of not been exceeded in the next 25, 50, 100, and 200 years are obtained along with corresponding values of velocity and displacement. The same detailed acceleration evaluation is then applied to the whole area of Greece by dividing it into cells of 0.5° lat × 0.5° long, and the results are illustrated through isoacceleration maps.Differences in magnitude and acceleration hazard maps reflect the fact that in acceleration hazard assessment the focal distance from a particular place in an important factor. The cities of Heraklion and Rodhos have the lowest acceleration hazard although the expected earthquakes may have large magnitude. Intermediate depth earthquakes characterise these two cities. Acceleration estimates, unlike magnitude hazard parameters, refer to a particular place and not to an area around it. Hence, even if two places have similar earthquake depth distributions, the hazards may differ significantly because of the different spatial distribution of the foci. This is observed in the case of Athens and Corinth. These cities have almost the same magnitude hazard, but the acceleration hazard is much lower for Athens where the hazard is mainly due to more distant earthquakes.The isoacceleration maps for Greece as a whole also define areas of high seismic hazard. These are the areas around Cephalonia and Leukas Islands in the Ionian Sea and the eastern Sporadhes, Lesbos Islands and Chalkidiki in the Northern Aegean Sea. At the 70% probability level the maximum acceleration is expected to be around 0.2g within the next 50 years. The areas where the maximum acceleration at the 70% probability level is expected to reach a value of 0.3g in the next 200 years are around Cephalonia and Leukas Islands and near the Dardanelles. 相似文献
38.
In a previous paper (Makropoulos andBurton, 1983) the seismic risk of the circum-Pacific belt was examined using a whole process technique reduced to three representative parameters related to the physical release of strain energy, these are:M
1, the annual modal magnitude determined using the Gutenberg-Richter relationship;M
2, the magnitude equivalent to the total strain energy release rate per annum, andM
3, the upper bound magnitude equivalent to the maximum strain energy release in a region.The risk analysis is extended here using the part process statistical model of Gumbel's IIIrd asymptotic distribution of extreme values. The circum-Pacific is chosen being a complete earthquake data set, and the stability postulate on which asymptotic distributions of extremes are deduced to give similar results to those obtained from whole process or exact distributions of extremes is successfully checked. Additionally, when Gumbel III asymptotic distribution curve fitting is compared with Gumbel I using reduced chi-squared it is seen to be preferable in all cases and it also allows extensions to an upper-bounded range of magnitude occurrences. Examining the regional seismicity generates several seismic risk results, for example, the annual mode for all regions is greater thanm(1)=7.0, with the maximum being in the Japan, Kurile, Kamchatka region atm(1)=7.6. Overall, the most hazardous areas are situated in this northwestern region and also diagonally opposite in the southeastern circum-Pacific. Relationships are established between the Gumbel III parameters and quantitiesm
1(1),X
2 and , quantities notionally similar toM
1,M
2 andM
3 although is shown to be systematically larger thanM; thereby giving a physical link through strain energy release to seismic risk statistics. Inall regions of the circum-Pacific similar results are obtained forM
1,M
2 andM
3 and the notionally corresponding statistical quantitiesm
1(1),X
2 and , demonstrating that the relationships obtained are valid over a wide range of seismotectonic enviroments. 相似文献
39.
Acta Geotechnica - Granular materials are often subjected to certain degrees of coating in natural conditions due to weathering and soil–environment interactions and the current literature... 相似文献
40.
Horst R. Beyer Kostas D. Kokkotas 《Monthly notices of the Royal Astronomical Society》1999,308(3):745-750
We present a mathematically rigorous proof that the r-mode spectrum of relativistic stars to the rotational lowest order has a continuous part. A rigorous definition of this spectrum is given in terms of the spectrum of a continuous linear operator. This study verifies earlier results by Kojima concerning the nature of the r-mode spectrum. 相似文献