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41.
Kourgialas Nektarios N. Koubouris Georgios C. Karatzas George P. Metzidakis Ioannis 《Natural Hazards》2016,83(1):65-81
In this work, a dynamic GIS modeling approach is presented that incorporates: a) geoinformatic techniques, b) 55-year historical meteorological data, and c) field measurements, in order to estimate soil erosion risk in intensively cultivated regions. The proposed GIS-based modeling approach includes the estimation of soil erosion rates due to surface water flow under current and future climate change scenarios A2 and B1 for the years 2030 and 2050. The soil erosion was estimated using the Universal Soil Loss Equation (USLE). The proposed soil erosion model was validated using field measurements at different sites of the study area. The results show that an extended part of the study area is under intense erosion with the mean annual loss to be 4.85 t/ha year−1. Moreover, an increase in rainfall intensity, especially for scenario B1, can generate a significant increase (32.44 %) in soil loss for the year 2030 and a much more (50.77 %) for the year 2050 in comparison with the current conditions. Regarding the scenario A2, a slight decrease (1.85 %) in soil loss was observed for the year 2030, while for 2050 the results show an adequate increase (7.31 %) in comparison with the present. All these approaches were implemented at one of the most productive agricultural areas of Crete in Greece dominated by olive and citrus crops.
相似文献42.
Georgios Panou Nikos Yannakakis Demitris Delikaraoglou 《Studia Geophysica et Geodaetica》2013,57(2):203-216
In this paper the linear fixed altimetry-gravimetry boundary-value problem is analyzed with respect to the existence and uniqueness of the solution. Nowadays, it is possible to determine very precisely points on the physical surface of the Earth by 3D satellite positioning and the problem is to determine the disturbing potential in an unbounded domain representing the exterior of the Earth. In order to establish realistic boundary conditions, a Dirichlet condition is imposed at seas and an oblique derivative condition on land. Then, mathematical methods are used within the frame of functional analysis for attacking the problem under consideration. Specifically, the Stampacchia theorem is used to decide upon the existence and uniqueness of the weak solution of the problem in a weighted Sobolev space. Finally, we confirm that the condition of validity for such a theorem has a geometrical interpretation. 相似文献
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Michas Georgios Pavlou Kyriaki Avgerinou Sophia-Ekaterini Anyfadi Eleni-Apostolia Vallianatos Filippos 《Journal of Seismology》2022,26(2):201-225
Journal of Seismology - On March 3, 2021, a strong shallow earthquake of magnitude Mw 6.3 struck Northern Thessaly, an area that lies in one of the most active fault zones of mainland Greece. The... 相似文献
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Eleftheria?PapadimitriouEmail author Georgios?Sourlas Vassilios?Karakostas 《Pure and Applied Geophysics》2005,162(5):783-804
The largest earthquake (M0=4.9·1027 dyn·cm) of the 20th century in the territory of Greece occurred south of Amorgos Island, causing extensive destruction in the southern Aegean area. It occurred on an ENE–trending normal fault that is seated parallel to the Islands southern coastline. Changes in the rates of moderate–size earthquakes (M 5.0) that occurred before and after the Amorgos earthquake, within circular regions centered on its epicenter with radii of 100, 150 and 200 km, are investigated. The rate for moderate–size events just before the main shock appears to be considerably increased when compared to those of either preceding or subsequent periods. Further inspection reveals that more evident seismicity fluctuations are attributed to distances exceeding 100 km. These changes may be indicative of a broad region that is approaching a high stress state prior to an eventual large earthquake. Close to the main event, that is, within the 100–km radius, a remarkable quiescence period lasting about two decades before its occurrence was observed. Changes in seismicity are discussed in combination with static stress changes calculated by the application of the stress evolutionary model that takes into account the coseismic slip associated with the larger events (M 6.5) since the beginning of the 20th century and the tectonic loading on the major faults in the study area. These larger events, as with the intermediate magnitude seismicity taking place at distances exceeding 100 km and which encircled the quiescent area observed during the last 22 years before the Amorgos earthquake, are well correlated with stress-enhanced areas in each stage of the evolutionary model. 相似文献
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In the present paper the differential equation of the temporal development of a landform (mountain) with a time dependent diffusion coefficient is solved. It is shown that the shape and dimensions of the landform at time t are independent of the specific variation of the diffusion coefficient with time; they only depend on the mean value of the diffusion coefficient in the time interval where the erosion process takes place. Studying the behaviour of the solution of the differential equation in the wave number domain, it is concluded that Fourier analysis may help in estimating, in quantitative terms, the initial dimensions, the age or, alternatively, the value of the diffusion coefficient of the landform. The theoretical predictions are tested on a hill of the southern part of the Ural mountainous region, in order to show how the results of the mathematical analysis can be used in describing, in quantitative terms, the morphological development of landforms due to erosion processes. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Zhi Zhang Robert B. Fleischman Jose I. Restrepo Gabriele Guerrini Arpit Nema Dichuan Zhang Ulina Shakya Georgios Tsampras Richard Sause 《地震工程与结构动力学》2018,47(10):1987-2011
A new floor connecting system developed for low‐damage seismic‐resistant building structures is described herein. The system, termed Inertial Force‐Limiting Floor Anchorage System (IFAS), is intended to limit the lateral forces in buildings during an earthquake. This objective is accomplished by providing limited‐strength deformable connections between the floor system and the primary elements of the lateral force‐resisting system. The connections transform the seismic demands from inertial forces into relative displacements between the floors and lateral force‐resisting system. This paper presents the IFAS performance in a shake‐table testing program that provides a direct comparison with an equivalent conventional rigidly anchored‐floor structure. The test structure is a half‐scale, 4‐story reinforced concrete flat‐plate shear wall structure. Precast hybrid rocking walls and special precast columns were used for test repeatability in a 22‐input strong ground‐motion sequence. The structure was purposely designed with an eccentric wall layout to examine the performance of the system in coupled translational‐torsional response. The test results indicated a seismic demand reduction in the lateral force‐resisting system of the IFAS structure relative to the conventional structure, including reduced shear wall base rotation, shear wall and column inter‐story drift, and, in some cases, floor accelerations. These results indicate the potential for the IFAS to minimize damage to the primary structural and non‐structural components during earthquakes. 相似文献
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Eren Şahiner Georgios S. Polymeris M. Altay Atlihan Selcuk Aktürk Niyazi Meriç 《第四纪科学杂志》2020,35(5):706-715
The aim of the present study is to attempt assessing the age of a monumental olive tree located between the Antique Cities of Militus (Didim-Aydın region) and Iasos (Milas-Muğla region). Wood from the trunk of an olive tree is not appropriate for conventional dating approaches such as dendrochronology or 14C. The sediments closely located surrounding and beneath the roots of the olive tree are considered indicative of the age of the planting event; therefore these sediments were dated using both quartz and feldspar luminescence signal protocols. Methodological aspects including the preheating plateaus, equivalent dose statistical approaches and dose rate using gamma spectrometry are also discussed, as dating of the associated palaeochannel sediments of the area are presented for the first time in the dating literature. The optically stimulated luminescence and/or infrared stimulated luminescence ages are extrapolated to date the event of the tree planting; it is the first time in the literature that an age is reported for an olive tree in the eastern Mediterranean region. The present study stands as the first experimental evidence that olive trees have been cultivated in the area since the Iron Age. 相似文献
50.
The Effect of the Stress Path on Squeezing Behavior in Tunneling 总被引：1，自引：0，他引：1
Summary The interplay between support systems and the rock when tunneling under squeezing conditions is normally studied by means
of two-dimensional analyses. The present paper shows that the underlying plane strain assumption involved in a two-dimensional
analysis may lead, under certain conditions, to ground pressure and deformation values that are considerably lower than those
produced by stress analyses that take into account spatial effects in the vicinity of the tunnel face. The differences are
due to the stress path dependency in the elasto-plastic behavior of the ground and, more specifically, to the inability of
the plane strain model to map the actual radial stress history, which involves a complete radial unloading (and, later, a
re-loading) of the tunnel boundary over the unsupported span. This inherent weakness of any plane strain analysis is relevant
from the design standpoint, particularly for heavily squeezing conditions that require a yielding support. For the majority
of tunneling conditions and methods, however, involving as they do the completion of a stiff support within a few meters of
the face, the errors introduced by the plane strain assumption are not important from a practical point of view. 相似文献