On the possibilities of using the power spectrum in some geological and geophysical problems     

Radu Botezatu 《Mathematical Geology》1970,2(3):303-305

  相似文献   

Macroseismic field of the March 4, 1977 Vrancea earthquake     

C. Radu  G. Polonic  I. Apopei 《Tectonophysics》1979,53(3-4)

The macroseismic field of the Vrancea earthquake of March 4, 1977, characterized by the following parameters : H = 19h 21m 56s, ø = 45.8°N, γ = 26.8° E, h = 95 Km, M = 7.2, I = VIIIMSK has been analyzed. The following problems were studied : area and shape of the isoseismals of intensity III–VIII ; elongation of the isoseismal ellipses and decrease of intensity with distance. The results confirm our previous studies (Radu and Apopei, 1978) of strong intermediate earthquakes, but render evidence for some peculiarities in the seismic intensity attenuation as well.  相似文献   

Inelastic displacement demand of RC buildings subjected to earthquakes generated by intermediate-depth Vrancea seismic source     

Olteanu  Paul  Vacareanu  Radu 《Natural Hazards》2021,109(3):2509-2534

Evaluating inelastic displacement demand of structures exposed to seismic hazard is required for the design of new buildings as well as for seismic risk assessment of existing structures. Most of the buildings are designed to withstand strong earthquakes by responding in the nonlinear range. Having special parts of the structure designed to develop a stable hysteretic behaviour allows the structure to deform in order to accommodate the displacement demand imposed by strong ground motions. This paper is centred on finding a correspondence between the maximum elastic and inelastic displacement responses of the single degree of freedom (SDOF) systems subjected to earthquakes generated by Vrancea seismic source. Vrancea intermediate-depth earthquakes are responsible for the seismic hazard throughout Romanian territory. They have distinctive features, such as large displacement demand and large predominant periods, which makes Romania a special seismic environment. Using a database of Romanian and Japanese strong ground motions generated by intermediate-depth earthquakes and performing nonlinear dynamic analysis on the SDOF oscillators following the Takeda model, this study estimates the inelastic to elastic displacement ratio of reinforced concrete systems. Soil conditions, epicentral distance and magnitude influence on inelastic response is analysed using constant ductility response spectra. The main findings of the study are: the local increase of the inelastic to elastic displacement ratio for type C soil (Eurocode 8 classification) for large magnitude earthquakes and the significant effect of soil conditions on the inelastic response of the SDOF systems. The inelastic amplification was evaluated using a functional form depending on system ductility, soil conditions and earthquake magnitude.

  相似文献   

Experimental testing on emulative connections for precast columns using grouted corrugated steel sleeves   总被引：1，自引：1，他引：0  

Viorel Popa  Andrei Papurcu  Dragos Cotofana  Radu Pascu 《Bulletin of Earthquake Engineering》2015,13(8):2429-2447

  相似文献   

An extended stability criterion for density-driven flows in homogeneous porous media     

Jude L. Musuuza  Sabine Attinger  Florin A. Radu 《Advances in water resources》2009

Stability of density-driven flows is a challenging problem with current applications in major areas like energy exploration, water pollution, nuclear and oil industries. The mathematical model for such flows is a system of coupled non linear partial differential equations. To study the physical stability of the system, we consider steady-state flow and perturb the solution of the full system of equations (without Boussinesq approximation) and investigate how it evolves in time: if the solution does not grow indefinitely, the system is called stable. The perturbations are treated as being the result of sub-scale interactions between the velocity field and the solute mass. Making use of a two-scale expansion of the solution, we derived extended stability criteria that include the effects of density, viscosity and flow velocity in flow configurations aligned parallel as well as orthogonal to gravity forces. Numerical simulations with the numerical simulator d³f$d^{3}f$ are presented to test the theoretical stability criteria.  相似文献   

Sediment Yield During Late Glacial and Holocene periods in the Lac Chambon Watershed,Massif Central,France     

Jean-Jacques Macaire  Gilles Bossuet  Alain Choquier  Constantin Cocirta  Patrick de Luca  Andr Dupis  Isabelle Gay  Eric Mathey  Pascal Guenet 《地球表面变化过程与地形》1997,22(5):473-489

A sediment budget for the Late Glacial and Holocene periods was calculated for the Lac Chambon watershed which is located in a formerly glaciated temperate crystalline mountain area. It appears that over 15 500 years: (1) 69 per cent of eroded particles have been displaced by gravity processes and then stored within the watershed, compared to 31 per cent that have been displaced by running water and evacuated outward; (2) the mean mechanical erosion due to gravity processes on the slopes amounted to 16·1 ±6 m and only developed on a quarter of the watershed surface, whereas the mean mechanical erosion due to running water amounted 1·24 ± 0·37 m and involved the whole watershed surface. The mean sediment yields due to gravity processes on slopes were 2300 ± 1360, 1770 ± 960 and 380 ± 100 m³ km⁻³ a⁻¹, respectively, for basalts, and basic and acidic trachyandesites. Values of sediment yield due to running water were 49±15, 120±36 and 79±24 m³ km⁻² a⁻¹, respectively, during the Bôlling–Allerôd, the Younger Dryas and the Pre-Boreal–Boreal periods. They were 56±17 and 166±50 m³ km⁻² a⁻¹ during the Sub-Atlantic period before and after 1360 a BP , respectively. These values reflect variations in the natural environment and the impact of human-induced deforestation. © 1997 by John Wiley & Sons, Ltd.  相似文献   

Testing polymineral post-IR IRSL and quartz SAR-OSL protocols on Middle to Late Pleistocene loess at Batajnica,Serbia     

Anca Avram  Daniela Constantin  Daniel Veres  Szabolcs Kelemen  Igor Obreht  Ulrich Hambach  Slobodan B. Marković  Alida Timar-Gabor 《Boreas: An International Journal of Quaternary Research》2020,49(3):615-633

The loess–palaeosol sequence of Batajnica (Vojvodina region, Serbia) is considered as one of the most complete and thickest terrestrial palaeoclimate archives for the Middle and Late Pleistocene. In order to achieve a numerical chronology for this profile, four sets of ages were obtained on 18 individual samples. Equivalent doses were determined using the SAR protocol on fine (4–11 μm) and coarse (63–90 μm) quartz fractions, as well as on polymineral fine grains by using two elevated temperature infrared stimulation methods, pIRIR₂₉₀ and pIRIR₂₂₅. We show that the upper age limit of coarse quartz OSL and polymineral pIRIR₂₉₀ and pIRIR₂₂₅ techniques is restricted to the Last Glacial/Interglacial cycle due to the field saturation of the natural signals. Luminescence ages on coarse quartz, pIRIR₂₂₅ and pIRIR₂₉₀ polymineral fine grains are in general agreement. Fine quartz ages are systematically lower than the coarse quartz and pIRIR ages, the degree of underestimation increasing with age. Comparison between natural and laboratory dose response curves indicate the age range over which each protocol provides reliable ages. For fine and coarse quartz, the natural and laboratory dose response curves overlap up to ~150 and ~250 Gy, respectively, suggesting that the SAR protocol provides reliable ages up to c. 50 ka on fine quartz and c. 100 ka on coarse quartz. Using the pIRIR₂₂₅ and pIRIR₂₉₀ protocols, equivalent doses up to ~400 Gy can be determined, beyond which in the case of the former the natural dose response curve slightly overestimates the laboratory dose response curve. Our results suggest that the choice of the mineral and luminescence technique to be used for dating loess sediments should take into consideration the reported limited reliability.  相似文献   

Local retrofit of exterior RC beam–column joints using thin RC jackets—An experimental study     

Chris G. Karayannis  Constantin E. Chalioris  George M. Sirkelis 《地震工程与结构动力学》2008,37(5):727-746

The use of a new type of reinforced concrete (RC) jacket for RC exterior beam–column connections damaged by seismic excitations is addressed and experimentally investigated. The proposed jacket has very small thickness and includes small diameter steel reinforcement. This jacketing applies at the joint region and at a small part of the columns and the beam. The main advantage of the proposed thin and locally applied jacket compared with the commonly used concrete jacket is the fact that its application is not restrained by space limitations, and since it slightly changes the initial size of the elements, the building's dynamics and seismic behaviour remain practically unaffected. For the needs of this study, 10 exterior beam–column joint subassemblages were constructed and subjected to increasing cyclic loading. Later, the damaged specimens were locally retrofitted using the proposed thin RC jackets and they were retested with the same load sequence. Three different specimen configurations with various amounts of shear reinforcement in the joint area were examined and two types of jackets (a) with light and (b) with dense reinforcement were applied. Test results indicated that the seismic performance of the retrofitted specimens was fully restored and in some cases substantially improved with respect to the performance of the same specimens in the initial loading, since they exhibited higher values of load capacity and hysteretic energy dissipation. Discussion for the conditions of the use of the examined jacketing technique either as a repair or as a strengthening method is also included. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Current trends and future challenges in groundwater vulnerability assessment using overlay and index methods   总被引：66，自引：7，他引：59  

R. C. Gogu  A. Dassargues 《Environmental Geology》2000,39(6):549-559

 The concept of groundwater vulnerability is a useful tool for environmental planning and decision-making. Many different methods have been developed for assessing this vulnerability. Hydrogeologists have failed to reach a consensus concerning the definitions of and reference terms for groundwater vulnerability assessment. Therefore, a review of vulnerability assessment and mapping methods providing a new classification system is necessary. This is focused on techniques that use the overlay and index class methods. New research challenges in vulnerability assessment are identified, especially the need for developing dynamic links between numerical models and overlay and index methods. Received: 28 October 1998 · Accepted: 31 May 1999  相似文献   

Groundwater quality and rural drinking-water supplies in the Republic of Moldova   总被引：1，自引：0，他引：1  

Ruslan Melian  Nicolai Myrlian  Alexander Gouriev  Constantin Moraru  Frank Radstake 《Hydrogeology Journal》1999,7(2):188-196

 This paper describes the results of a groundwater quality assessment conducted in two pilot areas, Balatina and Carpineni, in the Republic of Moldova. Shallow groundwater is the main source of drinking water in rural areas, but reliable data on its quality are currently insufficient for developing rural water-supply systems with standard designs. The main components of the study included a field sampling program (including pesticides), an evaluation of the reliability of existing drinking-water data, an analysis of land use and groundwater-pollution risks using GIS, and the formulation of recommendations to reduce risks for public health. Microbiological, nitrate, and selenium contamination are most serious in the villages. These contaminants should be given priority in addressing drinking-water aspects for rural water-supply development in the two pilot areas. Pollution occurs mainly due to poor sanitary conditions. In a few shallow wells, traces of selected pesticides were observed, but the effect of these levels of pesticides on public health is still unclear. Limited resources of shallow groundwater of good quality occur outside the villages. Additional pilot studies should be implemented to prove the technical and institutional feasibility of developing and protecting these resources. Received, September 1997 Revised, September 1998 Accepted, March 1999  相似文献