Assessment of the ground motion levels for the Vrancea (Romania) November 1940 earthquake     

Florin Pavel  Radu Vacareanu 《Natural Hazards》2015,78(2):1469-1480

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Evaluation of the seismic hazard for 20 cities in Romania using Monte Carlo based simulations   总被引：2，自引：0，他引：2  

Florin Pavel  Radu Vacareanu 《地震工程与工程振动(英文版)》2017,16(3):513-523

This work focuses on the evaluation of the seismic hazard for Romania using earthquake catalogues generated by a Monte Carlo approach. The seismicity of Romania can be attributed to the Vrancea intermediate-depth seismic source and to 13 other crustal seismic sources. The recurrence times of large magnitude seismic events (both crustal and subcrustal), as well as the moment release rates are computed using simulated earthquake catalogues. The results show that the largest contribution to the overall moment release for the crustal seismic sources is from the seismic regions in Bulgaria, while the seismic regions in Romania contribute less than 5% of the overall moment release. In addition, the computations show that the moment release rate for the Vrancea subcrustal seismic source is about ten times larger than that of all the crustal seismic sources. Finally, the Monte Carlo approach is used to evaluate the seismic hazard for 20 cities in Romania with populations larger than 100,000 inhabitants. The results show some differences between the seismic hazard values obtained through Monte-Carlo simulation and those in the Romanian seismic design code P100-1/2013, notably for cities situated in the western part of Romania that are influenced by local crustal seismic sources.  相似文献   

A hydrogeological conceptual approach to study urban groundwater flow in Bucharest city,Romania     

Mohamed Amine Boukhemacha  Constantin Radu Gogu  Irina Serpescu  Dragos Gaitanaru  Ioan Bica 《Hydrogeology Journal》2015,23(3):437-450

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Accuracy of numerical simulations of contaminant transport in heterogeneous aquifers: A comparative study     

F.A. Radu  N. Suciu  J. HoffmannA. Vogel  O. Kolditz  C.-H. ParkS. Attinger 《Advances in water resources》2011,34(1):47-61

This work deals with a comparison of different numerical schemes for the simulation of contaminant transport in heterogeneous porous media. The numerical methods under consideration are Galerkin finite element (GFE), finite volume (FV), and mixed hybrid finite element (MHFE). Concerning the GFE we use linear and quadratic finite elements with and without upwind stabilization. Besides the classical MHFE a new and an upwind scheme are tested. We consider higher order finite volume schemes as well as two time discretization methods: backward Euler (BE) and the second order backward differentiation formula BDF (2). It is well known that numerical (or artificial) diffusion may cause large errors. Moreover, when the Péclet number is large, a numerical code without some stabilising techniques produces oscillating solutions. Upwind schemes increase the stability but show more numerical diffusion. In this paper we quantify the numerical diffusion for the different discretization schemes and its dependency on the Péclet number. We consider an academic example and a realistic simulation of solute transport in heterogeneous aquifer. In the latter case, the stochastic estimates used as reference were obtained with global random walk (GRW) simulations, free of numerical diffusion. The results presented can be used by researchers to test their numerical schemes and stabilization techniques for simulation of contaminant transport in groundwater.  相似文献   

Ground motion simulations for seismic stations in southern and eastern Romania and seismic hazard assessment     

Florin Pavel  Radu Vacareanu 《Journal of Seismology》2017,21(5):1023-1037

This research focuses on the evaluation of soil conditions for seismic stations in southern and eastern Romania, their influence on stochastic finite-fault simulations, and the impact of using them on the seismic hazard assessment. First, the horizontal-to-vertical spectral ratios (HVSR) are evaluated using ground motions recorded in 32 seismic stations during small magnitude (M _W  ≤ 6.0) Vrancea seismic events. Most of the seismic stations situated in the southern part of Romania exhibit multiple HVSR peaks over a broad period range. However, only the seismic stations in the eastern-most part of Romania have clear short-period predominant periods. Subsequently, stochastic finite-fault simulations are performed in order to evaluate the influence of the soil conditions on the ground motion amplitudes. The analyses show that the earthquake magnitude has a larger influence on the computed ground motion amplitudes for the short- and medium-period range, while the longer-period spectral ordinates tend to be influenced more by the soil conditions. Next, the impact of the previously evaluated soil conditions on the seismic hazard results for Romania is also investigated. The results reveal a significant impact of the soil conditions on the seismic hazard levels, especially for the sites characterized by long-period amplifications (sites situated mostly in southern Romania), and a less significant influence in the case of sites which have clear short predominant periods.  相似文献   

Kappa and regional attenuation for Vrancea (Romania) earthquakes   总被引：1，自引：0，他引：1  

Florin Pavel  Radu Vacareanu 《Journal of Seismology》2015,19(3):791-799

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Removal of Nitroaniline From Water/Ethanol by Electrocoagulation Using Response Surface Methodology          下载免费PDF全文

Guy Bertrand Tamne  Charles Peguy Nanseu‐Njiki  Ede Bodoki  Robert Săndulescu  Radu Oprean  Emmanuel Ngameni 《洁净——土壤、空气、水》2016,44(4):430-437

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Solar Wind Electron Strahls Associated with a High-Latitude CME: Ulysses Observations     

M. Lazar  J. Pomoell  S. Poedts  C. Dumitrache  N. A. Popescu 《Solar physics》2014,289(11):4239-4266

Counterstreaming beams of electrons are ubiquitous in coronal mass ejections (CMEs) – although their existence is not unanimously accepted as a necessary and/or sufficient signature of these events. We continue the investigation of a high-latitude CME registered by the Ulysses spacecraft on 18?–?19 January 2002 (Dumitrache, Popescu, and Oncica, Solar Phys. 272, 137, 2011), by surveying the solar-wind electron distributions associated with this event. The temporal evolution of the pitch-angle distributions reveals populations of electrons that are distinguishable through their anisotropy, with clear signatures of i) electron strahls, ii) counter-streaming in the magnetic clouds and their precursors, and iii) unidirectionality in the fast wind preceding the CME. The analysis of the counter-streams inside the CME allows us to elucidate the complexity of the magnetic-cloud structures embedded in the CME and to refine the borders of the event. Identifying such strahls in CMEs, which preserve properties of the low β [<1] coronal plasma, gives more support to the hypothesis that these populations are remnants of the hot coronal electrons that escape from the electrostatic potential of the Sun into the heliosphere.  相似文献   

Effects of boundary conditions and partial drainage on cyclic simple shear test results—a numerical study     

Bin Wang  Radu Popescu  Jean H. Prevost 《国际地质力学数值与分析法杂志》2004,28(10):1057-1082

Owing to imperfect boundary conditions in laboratory soil tests and the possibility of water diffusion inside the soil specimen in undrained tests, the assumption of uniform stress/strain over the sample is not valid. This study presents a qualitative assessment of the effects of non‐uniformities in stresses and strains, as well as effects of water diffusion within the soil sample on the global results of undrained cyclic simple shear tests. The possible implications of those phenomena on the results of liquefaction strength assessment are also discussed. A state‐of‐the‐art finite element code for transient analysis of multi‐phase systems is used to compare results of the so‐called ‘element tests’ (numerical constitutive experiments assuming uniform stress/strain/pore pressure distribution throughout the sample) with results of actual simulations of undrained cyclic simple shear tests using a finite element mesh and realistic boundary conditions. The finite element simulations are performed under various conditions, covering the entire range of practical situations: (1) perfectly drained soil specimen with constant volume, (2) perfectly undrained specimen, and (3) undrained test with possibility of water diffusion within the sample. The results presented here are restricted to strain‐driven tests performed for a loose uniform fine sand with relative density D_r=40%. Effects of system compliance in undrained laboratory simple shear tests are not investigated here. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

A site evaluation campaign for a ground based atmospheric Cherenkov telescope in Romania     

Aurelian Andrei Radu  Tatiana Angelescu  Valentin Curtef  Florin Delia  Daniel Felea  Ioana Goia  Dumitru Ha?egan  Bogdan Lucaschi  Ancuta Manea  Vlad Popa  Ioan Rali??  Radu V?c?reanu 《Experimental Astronomy》2012,34(1):31-42

Around the world, several scientific projects share the interest of a global network of small Cherenkov telescopes for monitoring observations of the brightest blazars??the DWARF network. A small, ground based, imaging atmospheric Cherenkov telescope of last generation is intended to be installed and operated in Romania as a component of the DWARF network. To prepare the construction of the observatory, two support projects have been initiated. Within the framework of these projects, we have assessed a number of possible sites where to settle the observatory. In this paper we submit a brief report on the general characteristics of the best four sites selected after the local infrastructure, the nearby facilities and the social impact criteria have been applied.  相似文献