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This paper begins with a critical assessment of the concept of macroseismic intensity, on which traditional scales, such as MSK and EMS, are based. The main shortcoming identified is the model's failure to consider the spectral features of ground motion. This omission may lead to erroneous seismic zonation, as shown in the paper. As a result, the model is of little interest to engineers who must design and build safe structures while adopting economical solutions. The paper presents a way to radically improve this situation. The starting point for this approach was the experience of the destructive Vrancea earthquake of 1977.03.04, which made it clear that intensity appears to be different for structures having natural periods pertaining to different spectral domains. The solution proposed to the shortcomings of the traditional intensity concept is postulated on a system of analytical expressions, covering definitions of global intensities, of intensities related to oscillation frequency and of intensities related to a definite spectral band. The latter definition lies at the basis of a definition of discrete intensity spectra. Illustrative applications are presented, in relation to global intensities and to discrete intensity spectra. We then analyze an illustrative case in which the use of traditional macroseismic survey techniques led to erroneous seismic zonation. Finally, some conclusions and recommendations are presented. Based on the authors?? long-term experience, we strongly recommend close interaction between seismologists and engineers in working groups and joint projects targeted on radical improvement of the basic concepts of seismic intensity and of specific analysis procedures. 相似文献
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Given the significant worldwide human and economic losses caused due to floods annually, reducing the negative consequences of these hazards is a major concern in development strategies at different spatial scales. A basic step in flood risk management is identifying areas susceptible to flood occurrences. This paper proposes a methodology allowing the identification of areas with high potential of accelerated surface run-off and consequently, of flash-flood occurrences. The methodology involves assessment and mapping in GIS environment of flash flood potential index (FFPI), by integrating two statistical methods: frequency ratio and weights-of-evidence. The methodology was applied for Bâsca Chiojdului River catchment (340 \(\hbox {km}^{2}\)), located in the Carpathians Curvature region (Romania). Firstly, the areas with torrential phenomena were identified and the main factors controlling the surface run-off were selected (in this study nine geographical factors were considered). Based on the features of the considered factors, many classes were set for each of them. In the next step, the weights of each class/category of the considered factors were determined, by identifying their spatial relationships with the presence or absence of torrential phenomena. Finally, the weights for each class/category of geographical factors were summarized in GIS, resulting the FFPI values for each of the two statistical methods. These values were divided into five classes of intensity and were mapped. The final results were used to estimate the flash-flood potential and also to identify the most susceptible areas to this phenomenon. Thus, the high and very high values of FFPI characterize more than one-third of the study catchment. The result validation was performed by (i) quantifying the rate of the number of pixels corresponding to the torrential phenomena considered for the study (training area) and for the results’ testing (validating area) and (ii) plotting the ROC (receiver operating characteristics) curve. 相似文献
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The influence of climate on gravitational processes within the Jiu river valley: G.I.S. applications
The dynamics of gravitational processes (e.g. landslides) is altered due to variation in climatic parameters. We have recorded an increasing number of such events which affect human settlements. The most important aspect that has to be emphasized is the way gravitational processes change and condition land utilization. Due to these circumstances, the analysis of these processes has great importance within the middle sector of the Jiu Valley. In order to correlate the occurrence of gravitational processes with climatic data, we have been collecting data within this valley sector during the last 15 years. The aim of this study is to describe the succession and dynamics of present processes, which should act as an alarm signal for local authorities to take adequate mitigating measures. We observe an increase in the mean annual temperature and the mean amplitude (by approximately 1?C), in addition to the frequency and severity of dry years (1992, 2000), and the frequency of rain showers. We correlate these data with knowledge of the lithology, morphometry, and piezometric levels in order to identify areas with a high potential for gravitational processes using a Geographical Information System (G.I.S.). This analysis allows us to draw a map rendering each layer separately — lithology, pedology, slope, vegetation etc. We present a map that emphasizes the areas with high potential for the development of gravitational processes in the region of the Jiu valley. 相似文献
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Marius-Victor Birsan Alexandru Dumitrescu Dana Magdalena Micu Sorin Cheval 《Natural Hazards》2014,74(3):1899-1910
The Carpathian Mountains region cover areas from seven countries of central and southeastern Europe, the mountain chain having major regional influences on the temperate climate, specific to latitudes between 43°N and 49°N. In order to identify changes in the annual temperature extremes, the Mann–Kendall nonparametric trend test has been applied to several thermal indices, recommended by the expert team on climate change detection and indices. The indices were computed from gridded daily datasets of minimum and maximum temperature at 0.1° resolution (~10 km), available online within the framework of the project CarpatClim (climate of the Carpathian region) for the period 1961–2010. The results show decreasing trends in cold-related indices, especially in the number of frost days, and increasing trends in warm-related ones. The trend patterns are consistent over the region, i.e., there are no mixed trends for a given index. Regional differences in climate extreme trends within the Carpathian region are related to altitude, rather than latitude. The number of summer days is increasing over the entire area, while the number of tropical nights presents upward trends mainly at lower elevations. The Warm Spell Duration Index presents upward trends over 60 % of the region. The (annual) East Atlantic pattern shows strong correlations with the warm-related indices. Our results are in agreement with previous temperature-related studies in the region. 相似文献
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Using experimental data to reduce the single-building sigma of fragility curves: case study of the BRD tower in Bucharest, Romania 总被引：1，自引：0，他引：1
Matthieu Perrault Philippe Gueguen Alexandru Aldea Sorin Demetriu 《地震工程与工程振动(英文版)》2013,12(4):643-658
The lack of knowledge concerning modelling existing buildings leads to significant variability in fragility curves for single or grouped existing buildings. This study aims to investigate the uncertainties of fragility curves, with special consideration of the single-building sigma. Experimental data and simplified models are applied to the BRD tower in Bucharest, Romania, a RC building with permanent instrumentation. A three-step methodology is applied： （1） adjustment of a linear MDOF model for experimental modal analysis using a Timoshenko beam model and based on Anderson＇s criteria, （2） computation of the structure＇s response to a large set of accelerograms simulated by SIMQKE software, considering twelve ground motion parameters as intensity measurements （IM）, and （3） construction of the fragility curves by comparing numerical interstory drift with the threshold criteria provided by the Hazus methodology for the slight damage state. By introducing experimental data into the model, uncertainty is reduced to 0.02 considering Sd ） as seismic intensity IM and uncertainty related to the model is assessed at 0.03. These values must be compared with the total uncertainty value of around 0.7 provided by the Hazus methodology. 相似文献
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Bogdan Grecu Cristian Neagoe Dragos Tataru Felix Borleanu Bogdan Zaharia 《Journal of Seismology》2018,22(5):1275-1292
We present the first detailed investigation of the background seismic noise recorded in the Romanian-Bulgarian cross-border region over 3 years (2012–2015). We used the power spectral densities probability density functions (PSD PDFs) to study the noise variations in the period domain (0.025–1 s) as well as in the secondary microseism band (2–10 s). Strong diurnal variations and an increase of the noise levels during working days were observed at high frequencies at all stations, thus confirming the anthropic origin of the noise at low periods. The noise variations observed at longer periods (>?1 s) are relatively small among the stations and are related to season changes. The dominant feature in the noise spectra between 2 and 10 s is the double-frequency peak (DFP) whose amplitude increases and changes during winter. For a specific interval, from 25th to 27th of January 2014, when a storm was reported in the Black Sea area, the maximum of the DFP shifted from larger periods (~?5.5 s) at stations far from the Black Sea towards smaller periods (~?1.8 s) at stations located on the coastline. The polarization analysis showed that the short period double-frequency microseisms originating from the Black Sea dominate during the winter month. Finally, we showed that site conditions vary due to noise variations related to weather conditions in the Black Sea or to changes in anthropogenic noise sources. 相似文献
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Cheval Sorin Bulai Ana Croitoru Adina-Eliza Dorondel Ștefan Micu Dana Mihăilă Dumitru Sfîcă Lucian Tișcovschi Adrian 《Theoretical and Applied Climatology》2022,149(1-2):253-272
Theoretical and Applied Climatology - In the last decades, anthropogenic drivers have significantly influenced the natural climate variability of Earth’s atmosphere. Climate change has become... 相似文献
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The synchronization between the orbital motion and axial rotation of the two component stars of a binary system is reviewed.
Some previous published papers are mentioned and the general conclusion is outlined: If we shall use a rotating coordinate
system synchronous with one of the two stellar axial rotations, it is not possible to obtain a Jacobi integral and the Roche
geometry cannot be further analyzed. In addition, a theoretical approach is summarized in order to use the axial rotations
of the two component stars, even if the constants of the stellar structure (k2)1, (k2)2must be taken into consideration. So it is found that if the stellar angular velocities are higher than the corresponding
Keplerian angular velocity (ωi≫ ωk, i=
), the problem of the rotational effect could be of practical consideration. Finally, a theoretical relationship between the
two constants (k2)1and (k2)2of the stellar structure is established. 相似文献
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We present a numerical scheme for reactive contaminant transport with nonequilibrium sorption in porous media. The mass conservative scheme is based on Euler implicit, mixed finite elements, and Newton method. We consider the case of a Freundlich-type sorption. In this case, the sorption isotherm is not Lipschitz but just Hölder continuous. To deal with this, we perform a regularization step. The convergence of the scheme is analyzed. An explicit order of convergence depending only on the regularization parameter, the time step, and the mesh size is derived. We give also a sufficient condition for the quadratic convergence of the Newton method. Finally, relevant numerical results are presented. 相似文献