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1.
Mihnea Corneliu Oncescu 《Tectonophysics》1986,126(2-4)
Simple spectral theory of seismic sources was used to determine source parameters directly related to medium properties (stress drop, seismic efficiency and fracture energy) and quality factors of the Vrancea (Romania) seismic region. The results show an increase in maximum static stress drop, maximum seismic efficiency and fracture energy with depth. The seismic efficiency is magnitude independent, but the stress drop is magnitude independent only for events with ML > 3.8; below this value, the logarithm of stress drop increases quasi-linearly with magnitude. In the depth interval 50–160 km the stress drop increases with a slope of about 2–3 bar/km. The fracture energy per unit area of the fault has values of the order of 105–108 erg/cm2.The frequency independent quality factors indicate that the attenuation of P waves is generally higher than that of S waves and that Qp values are in agreement with recent tectonic models for the Vrancea region: total decoupling of the slab now sinking gravitationally is present only in the southwestern part of the Vrancea region, as suggested by the spatial position of intermediate depth hypocenters. 相似文献
2.
Structural damage in buildings designed according to the dissipative design philosophy can be significant, even under moderate earthquakes. Repair of damaged members is an expensive operation and may affect building use, which in turn increases the overall economic loss. If damage can be isolated to certain dissipative members realized to be removable following an earthquake, the repair costs and time of interruption of building use can be reduced. Dual structural configurations, composed of a rigid subsystem with removable ductile elements and a flexible subsystem, are shown to be appropriate for the application of removable dissipative element concept. Eccentrically braced frames with removable links connected to the beams using flush end‐plate bolted connections are investigated as a practical way of implementing this design concept. High‐strength steel is used for members outside links in order to enhance global seismic performance of the structure by constraining plastic deformations to removable links and reducing permanent drifts of the structure. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
3.
The Danube deep sea fan in the northwestem Black Sea has a lateral dimension of over 150 km and stretches from several hundred metres water depth down to the abyssal plain. Eight seismic sequences have been recognized in the fan complex. Each sequence consists of channel, levee and overbank deposits, as well as mass transport units. The Danube and the Ukrainian rivers have aggraded two surficial channel-levee systems which diverge and decrease in volume downfan. The channels of these systems have a low sinuosity, implying young age, steep gradients and/or limited sediment supply. Significant channel migration occurred in the course of fan development, which could be largely controlled by relative sea-level changes. The six youngest sequences mapped have been correlated to sea-level fluctuations from the post-Chaudian regression to the present day. 相似文献
4.
The influence of the acid–base properties of humic substances in natural waters on the buffer capacity value is considered. An alternative way of calculation of the ANC parameter taking into account the dual nature of the humus organic of waters is proposed. Zonal aspects of the distribution of natural waters over ANC values are evaluated, and the features affecting these parameters are singled out. 相似文献
5.
The results of experimental studies of the composition and specific features of humic substance isolated from typical soils of natural zones are given. The stability constants of metal complexes with humic substance are evaluated. The obtained experimental data are used to calculate the occurrence forms of metals in natural waters in the zones of taiga, forests, and steppes. The occurrence forms of metals are shown to be determined by the general chemistry of natural waters rather than stability constants of complexes with organic matter. 相似文献
6.
T. I. Moiseenko N. A. Gashkina M. I. Dinu T. A. Kremleva V. Yu. Khoroshavin 《Geochemistry International》2013,51(13):1031-1148
This paper reports the results of an extensive investigation of water chemistry in the small lakes of European Russia and Western Siberia along a climatic gradient. It was demonstrated that small lakes unaffected by any direct contamination can be used as indicators of natural geochemical conditions of water formation, as well as global and regional fluxes of airborne pollution and climate warming. A novel concept was developed for within- and between-zone variability in water chemistry over vast areas of tundra, taiga, forest, and steppe, and contributions of natural and anthropogenic factors to its formation under present-day conditions were estimated. A proposed predictive scenario showed that climate warming will result in an increase in water salinity in southern regions and ubiquitous phosphorus enrichment in terrestrial waters; the hydrologic and geochemical conditions of water formation in northern Siberia will change significantly in response to permafrost thawing. Zonal features in the development of anthropogenically-induced processes in terrestrial surface waters (acidification, eutrophication, and metal enrichment) were determined. It was demonstrated that, in addition to naturally acidified lakes with high contents of humic acids, acid lakes of anthropogenic origin occur over the whole humid region discussed here, and acidification processes were characterized for each subregion. The trophic status of lakes and limitation of their bioproductivity with respect to nutrients were estimated. The concentrations and distribution of trace elements were analyzed in terrestrial waters from various climatic zones of European Russia and Western Siberia, and the first estimates were obtained for the mean concentrations and coefficients of migration of a wide range of elements in terrestrial freshwaters. We distinguished a group of metal (Mo, As, U, Bi, Sb, Cd, Ag, Se, Re, Pb, Cd, W, etc.) the enrichment of which in natural waters results from their global dispersion in the environment. Experimental results and natural observations are presented on the processes of metal ion complexation with humus substances, and sequences of their increasing activity in competing for organic ligands were derived. Data are presented on the speciation of metals depending on natural water chemistry in the tundra, taiga, and steppe zones. The pioneering investigations on the geochemistry of natural waters allowed us to substantiate new regional norms for water quality. 相似文献
7.
8.
M. I. Dinu 《Water Resources》2010,37(1):65-69
Complex formation reactions with the interaction of fulvic and humic acids with zinc and iron ions in a model aqueous system.
The complexing ability of humic acids was experimentally proved to be much higher than that of fulvic acids. The complexing
ability of fulvic acids is found to decrease over time. The dependence of the complexing ability of heavy metals on the types
of ion and humic substances and the proportions of components in the solution is examined. The obtained experimental results
on the occurrence forms of heavy metals were compared with their theoretical estimates calculated for natural water bodies. 相似文献
9.
M. I. Dinu 《Geochemistry International》2017,55(10):911-926
Hypotheses of humus formation on the basis of polymerization and oxidation reactions were considered. The most popular models of several authors and the general understanding of the structural features of natural polymers were analyzed. Multivariate statistical analysis was performed for zonal factors affecting the formation of humic substances. Evolutionary changes in the understanding of the biospheric functions of humus substances were evaluated. Statistical procedures were proposed for the prediction of the physicochemical behavior of humus substances in environments. 相似文献
10.
Mechanisms of the acidification of precipitation at the expense of radiochemical effects were considered. The results of natural measurements of physicochemical and metrological parameters (pH, T, and radiation background) of atmospheric precipitation (rain and snow) are reported. The possible influence of radon radioactivity (decay energy) on physicochemical processes in the atmosphere was analyzed. A hypothesis was proposed on the mechanism of this process. 相似文献