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121.
Assessing the Vibrational Frequencies of the Cathedral of Cologne (Germany) by Means of Ambient Seismic Noise Analysis 总被引:1,自引:0,他引:1
Andreas Fäcke Stefano Parolai Sandra M. Richwalski Lothar Stempniewski 《Natural Hazards》2006,38(1-2):229-236
Ambient seismic noise measurements were conducted inside the Cathedral of Cologne (Germany) for assessing its frequencies
of vibration and for checking whether these occur in the range where soil amplification is expected. If this is the case,
damages may increase in case of an earthquake due to an increased structural response of the building. Analysis of the ratio
between the horizontal and vertical components of the spectra recorded at stations located inside the building as well as
the ratio between the corresponding components of the spectra recorded simultaneously inside the building and at a reference
station placed in the basement of the cathedral indicated several modes of vibration. Facilitated by these results an assessment
of the seismic vulnerability was attempted for a 2D ground motion scenario using the finite element method. 相似文献
122.
Awni T. Batayneh 《Hydrogeology Journal》2006,14(7):1277-1283
The alluvial aquifer is the primary source of groundwater along the eastern Dead Sea shoreline, Jordan. Over the last 20 years, salinity has risen in some existing wells and several new wells have encountered brackish water in areas thought to contain fresh water. A good linear correlation exists between the water resistivity and the chloride concentration of groundwater and shows that the salinity is the most important factor controlling resistivity. Two-dimensional electrical tomography (ET) integrated with geoelectrical soundings were employed to delineate different water-bearing formations and the configuration of the interface between them. The present hydrological system and the related brines and interfaces are controlled by the Dead Sea base level, presently at 410 m b.s.l. Resistivity measurements show a dominant trend of decreasing resistivity (thus increasing salinity) with depth and westward towards the Dead Sea. Accordingly, three zones with different resistivity values were detected, corresponding to three different water-bearing formations: (1) strata saturated with fresh to slightly brackish groundwater; (2) a transition zone of brine mixed with fresh to brackish groundwater; (3) a water-bearing formation containing Dead Sea brine. In addition, a low resistivity unit containing brine was detected above the 1955 Dead Sea base level, which was interpreted as having remained unflushed by infiltrating rain. 相似文献
123.
A. B. Kuznetsov M. A. Semikhatov A. V. Maslov I. M. Gorokhov E. M. Prasolov M. T. Krupenin I. V. Kislova 《Stratigraphy and Geological Correlation》2006,14(6):602-628
New data on Sr-and C-isotopic systematics of carbonate rocks from the Upper Riphean stratotype (Karatau Group of the southern Urals) are obtained for several southwestern sections of the Bashkirian meganticlinorium, which have not been studied before. The results obtained supplement the Sr-and C-isotopic information for the group upper horizons thus detailing chemostratigraphic characterization of the entire succession. Limestone and dolostone samples used to analyze the Sr isotope composition satisfy strict geochemical criteria of the isotopic system retentivity and have been subjected to preliminary treatment in ammonium acetate to remove secondary carbonate phases. Data on 255 samples of carbonate rocks (171 studied for the first time) show that δ13C value varies in the Karatau Group succession from ?2.8 to +5.9 ‰ V-PDB with several in-phase excursions from the general trend in all the sections studied in the area 90 × 130 km. The δ13C variation trend demarcates several levels in the carbonate succession of the Karatau Group suitable for objectives of regional stratigraphy and for C-isotope chemostratigraphic subdivision of the Upper Riphean. The results of Sr isotopic analysis of 121 samples (51 unstudied before) from the Karatau Group imply that rocks in its lower part (the Katav Formation and basal horizon of the Inzer Formation) experienced considerable secondary alterations, while limestones and dolostones of the overlying interval of the group are frequently unaltered. In the “best” samples satisfying geochemical criteria of the isotopic system retentivity, the 87Sr/86Sr initial ratio increases from 0.70521–0.70532 in the lower Inzer deposits to 0.70611 in the upper Min’yar carbonates, decreasing to <0.70600 near the top of the latter. Above the regional hiatus separating the Min’yar and Uk formation, this ratio grows from 0.70533 to 0.70605–0.70609 in the limestone succession of the last formation. 相似文献
124.
A new earthquake catalogue for central, northern and northwestern Europe with unified Mw magnitudes, in part derived from chi-square maximum likelihood regressions, forms the basis for seismic hazard calculations
for the Lower Rhine Embayment. Uncertainties in the various input parameters are introduced, a detailed seismic zonation is
performed and a recently developed technique for maximum expected magnitude estimation is adopted and quantified. Applying
the logic tree algorithm, resulting hazard values with error estimates are obtained as fractile curves (median, 16% and 84%
fractiles and mean) plotted for pga (peak ground acceleration; median values for Cologne 0.7 and 1.2 m/s2 for probabilities of exceedence of 10% and 2%, respectively, in 50 years), 0.4 s (0.8 and 1.5 m/s2) and 1.0 s (0.3 and 0.5 m/s2) pseudoacclerations, and intensity (I0 = 6.5 and 7.2). For the ground motion parameters, rock foundation is assumed. For the area near Cologne and Aachen, maps
show the median and 84% fractile hazard for 2% probability of exceedence in 50 years based on pga (maximum median value about
1.5 m/s2), and 0.4 s (>2 m/s2) and 1.0 s (about 0.8 m/s2) pseudoaccelerations, all for rock. The pga 84% fractile map also has a maximum value above 2 m/s2 and shows similarities with the median map for 0.4 s. In all maps, the maximum values fall within the area 6.2–6.3° E and
50.8–50.9° N, i.e., east of Aachen. 相似文献
125.
Relations between climatic variability and hydrologic time series from four alluvial basins across the southwestern United States 总被引:1,自引:3,他引:1
Hydrologic time series of groundwater levels, streamflow, precipitation, and tree-ring indices from four alluvial basins in the southwestern United States were spectrally analyzed, and then frequency components were reconstructed to isolate variability due to climatic variations on four time scales. Reconstructed components (RCs), from each time series, were compared to climatic indices like the Pacific Decadal Oscillation (PDO), North American Monsoon (NAM), and El Niño-Southern Oscillation (ENSO), to reveal that as much as 80% of RC variation can be correlated with climate variations on corresponding time scales. In most cases, the hydrologic RCs lag behind the climate indices by 1–36 months. In all four basins, PDO-like components were the largest contributors to cyclic hydrologic variability. Generally, California time series have more variation associated with PDO and ENSO than the Arizona series, and Arizona basins have more variation associated with NAM. ENSO cycles were present in all four basins but were the largest relative contributors in southeastern Arizona. Groundwater levels show a wide range of climate responses that can be correlated from well to well in the various basins, with climate responses found in unconfined and confined aquifers from pumping centers to mountain fronts. 相似文献
126.
Athanasios Maramathas 《Hydrogeology Journal》2006,14(7):1360-1366
A new approach to the method of artificial upraising of the water outlet point, for management and development of brackish karst springs, uses the MODKARST model. Brackish karst springs simulation can be used to estimate the necessary upraising of the spring elevation, so that sea-water intrusion is blocked. The consequent freshwater loss to the sea, due to this upraising, can also be estimated. The method has been applied to the periodically brackish karst Almiros spring at Heraklion of Crete, Greece. The spring simulation showed that the sea-water intrusion could be prevented through an artificial upraising of the water-outlet point, realized by the construction of a dam. The exact upraising has been estimated. Freshwater loss to the sea because of this upraising has also been estimated. The model could also be used as a tool for the management of the spring. For example, it was used to assess management options for the spring during the depletion period of the year 1994. The best scenario for the development of the spring during this period has been estimated. 相似文献
127.
128.
A salt water lens is found above fresh water under the shore between Dunkerque (France) and Nieuwpoort (Belgium). This inverse density distribution is in a dynamic equilibrium. It develops due to the infiltration of salt water on the back shore during high tide. Under this salt water lens, water infiltrated in the adjacent dune area flows towards the sea and discharges at the seabed. This water quality distribution differs from the classic salt water wedge under fresh water described in the literature. Here, the evolution to this water quality distribution is simulated with a density dependent numerical model. A large tidal range, shore morphology and a permeable groundwater reservoir are the main conditions for the observed water quality distribution. By altering these conditions, intermediate water quality distributions between the classic salt water wedge and the one discussed here develop. Based on these simulations, it is expected that similar kinds of inverse density distribution could be present in a number of coastal areas, which have tides, a gently sloping shore and a permeable substratum. 相似文献
129.
In the Sandıklı (Afyon) region, western Taurides, the Late Proterozoic rocks of the Sandıklı basement complex are composed of low-grade meta-sedimentary rocks (Güvercinoluk Formation) intruded by felsic rocks (Kestel Cayı Porphyroid Suite, KCPS). The KCPS is a deformed and highly sheared, dome-shaped rhyolitic body with a granitic core. Quartz porphyry dikes intrude both the slightly metamorphic igneous and the sedimentary rocks of the basement complex. Both the quartz porphyries and rhyolites were converted into mylonites with relict igneous textures. Geochemical data show that these felsic igneous rocks are subalkaline and mainly granitic in composition with SiO2 >72 wt% and Al2O3 >11.5 wt%. The chondrite-normalized incompatible trace element patterns are characterized by distinct negative Rb, Nb, Sr, P, Ti, and Eu with enrichment in Th, U, La, Ce, Nd, Sm, and Zr. The REE patterns of the felsic rocks indicate a strong enrichment in LREE but display slightly flat HREE patterns. According to geochemical characteristics and petrogenetic modeling, extrusive and intrusive rocks of the KCPS were probably derived from an upper continental crustal source (partial melting of granites/felsic rocks) by 18–20% fractional melting plus 18–20% Rayleigh fractional crystallization, which seems to be the most effective igneous process during the crystallization of the KCPS. Single zircon age data from the granitoids and fossils from the disconformably overlying sedimentary successions indicate that the metamorphism and the igneous event in the Taurides are related to the Cadomian orogeny. Based on the geological, geochemical and petrogenetic correlation of the post-collisional granitoids it is further suggested that the Tauride belt in western central Turkey was in a similar tectonic setting to the Gondwanan terranes in North Africa (Younger Granitoids) and southern Europe (Spain, France, Bohemia, Brno Massifs) during the Late Cadomian period. 相似文献
130.
Diurnal Variations of Hydrochemistry in a Travertine-depositing Stream at Baishuitai, Yunnan, SW China 总被引:6,自引:0,他引:6
Zaihua Liu Qiang Li Hailong Sun Changjun Liao Huaju Li Jinliang Wang Kongyun Wu 《Aquatic Geochemistry》2006,12(2):103-121
Diurnal variations of hydrochemistry were monitored at a spring and two pools in a travertine-depositing stream at Baishuitai,
Yunnan, SW China. Water temperature, pH and specific conductivity were measured in intervals of 5 and 30 min for periods of
1 to 2 days. From these data the concentrations of Ca2+, HCO3−, calcite saturation index, and CO2 partial pressure were derived. The measurements in the spring of the stream did not show any diurnal variations in the chemical
composition of the water. Diurnal variations, however, were observed in the water of the two travertine pools downstream.
In one of them, a rise in temperature (thus more CO2 degassing) during day time and consumption of CO2 due to photosynthesis of submerged aquatic plants accelerated deposition of calcite, whereas in the other pool, where aquatic
plants flourished and grew out of the water (so photosynthesis was taking place in the atmosphere), the authors suggest that
temperature-dependent root respiration underwater took place, which dominated until noon. Consequently, due to the release
of CO2 by the root respiration into water, which dominated CO2 production by degassing induced by temperature increase, the increased dissolution of calcite was observed. This is the first
time anywhere at least in China that the effect of root respiration on diurnal hydrochemical variations has been observed.
The finding has implications for sampling strategy within travertine-depositing streams and other similar environments with
stagnant water bodies such as estuaries, lakes, reservoirs, pools and wetlands, where aquatic plants may flourish and grow
out of water. 相似文献