The paper presents the results from the investigations of the effect of the local soil characteristics upon the seismic response at the surface of the Skopje city region. The SHAKE2000 computer program was used. Four soil profiles with a total thickness ranging between 7 m and 30 m were considered. The soil dynamic properties were defined by using data on the Skopje city region reported in literature. Horizontally, the soil layers were modeled as a one-dimensional soil column subjected to horizontal earthquake motion at the base. The seismic motions were defined using sets of four synthetic accelerograms compatible with the uniform hazard spectra at bedrock for return periods of 95, 475 and 1000 years. The results represent transfer functions as a representative measure of amplitude-frequency modification of local soils and absolute acceleration response spectrum at the free surface. The amplification factor was computed as a ratio between the acceleration spectra at the free surface and those at bedrock.
Nine bedrock and two till samples were analyzed to determine whether their chemical and physical properties could be used to distinguish between bedrock units and to differentiate local bedrock from overlying tills. The bedrock samples came from The North Cliff subsite of the Wellsch Valley Site, and the till samples from Jaw Face subsite. Eight of the nine bedrock samples show great similarity. However, their geochemical differences from the overlying Quaternary tills establish that the tills contain much material entrained, during one or more early Quaternary glaciations, from older bedrock outcrops to the north and northeast. The glaciers that laid down the tills appear to have reworked and concentrated elements compatible with a dry climate, probably formed by weathering during long interglacial, and perhaps preglacial, intervals when the surface was undergoing slow degradation.
Authors:M. Dainese, M. Scotton, F. Clementel, A. Pecile, and J. Lepš
We studied the floristic composition in the pastures of the Southern Alps (Trento Province, Italy). One hundred and five plots in seven different pasture plant communities were sampled: (1) nitrophilous, (2) montane mesic, (3) subalpine mesic, (4) calcareous montane, (5) calcareous subalpine, (6) acid montane, and (7) acid subalpine pastures. Forward selection and variation partitioning were applied to identify the most important factors controlling the species composition and plant traits in the pastures. Aggregated weighted averages were calculated for each plot using the published values of average height, specific leaf area, and seed mass for each species. Explanatory variables were recorded for each site to reflect climate, soil properties, and grazing pressure. We hypothesised that species composition and functional variation in pastures of the Southern Alps are controlled by three main environmental filters: climate, resource availability, and grazing pressure. We found that variables of climate and soil properties had a major role in explaining the species composition and variations in plant traits, while grazing pressure showed a lower independent effect. Species composition and plant traits depended mainly on temperature, soil fertility, and variables of bedrock type — soil pH. Our results confirm the importance of taking the effects of climate and resource availability into account when describing plant and community functions of grasslands.
Three plant fragments were collected from two landslide profiles and were radiocarbon-dated by accelerator mass spectrometry. Results reveal that the two landslides occurred around AD 1646 and AD 1278, respectively. Mössbauer spectroscopy indicates that the sliding mud contains more ferrous iron species (para-Fe2+ and pyr-Fe2+) and less ferric iron (para-Fe3+ and hem-Fe3+) than do the overlying debris rock and the underlying bedrock. This suggests strong reductive condition within the slip zone relative to the underlying bedrock. Such a redox profile is different from the normal weathering profile whose oxidative conditions become reductive with increasing depth. The change of redox conditions in the sliding mud layer is most likely related to the percolated groundwater which is active in the slip zone.
In Sardinia, the Italian island in the middle of the MediterraneanSea, there are many red soils developed on limestone or dolomite. Soil andunderlying bedrock samples from 5 different sites have been submitted to chemicaland mineralogical characterization, by using standard X-ray diffraction analysis,spectrochemical methods and instrumental neutron activation analysis. Obtainedresults are presented and discussed in terms of precision and accuracy. Traceelement concentration variation with depth is discussed as well as the enrichment/depletionratios between soils and rocks, and the rare-earth element distribution. Dataanalysis suggests for some soils a formation process based on the evolutionof the underlying bedrock, and for the other soils a formation process partlybased on the evolution of the local rock but with meaningful contributionsof external sources, both eolian and/or alluvial.
Authors:A. A. Tealeb, M. Sobaih, A. A. Mohamed, and Abdel-Rahman Kamal
The quarry blasting is one of the artificial explosions that produces stresses in the ground and may have a great effect on the near foundations. The estimation of the stress level either in the weathering layer or the bedrock is necessary for the safety of the existing buildings near the quarries. Cement Companies has been in operation since 1956 close to Helwan City, Egypt. Since then, new buildings and new communities were established in the area such as the City of 15th of May. For the safety of these buildings, detailed and continuous monitoring of the peak particle velocity of the quarry blasting operations was carried out since January 1997 till September 2000. The maximum values of the stress level for the weathering layer has been found smaller than that for the bedrock for both of the P- and S-waves. The damage observed in the buildings close to the quarry blasting operations, indicates that these stress levels are high.
The concentrations of Au, Ce, Cr, Eu, Hf, La, Lu, Sc, Sm, Th, U and Yb were determined by instrumental neutron activation analysis in 1200 samples of glacial till from Quebec by using a SLOWPOKE reactor. All these elements are lognormally distributed in the till which would suggest that their concentrations, while reflecting somewhat the composition of the bedrock, are apparently not regulated about a central value by any geological process.
Bedrock has an essential role in the formation of soils, it fundamentally determines mineral composition. The present research focuses on the minerals in forest soils formed in the Bükk Mountains (NE Hungary). The composition of soil minerals was in accordance with the geological features as well as with the changes in climate and vegetation, which provide a basis for tracking the past of the soil formation mechanisms (Nemecz, 2006). Thus, by studying the mineral composition the formation processes and development of the soils can be unveiled.According to the findings it can be assumed that the investigated soils, although formed primarily on solid limestone, cannot be the products of the weathering of limestone solely, as they also contain significant amounts of silicates. The major part of the soil forming materials presumably originates from earlier dust fallings or from alluvial deposits by erosion. The former assumption is confirmed by the fact that the investigated area is located at a high altitude, thus significant amounts of eroded material could only originate from a short distance, where the bedrock also consists of limestone. Further research is needed for more detailed knowledge on the mineral composition of the soils, thus on the development of the soils and the bedrock of the investigated area.
A technique using a small diameter probe and a portable alpha-particle scintillometer for sample collection and analysis has been developed. It is fast, efficient, cost-effective, and can be modified to accommodate a wide spectrum of sampling conditions. When soil-gas sampling for radon is combined with geophysical gamma-ray measurements, pedological characteristics of surficial materials, and geologic knowledge of bedrock, the combination forms a powerful technological basis for estimating radon potential of soils. The method can help provide information on a short time-frame so that local governments, land developers, and builders can take appropriate measures when planning new construction.