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251.
A Review of Studies Dealing with Tree Rings and Rockfall Activity: The Role of Dendrogeomorphology in Natural Hazard Research 总被引:1,自引:0,他引:1
M. Stoffel 《Natural Hazards》2006,39(1):51-70
Over the last few years, rockfall research has increasingly focused on hazard assessment and risk analysis. Input data on
past rockfall activity were gathered from historical archives and lichenometric studies or were obtained through frequency–volume
statistics. However, historical records are generally scarce, and lichenometry may only yield data with relatively low resolutions.
On forested slopes, in contrast, tree-ring analyses may help, generally providing annual data on past rockfall activity over
long periods. It is the purpose of the present literature review to survey the current state of investigations dealing with
tree-ring sequences and rockfall activity, with emphasis on the extent to which dendrogeomorphology may contribute to rockfall
research. Firstly, a brief introduction describes how dendrogeomorphological methods can contribute to natural hazard research.
Secondly, an account is provided of the output of dendrogeomorphological studies investigating frequencies, volumes or spatial
distributions of past rockfall activity. The current and potential strengths of dendrogeomorphology are then presented before,
finally, the weaknesses of tree rings as natural archives of past rockfall activity are discussed and promising directions
for further studies outlined. 相似文献
252.
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
253.
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
254.
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
255.
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
256.
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
257.
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
258.
Risk and uncertainty assessments for waste containment systems employing clay barriers often include spatial variability in
the hydraulic conductivity as part of the analysis. The two-parameter log-normal distribution is often used to describe the
spatial variability, but for compacted clays the three-parameter form can be more appropriate. A statistical hypothesis test
was developed that can be used to determine if the two- or three-parameter form of the log-normal distribution is more appropriate.
The test is based on a likelihood ratio, comparing likelihood functions for the two- and three-parameter forms at their maximums.
Likelihood functions are used assuming that a data set can be segregated into a set of distinct groups of hydraulic conductivities.
A step-by-step calculation procedure is described and the test is applied to data collected from 45 sites. 相似文献
259.
四川盆地紫色丘陵区的水土保持林低效化问题已较严重。研究了其土壤方面的成因。通过对土壤构造、土壤肥力特性、土壤结构性评价等研究,指出该区人工林地的土壤构造发育不正常,土壤腐殖质胶体积累量低。土壤结构质量差等林地土壤退化是土壤水土保持功能降低的主要原因。根据研究的初步结果,提出了相应的对策建议。 相似文献
260.
DENIS WOOD 《Geographical review》2006,96(2):229-258
ABSTRACT. The spatial world of the child comprises two great realms, “in’ and “out,’ more or less corresponding to the great behavioral domains of “got to’ and “doing nothing.’ Within the “got‐to’ domain–and thus “in’–are home, school, and other loci of secure, stable authority. Included in “doing nothing’–and so “out’–are street and yard, field and stream, pool hall and movie theater, the spaces of games, things to do, and really doing nothing. This study looks at the shifting relationships of these realms across the life cycle of kids in the highlands of Puerto Rico in 1969–1970. 相似文献