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81.
Grzegorz Beziuk 《Acta Geophysica》2012,60(1):140-156
Relationships for the mutual impedance of horizontal coplanar, vertical coplanar, perpendicular and vertical coaxial loop
antenna arrays operating at a high frequency, located over a layered conducting medium, have been derived. The relationships
take into account the occurrence of displacement currents in both the free space and the conducting medium. The relations
can be used for calculating the earth parameters in geophysical prospecting. The use of high frequency antenna array makes
it possible to determine distributions of apparent resistivity as well as apparent electrical permittivity. The potential
application of the measurements of mutual impedance of loop antennas operating at a high frequency to the geophysical examinations
is presented. The measuring system developed for this purpose is described. A simple method of interpreting the mutual impedance
measurements to obtain the traces of apparent resistivity and apparent permittivity of the investigated earth is given. 相似文献
82.
83.
Previous research on rock weathering crusts has revealed their large variability depending on the type of host rocks and development of weathering processes. The composition of crusts developed on natural sandstone exposures is less documented in the literature in comparison to those developed on architectonic stones. In both cases, previous research has focused mainly on the progress of salt weathering. This study considers the surfaces of sandstone tors in the Polish Outer Carpathians. The exposed parts of the rocks in this area are often covered by crust, which is up to several centimetres thick, and differs from the internal part in colour and composition. The crusts were characterized using light and electron microscopy, X‐ray diffractometry, thermal analyses, Mössbauer spectroscopy, bulk chemical analyses and sequential chemical extractions. Porosity was estimated by digital image processing. The following two hardened zones were observed: (1) thin (up to 30 µm), black, external layer, rich in carbon and composed of opal‐type silica, covered in places by sulphate incrustations and numerous spherical particles of anthropogenic origin; (2) thicker (up to several millimetres), internal part composed of a set of laminae of variable colouration, enriched in iron (oxyhydr)oxides (goethite and hematite) in comparison to the rock interior. Development of the crust results from silicon and iron redistribution during the sandstone alteration. The chief source of silica is hydrolysis of aluminosilicates, whilst that of iron is decomposition of aluminosilicates, carbonates and sulphides. Hematite is probably a result of goethite transformation. However, air pollutants may play an important role in the formation of sulphates. Silica and iron compounds affect the properties of the rock, hardening the surface and lowering porosity by formation of secondary cement. Crystallization of sulphate salts, in turn, may contribute to mechanical disintegration of the rock. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
84.
High energy release during seismic events induced by mining operation is one of the major dangers perturbing production in underground mines. In this work, temporal changes of seismic event parameters for one of the Rudna Mine (Poland) panels are investigated. The study aim was to find whether the temporal clustering of smaller events in different parameters can be observed before and after the high energy events (Ml?≥?3) in the mining panel. The method chosen for analysis was the study of temporal variation of fractal dimension of the seismic events parameter sets composed from: the interevent epicentral distance (dr), logarithm of seismic energy (lE), and interevent energy coefficient (dlE), which is the absolute difference between logarithms of energy of two consecutive events. Temporal variations study was performed in equivalent dimension (ED) space. The transformation of the seismic source parameters into ED space allowed to estimate and compare the temporal changes of the fractal dimension of different parameter spaces using the same method—correlation fractal dimension, and then easily compare the obtained temporal changes of fractal dimension of different parameter sets. The effect of grouping is expressed by decrease of fractal dimension, which is connected with the similarity of events parameter values. The temporal changes of the fractal dimension of seismicity before the strong induced events would indicate some initiation phase of the process leading to the high energy release. In the case of the studied Rudna Mine panel, the temporal behavior of the fractal dimension values in different parameter spaces before seismic events showed significant changes before three out of four events with CLVD dominant source mechanisms. 相似文献
85.
Microseismicity induced during fluid-injection: A case study from the geothermal site at Groß Schönebeck,North German Basin 总被引:1,自引:1,他引:0
Grzegorz Kwiatek Marco Bohnhoff Georg Dresen Ali Schulze Thomas Schulte Günter Zimmermann Ernst Huenges 《Acta Geophysica》2010,58(6):995-1020
The technical feasibility of geothermal power production in a low enthalpy environment will be investigated in the geothermal site at Groß Schönebeck, North German Basin, where a borehole doublet was completed in 2007. In order to complete the Enhanced Geothermal System, three massive hydraulic stimulations were performed. A seismic network was deployed including a single 3-component downhole seismic sensor at only 500 m distance to the injection point. Injection rates reached up to 9 m3/min and the maximum injection well-head pressure was as high as ~60 MPa. A total of 80 very small (?1.8 < M W < ?1.0) induced seismic events were detected. The hypocenters were determined for 29 events. The events show a strong spatial and temporal clustering and a maximum seismicity rate of 22 events per day. Spectral parameters were estimated from the downhole seismometer and related to those from other types of induced seismicity. The majority of events occurred towards the end of stimulation phases indicating a similar behavior as observed at similar treatments in crystalline environments but in our case at a smaller level of seismic activity and at lower magnitudes. 相似文献
86.
Zbyněk Engel Grzegorz Skrzypek Debajyoti Paul Wojciech Drzewicki Daniel Nývlt 《Journal of Paleolimnology》2010,43(4):609-624
This study presents detailed lithostratigraphy and stable carbon and nitrogen isotopic variations in a 520-cm-long sediment
core from a cirque basin in the Labsky důl Valley, Krkonoše Mountains, Czech Republic. Detailed study of the core reveals
five major periods of sedimentation during the last 7600 years: silt and sand deposition during ~7.6–5.1 ka cal BP, Sphagnum peat accumulation during ~5.1–4.0 ka cal BP, sandy silt and sand during ~4.0–2.8 ka cal BP, raised peat bog during ~2.8–2.0 ka cal
BP (Sphagnum peat), and sedimentation of sandy silt since ~2.0 ka cal BP. The δ13C values of the organic matter in the core vary in the range typical for C3 plants, from −24.35 to −27.68‰, whereas the δ15N values vary from −2.65 to +4.35‰. Core sections having ash contents ≥70% have δ15N > 1‰ and δ13C < −26‰, whereas those having ≤70% ash content have δ15N < 1‰ and δ13C > −26‰. Strong linear correlations are observed between δ13C and δ15N values as well as between C:N ratios and δ15N values in the horizons with ash content >10%, primarily for sand and silt horizons. On the other hand, poor correlations
between δ13C and C:N ratio, as well as δ15N and C:N ratio, were observed in Sphagnum peat layers (45–125 and 185–265 cm). We conclude that the primary stable isotope variations are not preserved in the layers
where significant correlation between δ15N and C:N ratio is observed. The relatively small δ13C variation in the uppermost Sphagnum peat layer suggests stable temperature during ~2.8–2.0 ka cal BP. 相似文献
87.
Extreme rainfall events are of particular importance due to their severe impacts on the economy, the environment and the society. Characterization and quantification of extremes and their spatial dependence structure may lead to a better understanding of extreme events. An important concept in statistical modeling is the tail dependence coefficient (TDC) that describes the degree of association between concurrent rainfall extremes at different locations. Accurate knowledge of the spatial characteristics of the TDC can help improve on the existing models of the occurrence probability of extreme storms. In this study, efficient estimation of the TDC in rainfall is investigated using a dense network of rain gauges located in south Louisiana, USA. The inter-gauge distances in this network range from about 1 km to 9 km. Four different nonparametric TDC estimators are implemented on samples of the rain gauge data and their advantages and disadvantages are discussed. Three averaging time-scales are considered: 1 h, 2 h and 3 h. The results indicate that a significant tail dependency may exist that cannot be ignored for realistic modeling of multivariate rainfall fields. Presence of a strong dependence among extremes contradicts with the assumption of joint normality, commonly used in hydrologic applications. 相似文献
88.
Witold Szczuciński Przemysław Niedzielski Grzegorz Rachlewicz Tadeusz Sobczyński Anetta Zioła Artur Kowalski Stanisław Lorenc Jerzy Siepak 《Environmental Geology》2005,49(2):321-331
Tsunami sediments deposited in a coastal zone of Thailand by the 26 December 2004 tsunami wave were sampled within 50 days after the event. All surface and ground waters in tsunami- inundated zone revealed significant salinity at that time. The tsunami sediments, composed mainly of fine to medium sand, contain significantly elevated contents of salts (Na+, K+, Ca+2, Mg+2, Cl and SO
4
−2
) in water-soluble fraction, and of Cd, Cu, Zn, Pb in the bioavailable fraction and As in the exchangeable fraction in relation to the reference sample. The origin of contaminants is marine, as well as litho- and anthropogenic. The salts and Pb, Zn and Cu reveal high correlation to each other and to the mean grain size (pore size and porosity). Serious environmental hazard exists in that region because, due to gentle morphology, there is a risk of migration of the contaminants into ground waters and food chain. 相似文献