A statistical model for estimating the accuracy of event location applied to a network of Scandinavian stations

A statistical model for estimating the errors of epicenter location and origin time is proposed and applied to the old Fennoscandian seismic network. An average crustal model (Sellevoll andPomeroy, 1968) and P and S wave residuals as a function of azimuth have been used. The calculations are carried out for different maximum detection ranges. The analysis shows relatively, small (1 km) standard errors of epicenter location of strong earthquakes for central Fennoscandia. The largest errors are found in the southern and eastern parts of Fennoscandia.On leave from Institute of Geophysics, Polish Academy of Sciences, Warsaw, Poland.     

The performance of the empirical models on industrial hydrocyclone design

Many empirical models have been used widely for designing hydrocyclones in industry. These empirical models consist of a set of design equations. Most of the design equations are based on the correlations obtained experimentally, using dimensionless similarity numbers. These equations have their limitations due to the specific systems used for model development. Therefore, in many cases, they cannot be used with confidence to predict the design of an individual separator, or the overall plant configuration that is required to meet different user requirements. A modified version of the existing design equations presented by previous researchers was developed. The design equations, describing four fundamental parameters: pressure drop, flow recovery to underflow, corrected cut size and classification function, were modified by fitting with set of experimental data to obtain the system-specific constant parameters. These modified design equations were then called, the fine-tuned design equations. Four sets of fine-tuned design equations describing all the fundamental parameters were constructed and used to predict the separation performance of many hydrocyclone operational systems at the Dow Chemical Company, Texas, USA. The performance of these equations is evaluated, and the limitations of their use are discussed, thus providing useful insights into hydrocyclone design.     

Sibsonian and non-Sibsonian natural neighbour interpolation of the total electron content value

In radioastronomy the interferometric measurement between radiotelescopes located relatively close to each other helps removing ionospheric effects. Unfortunately, in case of networks such as LOw Frequency ARray (LOFAR), due to long baselines (currently up to 1500 km), interferometric methods fail to provide sufficiently accurate ionosphere delay corrections. Practically it means that systems such as LOFAR need external ionosphere information, coming from Global or Regional Ionospheric Maps (GIMs or RIMs, respectively). Thanks to the technology based on Global Navigation Satellite Systems (GNSS), the scientific community is provided with ionosphere sounding virtually worldwide. In this paper we compare several interpolation methods for RIMs computation based on scattered Vertical Total Electron Content measurements located on one thin ionospheric layer (Ionospheric Pierce Points—IPPs). The results of this work show that methods that take into account the topology of the data distribution (e.g., natural neighbour interpolation) perform better than those based on geometric computation only (e.g., distance-weighted methods).     

Lignin degradation products as palaeoenvironmental proxies in the sediments of small lakes

The quantity and quality of lignin phenols (Σ8, Λ, S/V, C/V and (Ad/Al)_v) in the sediments of three small Lobelia lakes with neither inlets nor outlets were investigated and compared with palynological data and lithology of the profiles. The method of alkaline CuO oxidation was used. Substantial differences with respect to sedimentary lignin concentration and provenance recorded along the profiles and among the sites are in good agreement with pollen data describing the dominant type of vegetation and with indices of soil erosion in the lakes’ catchments. This relation shows that the compositions of lignin degradation products in these lakes are closely related to the local environmental conditions. In all the lakes gymnosperm wood is the main source of lignin products; however, each lake is characterized by different S/V index values. Especially good correlations were obtained between pine pollen proportions in sediments and the S/V index. The correlation between the C/V and (Ad/Al)_v indices indicates a higher degradation of organic matter when non-woody tissue is more abundant. This pilot study illustrates the usefulness and potential for a wider application of lignin oxidation products in palaeoecological reconstructions. This kind of data would be of special importance when investigating local presence/absence of woody plants and the role of angiosperms/gymnosperms in local vegetation. Estimates of lignin biodegradation levels, as well as the data on diagenetic processes, may afford supplementary information on possible disturbances in sedimentation.     

Different Borders‐Different Cooperation? Transborder Cooperation in Poland

The aim of this paper was to analyze the role of border and borderland type in transborder cooperation. To this end, 591 projects under six Interreg IIIA Programs in which Polish border regions participated from 2004 to 2006 were examined. These programs were compared to identify the various factors influencing projects in different border regions. Although research on cooperation usually focuses on a national scale, actual cooperation depends largely on regional and local conditions, which are the focus of this study. Despite a common legal and institutional framework, the Interreg projects were not all realized in the same way. Different local conditions had impacts on programs and implementation. Therefore, the effectiveness and achievement of transborder cooperation objectives depended on the modification of each program to specific regional conditions.     

Cadomian basement of the palaeozoic platform in central Europe

Summary In central Europe, evidence for Cadomian basement occurs from the Midlands Massif in the United Kingdom to the Moesian Platform in Romania. The patchily exposed basement rocks either have survived almost intact through the Phanerozoic (e.g. Lusatia), overstepped by different Palaeozoic strata, or have been reworked to various degrees (e.g. Erzgebirge) and involved in Variscan structures (e.g. Sudetes, Moravia). In the Polish and German lowlands, undated subsurface basement occurs below the Permo-Mesozoic cover and Variscan molasse and flysch successions. The mutual relationships between the various Cadomian fragments occurring within and/or below the Palaeozoic, both orogenic and platform successions, are far from fully understood.     

On the behaviour of liquefied soil

Engineering mechanics of liquefied soil is presented. Firstly, experimental methods and their results are described in order to show that liquefied soil can be approximated as a viscous fluid. The experiments proposed allow for determination of dynamic viscosity of liquefied soil, which is of the order of 10⁶ Ns/m². This value agrees with some theoretical estimates. Then, the model of viscous fluid is applied to practically important problems, in order to predict sinking of structures in liquefied subsoil, and to describe underwater flows of seabed. Enclosed examples show that the model and methods proposed lead to realistic results and, therefore, can be applied in engineering calculations.     

Generalized migration in frequency-wavenumber domain (MGF-K) in anisotropic media

In this paper, the background of MGF-K migration in dual domain (wavenumber-frequency K-F and space-time) in anisotropic media is presented. Algorithms for poststack (zero-offset) and prestack migration are based on downward extrapolation of acoustic wavefield by shift-phase with correction filter for lateral variability of medium’s parameters. In anisotropic media, the vertical wavenumber was determined from full elastic wavefield equations for two dimensional (2D) tilted transverse isotropy (TTI) model. The method was tested on a synthetic wavefield for TTI anticlinal model (zero-offset section) and on strongly inhomogeneous vertical transverse isotropy (VTI) Marmousi model. In both cases, the proper imaging of assumed media was obtained.     

Interpretation of tracer tests performed in fractured rock of the Lange Bramke basin, Germany

 Two multitracer tests performed in one of the major cross-fault zones of the Lange Bramke basin (Harz Mountains, Germany) confirm the dominant role of the fault zone in groundwater flow and solute transport. Tracers having different coefficients of molecular diffusion (deuterium, bromide, uranine, and eosine) yielded breakthrough curves that can only be explained by a model that couples the advective–dispersive transport in the fractures with the molecular diffusion exchange in the matrix. For the scale of the tests (maximum distance of 225 m), an approximation was used in which the influence of adjacent fractures is neglected. That model yielded nearly the same rock and transport parameters for each tracer, which means that the single-fracture approximation is acceptable and that matrix diffusion plays an important role. The hydraulic conductivity of the fault zone obtained from the tracer tests is about 1.5×10^–2 m/s, whereas the regional hydraulic conductivity of the fractured rock mass is about 3×10^–7 m/s, as estimated from the tritium age and the matrix porosity of about 2%. These values show that the hydraulic conductivity along the fault is several orders of magnitude larger than that of the remaining fractured part of the aquifer, which confirms the dominant role of the fault zones as collectors of water and conductors of fast flow. Received, April 1997 Revised, January 1998, August 1998 Accepted, August 1998     

Wavefield downward extrapolation for migration velocity analysis on Marmousi data-set

The authors present a method for estimation of interval velocities using the downward continuation of the wavefield to perform layer-stripping migration velocity analysis. The generalized, phase-shift migration MG(F-K) in wavenumber-frequency domain was used for fulltime downward extrapolation of the wavefield. Such downward depth extrapolation accounts for strong changes of velocity in lateral and vertical directions and helps in correct positioning of the wavefield image in complex structures. Determination of velocity is the recursive process which means that the wavefield on depth level z _n−1 (n = 0, 1, ...) is an input data-set for determination of velocity on level z _n . The velocity ν [x, z _n − z _n−1] can be thus treated as interval velocity in Δz _n = z _n − z _n−1 step. This method was tested on synthetic Marmousi data-set and showed satisfactory results for complex, inhomogeneous media.