A rectified map of recent vertical surface movements in the West Carpathians in Slovakia

The first-order relevelling network in Slovakia (International Relevelling Program) was supplemented by second-order relevelling lines measured at the time of the International Relevelling Program (1973–1978) or after its completions, in order to gain more detailed information on the movement activity of the West Carpathians in Slovakia. Mathematical evaluation of relevelling results allowed of drawing a map of recent vertical movements in the region at the scale of 1:1,000,000.The Czechoslovak Uniform Levelling Network of 1947–1962 and the 2nd Czechoslovak Relevelling Network of 1973–1983 constitute the geodetic basis of the map. The relative annual movement velocities, as related to the Initial Fundamental Benchmark Pitelová near Žiar nad Hronom (approximately in the centre of Slovakia) are represented by isolines at intervals of 0.5 mm per year.An analysis of the map 1952–1977 indicates an overall subsidence of lowland regions with respect to the mountanous regions of the West Carpathiams. Central Carpathian morphostructures feature uplifts, with some regions appearing to be stable. Over the entire period under study, the maximal values of vertical movements were + 1.0 mm/year (uplifts) and -4.0 mm (subsidences), the total range being 5 mm/year.     

Hydrogeological indications of recent movements of the earth's crust

Hydrogeologic indications of recent movements of the Earth's crust in two regions of North Tian-Shan have been studied. Comparison of ground-water level changes and variations of recent vertical movements according to benchmarks located near a well demonstrates their good correlation. The ground-water level varies out of phase with the direction of vertical movements. A correlation between level variation and seismic regime has been observed up to a well, located in a near-fault zone. In the region of the Kochkorskaya Depression, well observations show that against a background of constant increasing of level, sharp decays are observed. The latter can be connected with creep displacements. Hydrogeologic observations, together with periodic levelling enable us to study recent movements of the Earth's crust in detail.     

The dynamics of the northwestern border of the Carpathians

The border area between the Bohemian Massif and the Carpathians arc is covered by dense networks of repeated levellings as well as horizontal (triangulation, trilateration) measurements. The results were adjusted in separate vertical or horizontal networks respectively. Derived rates of vertical and horizontal movements are presented. The properties of these movements are discussed as a background to the tectonic development of the area under study.     

A new map of recent movements of the West Carpathians

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On the coupling of fluid dynamics and electromagnetism at the top of the earth's core

Abstract

A kinematic approach to short-term geomagnetism has recently been based upon pre-Maxwell frozen-flux electromagnetism. A complete dynamic theory requires coupling fluid dynamics to electromagnetism.

A geophysically plausible simplifying assumption for the vertical vorticity balance, namely that the vertical Lorentz torque is negligible, is introduced and its consequences are developed. The simplified coupled magnetohydrodynamic system is shown to conserve a variety of magnetic and vorticity flux integrals. These provide costraints on eligible models for the geomagnetic main field, its secular variation, and the horizontal fluid motions at the top of the core, and so permit a number of tests of the underlying assumptions.     

Investigation of the earth's crustal structure using earthquake and deep seismic sounding data obtained for the Carpathians

The joint analysis performed for the Carpathian region from seismological data (three-dimensional fields of velocities, areas of concentration of earthquake foci in the Vrancea focal zone) and interpretation of DSS data and those of other geophysical fields have permitted to obtain new evidence for the earth's crust and mantle structure in this region.     

Displacements of the earth's surface in seismic regions

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Quaternary vertical movements of the earth's surface in East-Central Europe

Fluvial terraces in mountain territories and granulometric cycles in fluvial sediment complexes show 300–400 m uplifts in mountain regions and about the same sized subsidences in major East-Central European basins during the Quaternary (−2.4 Ma). The vertical movements are not at all regular and equal in the mountains nor in the great basins. The number of the terraces is different in the valleys and their mutual proportions also differ. Similarly, some local Quaternary basins were developed deeper in the peripheries of the large basins while the central parts are shallow. There are also some stable blocks between the mountains and the lowlands, which did not move essentially during the last two and a half million years.The course and velocity of Pliocene and Quaternary subsidence were proved in a local sub-basin of the Carpathian mountain arch by paleomagnetic measurements of cores from two deep boreholes. In the Körös Basin, filled with fine-grained fluvial sediment, the sedimentation rate was 0.16–0.19 mm/y in the last 700.000 years; 0.15–0.16 mm/y during the proceding one million years; and 0.22–0.28 mm/y during the Pliocene (from −5.2 to −2.4 Ma).In sub-basins filled with coarse-grained sediments, the sedimentation rate was 0.3–0.4 mm/y during the Quaternary.     

On the parameters of the normal earth's gravity field

Summary The parameters of the normal Earth's gravity field, determined from contemporary satellite data are discussed and compared with the parameters of the normal Helmert system (1901 to 1909).Dedicated to Academician Alois Zátopek on His 65th Birthday     

On the excitation of the earth's seismic normal modes

Summary The excitation of the earth's normal modes is formulated as an initial value problem. The static state of the earth, stressed from its hydrostatic reference situation, is considered as the initial state. The initial state is relaxed, at the time of the earthquake, by the removal of the forces maintaining the departure from hydrostatic equilibrium. Expressions are derived for the coefficients giving the relative excitation of the individual modes for the cases where these forces are compensating volume forces or compensating tractions on the faces of a dislocation. It is demonstrated that a point slip dislocation has a body force equivalent in the form of a double couple with a deviatoric moment tensor. However, for a source with volume change no moment tensor equivalent can be found. The volume change, apart from an elastic effect which can be represented by an isotropic moment tensor, has a direct gravitational effect on the excitation. This effect is due to a balanced force field consisting of a point force at the source and a continuous distribution of volume forces throughout the earth. The latter distribution, if not taken into account, may give rise to artificial phases in the frequency spectrum of the normal modes.     

On the state of stress in the near-surface of the earth's crust

Five models for near-surface crustal stresses induced by gravity and horizontal deformation and the influence of rock property contrasts, rock strength, and stress relaxation on these stresses are presented. Three of the models—the lateral constraint model, the model for crustal stresses caused by horizontal deformation, and the model for the effects of anisotropy—are linearly elastic. The other two models assume that crustal rocks are brittle or viscoelastic in order to account for the effects of rock strength and time on near-surface stresses. It is shown that the lateral constraint model is simply a special case of the combined gravity-and deformation-induced stress field when horizontal strains vanish and that the inclusion of the effect of rock anisotropy in the solution for crustal stresses caused by gravity and horizontal deformation broadens the range for predicted stresses. It is also shown that when stress levels in the crust reach the limits of brittle rock strength, these stresses become independent of strain rates and that stress relaxation in ductile crustal rocks subject to constant horizontal strain rates causes horizontal stresses to become independent of time in the long term.     

Inviscid,frozen-flux velocity components at the top of earth's core from magnetic observations at earth's surface: Part 1. A new methodology

Abstract

Two alternative methods are described for obtaining inviscid velocity components at the surface of earth's liquid core, assumed perfectly conducting, given perfect and complete measurements of the geomagnetic main field and secular variation at earth's surface. The mantle is treated as a spherically-symmetric insulator for purposes of extrapolation to the core. Both methods utilize the vertical component of the induction equation and require one-dimensional interpolation along special curves on the core surface as the initial step. For the next step, the first method then utilizes the two horizontal components of the induction equation, whereas the second method relies on the horizontal components of Ohm's law. Both methods work within the confines of the ambiguity elucidated by Backus (1968) but nonetheless can still yield results of value, because the two horizontal velocity components are determined separately and at distinct locations. A brief comparison of the two methods suggests that the one, based in part on Ohm's law, should be superior from a practical viewpoint.     

Population dynamics of mayflies in a constant temperature spring stream in West Carpathians

We examined the life history and secondary production of four Ephemeroptera species (Baetis alpinus Pictet, 1843–1845, Baetis rhodani Pictet, 1843–1845, Rhithrogena carpatoalpina Klonowska, Olechowska, Sartoriet & Weichselbaumer, 1987 and Habroleptoides confusa Sartori & Jacob, 1986) in a temperature stable cold spring stream at Prosiek valley (Cho?ské vrchy Mts., West Carpathians, Slovakia). We have found asynchronous bivoltine life cycle for the most abundant species B. alpinus with growth rate positively correlated to photoperiod length. R. carpatoalpina have shown unusual asynchronous univoltine life cycle and B. rhodani have shown uncommonly low abundance in mayfly community. Total secondary production of mayfly community was very low, reaching 1654.8 mg DW m^?2 y^?1. We suggest that the observed asynchrony in growth could be related to the lack of temperature control.     

On the estimation of the heat flow at the earth's crust lower boundary

Summary The paper deals with a comparison of two models used in determining the heat flow q_M at the lower boundary of two-dimensional geothermal models of the Earth's crust. Method I is based on a linear relationship between the component of the surface heat flow, which is not generated by heat sources inside the model, and the heat flow q_M. This method uses a regularization process, in which the variation of the sought function q_M is limited from above. Method II is the most frequently used iterative method, in which the (i + 1)-th approximation of q_M is determined from the surface heat flow, corresponding to the i-th approximation of q_M used as a boundary condition in solving the direct problem. The comparison of both methods has revealed that the solution obtained by method I satisfies the supposed reality better than the solution obtained by method II. Method II is attractive especially for its simplicity. To eliminate the local variations of the estimated heat flow q_M, which are due to automatic transmission from the surface heat flow, a combination of method II with some smoothing procedure could be applied.

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On the dynamics of rotating fluids and planetary atmospheres: A summary of some recent work

An outline is given of some recent and current research in the Geophysical Fluid Dynamics Laboratory of the UK Meteorological Office, on the dynamics of rotating fluids and planetary atmospheres. Many of these investigations bear on the problem of creating a theoretical framework for atmospheric predictability studies.     

Radiation patterns of point sources situated close to structural interfaces and to the earth's surface

The seismic wave field is considerably influenced by local structures close to the source and to the receiver. This applies to sources and receivers situated close to localized inhomogeneities, to structural interfaces, to the earth's surface, etc. In this paper we concentrate our attention mainly to the ray-theoretical radiation patterns of point sources situated close to the structural interfaces and to the earth's surface. In numerical modeling of high-frequency seismic wave fields by the ray method, the interaction of the source with the earth's surface has not usually been taken into account.The proposed procedure of the computation of the radiation patterns of point sources situated directly on structural interfaces and on the earth's surface is based on the zero-order approximation of the ray method, assuming that the length of the ray between the source and the receiver is long. The derived equations are extended to point sources located close to structural interface, to the earth's surface and to thin transition layers using the hybrid ray-reflectivity method, seeervený (1989). The thin layer need not be homogeneous; it may include an arbitrary inner layering (transition layers, laminas, etc.) The only requirement is for the layer to be thin. Roughly speaking, we require its thickness to be less than one quarter of the prevailing wavelength. The hybrid ray-reflectivity method describes well even certain non-ray effects (tunneling.S ^* waves, etc.). Explicit analytical expressions for radiation patterns for all above listed point sources are found. These expression have a local character and may be easily implemented into computer codes designed for the routine computation of ray amplitudes and synthetic ray seismograms in 2-D and 3-D, laterally varying isotropic layered and block structures by the ray method.Numerical examples of radiation patterns ofP andS waves of point sources situated close to the earth's surface and to a thin low-velocity surface layer are presented and discussed. The explosive point source (center of dilatation) and the vertical and horizontal single force point sources are considered. It has been ascertained that the radiation patterns of point sources depend drastically on the depth of the source below the surface even if the depths vary within one quarter of the prevailing wavelength.