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  • Bounds and averages of seismic quality factor Q
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2020-01-17
    Ayman N. Qadrouh, José M. Carcione, Mamdoh Alajmi, Jing Ba

    Abstract An elastic two-phase composite, with no restriction on the shape of the two phases, has stiffness bounds given by the Reuss and Voigt equations, and a narrower range determined by the Hashin-Shtrikman bounds. Averages are given by the Voigt-Reuss-Hill, Hashin-Shtrikman, Gassmann, Backus and Wyllie equations. To obtain stiffness bounds and averages, we invoke the correspondence principle to compute the solution of the viscoelastic problem from the corresponding elastic solution. Then, seismic velocities and attenuation are established for the above — physical and heuristic — models which account for general geometrical shapes, unlike the Backus average. The approach is relevant to the seismic characterization of solid composites such as hydrocarbon source rocks.

    更新日期:2020-01-17
  • Time-migration velocity estimation using Fréchet derivatives based on nonlinear kinematic migration/demigration solvers
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2020-01-17
    Hao Zhao, Anders Ueland Waldeland, Dany Rueda Serrano, Martin Tygel, Einar Iversen

    Advanced seismic imaging and inversion are dependent on a velocity model that is sufficiently accurate to render reliable and meaningful results. For that reason, methods for extracting such velocity models from seismic data are always in high demand and are topics of active investigation. Velocity models can be obtained from both the time and depth domains. Relying on the former, time migration is an inexpensive, quick and robust process. In spite of its limitations, especially in the case of complex geologies, time migration can, in many instances (e.g. simple to moderate geological structures), produce image results compatible to the those required for the project at hand. An accurate time-velocity model can be of great use in the construction of an initial depth-velocity model, from which a high-quality depth image can be produced. Based on available explicit and analytical expressions that relate the kinematic attributes (namely, traveltimes and local slopes) of local events in the recording (demigration) and migrated domains, we revisit tomographic methodologies for velocity-model building, with a specific focus on the time domain, and on those that makes use of local slopes, as well as traveltimes, as key attributes for imaging. We also adopt the strategy of estimating local inclinations in the time-migrated domain (where we have less noise and better focus) and use demigration to estimate those inclinations in the recording domain. On the theoretical side, the main contributions of this work are twofold: 1) we base the velocity model estimation on kinematic migration/demigration techniques that are nonlinear (and therefore more accurate than simplistic linear approaches) and 2) the corresponding Fréchet derivatives take into account that the velocity model is laterally heterogeneous. In addition to providing the comprehensive mathematical algorithms involved, three proof-of-concept numerical examples are demonstrated, which confirm the potential of our methodology.

    更新日期:2020-01-17
  • Simple hysteresis loop model for rock magnetic analysis
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2020-01-10
    Carlos A. Vasquez, Sabrina Y. Fazzito

    Abstract A simple phenomenological model founded on Lorentzian functions is evaluated on the first derivative of magnetic hysteresis loops from several artificial samples with iron oxide/oxyhydroxide mixtures imitating natural sediments. The approach, which shows that hysteresis loops can be described by elementary analytical functions and provides estimates of magnetization parameters to a satisfactory degree of confidence, is applied with the help of standard data analysis software. Distorted hysteresis loops (wasp-waisted, goose-necked and pot-bellied shaped) from simulations and artificial samples from a previous work are reproduced by the model which allows to straightforwardly unmix the ferromagnetic signal from different minerals like magnetite, greigite, haematite and goethite. The analyses reveal that the contribution from the ferrimagnetic fraction, though present in a minor concentration (≤2.15 wt%), dominates the magnetization.

    更新日期:2020-01-11
  • Use of the radiocarbon method for dating of skeletal remains of a mass grave (Brno, the Czech Republic)
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2020-01-10
    Kateřina Vymazalová, Lenka Vargová, Ladislava Horáčková, Jiří Kala, Michal Přichystal, Ivo Světlík, Kateřina Pachnerová Brabcová, Veronika Brychová

    The dating of skeletal remains in archaeology is difficult, especially at findings without burial equipment. In this case, apart from literary and iconographic sources, anthropological and palaeopathological analyses, the radiocarbon dating method can also be used. We present an example where we used this procedure in the dating of the skeletal remains of an anonymous recent mass grave, found in the cellars of one of the houses in Brno (Czech Republic). On the basis of an assessment of the archaeological and anthropological context, in combination with radiocarbon dating, it could be concluded that the found skeletal remains were most likely of soldiers who died in the provisional military hospital as a result of injury or infection after the Battle of Austerlitz in 1805. An alternative hypothesis, that they are the remains of soldiers who died in the Battle of Hradec Králové in 1866, was excluded by radiocarbon dating.

    更新日期:2020-01-11
  • High frequency sky wave propagation during geomagnetic field reversals
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-12-20
    Mariano Fagre, Bruno S. Zossi, Erdal Yiğit, Hagay Amit, Ana G. Elias

    abstract The ionosphere, a plasma embedded in the Earth’s magnetic field, affects propagation of electromagnetic waves in the high frequency range since the refractive index at these frequencies depends on a combination of plasma density and magnetic field intensity and direction. In particular, the ground range of high frequency waves that reflect in the ionosphere, or sky waves, presents detectable Earth’s magnetic field effects. This field varies greatly, with the most drastic scenario being a polarity reversal. The spatial variability of the ground range during possible reversal scenarios is analyzed in the present work using numerical ray tracing. In order to isolate the magnetic field effect we exclude the effect of changing ionospheric conditions by considering a uniform ionosphere. Our results show that the ground range increases with increasing ray alignment with the field direction as well as with increasing magnetic field intensity. For the present field that is dominated by an axial dipole, the ground range is greatest for northward propagation at the magnetic equator. A similar situation occurs for a prevailing equatorial dipole with eastward propagation at the corresponding magnetic equator that here runs almost perpendicular to the geographic equator. For less dipolar configurations the ground range spatial variability becomes smaller. Although a reversal is foreseeable only in a very distant future, studying potential consequences during a reversal may highlight possible effects of dipole decrease which is already ongoing at present. In addition to the geophysical insight, our results may have applications for communication and radar systems.

    更新日期:2020-01-04
  • Application of non-stationary iterative time-domain deconvolution
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-12-05
    Ergun Erhan, Robert L. Nowack

    In this study, non-stationary iterative time-domain deconvolution (CNS-ITD) is investigated. The propagating wavelets are first estimated in several overlapping Gabor windows of the data. Matrix-vector operations in the time-domain are then performed by estimating a small number of columns of the wavelet matrix by interpolation within a sparse iterative estimation for the largest reflectivities. The iteration process is stopped when a minimum root mean square (RMS) residual or a maximum number of iterations is reached. Although initially formulated on the basis of work in earthquake seismology, CNS-ITD is a matching pursuit type of approach performed continuously in the time-domain for the non-stationary case. The results can then be convolved with a higher frequency wavelet in order to make the results stationary in time and to increase the resolution of the data. We first apply CNS-ITD to synthetic data with a time-varying attenuation, where the method successfully identifies the largest reflectors in the data. We then apply CNS-ITD to two observed shallow seismic datasets where improved resolution is obtained.

    更新日期:2020-01-04
  • Estimating a combined Moho model for marine areas via satellite altimetric - gravity and seismic crustal models
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-12-05
    Majid Abrehdary, Lars E. Sjöberg

    Abstract Isostasy is a key concept in geoscience in interpreting the state of mass balance between the Earth’s lithosphere and viscous asthenosphere. A more satisfactory test of isostasy is to determine the depth to and density contrast between crust and mantle at the Moho discontinuity (Moho). Generally, the Moho can be mapped by seismic information, but the limited coverage of such data over large portions of the world (in particular at seas) and economic considerations make a combined gravimetric-seismic method a more realistic approach. The determination of a high-resolution of the Moho constituents for marine areas requires the combination of gravimetric and seismic data to diminish substantially the seismic data gaps. In this study, we estimate the Moho constituents globally for ocean regions to a resolution of 1° × 1° by applying the Vening Meinesz-Moritz method from gravimetric data and combine it with estimates derived from seismic data in a new model named COMHV19. The data files of GMG14 satellite altimetry-derived marine gravity field, the Earth2014 Earth topographic/bathymetric model, CRUST1.0 and CRUST19 crustal seismic models are used in a least-squares procedure. The numerical computations show that the Moho depths range from 7.3 km (in Kolbeinsey Ridge) to 52.6 km (in the Gulf of Bothnia) with a global average of 16.4 km and standard deviation of the order of 7.5 km. Estimated Moho density contrasts vary between 20 kg m-3 (north of Iceland) to 570 kg m-3 (in Baltic Sea), with a global average of 313.7 kg m-3 and standard deviation of the order of 77.4 kg m-3. When comparing the computed Moho depths with current knowledge of crustal structure, they are generally found to be in good agreement with other crustal models. However, in certain regions, such as oceanic spreading ridges and hot spots, we generally obtain thinner crust than proposed by other models, which is likely the result of improvements in the new model. We also see evidence for thickening of oceanic crust with increasing age. Hence, the new combined Moho model is able to image rather reliable information in most of the oceanic areas, in particular in ocean ridges, which are important features in ocean basins.

    更新日期:2020-01-04
  • Random noise attenuation using a structure-oriented weighted singular value decomposition
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-10-25
    Yankai Xu, Siyuan Cao, Xiao Pan

    Singular value decomposition (SVD) is a useful method for random noise suppression in seismic data processing. A structure-oriented SVD (SOSVD) approach which incorporates structure prediction to the SVD filter is effcient in attenuating noise except distorting seismic events at faults and crossing points. A modified SOSVD approach using a weighted stack, called structure-oriented weighted SVD (SOWSVD), is proposed. In this approach, the SVD filter is used to attenuate noise for prediction traces of a primitive trace which are produced via the plane-wave prediction. A weighting function related to local similarity and distance between each prediction trace and the primitive trace is applied to the denoised prediction traces stacking. Both synthetic and field data examples suggest the SOWSVD performs better than the SOSVD in both suppressing random noise and preserving the information of the discontinuities for seismic data with crossing events and faults.

    更新日期:2020-01-04
  • Variance-covariance component estimation for structured errors-in-variables models with cross-covariances
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-10-25
    Zhipeng Lv, Lifen Sui

    In this contribution, an iterative algorithm for variance-covariance component estimation based on the structured errors-in-variables (EIV) model is proposed. We introduce the variable projection principle and derive alternative formulae for the structured EIV model by applying Lagrange multipliers, which take the form of a least-squares solution and are easy to implement. Then, least-squares variance component estimation (LS-VCE) is applied to estimate different (co)variance components in a structured EIV model. The proposed algorithm includes the estimation of covariance components, which is not considered in other recently proposed approaches. Finally, the estimability of the (co)variance components of the EIV stochastic model is discussed in detail. The efficacy of the proposed algorithm is demonstrated through two applications: multiple linear regression and auto-regression, on simulated datasets or on a real dataset with some assumptions.

    更新日期:2020-01-04
  • Determination of the local tidal parameters for the Borowiec station using Satellite Laser Ranging data
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-09-05
    Marcin Jagoda, Miłosława Rutkowska

    Abstract The values of regional tidal parameters h2, l2 associated with the tidal variations of ground stations were estimated for the Polish Satellite Laser Ranging (SLR) station Borowiec using SLR data. The study is based on satellite observations taken by the global network of ground stations during the period from January 1, 1999 until January 1, 2019 for monthly orbital arcs of the satellites LAGEOS-1 and LAGEOS-2. The adjusted regional values for h2 equalling 0.7308 ± 0.0008 and l2 equalling 0.1226 ± 0.0003 are discussed and compared with the nominal values of h2 and l2 given in the the International Earth Rotation and Reference Systems Service (IERS) standards and with other estimations of these parameters. Furthermore, the influence of the tidal parameters changes on estimation of the Borowiec station coordinates in the ITRF2014 reference frame was investigated. The analysis was carried out in two variants. The first one consisted in the determination of the Borowiec station coordinates with the use of the nominal values of the tidal parameters: h2 = 0.6078 and l2 = 0.0847 (IERS recommended values). In the second one, the Borowiec station coordinates were determined using the local tidal parameters estimated in this paper (h2 = 0.7308 ± 0.0008 and l2 = 0.1226 ± 0.0003). The differences between X, Y ,Z for Variant 1 and Variant 2 are −3.5, 3.3 and 4.2 mm, respectively.

    更新日期:2020-01-04
  • On the role of diffractions in velocity model building: a full-waveform inversion example
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-09-05
    Sergius Dell, Ivan Abakumov, Pavel Znak, Dirk Gajewski, Boris Kashtan, Andrey Ponomarenko

    Abstract Imaging of small-scale heterogeneities is important for the geological exploration in complex environments. It requires a processing sequence tuned to high-resolution model building. Conventional methods which use refractions or reflections might face problems in resolving small-scale features since they are visually close to the resolution of the reflection images. Additional information or an unconventional technology, which supports the reflection imaging, is thus of great interest. An unconventional method based on seismic diffractions naturally complements specular reflection imaging. Diffracted waves represent a direct seismic response from small-scale subsurface heterogeneities, such as inclusions with a characteristic size of the prevailing wavelength, or discontinuities in geological interfaces, such as faults and fractures. We investigate the rule of diffracted part of the wavefield on velocity model building using a full-waveform inversion (FWI) example. In order to best acknowledge refracted and reflected parts of the wavefield in FWI, we chose a synthetic data example which mimics the ocean-bottom nodes acquisition survey as it provides almost perfect conditions for FWI of diving waves, a standard tool for high-resolution model building. We show, that FWI using diving waves produces a well-resolved anomaly. Including other part of the wavefield, reflected waves, further improves the resolution of the velocity anomaly but also leads to a gentle overfitting due to missing illumination from the very steep anomaly flanks. Considering diffracted events in FWI improves the model resolution even further resulting in a detailed velocity model and correctly imaged anomaly in both vertical and lateral directions.

    更新日期:2020-01-04
  • Lithospheric strength of the Caroline Islands and its tectonic implications
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-10-25
    Mingming Wang

    The Caroline Islands are located in a broad zone near plate boundaries in southwestern Pacific. Accumulating evidence suggests that the hotspot origin alone cannot completely explain the formation of the Caroline Islands. To investigate the tectonic setting of their formation, we calculated the effective elastic thickness (Te) of the lithosphere beneath the Caroline Islands from an analysis of bathymetry and free-air gravity anomaly data by the admittance method. A synthetic model based on the actual bathymetry data of the Caroline Islands was developed for the finite window size biasing correction. The results show that the Te values of the Caroline Islands (4.5–11.5 km) are significantly lower than the Te expected for a normal oceanic lithosphere (23–50 km), and that the Te values can be approximated by the depth to the 150 ± 100°C isotherm. The low Te values indicate that the strength of the lithosphere beneath the Caroline Islands has been weakened by geological process. The thermal anomalies related to the Ontong Java Plateau and the South Pacific Isotopic and Thermal Anomaly, and the lithospheric fractures induced by interaction of plates are probable causes of the lithospheric strength reduction of the Caroline Islands.

    更新日期:2020-01-04
  • Simultaneous interpolation and denoising based on a modified thresholding method
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-10-25
    Jingjie Cao, Shangxu Wang, Wenquan Liang

    Abstract Seismic interpolation can provide complete data for some multichannel processing techniques such as time lapse imaging and wave equation migration. However, field seismic data often contains random noise and noisy data interpolation is a challenging task. A traditional method applies interpolation and denoising separately, but this needs two workflows. Simultaneous interpolation and denoising combines interpolation and denoising in one workflow and can also get acceptable results. Most existing interpolation methods can only recover missing traces but fail to attenuate noise in sampled traces. In this study, a novel thresholding strategy is proposed to remove the noise in the sampled traces and meanwhile recover missing traces during interpolation. For each iteration, the residual is multiplied by a weighting factor and then added to the iterative solution, after which the sum in the transformed domain is calculated using the thresholding operation to update the iterative solution. To ensure that the interpolation and denoising results are robust, the exponential method was chosen to reduce the threshold values in small quantities. The curvelet transform was used as sparse representation and three interpolation methods were chosen as benchmarks. Three numerical tests results proved the effectiveness of the proposed method on removing noise in the sampled traces when the minimum threshold values are correctly chosen.

    更新日期:2020-01-04
  • An optimized method to transform the Cartesian to geodetic coordinates on a triaxial ellipsoid
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-07-02
    Cheng Chen, Shaofeng Bian, Songlin Li

    A general triaxial ellipsoid is suitable to represent the reference surface of the celestial bodies. The transformation from the Cartesian to geodetic coordinates on the triaxial ellipsoid becomes an important issue in geodesy. In the literature, the vector iterative method and the Newton’s iterative method for solving the nonlinear system of equations or an algebraic fraction equation is applied to compute the geodetic coordinates, but may lead to the non-convergence regions. In this work, the universal algorithm including the Newton’s iterative solutions of an algebraic sextic equation for the points outside the equatorial plane and the analytic solutions for the points inside the equatorial plane are used to compute the geodetic coordinates. The numerical experiments show the algorithm is fast, highly accurate and well convergent. The algorithm is valid at any point inside and outside the celestial bodies including the points near the celestial bodies’ center and in the singular elliptical disc.

    更新日期:2020-01-04
  • Response of the electron density profiles to geomagnetic disturbances in January 2005
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-07-02
    Rumiana Bojilova, Plamen Mukhtarov

    Abstract The ionospheric response to geomagnetic storms is usually investigated by considering the variability of the critical frequency of the F2-layer (foF2) or the total electron content (TEC) because these two parameters are directly measured by the ionosonde stations and the Global Navigation Satellite Systems (GNSS). In the present paper, however, the reaction is explored by using the vertical profiles of the electron density, N(h), reconstructed by manually scaled ionosonde measurements at the station Sofia (42.4°N, 23.2°E). The mid-latitude ionosheric response to three geomagnetic storms that occurred in January 2005 is presented as this period has been selected because no major sudden stratospheric warming occurred during this month, and the winter 2005 is given in the literature as an example of a “normal” year. Hence the observed ionospheric response to the considered geomagnetic storms can be attributed mainly to the external forcing. Besides the traditional parameters foF2 and TEC, a particular attention is paid to the variability of the peak electron density height (hmF2). This study reveals for the first time that the main contribution to the response of the midlatitude ionosphere to moderate/intense winter geomagnetic storms is associated with significant enhancements of short-period quasi-diurnal oscillations with period of 6–7 hours observed in both foF2 and hmF2. An explanation of the main mechanisms responsible for the distortion of the diurnal ionospheric variability during these storms is offered. This result is especially important for the ground-based HF radio communications.

    更新日期:2020-01-04
  • Using magnetic susceptibility measurements to differentiate soil drainage classes in central Iran
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-08-02
    Majid Gholamzadeh, Shamsollah Ayoubi, Fatemeh Sheikhi Shahrivar

    We examine the potential of magnetic susceptibility measurements to discriminate different soil drainage classes in the Gandoman region, central Iran. Four soil drainage classes, comprising poorly drained (PD), somewhat poorly drained (SPD), moderately well drained (MWD) and well drained (WD), were identified, and a total number of 48 soil profiles were excavated and studied. The soil samples were collected from all studied profiles from the genetic horizons individually. Magnetic susceptibility was measured at both low (0.46 kHz) and high (4.6 kHz) frequencies. The crystallized and amorphous iron forms were also measured using citrate-bicarbonate-dithionite solution and oxalate-ammonium extracts, respectively. The highest magnetic susceptibility was observed in WD soils, whereas the lowest susceptibility was observed in PD soils. The results of the predictor models developed by discriminate analysis showed that the use of magnetic susceptibility and iron forms could correctly predict about 90.9, 78.6, 85.7 and 88.9% of all profiles in WD, MWD, SPD and PD classes, respectively. Overall, the results indicate that magnetic susceptibility could be applied as a marker for the discrimination of drainage classes in the study area. Magnetic susceptibility is thus a quickly accessible and low-cost indicator for soil drainage classes for landownerships and subsequent analyses.

    更新日期:2020-01-04
  • Robustness of M split(q) estimation: A theoretical approach
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-07-02
    Robert Duchnowski, Zbigniew Wiśniewski

    Msplit(q) estimation is a development of M-estimation which is based on the assumption that a functional model of observations can be split into q competitive ones. The main idea behind such an assumption is that the observation set might be a mixture of realizations of different random variables which differ from each other in location parameters that are estimated. The paper is focused on the robustness of Msplit(q) estimates against outlying observations. The paper presents derivatives of the general expressions of the respective influence functions and weight functions which are the main basis for theoretical analysis. To recognize the properties of Msplit(q) estimates in a better way, we propose considering robustness from two points of view, namely local and global ones. Such an approach is a new one, but it reflects the nature of the estimation method in question very well. Thus, we consider the local breakdown point (LBdP) and the global one (GBdP) that are both based on the maximum sensitivities of the estimates. LBdP describes the mutual relationship between the “neighboring” Msplit(q) estimates, whereas GBdP concerns the whole set of the estimates and describes the robustness of the method itself (in more traditional sense). The paper also presents GBdP with an extension, which shows how an outlier might influence Msplit(q) estimates. The general theory proposed in the paper is applied to investigate the squared Msplit(q) estimation, the variant which is used in some practical problems in geodesy, surveying, remote sensing or geostatistics, and which can also be applied in other geosciences.

    更新日期:2020-01-04
  • Suitable gravity interpolation technique for large data gaps in Africa
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-08-02
    Hussein A. Abd-Elmotaal, Norbert Kühtreiber

    Abstract The gravity database for the IAG African Geoid Project contains significantly large data gaps. These large data gaps affect the interpolation precision of the reduced gravity anomalies needed for the determination of the gravimetric geoid for Africa. Our aim is to develop a suitable interpolation technique that can be used for a proper gravity interpolation within large data gaps. A gap of 10° × 5° in the latitude and longitude directions, respectively, located at the high lands of Ethiopia has been artificially created within the gravity data set for Africa. The rest of the data set has been used to interpolate the gravity values at the gap points; then a comparison between the interpolated and the actual data values at the artificial data gap has been carried-out to determine the accuracy of the used interpolation technique. The unequal weight least-squares prediction (with the optimum curvature parameter at the origin) with an underlying grid at the gap areas computed by the satellite-only GO CONS GCF 2 DIR R5 model till degree and order 300, has been proposed as the developed interpolation approach. For comparison purpose, the Kriging interpolation technique has also been tested. Both the classical residual terrain modeling reduction and the window technique, suggested earlier by the authors to get rid of the double consideration of the topographic-isostatic masses within the data window in the framework of the remove-restore technique, have been used for the reduction process. A comparison between the data and interpolated values of the gravity at the gap points has been carried out. The results show that the developed interpolation technique gives better interpolation accuracy at the artificial data gap.

    更新日期:2020-01-04
  • The day-to-day effects of strong geomagnetic disturbances on the North Atlantic Oscillation in the winter periods of years 1951–2003
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-05-17
    Josef Bochníček, Ján Šimkanin, Pavel Hejda, Radan Huth

    The day-to-day effects of the strong geomagnetic disturbances on geopotential heights (GPH) in the winter lower atmosphere were described in many papers in the beginning of 1970s. These works focused on the North-East Pacific, while the North Atlantic was until now omitted. Our aim is therefore to investigate the possible effect of strong geomagnetic disturbances on the lower atmosphere GPH changes over the winter North Atlantic on the day-to-day time scale, represented by the daily index of the North Atlantic Oscillation (NAO). The investigated intervals are winter periods (December-March) of 1951–2003. The daily NAO average values in 3-day intervals before and after the disturbance onsets are compared. The graphs of NAO differences are complemented by the maps of GPH differences. The NAO response to geomagnetic disturbance, as registered on the day-to-day time scale, also shows a change in its behaviour around the year 1970. This response reaches its highest values in the years 1951–1969, usually 2–5 days following the onset of geomagnetic disturbances. Intensity of the response depends on the disturbance intensity (the largest differences were associated with extremely strong disturbances).

    更新日期:2020-01-04
  • Comparison of two different approaches for computing the gravitational effect of a tesseroid
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-05-17
    Anna Maria Marotta, Kurt Seitz, Riccardo Barzaghi, Thomas Grombein, Bernhard Heck

    Abstract Forward modelling in the space domain is a very important task in geodesy and other geosciences. From topographical or isostatic information in the form of digital terrain model (DTM) and density model, the effects of these parameters or their derivatives on the gravity potential can be evaluated for different applications. In most cases, height or height-layer models are in use, which are gridded with respect to spherical coordinates. This holds for global as well as regional or even local applications. The definition of the spherical gridlines leads immediately to the spherical volume element, that is, the tesseroid. Only in the specific case that the observation point is located on the symmetry axis of the spherical coordinate system does the Newton integral have a closed analytical solution. More specifically, the effect of a tesseroid can be determined by evaluating the analytical solution of a segment of a spherical zonal band. To apply this aspect in practice, the DTM must be transformed into the local spherical azimuthal system of the observation point (UNIPOL approach). In the general case, the Newton integral can be solved, for example, using a Taylor series expansion of the integral kernel and a subsequently applied term-wise integration (GIK approach). Within this contribution, the two fundamentally different tesseroid approaches, namely, the GIK and the UNIPOL approach are compared. This comparison is performed, in particular, with regard to the required computational time and the approximation error under different test scenarios. The numerical studies show that both approaches are equivalent in terms of accuracy for both the gravitational potential and gravity; however, the UNIPOL approach is more time consuming because, for each observation point, the whole DTM must be transformed. Small numerical differences exist between the compared approaches for special constellations regarding the source point and the observation point.

    更新日期:2020-01-04
  • Topographic effects up to gravitational curvatures of tesseroids: A case study in China
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-08-24
    Xiao-Le Deng, Wen-Bin Shen

    Abstract Topographic effects on gravity field modeling are important for geodesy, geophysics and related geosciences. In this study we evaluate the gravitational effects of tesseroids in spherical coordinates, including the gravitational potential (GP), gravity vector (GV), gravity gradient tensor (GGT) and especially the gravitational curvatures (GC). With the adaptive discretization stack-based algorithm by Gauss-Legendre quadrature approach, the optimized distance-size ratio values (D) of the GC components are analyzed. Numerical experiments demonstrate that the difference percentage values of the GC components (e.g., Vxxz, Vyyz and Vzzz) are larger at the range of D ∈ [0; 10] compared to those of the GP, GV and GGT components (i.e., V, Vz, Vzz). Different distance-size ratio values D = 6, 7, 14, 30, 35, 41 and 50 for the GC component Vzzz are recommended to reach the 0.1% threshold error at corresponding computational heights 260, 150, 50, 10, 8, 6 and 4 km. Moreover, the forward modeling for the gravitational effects up to GC of tesseroids based on the ETOPO1 model in China is investigated. The GC functionals could help to extend the knowledges of interior structures of the Earth and other planetary objects.

    更新日期:2020-01-04
  • Employing the bilateral filter to improve the derivative-based transforms for gravity and magnetic data sets
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-05-27
    Jun Wang, Xiaohong Meng

    In the literature, there are numerous derivative-based transforms for gravity and magnetic data sets, with which relevant features can be highlighted. However, almost all of them face the problem of instability in derivative calculation. Therefore, before applying derivative-based transforms, noise reduction is often applied to improve the quality of the data. Nevertheless, the application of conventional filters typically blurs horizontal gradients in the data, which can adversely affect subsequent transforms, for example, the sharp boundaries of the causative bodies may be obscured. To handle the above issue, this study is the first to employ the bilateral filter, used in digital image processing, for improving the derivative-based transforms for gravity and magnetic data sets. The filter replaces each data point by a weighted average of its neighbors. The established weights take into account both the geometric and amplitude closeness between the data points used. Synthetic tests indicate that the proposed method can effectively filter potential field data without distorting the structural features greatly. Thus, the performance of subsequent derivative-based transforms can be improved. The new method was applied to the magnetic data collected over the Dapai polymetallic deposit in Fujian Province, South China. This real example shows that the results obtained from the proposed method contain more pronounced features of existing faults and thus contributes to further geological interpretation.

    更新日期:2020-01-04
  • Deep lithospheric structure beneath the Polish part of the East European Craton as a result of magnetotelluric surveys
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-05-27
    Szymon Oryński, Wojciech Klityński, Anne Neska, Katarzyna Ślęzak

    Abstract A fundamental tectonic boundary between the Precambrian East European Craton (EEC) and the younger Phanerozoic mountain belts of Europe runs through Poland. Whereas the transition zone between both tectonical units was intensely investigated by means of electromagnetic methods in the past, the image of electric conductivity of the EEC itself has not been detailed so far. In the present study the lithospheric structure beneath the northeast of Poland is investigated by means of three parallel magnetotelluric profiles. As a result the Polish part of the craton does not appear as homogeneously highresistive as repeatedly reported. Beneath a shallow (from 2 to 4 km) sedimentary layer a less resistive structure (several hundred Ωm) under all three profiles in mid-crustal to upper mantle depth becomes apparent in the high-resistive background. It spatially coincides with a magmatic body of the Upper Proterozoic age called Śniardwy lake gabbro intrusion.

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  • IRG2018: A regional geoid model in Iran using Least Squares Collocation
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2019-05-27
    Sabah Ramouz, Yosra Afrasteh, Mirko Reguzzoni, Abdolreza Safari, Abdoreza Saadat

    The aim of this study is to determine an accurate geoid model for Iran based on the Least Squares Collocation method in the framework of the Remove — Compute — Restore technique. In areas suffering from a lack of homogeneous and accurate gravity anomaly data, as is the case of Iran, the choice of the most compatible global gravity model has a significant impact on the estimated form of the geoid. Different combined and satellite-only global gravity models were therefore analyzed for Iran, and EIGEN6C4 was selected as the best one. The Shuttle Radar Topography Mission height model was used for the residual terrain correction. The covariance modeling, a crucial step in the Least Squares Collocation method, was based on two strategies. In the first, the study area was divided into four sub-areas, and then an individual empirical covariance was computed and a covariance model fitted to each of them. In the second, an empirical covariance was computed using all terrestrial gravity data, and a unique covariance model was fitted to it. Despite some border effects, the former strategy showed slightly better performance according to the resulting statistics, and therefore it was preferred for the estimation of the geoid model called IRG2018. To remove the offset of IRG2018 with respect to GNSS/Leveling-derived geoid heights, two alternative approaches were tested: subtracting a fitting polynomial surface or directly using the GNSS/Leveling data as an input to the IRG2018 computation process. Evaluation of the results, based on an independent control set of approximately half of available GNSS/Leveling points, showed an advantage of the latter approach, with an estimated accuracy of about 20 cm in terms of RMS.

    更新日期:2020-01-04
  • On the figure of the earth’s equipotential surface from satellite orbit dynamics
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1969
    Milan Burṥa

    РезюмеИсходя иэ определений гармоник геопотенциала по воэмущениям орбит спутников, дается вывод строгих формул полой кривиэны, направляющих косинусов внешней нормали и других характеристик формы соответствующей уровенной поверхности. Сопоставляя эти величины с соответствующими величинами для поверхности, эа относимости, эа которую принимается трехосный эллипеоид, получены выражения для аномалий кривизны и составляющих уклонений отвеса в длоскости меридиана и первиго вертикала. Под условием минимума суммыквадратов этих величин определимы фундаментальные параметры формы эемли, т. е. полярное и экваториальное сжатия и ориентировка осей экваториального эллипса грехосного еллипсоида, наиболее подходящего к исследуемой поверхности.

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  • Is there any relation between the sun's motion and global seismic activity?
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1986
    Ivanka Jakubcová,Miloš Pick,Vít Kárník,Jan Vondrák

    РезюмеВременныŭ ря¶rt;глобaльноŭ сеŭсмuческоŭ энергuu (1900–1982г.) был коррелuровaн с ря¶rt;ом F=|г|,г¶rt;е |г| aбсолюmное знaченuе uзменuŭ ускоренuя Солнцa. Дляглубокофокусных землеmрясенuŭ (h>60 км) u ¶rt;ля верояmносmu Р=0.95 коеффuцuенm корреляцuu ¶rt;осmuгaеm0.45. Для nоверхносmных землеmрясенuŭ зaвuсuмосmь не былa nо¶rt;mверж¶rt;енa.SummaryThe seismic energy released by global earthquake activity with time was correlated with F=|г|, where |г| is the absolute value of the change of the Sun's acceleration with time. For deep earthquakes and probability P=0.95, the coefficient of correlation was found to be around 0.4. For shallow earthquakes, the dependence was not proved.

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  • On the question of crustal structure study by group and phase velocities of surface waves
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1965
    Sh. S. Ragimov

    РезюмеГоворится о наличии следующих друг за другом групп волн Рэлея. На базе сравнения теоретических дисперсионных кривых с экспериментальными дисперсионными кривыми групповых скоростей волн Рэлея показывается, что наличие второй группы возможно быть обусловлено гранитным и осадочным слоями. Показывается, что используемый в настояшее время метод фазовых скоростей поверхностных волн для определения строения земной коры может значительно исказить действительную картину. Это происходит от того, что при определении строения земной коры не учитывют влияния различий в строении коры на трассах эпицентр—станция вне участка расположения станций в то время, как это надо учитывать, и в опорную формулу по определению фазовых скоростей необходимо внести определенную поправку. Сделать все это очень трудно. Поэтому, во избежание неясностей при трактовке получаемого строения коры в районе расположения станций, целесообразно использовать метод фазовых скоростей только тогда, когда станции и эпицентр находятся в створе. Получаемая в створе экспериментальная дисперсионная кривая может бять принята за опорную для выявления строения коры по другим направлениям.

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  • On the determination of secular changes in the geomagnetic field
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1962
    Gustáv Siráň

    РезюмеВековые изменения магнитного поля Земли в своей совокупности наглядно характеризуются изменением параметров соответствующих шаровых функций, в виде которых магнитный потенциал Земли представляется. Приводятся вековые изменения параметров функции Y2 (Θ, γ) для отделяных эпох. Выражение геомагнитного поля в виде поля мультиполей, хотя и лишено физической реальности, однако же дает наглядное представление об его измененях. Из табл. 1 ясно прослеживаются изменения происходящие в магнитных свойствах Земли. Здесь видны западное и северное двизения осей квадруполя, при чем западное движение преобладает. Момент функцииY2 (Θ, γ) в периоде 1829–1958 гг. по сравнению с 1829 г. возрос на 54%.

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  • Modified earth model free-air gravity anomaly for use in vening Meinesz's formula
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1970
    Jnanendra Chandra Bhattacharji

    Die Stokes'sche Auffassung der Kondensation topographischer Massen wird bei der Reduktion der auf der Erdoberflache beobachteten Schwerewerte auf das durch das Huntersche Modell der Erde gegebene Niveau ausgenutzt. Die Freiluftanomalien des modifizierten Erdmodells werden abgeleitet, ohne jeglichen empfindlichen Co-Geoid, wie es bei anderen Methoden der Fall ist, einzufuhren. Diese Anomalien kann man direkt in der Vening Meineszschen Formel fur die Berechnung der Lotabweichungen auf der Erdoberflache benutzen. Dieses Verfahren hat den Vorteil, dass man keine weiteren Berichtigungen einzufuhren braucht, die bei der Uberfuhrung der Lotabweichungen auf die wirkliche Erde under Anwendung der Molodenski-Formel oder der Reduktion fur das Huntersche Erdmodell notwendig sind. Die Wirkung dieser Krummungsund Schwerefehler, sowie der in den Dichten topographischer Massen vorausgesetzten Fehler wird durch die Einfuhrung des Berechnungsverfahrens wesentlich vermindert.

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  • Rndr Ing. Václav Staněk — In Memoriam
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1975
    Josef Böhm

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  • Deflections of the vertical at Potsdam
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1967
    Miloš Pick

    РезюмеОпределяется абсолютнсе уклонение отвеса в исходном пункте Потсдам относительно астрономического эллипсоидаa=6378 160 м, α=1∶298,25. В выводе использованы 2 метода: посредством уравнения общего уклонения отвеса (2) и через общее уравнение Лапласа (3). В качестве исходного материала был использован каталог Бомфорда уклонений отвеса в т. наз. Европейской системе [4]. В первом случае использовалось 2019 уравнений σ, 1360 ур. ηλ и 342 ур, ητ. Для общего ур. Лапласа было использовано 216 значений. По первому уравниванию были получены результаты (4), по второму же (5). По этим результатам были выведены „абсолютные” уклонения отвеса в пункте Потсдам, отнесенные к астрономическому эллипсоиду. Наши результаты были далыше сравнены с результатами иных авторов. Все результаты дыли до сравнивания переведены в общую систему. Были учтены поправки за изменение параметров эллипсоида (8) или же (9) и поправки за изменение положения поверхности относимости относительно Земли. Результирующие значения были распределены в 4 группы: a) гравиметрически определенные уклонения отвеса, b) спутниковые значения, c) сравнение гравиметрических и астрономо-геодезических данных, d) уклонения отвеса, определенные астрономо-геодезическим путем. Оказывается, что нет никакой систематической разности между отдельными способами определения уклонений отвесса. После исключения нескольких отклоняющихся результатов мы получим следуюшие средние значения абсолютного уклонения отвеса в пункте Потсдам относительно астрономического эллипсоида σ=8,0″, η=+2,4″.

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  • Reflection and transmission coefficients for transition layers
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1974
    Vlastislav Červený,Jiří Vaněk

    SummaryFormulae are derived for the reflection and transmission coeficients of plane elastic waves for a transition layer. Haskell's technique and the so-called delta matrices[5, 7] are used for this purpose. No problems are encountered in deriving the reflections and transmission coefficients from Haskell's matrices[3]. However, in some cases Haskell's matrices do not guarantee the accuracy required. For this reason attention is mainly devoted to deriving the reflection and transmission coefficients from the delta matrices. In deriving the transmission coefficients use is made of the fact that some3×3 subdeterminants of the delta matrices are squares of the3×3 subdeterminants of Haskell's matrices.

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  • Experimental measurements of seismic velocities on core samples and their dependence on mineralogy and stress; Witwatersrand Basin (South Africa)
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2016
    Nomqhele Z. Nkosi,Musa S. D. Manzi,Gillian R. Drennan,Halil Yilmaz

    Physical property measurements were integrated with mineralogical analyses to better understand the nature of the seismic reflectivity of the deepest (>3.5 km depth) gold ore body (Carbon Leader Reef). The CLR lies at depths between 3.5 km and 4.5 km below the surface. Over 50 drill-core samples were selected for geochemical analyses, density and seismic velocity measurements. Ultrasonic measurements were conducted at ambient and elevated stresses, using transducers operating at 0.5 MHz. The study reveals that P-wave velocities generally increase with increasing bulk density. The CLR conglomerate, the gold-bearing reef, has slightly higher P-wave velocity (∼5070–5468 m/s) and density values (∼2.78 g/cm3) amongst the quartzitic units, possibly due to its massive pyrite content. The quartzite hangingwall and footwall rocks to the CLR exhibit similar P-wave velocity (∼5028–5480 and ∼4777–5211 m/s, respectively) and density values (∼2.68 and 2.66 g/cm3, respectively). The reflection coefficients calculated at the interface between the CLR conglomerate and its hangingwall and footwall units range between ∼0.02 and 0.05 which is below the required minimum reflection coefficient value of 0.06 to produce a strong reflection between two lithological boundaries. This suggests that seismic reflection methods might not be able to directly image the CLR, as observed from its poor reflectivity in the 3D seismic data. Samples were also subjected to stresses of up to 65 MPa to simulate in situ-like conditions and to investigate the dependence of seismic velocities on applied stresses. P-wave velocities increase with progressive loading, but at different rates in shale and quartzite rocks as a result of the presence of micro-defects.

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  • International Symposium on Seismic Models
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1965
    Organizing Committee

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  • On the non-tidal secular acceleration of the Earth's rotation
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1986
    Milan Burṥa,Zdeněk Šimon

    РезюмеИсхо¶rt;я uз нaблю¶rt;aемого векового уменъщенuя вmороŭ зонaлъноŭгaрмонuкu [5], вычuслено ¶rt;обaвочное nоложumелъное вековое ускоренuе земного врaщенuя. Оmмечено его сооmвеmсmвuе нaблю¶rt;aемому вековому уменъшенuю угловоŭ скоросmu врaщенuя Землu, m.к. nосле¶rt;нее nо абсолюmноŭ велuчuне менъше, чем ¶rt;олжно быmъ nо океaнuческuм nрuлuвaм.SummaryThe secular positive acceleration of the Earth's rotation has been computed on the basis of the observed secular decrease of the second zonal harmonic[5]. It corresponds to the observed secular deceleration of the Earth's rotation which should be greater because of oceanic tides.

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  • Contribution to the experiment of axiomatizing the theory of turbulent diffusion
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1978
    Jiří Horák,Jan Navrátil

    SummaryThe efforts to axiomatize the theory of turbulent diffusion, founded on the theory of Markovian random processes, are based on the principal logical algebraic aspects of the concept of modelling.

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  • Reflected waves in finely layered tilted orthorhombic media
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2016
    Yuriy Ivanov,Alexey Stovas

    Upscaling in seismics is a homogenization of finely layered media in the zero-frequency limit. An upscaling technique for arbitrary anisotropic layers has been developed by Schoenberg and Muir. Applying this technique to a stack of layers of orthorhombic (ORT) symmetry whose vertical symmetry planes are aligned, results in an effective homogeneous layer with orthorhombic symmetry. If the symmetry planes in a horizontal orthorhombic layer are rotated with respect to vertical, the medium is referred to as tilted orthorhombic (TOR) medium, and the stack composed of TOR layers in zero-frequency limit will produce an effective medium of a lower symmetry than orthorhombic. We consider a P-wave that propagates through a stack of thin TOR layers, then it is reflected (preserving the mode) at some interface below the stack, and then propagates back through the same stack. We propose to use a special modified medium for the upscaling in case of this sequential down- and up-propagation: each TOR layer in the stack is replaced by two identical TOR layers whose tilt angles have the opposite algebraic sign. In this modified medium, one-way propagation of a seismic wave (any wave mode) is equivalent to propagation of a pure-mode reflection in the original medium. We apply this idea to study the contribution from an individual layer from the stack and show how the approach can be applied to a stack of TOR layers. To demonstrate the applicability of the model, we use well log data for the upscaling. The model we propose for the upscaling can be used in well-seismic ties to correct the effective parameters obtained from well log data for the presence of tilt, if latter is confirmed by additional measurements (for example, borehole imaging).

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  • Spectrum of the geomagnetic field in central Europe
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1972
    Alla Džodenčuková,Oldřich Praus

    РезюмеСmamья nосвященa воnросу uзученuя сnекmрaеомaнumноо nоля нa mеррumорuu Сре¶rt;неŭ Евроnы. В чaсmносmu рaссмоmренa 27-¶rt;невнaя вaрuaцuя с ее высшuмuaрмонuческuмu nо мamерuaлaм 7 сре¶rt;неевроnеŭскuх обсервamорuŭ в nерuо¶rt; 1960–68. С¶rt;елaны некоmорые выво¶rt;ы оmносumельно сnекmрaльноо сосmaвa всех mрех комnоненmовеомaнumноо nоля nрu рaзных уровнях солнечноŭ aкmuвносmu.

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  • Comparison of Ray Methods with the Exact Solution in the 1-D Anisotropic “Simplified Twisted Crystal” Model
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2004
    Petr Bulant,Luděk Klimeš,Ivan Pšenč́ık,Václav Vavryčuk

    The exact analytical solution for the plane S-wave, propagating along the axis of spirality in the simple 1-D anisotropic “simplified twisted crystal” model, is compared with four different approximate ray-theory solutions. The four different ray methods are (a) the coupling ray theory, (b) the coupling ray theory with the quasi-isotropic perturbation of travel times, (c) the anisotropic ray theory, (d) the isotropic ray theory. The comparison is carried out numerically, by evaluating both the exact analytical solution and the analytical solutions of the equations of the four ray methods. The comparison simultaneously demonstrates the limits of applicability of the isotropic and anisotropic ray theories, and the superior accuracy of the coupling ray theory over a broad frequency range. The comparison also shows the possible inaccuracy due to the quasi-isotropic perturbation of travel times in the equations of the coupling ray theory. The coupling ray theory thus should definitely be preferred to the isotropic and anisotropic ray theories, but the quasi-isotropic perturbation of travel times should be avoided. Although the simplified twisted crystal model is designed for testing purposes and has no direct relation to geological structures, the wave-propagation phenomena important in the comparison are similar to those in the models of the geological structures.In additional numerical tests, the exact analytical solution is numerically compared with the finite-difference numerical results, and the analytical solutions of the equations of different ray methods are compared with the corresponding numerical results of 3-D ray-tracing programs developed by the authors of the paper.

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  • Accuracy and reliability of magnetic parameters determined by astatic magnetometer
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1990
    Richard Chvojka

    РезюмеОбновленuе aсmamuческuх мa¶rt;нumомеmров mребуеm усоверщенсmвовaнuя uзмерumельных u вычuслumельных nроче¶rt;ур с uсnольэовaнuем сущесmвующеŭ комnвюmерноŭ mехноло¶rt;uu. Пре¶rt;лa¶rt;aеmся сmamuсmuчесaя мо¶rt;елв, оmорaя основaнa нa свяэях меж¶rt;у мa¶rt;нumuческuмu naрaмеmрaмu uэмеряемх обрaэчов u энaченuямu nоля, uэмеряемымu мa¶rt;нumомеmром. В сmamье у¶rt;еляеmся ¶rt;лaвное внuмaнuе mочносmu u ¶rt;uanaэонaм нa¶rt;ежносmu nроuэво¶rt;ных naрaмеmров.SummaryInnovation of astatic magnetometers requires improvement of measuring and computation procedures taking advantage of existing computer technology. A statistical model is proposed which is based on relations between the magnetic properties of measured samples and values of the field measured by a magnetometer. The paper focuses on the accuracy and confidence intervals for the parameters derived.

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  • Magnetotelluric resistivities in models with dipping interfaces
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1973
    Oldřich Praus,Václav Červ,Alexej Verner,Tibor Kolbenheyer

    РезЮмеПрuбо¶rt;яmся резуельmamы чuсленных рещенuŭ урaвненuя Гельмольцa ворuзонmaльно нео¶rt;норо¶rt;ноŭ облaсmu с nросmым нaклонным конmaкmом ¶rt;врх сре¶rt; с рaзлuчнымu элекmрuческuмu nрово¶rt;uмосmямu в случaях Н- u Е-nолярuзaцuŭ. Анaлuзuрыжmся maкже мо¶rt;елu с нaклонным конmaкmом ¶rt;вух сре¶rt; зaлеaющuх нaорuзонmaлвно о¶rt;норо¶rt;ном nрово¶rt;ящем слое ¶rt;ля Н-nолярuзaцuu. Иссле¶rt;уеmся nове¶rt;енuе nоверхносmных uмnе¶rt;aнсов u кaжсущuхся соnроmuвленuŭ u рaссмamрuвaжmся сооmвеmсmвужщuе uскaженuя мaнumоmеллурuческuх крuвых зон¶rt;uровaнuя в рaзлuчных mочкaх в¶rt;олв nрофuля, nересекaющео нaклонныŭ конmaкm нa nоверхносmu Землu.

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  • On the role of solar Lyman alpha radiation in radio-wave absorption in theD-region
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1983
    Josef Boška,Jan Lašťovička,Vojtěch Letfus

    РезюмеСрaененuе uзмеренuŭ nоглощенuя рa¶rt;оволн нa чaсmоmе 2775 кГц (меmо¶rt; АЗ, Кuль — Пaнскa Вес, fекв=1 мГц) со сnуmнuковымu uзмеренuямu солнечного лaŭмaн aльфa u ренmгеновского uзлученuя в леmнuх сезонaх 1969, 1970 u 1972го¶rt;ов nокaзaло, чmо лaŭмaн aльфa uзлученuе ясно nреоблa¶rt;aеm в nолгощенuu в невсnышечных условuях. Ренmген uгрaеm сущесmвенную роль mолько в uзменчuвосmu nоглощенuя. Оnmuмaльные урaвненuя ¶rt;aюm nроnорцuонaльносmь L ∼ Fионизm, m=1,1−1,5 (ме¶rt;uaнные знaченuя зaвuсящuе оm х). Прuмененuе nоnрaвкu ренmгеновскuх ¶rt;aнных nо [18] nовышaеm роль ренmгенa в nоглощенuнuu, но некоmорые ¶rt;ругuе резульmamы, кaк знaченuя m, nочmu не зaвuсяm оm nоnрaвкu. Прuво¶rt;яmся оценкu некоmорых крumuческuх уровнеŭ влuянuя ренmгенa нa nоглощенuе u эффекma солнечного цuклa. Резульmamы uмеюm облaсmь nрuмененuя в nрогнозuровaнuu nоглощенuя u в aэрономuu нuжнеŭ uоносферы (оценкu NО um¶rt;.).

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  • Ray tracing and geodesic deviation of the SH and SV reference rays in a heterogeneous generally anisotropic medium which is approximately uniaxial
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2017
    Luděk Klimeš,Petr Bulant

    The coupling ray theory is usually applied to anisotropic common reference rays, but it is more accurate if it is applied to reference rays which are closer to the actual wave paths. If we know that a medium is close to uniaxial (transversely isotropic), it may be advantageous to trace reference rays which resemble the SH–wave and SV–wave rays. This paper is devoted to defining and tracing these SH and SV reference rays of elastic S waves in a heterogeneous generally anisotropic medium which is approximately uniaxial (approximately transversely isotropic), and to the corresponding equations of geodesic deviation (dynamic ray tracing). All presented equations are simultaneously applicable to ordinary and extraordinary reference rays of electromagnetic waves in a generally bianisotropic medium which is approximately uniaxially anisotropic. The improvement of the coupling–ray–theory seismograms calculated along the proposed SH and SV reference rays, compared to the coupling–ray–theory seismograms calculated along the anisotropic common reference rays, has already been numerically demonstrated by the authors in four approximately uniaxial velocity models.

    更新日期:2020-01-01
  • On Gravity Inversion for Point Mass Anomalies by Means of the Truncated Geoid
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1997
    Peter Vajda,Petr Vaníček

    AbstractThe physical meaning of the truncated geoid, which is defined by the convolution of gravity anomalies with the Stokes function on a spherical cap of specified radius, has been studied by the authors. They investigated its relation to the density distribution, generating the surface gravity, and its potential use in inversion. Some progress results for simulated studies on point mass anomalies are presented. The behavior of the truncated geoid is controlled by the radius of the integration domain, hereinafter referred to as the truncation parameter, which is treated as a free parameter. The change of the truncated geoid in response to the change of the truncation parameter was studied in the context of the simulated mass distributions. By means of such computer simulations we have managed to demonstrate the clear sensitivity of the truncated geoid to the depths, in addition to the horizontal positions, of point mass anomalies generating the synthetic surface gravity. The objective of this paper is to illustrate, with the help of computer simulation as the method of our study, the contribution of the truncated geoid to the solution of the gravimetric inverse problem. Further work towards employing the truncated geoid in gravity exploration is being conducted.

    更新日期:2020-01-01
  • Теория Определения Непараллельностей Малой Оси Референц-эллипсоида Полярной Оси Инерции Земли И Плоскостей Исхдоного Астрономического И Геодезического Меридианов По Наьлюдениям Искусственных Спутников Земли
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1961
    Milan Burṥa

    ZusammenfassungDie Vorbedingungen der Parallelität der Nebenachse des geodätischen Referenzellipsoids mit der Rotationsachse der Erde und der Parallelität der Ebene des geodätischen Ausgangsmeridians mit der Ebene des Greenwicher astronomischen Meridians, auf denen die angewendeten Grundbeziehungen der geodätischen und astronomischen Größen (1) beruhen, werden allgemein nicht erfüllt. Bisher konnten jedoch nicht die Unparallelitäten (aus den üblichen astronomisch-geodätischen Beobachtungen) der erwähnten Achsen und Ebenen bestimmt und infolgedessen diese Vorbedingungen überprüft werden. Zur Zeit besteht die Möglichkeit ihrer Bestimmung, und zwar an Hand von Lagebeobachtungen künstlicher Erdsatelliten, wie aus der vorliegenden Arbeit ersichtlich ist. Vorausgesetzt wird, daß auf einigen (mehr als zwei) geodätischen Stationen, deren geodätische Koordinaten (bestimmt mittels der projektiven, Methode), Quasigeoidhöhe und Normalhöhe bekannt sind, die topozentrischen Äquatorealkoordinaten, bzw. die topozentrische Entfernung des künstlichen Erdsatelliten gemessen worden sind, und daß für die Zeit der Beobachtung auch die geozentrischen Äquatorealkoordinaten, bzw. die geozentrische Entfernung, bekannt sind. Aus diesen Größen können sechs unabhängige Orientierungselemente des Referenzellipsoids abgeleitet werden, z. B. die Koordinaten seines Mittelpunktes in Bezug zum Erdschwerpunkt und drei seine Achsenrichtung bestimmende Winkelgrößen. Aus diesen Werten können dann die Größen (14) der Unparallelität der nebenachse des Referenzellipsoids mit der Rotationsachse der Erde und (16) der Unparallelität der Ebene des geodätischen Ausgangsmeridians mit der Ebene des Greenwicher astronomischen Ausgangsmeridians errechnet werden.

    更新日期:2020-01-01
  • Droplet Concentration and Size Distribution in Haze and Fog
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1997
    Josef Podzimek

    Fog (haze) droplet concentrations and size distributions were measured at five sampling sites representing rural and urban regions and a highly polluted marine-urban environment. Droplet imprints in a thin gelatine layer were evaluated and compared to the measurement by light scattering instruments. This enabled conditions for the application of the logarithmic-normal size distribution and for the classification of typical fog droplet size distributions to be established. In particular, the parameters featuring the width and asymmetry of a size distribution were suggested and calculated. Advantages and drawbacks of the applied droplet sampling and evaluation technique are discussed in more detail.

    更新日期:2020-01-01
  • Changes of stability of remanent magnetization with the concentration of vacancies in titanomagnetites
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1979
    Vladimír Kropáček,Aleš Kapička,Alois Zátopek

    РезюмеОбсуж¶rt;aеmся влuянuе сmрукmурных ¶rt;ефекmов нa осmamочную нaмaнuченносmь бaзaльmов u ее uзмененuя nрu мехaнuческом нanряженuu. Резульmamы nокaзывaюm, чmо mочечные ¶rt;ефекmы являюmся о¶rt;нuм uз вaжных фaкmоров, сущесmвенно влuяющuх нa высоmу nоmенцuaльнных бaрьеров u ¶rt;вuженuе ¶rt;uслокaцuŭ. С nовыщaющеŭся конценmрaцuеŭ вaкaнцuŭ в несmенuо меmрuческuх mumaномaнеmumaх увелuчuвaеmся сmaбuльнoсmь осmamочноŭ нaмaнuченхосmu.

    更新日期:2020-01-01
  • Identification of magnetic minerals by scanning electron microscope and application of ferrofluid
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2005
    Gunther Kletetschka,Agnes Kontny

    Magnetic minerals are mostly identified by a combination of rock magnetic and microscopic techniques and the ferrofluid method in combination with an optical microscope was applied during the last decades. But today, scanning electron microscopy (SEM) is preferred for the observation of mineral phases because its depth of focus and resolving capability at the same magnification. In this study, we report on a method, which allows ferrofluid application under the SEM. We coated a polished basalt sample containing titanomagnetite grains with high demagnetizing fields, with a colloidal suspension containing magnetite particles (ferrofluid) ranging in size between 11 and 20 nm. Due to large gradients of multidomain grains the ferrofluid particles adhered to their surfaces. Other grains of similar composition present (ilmenohematite) but with low demagnetizing fields do not generate large magnetic gradients and therefore do not attract the colloidal particles. Upon evaporation of the ferrofluid and covering the sample with conducting material the magnetic grains with high demagnetizing field are easily identifiable under the scanning electron microscope. The different mineralogy observed by this method is confirmed by temperature dependent variation of magnetic susceptibility, revealing titanomagnetite and ilmenohematite as magnetic carriers in the basaltic samples.

    更新日期:2020-01-01
  • 更新日期:2020-01-01
  • Quantitative interpretation of local gravity anomalies for case of circular cylinder with vertical axis
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1965
    Břetislav Beránek

    РезюмеРешается проблема прямой и обратной задачи для тела формы вертикального кругового цилиндра. Задача решается применением аппроксимативных трансформаций аномалий силы тяжести, описанным в [1]. Значение трансформированной величины, вычисляемой в максимуме аномалии в зависимости от значения радиусаr сравнивается с теоретическим значением трансформированных величин, вызванных круговым цилиндром с вертикальной осью. Задачей является нахождение функцииf для возмущающего тела в выражении (1). Задача решена для аппроксимационного трансформационного уравнения применяемого для расчета вторых производных силы тяжести. Для расчета теоретических кривых применены два способа, данные уравнениями (12) и (21). Оказывается, что для численного расчета более выгодным является вторый вариант (формула (21)). Были вычислены теоретические кривые для бесконечного кругового цилиндра и для кругового пласта (37), которые являются предельными случаями для цилиндра с конечными размерами. Длячисленного способа вычисления интегралов (22′) и (38) применен метод механической квадратуры по формуле (23), приведенной в [4]. Способ количественной интерпретации, описанный в настоящей работе, дает возможность существенно уточнить определение глубины верхней плоскости вертикального цилиндра, которая для целей количественной интерпретации является самой основной задачей. Представленный способ дает возможность решать обратную задачу для вертикального цилиндра, которая до сих пор другими методами не решалась.

    更新日期:2020-01-01
  • Time variations of the relationships between the North Atlantic Oscillation and European winter temperature and precipitation
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2007
    Romana Beranová,Radan Huth

    The degree of stationarity of relationships between the NAO index and long European temperature and precipitation series in winter is quantified by running correlations with a time window of 31 years at 29 and 27 stations in Europe, respectively. They indicate major nonstationarities in the NAO-to-surface climate relationships at most stations. The temporal course most common for correlations with temperature is a slight change prior to about 1950, followed by an increase; for precipitation, a typical course is a decrease in the first half of the 20th century, followed by an increase. The temporal variations in correlations do not result from the presence of trends in the time series. The periods of high correlations with temperature are accompanied with an eastward shift of both NAO action centres; the eastward shift is thus at least partly responsible for the time variations in correlations.

    更新日期:2020-01-01
  • Ionisation Durch Erdsatelliten
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1962
    Ludmila Třísková

    РезюмеИзмерения показывают, что в окрестности искусственного спутника Земли образуется область с повышенной электронной концентрацией. Проведенный анализ ситнала спутника позволяет заключить, что ионизированная область находится перед спутником. В работе обьясняется возникновение указанной области ионизацией частицами, ускореными спутником, тех компонент атмосферы, для ионизации которых энергия упруго отраженных частиц достаточна. Далее проведен анализ предложенного механизма.

    更新日期:2020-01-01
  • Ergebnisse der Berechnung eines geothermischen Schnittes im Bereich des Erzgebirges in Abhängigkeit von den Eingabedaten
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1978
    Christian Oelsner,Vladimír Čermák

    SummaryTemperature depth sections have been computed for different models of a two-dimensional geological profile running 120 km in WSW — ENE direction close to the ridge of the Saxonian Ore Mountains. In the area of the deep fracture of Jáchymov the isotherms are showing a large temperature high.

    更新日期:2020-01-01
  • Colour schlieren representation of compressional-stress fields with respect to focal zone study
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 1973
    Jan Kozák,Vlastilav Červený

    SummaryA method of colour schlieren recording of the compressional-stress field gradients, suitable for focal zone study on models, is suggested. The study presents colour schlieren records of the compressional-stress fields in loaded square plates, containing inhomogeneities which give instant quantitative information on these fields. If the inhomogeneity is shaped like Griffith's diagonal slit, good agreement is demonstrated between the experiment and the theoretical calculation of the compressional-stress field in a model.

    更新日期:2020-01-01
  • 更新日期:2020-01-01
  • Merging of Airborne Gravity and Gravity Derived from Satellite Altimetry: Test Cases Along the Coast of Greenland
    Stud. Geophys. Geod. (IF 1.293) Pub Date : 2002
    Arne Vestergaard Olesen,Ole Baltazar Andersen,Carl Christian Tscherning

    The National Survey and Cadastre - Denmark (KMS) has for several years produced gravity anomaly maps over the oceans derived from satellite altimetry. During the last four years, KMS has also conducted airborne gravity surveys along the coast of Greenland dedicated to complement the existing onshore gravity coverage and fill in new data in the very-near coastal area, where altimetry data may contain gross errors. The airborne surveys extend from the coastline to approximately 100 km offshore, along 6000 km of coastline. An adequate merging of these different data sources is important for the use of gravity data especially, when computing geoid models in coastal regions.The presence of reliable marine gravity data for independent control offers an opportunity to study procedures for the merging of airborne and satellite data around Greenland. Two different merging techniques, both based on collocation, are investigated in this paper. Collocation offers a way of combining the individual airborne gravity observation with either the residual geoid observations derived from satellite altimetry or with gravity derived from these data using the inverse Stokes method implemented by Fast Fourier Transform (FFT).

    更新日期:2020-01-01
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