Showing papers in "Acta Geodaetica Et Geophysica Hungarica in 2012"

Estimation of the electric resistivity distribution (EURHOM) in the european lithosphere in the frame of the eurisgic WP2 project

Abstract: In connection with the EURISGIC WP2 project the authors present those procedures which have been used to construct a map in cells on the electrical resistivity distribution in Europe at least till to the asthenosphere. The data are based on the deep magnetotelluric soundings published in the international literature. This map is the basis of the calculation of the induction risk endangering the electric network and communication systems.

Comparing GLONASS-only with GPS-only and hybrid positioning in various length of baselines

Abstract: Nowadays, GPS is the best positioning system with its constellation, but number of GLONASS satellites increased to the required number, with launched new ones, for positioning. With recent revitalization of GLONASS, a great number of high precision GLONASS and GPS/GLONASS receivers have been produced. In this paper, baselines of two networks have been analyzed in order to assess the usability of GLONASS on global positioning. In both networks, repeatabilities of results were investigated by using GPS, GLONASS and GPS/GLONASS data. Results revealed that repeatabilities of all baselines by using GLONASS observations are not consistent when compared to the GPS and GPS/GLONASS.

A theory on geoid modelling by spectral combination of data from satellite gravity gradiometry, terrestrial gravity and an Earth Gravitational Model

Abstract: In precise geoid modelling the combination of terrestrial gravity data and an Earth Gravitational Model (EGM) is standard The proper combination of these data sets is of great importance, and spec

One-dimensional P-wave velocity model for the territory of Hungary from local earthquake data

Abstract: We determined a new one-dimensional P-wave velocity model for the territory of Hungary based on the first arrival times of local earthquakes. During the computations 910 P-wave arrival data of 86 events from the time period between 1985 and 2010 have been used. The applied methodology is a combination of a genetic algorithm based procedure and an iterative linearized joint inversion technique. The preferred velocity profile has been chosen from the best models based on the data of a series of controlled explosions.

Estimation of subsurface strata of earth using adaptive neuro-fuzzy inference system (anfis)

Abstract: Soft computing techniques are widely used for the applications on most of the nonlinear problems related to the real world. Earth’s most of the nonlinear characteristics exhibit the uncertainty problem that has to be interpreted with most of the advanced soft computing tools. Here the three layer electrical resistivity data has taken for interpreting the subsurface parameters of the earth using Adaptive NeuroFuzzy inference (ANFIS) technique. ANFIS can be predictably used for most of the nonlinear problems. Its membership functions and rules with adjustable parameters will help the interpretation technique with less error percentage results. In the present study, the program is specially designed for the interpretation of three layer electrical resistivity data. The network model is successful in training with large number of data sets available. Interpretation using ANFIS technique will give the promising results with good accuracy. With much less error percentage, the program supports all types of three layer electrical resistivity data more than a conventional method can do. Typical problems with parameter estimation can be done more efficiently with this ANFIS program.

Interval inversion of borehole data for petrophysical characterization of complex reservoirs

Abstract: Wireline logging surveys are routinely used for the reconnaissance and quantitative characterization of multi-mineral hydrocarbon structures. The interpretation of well-logging data, however, is quite a challenging task, because the conventionally used local inversion procedure becomes either an underdetermined or a slightly overdetermined problem that may result in poor parameter estimation. In order to determine the petrophysical model composed of several parameters, such as specific volumes of matrix components, water saturation, primary and secondary porosity and numerous zone-parameters, in a more reliable way a new inversion methodology is required. We suggest a joint inversion technique for the estimation of model parameters of multi-mineral rocks that inverts data acquired from a larger depth interval (hydrocarbon zone). The inverse problem is formulated assuming homogeneous intervals within the zone to get a highly overdetermined inversion procedure. The interval inversion method has been applied to shaly sandy hydrocarbon reservoirs, in this study, that is used for the estimation of petrophysical parameters of complex reservoirs. Numerical results with synthetic and field data demonstrate the feasibility of the inversion method in investigating carbonate and metamorphic structures.

Fourier transformation as inverse problem — An improved algorithm

Abstract: This paper presents a new algorithm for the inversion-based 1D Fourier transformation. The continuous Fourier spectra are assumed as a series expansion with the scaled Hermite functions as square-integrable set of basis functions. The expansion coefficients are determined by solving an over-determined inverse problem. In order to define a quick and easy-to-use formula in calculating the Jacobi matrix of the problem a special feature of the Hermite functions are used. It is well-known, that the basic Hermite functions are eigenfunctions of the Fourier transformation. This feature is generalized by extending its validity for the scaled Hermite functions. Using the eigenvalues, given by this generalization, a very simple formula can be derived for the Jacobi matrix of the problem resulting in a quick and more accurate inversion-based Fourier transform algorithm. The new procedure is numerically tested by using synthetic data.

3D crustal structure and its tectonic implication for nile delta and greater cairo regions, egypt, from geophysical data

Abstract: In the present study the crustal structures of Nile Delta, including Greater Cairo province, and its surroundings, were evaluated using 3D forward gravity and magnetic modeling. The interpretation is also based on the seismic reflection results, well logs data and previous density models. The present results allow to improve the understanding of both the crustal thicknesses and density distributions between the sedimentary cover and the upper mantle in the study area.The high Bouguer anomalies near the Mediterranean coast are mainly caused by deep-seated structures. The crust beneath the Mediterranean coastal region is typically continental, with a thickness of 24 km beneath Rositta and Damitta branches, which increases toward the south. The Greater Cairo province has been modeled with maximum crustal thickness of ca. 34 km. The negative gravity anomalies with minimum values are due to the effect of sedimentary cover and/or basement relief geometry.The main results of this work suggest that the study area...

Dry density derived by factor analysis of engineering geophysical sounding measurements

Abstract: Statistical processing of engineering geophysical sounding data is applied to the determination of dry density as an important geotechnical parameter of shallow formations. Dry density has been measured in laboratory or in the field as point information. In order to get more extensive results, dry density is extracted from high-resolution penetration logs. Dry density is related to measured bulk density as well as porosity and shale volume computed directly from engineering geophysical sounding data. The most critical parameter for the calculation is water saturation, which is estimated by factor analysis of all penetration logs. This approach is based on a strong linear correlation between water saturation and one of the extracted variables (factors). The interpretation method is tested in twelve penetration holes drilled in a Hungarian location. A 2D multi-well application is presented, in which the spatial distribution of dry density between the drill-holes is given. A local relationship between bulk density and dry density is also estimated. The study demonstrates that dry density can be estimated as continuous and in-situ information to support geotechnical operations in soil environments.

Geomechanical time series and its singularity spectrum analysis

Abstract: The multifractal analysis is applied to the study of geomechanical monitoring time series. Estimation of singularity spectra parameters within moving time window for this monitoring time series provides a possibility for splitting the history of observations into few adjacent fragments which could reflect e.g. hidden different states of the rock massif in the vicinity of measuring station. In this contribution, analysis of time series of measured distances is presented. A laser distance meter

Risk and geodynamically active areas of the Carpathian lithosphere on the base of geodetical and geophysical data

Abstract: This paper illustrates the application of multidisciplinary data analysis to the Carpathian-Pannonian Region and on the basis of geodetical data presents verification of a tectonic model of the Carpathian-Pannonian lithosphere with impact on the possible risk and activity of the geodynamic and kinematical zones in consequence of the post-subduction processes. This approach and analyses can be used for the analyses any Carpathian area from the point of view of the recent movements tendencies. All available mentioned geodata were verified and unified on the basis of the same scale and in the Western Carpathians on the remote sensing data, too. Independent GPS epoch-wise observing campaigns took place in several regions and the whole territory is now covered by tens of permanent stations. The long-term observational series from permanent stations generally yield reliable site velocities, however, distribution of such stations is not dense enough to provide velocity field with sufficient resolution all over the monitored region. In the paper we also shortly describe velocity fields available from various national and regional GPS geo-kinematics projects. The heterogeneous velocity fields have been homogenized and used for construction of the intraplate GPS velocities in Central and South-East Europe and their interpretation, focusing on the chosen active zone. As one of most important we consider — so called — “rebounding area” in East Carpathians. The proposed interpretation and solution enable to consider new view on the Pliocene to recent period.

Quality description for gravimetric and seismic moho models of fennoscandia through a combined adjustment

Abstract: The gravimetric model of the Moho discontinuity is usually derived based on isostatic adjustment theories considering floating crust on the viscous mantle. In computation of such a model some a priori information about the density contrast between the crust and mantle and the mean Moho depth are required. Due to our poor knowledge about them they are assumed unrealistically constant. In this paper, our idea is to improve a computed gravimetric Moho model, by the Vening Meinesz-Moritz theory, using the seismic model in Fennoscandia and estimate the error of each model through a combined adjustment with variance component estimation process. Corrective surfaces of bi-linear, bi-quadratic, bi-cubic and multi-quadric radial based function are used to model the discrepancies between the models and estimating the errors of the models. Numerical studies show that in the case of using the bi-linear surface negative variance components were come out, the bi-quadratic can model the difference better and delivers errors of 2.7 km and 1.5 km for the gravimetric and seismic models, respectively. These errors are 2.1 km and 1.6 km in the case of using the bi-cubic surface and 1 km and 1.5 km when the multi-quadric radial base function is used. The combined gravimetric models will be computed based on the estimated errors and each corrective surface.

Probabilistic seismic hazard assessment of Albania

Abstract: A new probabilistic seismic hazard assessment for Albania is carried out using the smoothed gridded seismicity approach. Albania’s earthquake catalogue is already revised and expanded, covering a study area limited by 38–44.5°N Latitude and 18–24°E Longitude, and the time period from 58BC to 31/12/2008. The ground motion hazard map is presented over a 10 km grid in terms of peak ground acceleration for 10% probability of exceedance in 50 years, corresponding to 475-year return period. The reference site condition is firm rock, defined as having an average shear-wave velocity in the upper 30 m of the crust of 800 m/sec. It is the standard reference site condition used by the European seismic code (Eurocode 8) for seismic zonation and building codes. The main finding is that if this map is accepted as a reference indicator to establish a new regulatory national seismic zonation, design acceleration will be much higher than that applied in the current regulation. This implies that the competent authorities should take into consideration the obtained results to improve the existing design code in a more reliable and realistic basis in order to increase the safety level of constructions in the country.

Development of a site-specific ZHD model using radiosonde data

Abstract: Estimation of precipitable water vapor (PWV) in the atmosphere using ground based GPS (Global Positioning System) data requires an appropriate model for computation of zenith hydrostatic delay (ZHD). Presented herein is a site-specific ZHD model (SSM) for a station at New Delhi, India. The model has been developed by regressing one-year atmospheric vertical profile data collected through radiosonde. The model based on surface atmospheric pressure at the station, has been validated invoking data of three more years. The ZHD values estimated through the model disagree at the 0.3 mm level with ZHD values obtained from raytracing of radiosonde data. Further, Saastamoinen ZHD model provides an error about 0.23 mm rms while about 0.19 mm by the developed model (SSM). Thus, developed SSM can be used for precise estimation of PWV.

The new fundamental gravimetric network of Slovenia

Abstract: The paper presents all stages of the development and processing of the fundamental gravimetric network of Slovenia, which consists of a zero order network, which has six absolute gravity stations, and twenty nine first order gravimetric stations. Descriptions are given of the design of the network, the geological assessment of the gravimetric stations, the gravity survey of the first order network, and the post-processing and adjustment of the gravimetric observations, which was performed in two stages. First the observations in the zero order network were adjusted as a free network, and then a standard adjustment of the first order network was performed. Finally, the adjusted gravity values at the stations were analysed against the Potsdam system, which was the basis of all previous gravimetric calculations in Slovenia. In the analyses an equation for the transformation of gravity values between the Potsdam system and the IGSN71 system (International Gravity Standardization Network 1971) has been derived.

Evaluation of NRTK positioning using the RENEP and RAP networks on the Southern border region of Portugal and Spain

Abstract: Nowadays, the Continuously Operating Reference Station (CORS) network, combined with network RTK corrections (NRTK solution), is a widely used technique for high-accuracy positioning in real time. This “active” network realizes a reference frame and propagates it to the users. In border regions the coherence between the reference frames propagated by neighboring active networks is a critical problem. In this study the test results of post-processed and simultaneous NRTK positions at six test points located in the border region between Portugal and the Community of Andalusia, in the south west of the Iberian Peninsula, are presented. The analysis is based on two GNSS active networks present in this border region, namely RENEP (Portugal) and RAP (Community of Andalusia, Spain), a national and a local RTK network respectively, with similar characteristics. Upon comparing the post-processed position for each test point, as estimated with respect to each of the two active networks analyzed, the discrepancies found in 3D were less than 2 centimeters. The results of network-based RTK positioning were found to be successful within a 2 cm precision level in the east and north components and 4 cm for the up component. The results also confirm that the NRTK positioning accuracy is about 2 cm in horizontal and 4 cm in vertical, which can satisfy the requirement of real-time positioning users at a centimetric accuracy level, even in border regions considering extrapolated NRTK solutions.

A simple proof of the solutions of the Helmert- and the overdetermined nonlinear 7-parameter datum transformation

Abstract: The laws of nature in general, and the relations and laws in geodesy in particular can be expressed in most cases by nonlinear equations which are in general solved by transforming them to linear form and applying iteration. The process of bringing the equations to linear form implies neglections and approximation. In certain cases it is possible to obtain exact, correct solutions for nonlinear problems. In the present work we introduce parameters into the rotation matrix, and using this we derive solutions for the 2D and 3D similarity transformations. This method involves no iteration, and it does not require the transformation of the equations to linear form. The scale parameter is determined in both cases by solving a polynomial equation of second degree. This solution is already known, but our derivation is worth consideration because of its simple nature.

Application of the ace algorithm on hydrogeological monitoring data from the Bükk Mountains

Abstract: This paper introduces the alternating conditional expectation (ACE) algorithm of Breiman and Friedman (1985) in multiple regression problems in groundwater mon- itoring data analysis. This special inverse nonparametric approach can be applied easily for estimating the optimal transformations of different groundwater monitor- ing data from the Bukk Mountains to obtain maximum correlation between ob- served aquifer variables. The approach does not require ap rioriassumptions of a mathematical form, and the optimal transformations are derived solely based on the groundwater data set. The advantages and applicability of the proposed approach to solve different multiple regression problems in hydrogeology or in groundwater man- agement are illustrated by means of case studies from a Hungarian karst aquifer. It is demonstrated that the ACE method has certain advantages in some fitting problems of groundwater science over the traditional multiple regression. In the past, different groundwater monitoring data (like groundwater level, ground- water temperature and conductance, etc.) had been used for groundwater manage- ment purposes in the Bukk Mountains. One of the difficulties in earlier approaches has been the need to make some kind of assumption of the expected mathematical forms among the investigated reservoir and petrophysical variables. By using non- parametric regression, the need to assume a specific form of model is avoided, and a clearer vision of the relationships between aquifer parameters can be revealed in the Bukk Mountains, where karst water is the main source of potable water sup- ply. Complex monitoring data from the Bukk Mountains were analyzed using the ACE inverse method, and results were verified successfully against quantitative and qualitative field observations.

2.5D geoelectric inversion method using series expansion

Abstract: This paper presents the principles of a new inversion method used for the determination of 3D geological structures. The horizontal variations of the layer parameters i.e. layer thicknesses and resistivities are discretized in the form of series expansion. The unknown coefficients of the series expansion are determined by an iterative linearized inversion method using weights specified by the Most Frequent Value Method (MFV). The result of the inversion is estimated from the data of the bi-directional VES (Vertical Electric Sounding) measurements with Schlumberger array in each profile and in multiple profiles. A 3D Finite Difference method was applied to forward modelling, however, the structure is approximated along the profile with a 2D model discretized by single-variable series expansion. The 3D forward modeling procedure gives the opportunity to calculate data measured in two or multiple directions. The suggested interpretation method gives an approximate solution. Proceeding more accurate 3D inversion will be provided by the binary series expansion.

Interpretation of the Total Magnetic Field Anomalies Measured by the CHAMP Satellite Over a Part of Europe and the Pannonian Basin

Abstract: In this study we interpret the magnetic anomalies at satellite altitude over a part of Europe and the Pannonian Basin. These anomalies are derived from the total magnetic measurements from the CHAMP satellite. The anomalies are reduced to an elevation of 324 km. An inversion method is used to interpret the total magnetic anomalies over the Pannonian Basin. A three dimensional triangular model is used in the inversion. Two parameter distributions, Laplacian and Gaussian are investigated. The regularized inversion is numerically calculated with the Simplex and Simulated Annealing methods and the anomalous source is located in the upper crust. A probable source of the magnetization is due to the exsolution of the hematite-ilmenite minerals.

Random noise reduction capability of the Hermit polynomial based Least Squares Fourier Transform method

Abstract: Treating the Fourier transform as an over-determined inverse problem is a new conception for determining the frequency spectrum of a signal. The concept enables us to implement several algorithms depending on the applied inversion tool. One of these algorithms is the Hermit polynomial based Least Squares Fourier Transform (H-LSQ-FT). The H-LSQ-FT is suitable for reducing the influence of random noise. The aim of the investigation presented in the paper was to study the noise reduction capability of the H-LSQ-FT in some circumstances. Four wavelet-like signals with different properties were selected for testing the method. Examinations were completed on noiseless and noisy signals. The H-LSQ-FT provided the best noise reduction for the noisy signal having low peak frequency and wide band width. Finally, the results obtained by the H-LSQ-FT were compared to those of other traditional methods. It is showed that the H-LSQ-FT yields better noise filtering than these methods do.

Impact of compensating mass on the topographic mass : A study using isostatic and non-isostatic Earth crustal models

Abstract: Impact of compensating mass on the topographic mass : A study using isostatic and non-isostatic Earth crustal models

A very short note on the origins of correlated bivariate normal distribution with particular relevance to earth sciences

Abstract: In the community of geodesy it is well-known that the famous normal distribution is originated from the mathematical analysis of observational errors in astronomical and geodetic measurements. However, as far as we know this aspect of scientific history which is of considerable interest for the community of earth sciences has rarely been considered in the literature of earth sciences. In geodesy and related areas the bivariate normal distribution is one of the most frequently used probability distributions. Nowadays, in a wide range of problems arising from diverse areas of geodesy, geophysics, photogrammetry and astronomical geodesy we encounter numerous applications of the univariate and multivariate normal distributions. In the present paper the historical role of earth sciences in the origins of the bivariate normal distribution is briefly discussed. Some new evidences of Bravais’ contribution to the origin of the correlated bivariate normal distribution are considered. The new evidences and refinements established in this paper convey such a general methodological and intellectual content that is useful for the community of geodesy, geophysics, and furthermore in earth sciences.

Resolution and ambiguity studies for a series expansion based multilayer refraction inversion method

Abstract: The paper discusses the characteristics and feasibility of a multilayer kinematic refraction inversion method that is applicable to estimate the — even laterally changing — parameters of a geological model in the simultaneous evaluation of refraction data. The studied method has been developed at the Department of Geophysics of the University of Miskolc for the interpretation of parameters (layer thicknesses and seismic velocities) using series expansion based on adequately chosen basis functions. Besides revealing its resolution properties, ambiguity studies are also presented on synthetic data sets. In the terminology of refraction inversion uncertain and ambiguous results are frequently encountered problems in multilayer cases when all parameters (or all coefficients describing the parameters) are estimated simultaneously in the same inversion procedure. Results of resolution and ambiguity analyses of synthetic data sets and field examples are shown in this study.

Geometric interpretation and precision analysis of algebraic ellipse fitting using least squares method

Abstract: This paper presents a new approach for precision estimation for algebraic ellipse fitting based on combined least squares method. Our approach is based on coordinate description of the ellipse geometry to determine the error distances of the fitting method. Since it is an effective fitting algorithm the well-known Direct Ellipse Fitting method was selected as an algebraic method for precision estimation. Once an ellipse fitted to the given data points, algebraic distance residuals for each data point and fitting accuracy can be computed. Generally, the adopted approach has revealed geometrical aspect of precision estimation for algebraic ellipse fitting. The experimental results revealed that our approach might be a good choice for precision estimation of the ellipse fitting method.

The pressure dependence of acoustic velocity and quality factor — New petrophysical models

Abstract: In this study we introduce new rock physical models which describe the pressure dependence of seismic velocity and quality factor. The models are based on the idea (accepted in the literature) that microcracks in rocks are opened and closed under the change of pressure. The models were applied to acoustic P wave velocity data measured on core samples originated from oil-drilling wells (27 samples) and also seismic velocity and quality factor data sets published in international literature. During the measurements the pulse transmission and the spectral ratio techniques were used. Measurements were carried out at various incremental pressures and parameters of the models were determined by linearized inversion methods. The calculated data matched accurately with measured data proving that the new rock physical models apply well in practice.

Determination of vertical gradients of gravity by series expansion based inversion

Abstract: All the elements of the Eotvos tensor can be measured by torsion balance, except the vertical gradient. The knowledge of the real value of the vertical gradient is more and more important in gravimetry and geodesy.

Some remarks on linear least squares fits with errors in both coordinates

Abstract: The exact least squares line fit with errors in both coordinates (Reed 1992) is investigated together with the approximate solution based on the formalism of the linear Gauss-Helmert model or the unified adjustment approach of the classical textbook by Mikhail (1976). The similarities and the differences are described in details. In spite of the small differences the exact solution is preferable and the calculations are simpler. This paper does not deal with the errors-in-variables (EIV) models solved by the total least squares (TLS) principle, since the exact line fit solution is used to validate this general approach, which is basically designed to solve more sophisticated nonlinear tasks. In the most general case the fit of Person’s data with York’s weights is iteratively solved starting with the arbitrary zero initial value of the slope. The test computation with different but systematically chosen weights proved that in special cases — e.g. the weighted least squares sum of the distances between the data points and the estimated line is minimised — there is no need for iterations at all. It is shown that methods described by Detrekői (1991) and Zavoti (2012) are special cases of the general exact solutions. Reed (1992) derived the variances of the slope and intercept parameters without their covariance. The simple linear estimation of variance-covariance matrix of the exact solution is also demonstrated. The importance of the stochastic models coupled with exact solution is also demonstrated.

The considering the galvanic and induction effects in the inversion of vertical electric dipole transillumination measurement

Abstract: The use of vertical electric dipole transmitter and receiver turns out to be advantageous in the exploration of lateral inhomogeneities of high resistivity layers by transillumination measurement. Geological information can be made clearer by transformation of the amplitude response to apparent resistivity spectrum. The apparent resistivity calculated by the geometric factor in the quasistationary frequency range depends decisively on the galvanic effect of the high resistivity layer containing the electrodes. In the so called frequency dependent inductive apparent resistivity deduced based on the amplitude response of the uniform half — respectively full — space at low frequencies mainly the effect of the shoulder formation, at frequencies high enough the effect of the resistive layer containing the electrode will dominate. The knowledge of these apparent resistivities on the one hand helps the determination of the effective resistivity, which is independent of the ray-length and indicates the continuity or discontinuity of the resistive layer along the equatorial plane. On the other hand in the case of transilluminations with areal coverage they can be used in the selection of the horizontal-layered, uniform start model, needed in the reconstruction of the spatial distribution of the resistivity-variation. Reconstructions of measured and simulated data demonstrate the applicability of the procedure.

2D inversion processing of geoelectric measurements with archaeological aim

Abstract: The paper presents the opportunities of archaeological applications of the geoelectric geophysical methods. The electrical conductivity properties of buried archaeological objects (wall relics, roads, channels, graves, metal objects, etc.) measurably differ from the electrical conductivity properties of soils and rocks covering archaeological objects. So these archaeological objects are detectable with geoelectric measurements performed on the surface of the Earth. The paper outlines the relation between the electrical parameters of individual archaeological objects and the medium covering them; and it supports the archaeological adaptability of geoelectric methods with the presentation of the results of field measurements.