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Earth and environmental sciences cover all planetary and Earth science aspects, including solid Earth processes, development of Earth, environmental issues, ecology, marine and freshwater systems, as well as the human interaction with these systems.
Earth and Environmental Sciences
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.
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.
This paper introduces the alternating conditional expectation (ACE) algorithm of Breiman and Friedman (1985) in multiple regression problems in groundwater monitoring data analysis. This special inverse nonparametric approach can be applied easily for estimating the optimal transformations of different groundwater monitoring data from the Bükk Mountains to obtain maximum correlation between observed aquifer variables. The approach does not require a priori assumptions 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 management 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, groundwater temperature and conductance, etc.) had been used for groundwater management purposes in the Bükk 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 nonparametric 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 Bükk Mountains, where karst water is the main source of potable water supply. Complex monitoring data from the Bükk Mountains were analyzed using the ACE inverse method, and results were verified successfully against quantitative and qualitative field observations.
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.
All the elements of the Eötvös 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.Determination of the 3D gravity potential W(x, y, z) can be produced by inversion reconstruction based on each of the gravity data W z(= g) measured by gravimeters and gravity gradients W zx, W zy, W Δ, W xy measured by torsion balance. Besides vertical gradients W zz measured directly by gravimeters have to be used as reference values at some points. First derivatives of the potential W x, W y (can be derived from the components of deflection of the vertical) may be useful for the joint inversion, too. Determination of the potential function has a great importance, because all components of the gravity vector and the elements of the full Eötvös tensor can be derived from it as the first and the second derivatives of this function. The second derivatives of the potential function give the elements of the full Eötvöstensor including the vertical gradients, and all these elements can be determined not only in the torsion balance stations, but anywhere in the surroundings of these points.Test computations were performed at the characteristic region of a Hungarian plate area at the south part of the Csepel Island where torsion balance and vertical gradient measurements are available. There were about 30 torsion balance, 21 gravity and 27 vertical gradient measurements in our test area. Only a part of the 27 vertical gradient values was used as initial data for the inversion and the remaining part of these points were used for controlling the computation.
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.
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.
The results of model calculation (direct problem solutions above model parameter space) determine an embedded continuous and differentiable surface in the Euclidean space of measurements. This multidimensional subspace contains the possible expected values of measurement vectors according to the assumed rock model as a projection of measurement points (expressing the model and real rock equivalences). The model parameters are the natural coordinates of this subspace, determining a contravariant curvilinear coordinate system (“flat world” for the inversion). The local curvature of this surface is very important factor of covariance matrices and the possible bias of estimated parameters. In this article the role of curvature is discussed and the shortage of conventional (first order) inversion is demonstrated by simple example and the possibility of bias correction.
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.
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.
