bluuebunny/crossref_metadata_2025_split huggingface dataset:
A DISCUSSION ON SEISMIC BINARY GAIN SWITCHING AMPLIFIERS *
Authors: SIEMS LEE , HEFER FRED W. 
Published: April 2006

ABSTRACTGeophysical field equipment has undergone rapid changes in the past decade; from simple AGC amplifiers and galvo cameras to binary gain switching amplifiers and digital recorders, all in an attempt to keep pace with the new geophysical interpretive methods developed, and the growing acceptance of the terminology, methods, and philosophy of communication theory.The additional tools of the digital recorder and digital computer make it possible to utilize these new techniques in geophysical processing. Accomplishing these new techniques demands severe requirements on the digital field recording process in handling the decreasing energy return from the seismometer, and to fully realize the capabilities of digital techniques in reducing data. Simple automatic gain control may be used. However, in the more sophisticated interpretive methods, such as autoregression and deconvolution, it is necessary to reconstruct the actual energy levels in the computer. Recording the control signal used in master AGC or programmed gain control may prove satisfactory; however the accuracy of control versus gain is limited to I% for such analog instrumentation.To utilize the computer to its fullest extent, and to accurately perform these new techniques, requires an accuracy of I% or better. This accuracy is obtainable by using a step gain control where the gain is increased by fixed steps in which each step represents a gain in amplification by a constant factor. The accuracy in this case can be made dependent only on the tolerance of resistors used as attenuators or feedback elements. Preferably the constant factor of gain steps should be a number easily handled by the computer. By using 6 db steps it becomes a simple matter to shift binary numbers, such as multiplying or dividing by 10 in the decimal system.The requirements or parameters for such an amplifier system, and the elements of the amplifier necessary to achieve these requirements are presented.
TWO DIMENSIONAL STRAKHOV'S FILTER FOR EXTRACTION OF POTENTIAL FIELD SIGNAL*
Authors: NAIDU P. S. 
Published: April 2006

AbstractA two dimensional linear filter operator based on Strakhov's method for the extraction of a potential field signal (gravity or magnetic) from a background of homogeneous random noise has been developed. An algorithm to solve for the coefficients of the operator is given together with the corresponding computer program in FORTRAN language. It may be used on any machine using FORTRAN IV. A few examples of the operator are also included.
RESPONSE OF A TWO‐LAYER GROUND TO AN INFINITE CABLE CARRYING ALTERNATING CURRENT WITH REFERENCE TO TURAM ANOMALIES *
Authors: DIZIOǴLU MEHMET Y. 
Published: April 2006

ABSTRACTA formula is developed for the vertical magnetic field due to an alternating current passing through a long horizontal cable placed on a two‐layer ground. The variations of the phase and amplitude ratio of the vertical field, along profiles perpendicular to the cable line are investigated. Within the limits encountered in practice, it is found that if the upper layer is conductive, as compared to the lower layer, the phase may vary appreciably whereas the amplitude ratio changes as in the case of vacuum.
EXPERIMENTELLE METHODEN UND EINE APPARATUR ZUR UNTERSUCHUNG DER BEZIEHUNGEN ZWISCHEN HYDRAU‐LISCHEN UND ELEKTRISCHEN EIGENSCHAFTEN LOSER UND KUNSTLICH VERFESTIGTER POROSER MEDIEN *
Authors: SCHOPPER JÜRGEN R. 
Published: April 2006

ABSTRACTIn [50] and [51] a theory has been developed relating formation factor, permeability and porosity of porous sedimentary rock by means of statistical parameters of the pore system, and further, tying those statistical parameters to other macroscopically measurable quantities like capillarity, capillary retention, flow dispersion etc. This paper deals with experimental methods and apparatus for checking the theoretically derived relations using columns of packed loose or artificially consolidated sands or other granular matter. Some initial experiments, mainly intended for checking out equipment and methods are reported. The discussion of the results so far shows good agreement with the theory in most cases, except for the irreducible water saturation. However, for a definite statement on the general validity of the theory more data must be accumulated.
RESISTIVITY SOUNDING ON A TWO‐LAYER EARTH WITH TRANSITIONAL BOUNDARY*
Authors: MALLICK K. , ROY A. 
Published: April 2006

ABSTRACTA theoretical solution is obtained for the problem of a two‐layer earth with transitional boundary. In practice, the transition layer can stand for the weathered zone in hard rock areas where the degree of weathering diminishes with depth. Master curves and tables of data are presented for the case when the lower half‐space is infinitely resistive.
DEEP SEISMIC SOUNDING OF THE EARTH'S CRUST IN THE AREA OF THE DINARIDES AND THE ADRIATIC SEA*
Authors: DRAGAŠEVIÍ T. , ANDRIC B. 
Published: April 2006

AbstractDeep seismic sounding was performed along two profiles which cross at the Dinarides area right angles. One of the profiles goes far into the Adriatic Sea.Besides considerations on the lithophysical conditions, characteristics of the registered waves are analysed. The amplitude curves and curves of amplitude ratios are shown. Special attention was paid to the frequency of the registered waves.In order to obtain a better knowledge of the registered wave pattern three‐component recordings of waves were carried out. The analysis of the records obtained is given, with particular regard to the possibility of creating converted waves.The Earth's crust structure along the profiles II and III is given.
ANALYSIS OF GRAVITY ANOMALIES OF TWO‐DIMENSIONAL FAULTS USING FOURIER TRANSFORMS*
Authors: SHARMA BIJON , GELDART L. P. 
Published: April 2006

ABSTRACTThe Fourier transform formula for a two‐dimensional fault truncating a horizontal bed at an arbitrary angle of inclination is derived. The amplitude spectrum of the Fourier transform is found to give information about the depth to the top of the upper part of the faulted bed and the inclination of the fault‐plane. Under suitable conditions the thickness and the displacement of the bed involved can be obtained. With actual field data, these transforms can be obtained at discrete points by a Fourier analysis of the gravity anomaly. A field example from the Logan fault area near Montreal, Que., Canada, is given.
TRANSIENTS AND FIELD BEHAVIOUR IN INDUCED POLARIZATION*
Authors: BERTIN J. , LOEB J. 
Published: April 2006

ABSTRACTThis paper deals with electromagnetic fields in the so called “Transient Induced Polarization Technique”. Field equations are integrated in the case of a polarizable sphere inbedded in a sterile overburden. The existence of a remanent polarization vector P which slowly decays once the charging current has been cut off is taken as the initial condition. When the surface between the air and overburden is (as a first step) disregarded, the Laplace transform of the EM fields is given. The integral of the electric field (which is fairly often the result of prospection work) is independent of the various time constants related to electrochemical processes, but it stands as a good measurement of the total electrostatic dipole created by the charging current.We investigate the geometrical circumstances that can bring negative values of I.P. signal. Such negative values can be found in two cases: 1. The discharge currents are. distorted by the ground surface. 2. The I.P. signal is picked up by electrodes inside the polarizable material.The last part is dedicated to an account of experimental work performed on models and of an actual case history.The mathematical derivations are included in an appendix.
QUELQUES APPLICATIONS DE LA THEORIE DE LA PREDICTION AU TRAITEMENT DES DONNEES SISMIQUES*
Authors: HEMON CH. 
Published: April 2006

AbstractIn the case of simple time series it is shown that prediction operators can be considered as deconvolution operators which are easily obtained.These operators possess the special feature of having a minimum phase, and their spectrum modulus represents, with a good dynamic range, the reciprocal of the square root of the modulus of the original autocorrelation spectrum.A generalization of the simple time series theory to the functions of two independent variables is possible in as much as, on a given section, the application of the multiple time series method enables the function of time and distance variables to have well‐defined statistical properties; it is necessary, in particular, that the processes involved are stationary with respect to the two independent variables.In the case of multiple time series the application of the Prediction Theory permits greater uniformity of the traces because it enhances the events which show a good correlation between traces and, on the other hand, tends to minimize the random events which cannot be correlated between traces. The signal‐to‐noise ratio is thus increased to a great extent.
THE ELECTRICAL CURRENT PATTERN INDUCED BY AN OSCILLATING MAGNETIC DIPOLE IN A SEMI INFINITE CONDUCTIVE THIN PLATE*
Authors: KOEFOED O. , STRUYK A. P. 
Published: April 2006

AbstractIn a paper by Koefoed and Kegge (1968), which was based on previous work of Wesley (1958), the electrical current pattern has been derived that is induced by an oscillating magnetic dipole in a semi‐infinite thin plate of infinitesimal resistivity.In the present paper, the range of validity of the assumptions, on which the work of Wesley is based, is subjected to a theoretical analysis. It is found that the decisive factor for the validity of Wesley's derivation is the quotient of the square of the penetration depth of the electrical current over the product of the thickness of the plate and a distance that is indicative of the size of the current loops in the plate. Wesley's derivation is shown to be valid only when this factor is negligible. It is also shown that in this condition the imaginary component of the anomaly must be negligible.Model experiments are described in which the electrical current pattern is studied also in the range in which the derivation of Wesley is not valid. The procedure used in these model experiments was to measure the tangential component of the magnetic field strength very close to the metal plate that simulated the conductive dyke.In order to express the results of the measurements in terms of the imaginary to real ratio, these results are compared with an interpretation graph for field measurements that was published by Hedström and Parasnis (1958). It is found that the current pattern in the plate is essentially the same as that which follows from Wesley's derivation, provided that the imaginary to real ratio is less than one third. The measurements do not permit to draw conclusions regarding the current pattern in the plate in conditions that correspond to larger values of the imaginary to real ratio.
THE DELINEATION OF THE BEDROCK CONFIGURATION OF PART OF PORT JACKSON, NEW SOUTH WALES, WITH A BOOMER SYSTEM*
Authors: EMERSON D. W. , PHIPPS C. V. G. 
Published: April 2006

AbstractA high resolution Boomer system was used to investigate the bedrock configuration of part of Port Jackson, New South Wales. The continuous reflection profiling technique was successful in delineating a channel incised in bedrock under a thickness of up to 60 m. of unconsolidated sediment covered by up to 20 m. of water.
REFLEXIONS SUR LES APPLICATIONS DE LA TRANSFORMEE DE FOURIER EN SISMIQUE ET EN GRAVIMETRIE*
Authors: JACQMIN A. , PEKAR L. 
Published: April 2006

ResumeDe nombreuses études ont été effectuées jusqu'à ce jour sur la Transformée de Fourier et ses applications en géophysique. En particulier, depuis ľavènement des ordinateurs qui ont entraîe la digitalisation de la principale méthode, sismique réflexion, les différentes techniques de traitement numérique ont fait ľobjet ?innombrables communications. La gravimétrie a toujours été une méthode numérique. Mais il est évident que pour elle également, de nouvellés possibilités se sont ouvertes. Aussi les gravimétriciens s'intéressent de plus en plus à la théorie et aux applications fondées sur ľétude des spectres en fréquences que permet la Transformée de Fourier. Depuis les travaux de C. A. Schwartz, W. Sokoloff et W. C. Dean, ?autres idées intéressantes, concernant le traitement de ľinformation gravimétrique, sont apparues: calcul du gradient vertical (V. Baronov), interprétation des anomalies à partir de leur spectre (M. E. Odegard et J. Berg Jr.), calcul des isopaques gravimétriques (J. L. Bible) etc….Toutes ces idées, toutes ces techniques ont le même but: faciliter ľinterprétation. Mais tout en ayant le même but et ayant affaire au même genre de difficultiés, il semble que le gravimétricien et le sismicien se soient elabores, chacun de leur côté, des outils sans se soucier du fait que leurs méthodes, et plus spécialement leur méthode de traitement de mesures brutes, sont, sinon identiques, du moins très semblables et que par conséquent les perfectionnements atteints dans une méthode peuvent servir ľautre.Ľobjet de la présente communication sera de repenser la philosophie des deux méthodes, sismique et gravimétrie, depuis ľexécution des mesures en passant par les principales méthodes de traitement, pour aboutir àľinterprétation, en se plaçant à deux points de vue complémentaires ?ailleurs:– Bien que les traitements numériques se fassent le plus souvent dans le domaine fonctionnel par les convolutions, il est bien plus facile de comprendre et de concevoir ces traitements si ľon raisonne alternativement grâce à la Transformée de Fourier dans le domaine fonctionnel et dans le domaine spectral.– En raisonnant en fréquences, il n'y a pas de différence de principe entre la sismique et la gravimétrie. Une courbe, graduée en milligals fonction de distance, et une trace sismique, représentant les variations de tension ?un galvanomètre en fonction du temps, sont, du point de vue de la Transformée de Fourier, identiques.Dans cet esprit on abordera les sujets suivants:– Signal sismique et signal gravimétrique– Problème ?échantillonnage en gravimétrie (espacement de mesures variable)– Filtrages.•Présentation et commentaires de spectres de quelques exemple syntétiques et pratiques•Filtrage en nombre ?onde•Filtrage en fréquences.•Problème de la fréquence o (dérivées horizontale et verticale)– Autres applications de la Transformée de Fourier en gravimétrie.
REMARQUES SUR L'INTERPRETATION DES SONDAGES DE POLARISATION PROVOQUEE ESSAI DE THEORIE QUANTITATIVE *
Authors: VAN NGOC PHAM , ROUSSEL J. , TOURNIER Et D. 
Published: April 2006

RÉSUMÉLa polarisation provoquée (P.P.) est un phénomène particulièrement complexe non seulement du point de vue des mécanismes physiques qu'elle met en jeu, mais aussi du point de vue mathématique. A cause de ľanalogie que présentent les techniques expérimentales de sondage électrique classique de résistivité?une: part, et de sondage P.P. ?autre part, on éprouve une certaine tendance à interpréter les données du second à la manière du premier. C'est pourquoi il nous a semblé utile de calculer un modèle mathématique idéalisé et schématisé qui permette tout au moins de se rendre compte de ľallure générale du phénomène auquel on peut s'attendre. On s'est placé dans le cas le plus simple, celui ?une couche mince polarisable qui présenterait la même conductibilitéélectrique que le milieu dans lequel elle est intercalée. On se propose de fournir le résultat de ce calcul pour le cas simple ?une seule électrode ?injection et ?une seule électrode de mesure et, à partir de ces données, de calculer ľallure ?un sondage P.P. de type classique avec quadripôle Wenner.On compare ensuite le diagramme calculé avec une courbe expérimentale obtenue sur un modèle figurant une couche mince de minerai disséminé II s'avère, en fin de compte, que ľallure générale du phénoméne fournit une base de contrôle solide àľexpérimentation sur modèles réduits.
THE CORRELATION OF SEISMIC VELOCITIES WITH FORMATIONS IN THE SOUTH‐WEST OF SCOTLAND *
Authors: HALL JEREMY 
Published: April 2006

ABSTRaCTIn seismic studies being carried out to elucidate the structure at depth of the Midland Valley rift and the Tertiary igneous province in the West of Scotland, a lack of deep boreholes makes the collection of velocity data imperative for identification of seismic events and for determinations of depth. Three methods are used to investigate the correlation of seismic velocities and geological formations. The results show as strong a dependence of velocity on method of measurement as on lithology and the wide spread of values within a given formation makes the attribution of discrete velocity ranges to specific formations impossible. Changes of velocity are more significant than absolute values. The variations in both are discussed.
A STUDY ON THE DIRECT INTERPRETATION OF RESISTIVITY SOUNDING DATA MEASURED BY WENNER ELECTRODE CONFIGURATION*
Authors: CHAN SIEW HUNG 
Published: April 2006

AbstractThis paper describes certain procedures for deriving from the apparent resistivity data as measured by the Wenner electrode configuration two functions, known as the kernel and the associated kernel respectively, both of which are functions dependent on the layer resistivities and thicknesses. It is shown that the solution of the integral equation for the Wenner electrode configuration leads directly to the associated kernel, from which an integral expression expressing the kernel explicitly in terms of the apparent resistivity function can be derived. The kernel is related to the associated kernel by a simple functional equation
image
where K1(λ) is the kernel and B1(λ) the associated kernel.Composite numerical quadrature formulas and also integration formulas based on partial approximation of the integrand by a parabolic arc within a small interval are developed for the calculation of the kernel and the associated kernel from apparent resistivity data. Both techniques of integration require knowledge of the values of the apparent resistivity function at points lying between the input data points. It is shown that such unknown values of the apparent resistivity function can satisfactorily be obtained by interpolation using the least‐squares method. The least‐squares method involves the approximation of the observed set of apparent resistivity data by orthogonal polynomials generated by Forsythe's method (Forsythe 1956). Values of the kernel and of the associated kernel obtained by numerical integration compare favourably with the corresponding theoretical values of these functions.
NATURAL POTENTIAL ANOMALIES AS A QUANTITATIVE INDEX OF THE RATE OF SEEPAGE FROM WATER RESERVOIRS*
Authors: BOGOSLOVSKY V. A. , OGILVY A. A. 
Published: April 2006

AbstractWater seepage from reservoirs causes appreciable anomalies of natural electric fields. The possibility of mapping leakage places by means of the SP method has been discussed by the authors in an earlier report. Further work has shown that detailed measurements of the natural electric field allow to determine the seepage rates from individual areas of a water reservoir in relative units. If data on the total discharge from a water reservoir are available, the conventional seepage units can be converted into absolute ones. Using this technique on a water reservoir in Armenia has permitted to control the change of the leakage rate as hydroinsulation operations were in progress. It has been established that as a result of shielding the bottom with clay material leakage from the central part of the reservoir has stopped. On the other hand, construction of cement seepage‐proof protection has had so far no appreciable positive effect.
A TWO‐LAYER GROUND IN THE FIELD OF AN INFINITELY LONG CABLE*
Authors: BEZVODA V. , SEGETH K. 
Published: April 2006

AbstractWhen the fixed‐source electromagnetic method is applied the quantities measured are influenced by the resistivity of the whole environment. This occurs mostly in the cases of measurements in areas with prevailing high resistivities, and if a weathered layer with considerably lower resistivity than that of the original rock has been formed near the surface. For this reason it is important to be acquainted with the properties of the two‐layer ground with an overlying conductive layer.In the present paper attention will be drawn to theoretical calculations connected with the field of the homogeneous ground and that of the two‐layer ground.
POINTE AUTOMATIQUE*
Authors: BOIS P. , LA PORTE M. 
Published: April 2006

AbstractThe automatic picking of seismic sections replaces the slow and painstaking task of manual reflection plotting with rapid and economical processing by computer. Essentially, reflection picking is a decision‐making problem which also can be considered as a sort of filtering. Mathematically this means multiplying the seismic data matrix by a more or less complex decision operator.For the sake of economy, we give an initial solution for simple cases which only require easily automatized decision‐making criteria.We describe another more elaborate method for use in examining seismic phenomena which are more difficult to spot.The process used is based on the recognition of shapes and consists first of all of determining a series of characteristics capable of identifying each reflection on each trace and then of comparing these different characteristics from trace to trace so as to be able to judge the continuity or discontinuity of the reflections.Automatic picking thus leads to a schematic time‐section in which only the horizons found by calculation are retained. An automatic migration program then transforms this time‐section into a depth‐section.
DETERMINATION OF ELECTRIC ROCK PARAMETERS FROM THE FIELD STRUCTURE OF A MAGNETIC DIPOLE*
Authors: BITTERLICH W. , KELLNER A. W. 
Published: April 2006

AbstractIn the theoretical part of the present paper, formulas have been analyzed for a magnetic dipole in a homogeneous and unbounded medium. The magnetic field is elliptically polarized in the region between the quasistatic zone and the far field. Since the position and the shape of the polarization ellipses depend on the complex wave number, k, it is possible to determine k by measuring the polarization ellipses. From k, the conductivity and the dielectric constant of the medium are easily calculated. The functions required for the measuring method have been computed and plotted in graphs.In the experimental part it was examined how far the theory may be applied to measurements of propagation through rock at frequencies ranging from 100‐1000 kHz. These measurements showed that reasonably defined mean values of rock parameters can be given only if the deviations of the field from the theoretically expected field are not too high. These deviations have been named field distortions and have been examined by means of statistical methods (variance ratio tests). Gallery cavity and inhomogeneity or anisotropy of the medium account for these distortions.
AN EXAMPLE OF CHROMITE PROSPECTION BY MAGNETICS*
Authors: BOSUM W. 
Published: April 2006

AbstractResults of rock magnetic investigations and magnetic field measurements in the Logar Valley, Afghanistan, are presented. Rock magnetic investigations on samples of the ore and the country rock have demonstrated that the chromite is strongly magnetic, whereas the country rock has proved predominantly non‐magnetic, partly weakly magnetic. The isanomalic maps show strong anomalies of some 1000 γ above the known chromite occurrences. Anomalies of the country rock amounting to some 100 γ have been observed only above basic dikes. The measured anomalies have been interpreted quantitatively by 2‐ and 3‐dimensional models. This interpretation is demonstrated and the question of chromite detection discussed. Model graphs are used to investigate in detail whether the extension in depth of ore bodies can be estimated.