bluuebunny/crossref_metadata_2025_split huggingface dataset:
INTERPRETATION QUANTITATIVE EN GRAVIMETRIE OU MAGNETISME A PARTIR DE CARTES TRANSFORMEES DE GRADIENT VERTICAL*
Authors: GERARD A. , GRIVEAU P. 
Published: April 2006

AbstractA discussion is given of the requirements, the advantages and the methods to be considered in attempting the quantitative interpretation of gravity or magnetic fields from computed maps of the vertically derived field.The transform which is used here is the first vertical derivative (or vertical gradient) with or without downward continuation, but the computed maps are in fact obtained by a controllable Fourier method in which two kinds of operations can be simultaneously performed in complete independance: on one hand the separation of any part of the data by frequency cut‐off, and on the other hand the transformation by vertical derivation or continuation of the part which is retained.Taking as raw data either actual surveys or artificially constructed maps, it is first shown how separated and transformed maps of this type can be efficiently obtained under quite flexible conditions, using a special computer program. It is further seen that for correctly controlled filterings the accuracy of the computed maps actually permits to take them as the basis for quantitative interpretation.To effect this, any one of the conventional methods which make use of equivalent model computations may in the first place be adapted to the interpretation of gradients, with the benefits, however, of an enhanced lateral separation of the anomalies and of a large attenuation of the regional effects.Particularly, the delineation of horizontal contours for even fairly complex models can often be made directly in a sufficiently safe way on the anomalies as they show on the vertical gradient maps. This greatly accelerates the process of determining equivalent model bodies.More special methods of interpretation can also be designed by taking into account first the fact that the vertical derivation of the field amounts to an operation of separation on the field's sources themselves, and in addition the availability of the frequency form of the information as a result of using a Fourier method of transform computation.Trial utilisations of various such interpretation processes of either the conventional or the less conventional type, are presented especially in connection with an interpretation study on transformed maps of parts of an offshore aeromagnetic survey (English Channel).
ANALYSE SEQUENTIELLE*
Authors: BOIS P. 
Published: April 2006

AbstractVarious authors have recently studied the Walsh and Hadamard transforms for functions with one or two variables. Like the Fourier transform they may be obtained by using the Cooley‐Tukey algorithm. They can be calculated all the faster because Walsh functions have only values equal to + 1 or − 1. The complex number multiplications in the Fourier transform are replaced by additions and subtractions of real numbers.These transforms are more general than that of Fourier because the concept of sequency, i.e. the mean number of zeros per time unit, is substituted for that of frequency.These transforms already have numerous applications to signal transmission. We describe some in the field of seismic prospecting, in particular the compression of the information contained in seismic traces.
DIGITAL PROCESSING OF REFRACTION DATA STUDY OF FIRST ARRIVALS*
Authors: PERALDI R. , CLEMENT A. 
Published: April 2006

AbstractIt has been necessary to resort to the use of “long‐line” refraction marine operations in certain areas where it proved impossible to eliminate singing from reflection records despite the number and variety of programs at our disposal for this purpose.Experience has shown that manual processing of offshore refraction records takes a disproportionate length of time in comparison with the surveys themselves, and this is incompatible with the requirements for choosing the site of an exploration well. It thus became necessary to find an “industrial approach” to the solution of this processing problem.It was apparent that automatic picking could also facilitate the interpretation of land refraction data, and that in the case of both marine and land work the interpretations would be more accurate when factors were taken into account which could not be considered when working without the aid of a digital computer.For these reasons a set of programs was developed for automatic picking and interpretation of refracted arrivals.The picking itself consists in searching for the maximum values of the normalized cross‐correlation functions of the traces with a “model” trace. The first results thus supplied are: “picked” times, intercept times, maximum values of the correlations, and the values of the tie constants between overlapping spreads.Next, the construction of the relative intercept time curves is performed; a statistical analysis of these curves then allows the determination of the offset distance.From these elements,⊙ either the delay time curve is produced, after ensuring correct reciprocal times by means of additional minor corrections.Such work is carried out in order to enable the geophysicist to gain a sound idea of the quality of the interpretation. To assist in this aim, part of the trace on both sides of the pick is plotted on the final documents. Valid groupings of several traces involving the same amount of refraction data are thus possible.⊙ or the refractor depth is constructed with the wavefront method, making use of the relative intercept times.Such a procedure, which is normally applied to first breaks, can also be used for later arrivals exhibiting slight interference and should represent an important step towards processing secondary arrivals with high interference.The development of this package, in response to a need which is shared by both SNPA and CGG, is the result of the joint efforts of the Geophysical Group of SNPA's Pau Research Center and CGG's Technical and Scientific Departments.
AN INTERPRETATION THEORY FOR INDUCED POLARIZATION VERTICAL SOUNDINGS (TIME‐DOMAIN)*
Authors: PATELLA D. 
Published: April 2006

AbstractIn this paper it is shown how one may obtain a generalized Ohm's law which relates the induced polarization electric field to the steady‐state current density through the introduction of a fictitious resistivity defined as the product of the chargeability and the resistivity of a given medium.The potential generated by the induced polarization is calculated at any point in a layered earth by the same procedure as used for calculating the potential due to a point source of direct current.On the basis of the definition of the apparent chargeability ma, the expressions of ma for different stratigraphie situations are obtained, provided the IP measurements are carried out on surface with an appropriate AMNB array. These expressions may be used to plot master curves for IP vertical soundings.Finally some field experiments over sedimentary formations and the quantitative interpretation procedure are reported.
COMPARISON OF TIME, FREQUENCY, AND PHASE MEASUREMENTS IN INDUCED POLARIZATION*
Authors: ZONGE K. L. , SAUCK W. A. , SUMNER J. S. 
Published: April 2006

AbstractIn comparing the similarity between time, frequency, and phase measurements as used in the induced polarization method of geophysical prospecting, parameters must first be defined and the basis for comparison established. The conditions for mathematical equivalence then follow in a natural sequence. Laboratory measurements are made on a variety of rock samples to indicate the type of comparison and correlation expected from field measurements.Results indicate that frequency domain and phase measurements are equivalent, but two frequency domain measurements are needed to produce the same amount of polarization information as a single phase measurement. Frequency and time domain measurements will be similar but never equivalent due to the basic differences in their respective parameter definitions.
INFLUENCE OF NUMBER AND SPACING OF SENSORS ON THE EFFECTIVENESS OF SEISMIC ARRAYS*
Authors: HARTENBERGER R. A. , Van NOSTRAND R. G. 
Published: April 2006

RésuméDe préférence, les sismographes seront disposés dans un lieu sans bruit, oú il n'y aurait pas besoin de patternes. Par contre, si les bruits sont tels qu'une patterne est nécessaire, l'objectif de la patterne est d'améliorer le rapport signal/bruit et donc de rendre le signal le plus utile possible. La patterne sera dessinée en fonction des charactéristiques du signal, des charactéristiques du bruit, et de la géologie du site.Il a été démontré que, dans le sens pratique, l'opération optimum sur les données d'une patterne est représentée par le proces “delai et somme”. L'augmentation du nombre N de senseurs sur une surface donnée diminue les espacements entre les senseurs et peut augmenter la coherence entre les bruits enrigistrés aux senseurs voisins, donnant donc moins d'amélioration au rapport signal/bruit que la √N anticipée. L'augmentation du nombre de senseurs par l'augmentation proportionnelle de la surface de la patterne peut resulter en la détérioration du signal, et peut également donner moins d'amélioration que la √N Ces deux effets, ainsi que l'élément économique, combinent à limiter le nombre de senseurs qui peuvent être employés.Bien que les données sur lesquelles l'on a basé ces conclusions soient tirées de la sismologie conventionnelle, ces principes sont également valables pour l'exploration sismique et pour d'autres mesures géophysiques qui emploient des dispositifs dans lesquelles plusieurs senseurs sont requis.
IMPEDANCE OF A PLANE ELECTROMAGNETIC WAVE AT THE SURFACE OF A LAYERED CONDUCTING EARTH WITH DIPPING ANISOTROPY*
Authors: NEGI J. G. , SARAF P. D. 
Published: April 2006

AbstractThe problem of a plane wave incident on a non‐isotropic dipping layer lying over an isotropic conducting substratum has been studied and some numerical results are presented to show the effects of

degree of anisotropy m,
conductivity contrast between the substratum to the upper layer b,
angle of inclination of the axis of anisotropy α,

on the variation of amplitude and phase difference of the wave impedance with the normalized skin‐depth (d/δ1).
TRANSIENT ELECTROMAGNETIC RESPONSE NEAR A FAULT ZONE*
Authors: GEYER R. G. 
Published: April 2006

AbstractRecent improvements in instrumentation and field techniques have made time domain electromagnetic methods more acceptable. This acceptance has prompted further theoretical work for use in the interpretation of field data.The asymptotic solutions for the transient electromagnetic field components in the vicinity of a fault zone separating two media of high resistivity contrast are obtained for low frequency or late time. Excitation is by normally incident plane waves at the earth's surface. Because of the slow convergence of the asymptotic time series expansions, a numerical polygonal inversion is performed on the real part, or in‐phase term, of the time‐harmonic surface expressions for the electric and magnetic field components.For both impulsive and step excitation the transient electric field normal to the contact is more sensitive to changes in the structural attitude of the fault plane than the transient electric field parallel to the contact. The transient anomalous vertical magnetic field for either impulsive or step excitation appears to be most diagnostic of dip angle, although waveform shape does not seem to be significantly dependent on the slope of the fault. For dip angles greater than 90 degrees, as measured on the poorly conducting side of the contact, all field components become more insensitive as indicators of the structural attitude. The results presented here should be useful in obtaining several geologic parameters descriptive of a fault zone or lateral resistivity inhomogeneity from transient electromagnetic soundings; they should also provide an aid to differentiating with available geological information between layering effects on transient electromagnetic responses and effects largely due to lateral changes in resistivity.
A NEW ENERGY SOURCE FOR MARSH AREAS *
Authors: BADGER A. S. , GUNDLACH W. J. 
Published: April 2006

AbstractMany practical energy sources are available for land use and likewise a goodly number for marine operations. However, the transitional region between navigable water and negotiable land is poorly served. The vehicles that are capable of operating amphibiously are limited in the pay‐load they can transport, and in the bulk of apparatus that can be operated from the space available. The Flex‐O‐Gun (Trademark of Geo Space Corporation) is a new, lightweight gas exploder designed to meet the requirements for operation in rivers, bays, and marsh areas not generally accessible to the larger, heavier systems such as the Dinoseis (Trademark of Atlantic Richfield Company), Vibrator and Air Guns. Weighing less than 70 kilograms, the Flex‐O‐Gun requires only modest sources of oxygen and propane and the associated firing equipment for operation.The gun delivers energy by the sudden introduction into the water of high pressure gases resulting from detonation. The device is unique in that the underwater gun assembly contains no gas mixing or firing elements. A flexible, metallic hose conveys the charge of mixed gases and subsequent detonating flame to the gun from control and firing mechanisms located above the surface. With its small weight and total space requirements, the Flex‐O‐Gun can be operated from small boats, buggies, or trucks, and is easily transported.In this paper the features of the gun are described and the results given of tests of its operations. An implanting device is also discussed which extends its application to viscous formations. The device employs water jets mounted below the gun to wash down a hole and insure placement of the gun at depths to obtain maximum energy output.
SEISMIC REFRACTION ON CONTINENTAL SHELVES WITH DETECTORS ON SEA FLOOR *
Authors: AVEDIK F. , RENARD V. 
Published: April 2006

AbstractSeismic refraction at sea and on continental shelves requires most of all a precise positioning of the shooting and receiving stations and a good signal to noise ratio.A new system has been developed using detectors anchored on the sea floor and radio transmission of signal for refraction work on continental shelves. This technique satisfies both requirements. The system has been tested in the western Channel in December 1971.
ELECTROMETRIC OBSERVATIONS OF ANTIFILTRATIONAL CEMENTATION CURTAINS *
Authors: BOGOSLOVSKY V. A. , OGILVY A. A. 
Published: April 2006

AbstractCreation of antifiltrational cementation curtains needed to prevent increased seepage from water reservoirs is a rather labour‐consuming and costly measure. High cost of such curtains necessitates careful checking of the quality of cementation as well as the strength and stability of the solidified cement which is being formed in the pores and fissures of injected rocks.The traditional methods of control are rather labour‐consuming and do not allow observations during process of cementation. The advantage of electrometric observations of cementation curtains lies in the possibility of making measurements on the surface from the moment of pumping slurry into a borehole up to the termination of cement hardening.The laboratory investigations carried out by the authors demonstrate an increase in the specific electrical resistivity of a cement in the course of hardening as well as the existence of a functional dependence between the electrical and strength parameters which allows to use the resistivity method for checking the cement strength.Methods of electrometric observations of cementation curtains are dependent on the particular features of cementation and the curtain dimensions. The observations are usually conducted in a network of profiles parallel to the curtain axis. The cement slurry spreading in the space is studied on the maps of ρa and geoelectrical sections obtained at different distances from the feed line. Zones of the strongest absorption of cement slurry are indicated by resistivity minima. The electrometric observations should be compared with the data on cement expenditure in the boreholes.The cement strengthening is monitored by comparing the results of control observations consecutively conducted in 1‐2 months following the cementation, with utilization of the ρa maps and graphs. If the specific resistivities of the skeleton of the enclosing rocks and the filler of cavities are known, one can approximately evaluate the changes in the cement strength in absolute units (kg/cm2).By way of example, the authors give the results of electrometric observations conducted to evaluate the quality of an antifiltrational curtain on one of the high‐mountain water reservoirs in Armenia.
THREE‐DIMENSIONAL SEISMIC MODELING FOR ARBITRARY VELOCITY DISTRIBUTIONS *
Authors: DOBECKI T. L. 
Published: April 2006

AbstractThe growing awareness of the significance of three‐dimensional interpretation of seismic reflection data carries with it a need for better understanding of the role of the velocity configuration in the production of reflection patterns. Modeling the reflection responses of a simple dipping plane reflector through velocity models of various degrees of complexity demonstrates the importance of overlying velocities in determining the reflection pattern.Modeling is accomplished using a raytracing technique which determines total travel time of the normal incidence raypath through an arbitrary iso‐velocity layer model.
A STUDY ON THE DIRECT INTERPRETATION OF DIPOLE SOUNDING RESISTIVITY MEASUREMENTS OVER LAYERED EARTH *
Authors: DAS BY U. C. , GHOSH D. P. 
Published: April 2006

AbstractDipole sounding resistivity measurements over layered earth can be interpreted directly by adapting the procedure given by Koefoed (1968) for Schlumberger system. To carry out the first step of the interpretation leading to the determination of the raised kernel function, partial resistivity functions for the dipole method are derived and given in the form of standard curves. The second step involving the derivation of layering parameters from the kernel being independent of the electrode configurations remains unaltered. The applicability and limitations of the method are discussed.
AN INTERPRETATION SYSTEM FOR GEO‐ELECTRICAL SOUNDING GRAPHS *
Authors: DEPPERMANN K. 
Published: April 2006

AbstractFor the two and three layer cases geo‐electrical sounding graphs can be rapidly and accurately evaluated by comparing them with an adequate set of standard model graphs. The variety of model graphs required is reasonably limited and the use of a computer is unnecessary for this type of interpretation.For more than three layers a compilation of model graphs is not possible, because the variety of curves required in practice increases immensely. To evaluate a measured graph under these conditions, a model graph is calculated by computer for an approximately calculated resistivity profile which is determined, for example, by means of the auxiliary point methods. This model graph is then compared with the measured curve, and from the deviation between the curves a new resistivity profile is derived, the model graph of which is calculated for another comparison procedure, etc. This type of interpretation, although exact, is very inconvenient and time‐consuming, because there is no simple method by which an improved resistivity profile can be derived from the deviations between a model graph and a measured graph.The aim of this paper is, on the one hand, to give a simple interpretation method, suitable for use during field work, for multi‐layer geo‐electrical sounding graphs, and, on the other hand, to indicate an automatic evaluation procedure based on these principles, suitable for use by digital computer.This interpretation system is based on the resolution of the kernel function of Stefanescu's integral into partial fractions. The system consists of a calculation method for an arbitrary multi‐layer case and a highly accurate approximation method for determining those partial fractions which are important for interpretation. The partial fractions are found by fitting three‐layer graphs to a measured curve. Using the roots and coefficients of these partial fractions and simple equations derived from the kernel function of Stefanescu's integral, the thicknesses and resistivities of layers may be directly calculated for successively increasing depths.The system also provides a simple method for the approximative construction of model graphs.
EXEMPLES D'APPLICATION DE TRAITEMENTS AUTOMATIQUES À L'INTERPRÉTATION DE SONDAGES ELECTRIQUES *
Authors: DUPRAT A. , GOLÉ F. , ROCROI J. P. 
Published: April 2006

RésuméIl est maintenant courant d'employer l'ordinateur pour interpréter les sondages électriques. Cependant, le problème à résoudre en prospection électrique n'admettant pas une solution unique, le but des traitements automatiques consiste simplement à fournir plusieurs hypothèses qui aident à bâtir une interprétation géologique des mesures géophysiques. C'est, d'ailleurs, ce qu'on recherche aussi par la comparaison visuelle des courbes de terrain avec des abaques précalculés. Mais, tandis que l'interprétation manuelle, pour conduire à des solutions qui respectent les mesures faites sur le terrain, exige un temps très long, le traitement automatique fournit immédiatement des solutions compatibles avec les courbes àétudier.Les procédés employés s'adaptent aux divers besoins de la prospection: ils peuvent traiter aussi bien la station isolée que les profils de sondages électriques. C'est ce qu'on se propose de montrer, à l'aide de quelques exemples tirés d'études récentes.
RESISTIVITY TYPE CURVES OVER OUTCROPPING VERTICAL DYKE—I *
Authors: KUMAR RAKESH 
Published: April 2006

AbstractThe theoretical horizontal resistivity profiles over an outcropping vertical dyke for various parameters‐electrode spacing, vein‐width and resistivity contrast—with inline alpha, beta and gamma‐Wenner electrode systems are described. The resistivity profiles present a most bewildering variety of shapes as compared to those in resistivity soundings. The analysis of type curves suggests suitable electrode configuration for detection of wide, moderately wide, and thin veins. The negative apparent resistivity values on the gamma anomalies for resistive vein over certain vein‐widths of higher positive values of resistivity reflection factor contradict the concept of apparent resistivity hitherto held.
RESISTIVITY TYPE CURVES OVER OUTCROPPING VERTICAL DYKE—II *
Authors: KUMAR RAKESH 
Published: April 2006

AbstractThe theoretical horizontal resistivity profiles Over an outcropping vertical dyke with two‐electrode and Schlumberger electrode systems are discussed. The two‐electrode array seems very useful in locating the highly conducting thick or thin vein, while the Schlumberger (gradient) array is suited to detect the conducting vein of low and moderately high resistivity contrast and as well as the resistive vein of all widths and resistivity contrasts. Besides, the inline gradient array has a distinction of establishing a clue to evaluate the resistivity contrast of the vein.