bluuebunny/crossref_metadata_2025_split huggingface dataset:
GEOELECTRIC EXPLORATION OF INCLINED THIN BEDS AND ORE VEINS*
Authors: ŠUMI F. 
Published: April 2006

ABSTRACTSThe equation for the deformation of the homogeneous electrical field caused by a long inclined thin plate, is given. By means of this equation a diagram is designed for the direct depth determination of the upper and the lower edge and for the inclination of the plate. The equation and the diagram are proved by small scale model measurements and applied in field exploration.
DESIGN PRINCIPLES FOR SEISMIC REFLECTION AMPLIFIERS*
Authors: HERMONT A. J. 
Published: April 2006

ABSTRACTDuring the last two years the Exploration and Production Research Laboratory, Shell Development Company, Houston, Texas, had occasion to evaluate a number of seismic amplifier channels submitted by various seismic contractors and manufacturers. From this study, material for the present paper has been collected.The modern trends to be found in the electrical design of up‐to‐date equipment are reviewed, and opinions of the E & P Research Laboratory, not necessarily shared by the industry, are expressed. No specific designs are mentioned, the material being presented in a general way.The over‐all elementary channel is discussed briefly and the various components are described functionally.Filtering is mentioned from a point of view of minimum requirements for an average reflection survey, and absolute sensitivity, minimum useful signal voltage from a geo‐phone, and noise are discussed.Gain control is treated in two regions–the automatic control region and the initial control region. For the former, static and dynamic control characteristics are discussed, and the factors influencing the control range are brought out. For the latter, it is pointed out when a system is said to require obligatory or optional initial suppression.Harmonic distortion, originating in the inductive components of the input circuit due to low‐frequency roller energy, is presented in a manner facilitating understanding of the distribution of low‐frequency filtering along the channel.
INTERPRETATION METHOD FOR WELL VELOCITY SURVEYS
Authors: WALLING DEAN , SAVIT CARL H. 
Published: April 2006

ABSTRACT“Cable” and other extraneous energy in well velocity surveys may be identified and distinguished from “formation” energy by using phase relationships. Conventional instruments with at least two different narrow band‐pass filters provide sufficient data to achieve good results even in the presence of extreme amounts of interference. The method is illustrated by laboratory tests and an actual well survey.
SUPERMULTIPLICATION DES CHARGES ET DES SISMOGRAPHES AU SAHARA (ZONE NORD)*
Authors: POMMIER GILBERT , RICHARD HENRI 
Published: April 2006

ABSTRACTIn desert countries, reflection seismic prospecting is often very difficult due to bad surface conditions, which adversely affect the quality of the reflections. From the beginning the Northern Sahara proved to be particularly unfavourable. In 1954 a series of systematic tests led to a shooting method which gave satisfactory results. This method used a high multiplicity of the shotholes (up to 100 per shotpoint) combined with a high multiplicity of geophones (up to, and sometimes more than 100 per trace). The method has proved effective and relatively economical to run since 1954. The evident conclusion is, that, under special conditions, high multiplicity may be very helpful in the future.
THEORETISGHE UNTERSUCHUNGEN ÜBER DEN EINFLUSS DER VERWITTERUNGSSCHICHT AUF DAS SPEKTRUM ELASTISCHER WELLEN IN DER REFLEXIONSSEISMIK
Authors: MENZEL HEINZ , ROSENBACH OTTO 
Published: April 2006

AbstractThe following assumptions are made in the mathematical treatment of the problem. Below a plane earth's surface there is a three‐layered elastic medium the interfaces of which are parallel to the earth's surface. The uppermost layer represents the weathered layer in which the velocity of propagation of seismic waves increases linearly with depth. The two lower layers, the so‐called intermediate layer and the substratum each have a constant velocity. The surface of the earth is acted on simultaneously by a normal pressure N in the form of a Heaviside pulse. The seismic wave thus generated is propagated through the elastic media.The aim of the investigation is to study the shape of the wave1) in the intermediate layer, after the wave has entered it the first time2) at the earth's surface, after the wave has been reflected once at the interface between the intermediate layer and the substratum.The mathematical solutions can in both cases be expressed as series of Bessel functions. Some numerical examples illustrate the quasi‐periodic nature of the solutions. The pseudo‐frequency is determined by the gradient of velocity in the uppermost layer; it assumes a value of approximately 50 c.p.s. for a gradient of appr.
ÉTUDE DES VITESSES DU KARROO À MADAGASCAR*
Authors: CHEREAU J. Y. 
Published: April 2006

AbstractThe Karroo of Madagascar is a thick continental deposit of sandstone with some shale, but no characteristic beds. Where it outcrops, velocities have been measured through bore hole surveys. It seems that they depend primarily on the age, but long refraction soundings show a progressive increase of the velocity with depth and a weak differentiation of the marker beds. These results may possibly be brought in accordance by discriminating between the present position and the deepest position of a bed through its geologic history. Thus we must admit very important erosions which, according to regional geologic data, seem possible. If we make the appropriate correction due to this distinction, all the velocity measurements fall near the curve proposed by Faust for an average shale and sand section.
SOME PRACTICAL RESULTS OF AIRBORNE ELECTROMAGNETIC PROSPECTING IN SWEDEN*
Authors: TÖRNQVIST G. 
Published: April 2006

AbstractIn 1956 a total profile length of about 10,000 kilometers was surveyed in Sweden by a new airborne electromagnetic method. The purpose of the survey was to direct ground parties to areas where conducting ore bodies (sulphides etc.) might be found and to eliminate barren ground. In this method an electromagnetic rotating field is used and the variations in both the real and imaginary components of the applied field are measured. The airborne work can be done with one plane towing a bird on a long cable or with two planes without cable connection. The two‐plane method has proved to have definite advantages over other methods, as shown by practical examples. The relation between the magnitude of the anomaly over background noise in relation to the flying altitude and the transmitter‐receiver distance is demonstrated, as well as different types of anomalies obtained. The use of this airborne method for the mapping of shallow structures in oil field terrains is discussed.The equipment for the ensuing electromagnetic ground investigations is briefly described and examples are given of anomalies obtained.
SOME MODEL EXPERIMENTS RELATING TO ELECTROMAGNETIC PROSPECTING WITH SPECIAL REFERENCE TO AIRBORNE WORK*
Authors: HEDSTRÖM E. H. , PARASNIS D. S. 
Published: April 2006

AbstractAfter a discussion of the underlying principles, some electromagnetic model experiments made primarily in connection with the development of the ABEM airborne method are described. The experiments were made on thin vertical and horizontal conductors of “infinite” extent with coil arrangements involving one transmitter and one receiver unit. The in‐phase and out‐of‐phase components of the field picked up by the receiver were measured in percent of the amplitude of the normal field at the receiver. In this case 1° phase‐shift corresponds to 1.75 % of the normal field amplitude. The experiments were made on a scale 600–2000 times smaller than the natural scale. The ores and overburdens normally encountered in the field were simulated by sheets of Cu, Al, Zn and Pb of varying thicknesses. The frequencies used were 500, 880 and 1500 c/s. The variation of the secondary fields with the thickness, resistivity and depths of the conductors causing them is discussed in some detail. The bearing of the laboratory work on ground and especially airborne electromagnetic methods is indicated. A few miscellaneous experiments are also described. The results of an airborne survey over a known ore body and those of the corresponding model experiments are given. The ABEM airborne electromagnetic method and the so‐called “Canadian” method are briefly compared in the light of the model experiments described.
SEISMIC MODEL EXPERIMENTS CONCERNING REFLECTED REFRACTIONS*
Authors: KOEFOED O. , VAN EWYK J. G. , BAKKER W. T. 
Published: April 2006

ABSTRACTSeismic model experiments are described in which long strips of plexiglass were used as models. One end of the strip was sawn off at an oblique angle and, at the opposite end, the strip was excited by means of a barium titanate transducer. The experiments showed that, if the width of the strip was sufficiently small, an anomalous reflection against the oblique end occurred which travelled in the longitudinal direction of the strip. This anomalous reflection did not occur when the width of the strip was large. These results are explained on the basis of Fresnel's theory. It is inferred that, in the subsurface, refracted waves may be reflected against fault planes without the law of reflection being satisfied, provided that the refracted wave is propagated in a sufficiently thin high velocity layer.
SYMPOSIUM ON CHANGES OF SHAPE OF SEISMIC PULSES*
Authors: ANSTEY N. A. 
Published: April 2006

ABSTRACTTheoretical work on seismic pulse propagation must, of necessity, use advanced mathematical methods. To the general reader these researches may seem far removed from the necessities of commercial geophysics; this paper attempts to show in non‐mathematical terms that the basic potential of the seismic method permits the obtaining of considerably more information than is currently expected, and that, of all the advances which are required to realise that potential, a knowledge of the laws governing the transmission of the seismic pulse is most desired.
ASPECTS THÉORIQUESIET PRATIQUES DE LA DÉTERMINATION DES VITESSES D'INTERVALLE EN SISMIQUE RÉFLEXION*
Authors: CHEREAU J. Y. , LEDOUX Y. 
Published: April 2006

AbstractConventional or continuous velocity logging generally fail to solve the problem of velocities in the whole area of a seismic survey. Surface measurements often bring a large amount of additional information: effect of shallow layers, change of facies, correlations. The authors present a theoretical view on the physical meaning of interval velocities. After a short synthesis of the diverse formulae formerly proposed (Faust, West), the practical manner of using these formulae and the accurate interpretation obtained with the help of geological and geophysical data are shown. Several characteristical examples are finally explained and commented on.
SOME DEPTH FORMULAE FOR LOCAL MAGNETIC AND GRAVITY ANOMALIES
Authors: SMITH R. A. 
Published: April 2006

AbstractSome mathematical inequalities are proved and their relevance to the interpretation of local magnetic and gravity anomalies is discussed. They can be applied to the readings of either a vertical magnetometer or a total field magnetometer or a gravimeter and yield a maximum possible value for the depth below the earth's surface of the top surface of the body producing the anomaly.
ON THE DETECTION OF A SPRING OF MINERAL WATER AT BAD PETERSTAL, SCHWARZWALD, AS A RESULT OF PREVIOUS CO2– MEASUREMENTS IN THE GROUND AIR
Authors: BUDDE E. 
Published: April 2006

AbstractIn nine small areas in the Black Forest measurements were made of the CO2 content of ground air, using a method which is based on the difference in heat conductivity between CO2 on one side and N2 and O2 on the other. Measurements during four days yielded four strong CO2 anomalies. At one of these a well was sunk, which gave a considerable discharge of mineral water.
SYMPOSIUM ON THE USE OF BOREHOLE DATA IN GEOPHYSICAL EXPLORATION*
Authors: LEVANTO A. E. 
Published: April 2006

AbstractA 3‐component flux gate magnetometer has been built for use in 1½ inch drill‐holes. It has an accuracy of 1 mgs. It requires 2–3 men to operate it and they can take measurements in up to 3 100 metre holes in one day. The instrument has definitely proved its worth in describing the‘general’ geology of an ore‐body, and it is now used on a routine basis.
ON ELASTIC SURFACE WAVES AT A CYLINDRICAL HOLE IN AN INFINITE SOLID*
Authors: STILKE G. 
Published: April 2006

AbstractSolutions for the propagation of elastic waves at the surface of a cylindrical hole of infinite length are derived from the wave equation for a perfectly elastic and isotropic medium. It is found that the phase and group velocities depend on the ratio between the wave length and the circumference of the cylindrical hole. These surface waves can be classified into different orders. They differ in the calculated dispersion curves, in the range of possible wave lengths (cut‐off‐frequencies), and in the amplitude proportion of the components of the displacement vector. For very short wave lengths these waves converge to normal Rayleigh waves.These results are used to explain some of the multiple onsets and disturbances on seismograms, obtained in practical seismic investigations in the mines of Siegerland.The conformity of theoretical and practical results is limited, because the idealised suppositions on which the computation is based, such as perfect elasticity, homogeneous and isotropic medium, and circular cross section of the mine gallery are met only approximately in practice.
IMPROVEMENT IN THE QUALITY OF DEEP REFLECTIONS BY UNIFORMLY LINEAR SHOTPOINT ARRAYS*
Authors: PIERAU H. , MULLER W. 
Published: April 2006

AbstractBy means of demonstration material, the author reports on the successful application of a shooting technique for seismic reflection operations, which has proved to work satisfactorily in those parts of the North‐West German prospective oil area which are unfavourable to reflections. The shooting technique is characterized by uniformly linear shotpoint arrangements which are parallel with the geophone spread and reach from one end of the spread to the opposite. All charges are detonated simultaneously.Technical details of the method are discussed, particularly the problem of the most favourable geophone spreads in continuous profiling as well as the position of the uphole geophone. The difference in quality of reflections obtained by the normal pattern shooting and the linear shotpoint arrangement is demonstrated by seismograms. The special problems involved in the interpretation of the seismic records are referred to.
AN EXAMPLE OF THE IMPORTANCE OF NATURAL REMANENT MAGNETIZATION IN THE INTERPRETATION OF MAGNETIC ANOMALIES
Authors: GIRDLER R. W. , PETER G. 
Published: April 2006

AbstractAn example is given from the Gulf of Aden of a total intensity magnetic anomaly which cannot be explained by a body assumed to be magnetized in the direction of the Earth's present magnetic field. It is enferred that the natural remanent magnetization is much greater than the induced magnetization and computations have been made which suggest the presence of igneous rocks with a reverse magnetization. The example illustrates that it is important to know the ratio of remanent to induced magnetization and the direction of remanent magnetization for the correct interpretation of magnetic anomalies.
DIRECTIONAL SCANNING WHEN PLAYING‐BACK SEISMIC MAGNETIC RECORDS*
Authors: SEELIS KARL‐HEINZ 
Published: April 2006

AbstractIn this paper we describe and give examples of procedures of magnetic playback which make it possible to emphasize particular reflections with respect to other reflections of differing step‐out. The procedure consists of 100% mixing between non‐adjacent channels, using either direct or, more frequently, reversed‐polarity mixing signals. This procedure allows the effective separation of differently inclined reflections.
PHENOMENES ANORMAUX EN SISMIQUE REFLEXION*
Authors: MICHON D. 
Published: April 2006

AbstractAbnormal phenomenons such as refractions and diffractions are more readily seen on cross‐sections produced in magnetic processing offices than on single records. The result is that the understanding of these phenomenons intervenes more and more in the interpretation of the data.Our purpose is to proceed here to a restatement of the geometric properties related to these phenomenons and to make an attempt to distinguish between what is useful for the interpretation and what is not.To begin with we shall call our attention on diffractions and refractions over faults permitting to recognize the faults or to precise them, then on diffractions caused by irregularities of the surface forming the common boundary of heterogeneous media (more or less deep erosion surface, basement rock, …). The following phenomenons are classified as parasites:

refractions following very shallow horizons, mostly related to topographic accidents,
diffractions on the upward path caused by shallow faults,
diffractions in the horizontal plane, found either in marine seismic or in case of heterogeneities “wrapt up” inside of an homogeneous overthrust.
ETUDE SUR MODELE ULTRASONIQUE DU PROBLEME DES COUCHES MINCES EN SISMIQUE REFRACTION
Authors: LAVERGNE M. 
Published: April 2006

AbstractDifficulties may arise in refraction seismic surveys in the case of thin layers.Seismograms have been realized by means of ultrasonic model techniques and have led to some results about the propagation of refracted waves along thin layers. The velocities of propagation have been determined as a function of the layer thickness.When the layer thickness is small compared to the wave length, it is shown that:— the velocities of propagation of refracted waves can be up to 6 % less than the velocities along thick layers.— the attenuation of amplitude with distance becomes large.— the determination of depth from measurements of delays gives doubtful results.Experiments have been run on two dimensional models but extension of the results to three dimensional cases is possible.
THE INDUCED POLARIZATION METHOD IN ORE INVESTIGATION*
Authors: ŠUMI F. 
Published: April 2006

AbstractThe method of induced polarization is being more and more used for sulphide ore exploration. The purpose of the present paper is to show that the decay‐time of the polarization curve represents a characteristic property of polarized media and consequently of various ores. The decay‐times for various minerals, determined by laboratory measurements, are given in table form. Although the intervals of the decay‐times partially overlap, the decay‐time does to a certain degree supplement the data of induced polarization. Further, a method of interpretation in cases in which there is a superposition of the polarization effects of bodies with different decay‐times, is discussed. Laboratory results as well as examples of field and bore hole measurements, in cases in which standard geophysical methods did not yield satisfactory results, are given.
ELIMINATION DE L'EFFET DES VAGABONDS INDUSTRIELS DANS UNE PROSPECTION PAR COURANTE TELLURIQUES*
Authors: KUNETZ G. 
Published: April 2006

AbstractSeveral methods for eliminating the effects of stray currents on telluric measurements are described.In the Lyon area the source of the stray currents is formed by the tramways of the city. Since Lyon receives no electric current from outside, its influence may be described as that of a conglomeration of dipoles. The law of decay with distance of a source of this type is derived. The constants which interverne in this law are determined experimentally from the observations close to the city, where the telluric field is small compared with that of the stray currents.In South Eastern France it is possible, under favourable conditions, to distinguish on the telluric registrations between the variations of the telluric field and those of the stray current field, due to a difference in character between the two. This permits an isocorrection line map to be drawn.In a survey in Morocco, a base net of telluric values was established by measurements during magnetic storms, when the activity of the telluric field is very strong and supersedes the stray currents. In the routine measurements only those events were utilised which tied in well with the base net.The method first mentioned is discussed in detail. Of the two others only the principles are indicated and some results shown.
THE VARIATION OF THE ELASTIC CONSTANTS OF ROCKS WITH FREQUENCY*
Authors: BRUCKSHAW J. M. , MAHANTA P. C. 
Published: April 2006

AbstractA method has been developed for the measurement, in the laboratory, of the variation of the elastic properties of rocks in the frequency range 40–120 cycles/sec. In addition, the observations yield information concerning the internal dissipation of energy over this range. A number of rock specimens have been examined and the results are compared with those of other investigators.
LA “COUPE SISMIQUE VECTORIELLE”*
Authors: PICOU CLAUDE , UTZMANN RENE 
Published: April 2006

AbstractThe coefficient of resemblance is defined in the following way:Consider a group of four traces on a seismic record. For a given time t add the six products that can be formed by multiplication of the signal strengths recorded on two of these four traces. By doing this for all values of t, a new signal is obtained that can be smoothed by having it pass through an appropriate filter. The result of this smoothing procedure is called the smoothed coefficient of resemblance Γ.Instead of multiplying the signals of two traces at the same time t, the signal of the first trace can be taken at time t‐3θ/2, of the second trace at t‐θ/2, of the third trace at t+θ/2 and finally of the fourth trace at t+ 3θ/2. Thus coefficients of resemblance are obtained that depend on the dip θ.For each value of θ a plotting system is triggered when Γ has a maximum with respect to time. Then a vector is plotted having a thickness proportional to Γ and a dip determined by θ. If no optical mixing takes place, the vector covers just one trace of the new vectorial registration; in case of optical mixing the vector covers a number of these traces. All vectors belonging to a certain group of traces of the seismic record appear on one trace of the vectorial presentation, so one trace includes all values of θ.Alternatively the plotting can be triggered when the corresponding sum of the signals of the four traces passes through a maximum. In this latter case the triggering can be conditioned by the maxima of Γ.The article discusses the influence of:— the optical mixing,— the integration time determined by the band width of the smoothing filter,— the method of triggering,— the way the seismic traces that have to form a group are selected (electrical mixing).A consequence of the method is that both phase alignments and energy bursts have an influence on the vectorial registration.
EXACT SOLUTION OF THE REFLECTION AND REFRACTION OF ARBITRARY SPHERICAL COMPRESSIONAL WAVES AT LIQUID‐LIQUID INTERFACES AND AT SOLID‐SOLID INTERFACES WITH EQUAL SHEAR VELOCITIES AND EQUAL DENSITIES*
Authors: BORTFELD R. 
Published: April 2006

AbstractA new method of treating three‐dimensional elastic wave problems is described by applying it to the most simple case of the reflection and transmission of arbitrary homogeneous spherical compressional waves at plane liquid‐liquid interfaces. The case of plane solid‐solid interfaces with equal shear velocities and equal densities can be treated under the same heading.The step‐response is obtained from the expressions for sinusoidal source excitation by a simple direct integration. The solutions for arbitrary source excitations are given in the usual way by the superposition integral. The solutions are proved by inserting them into the differential equations, followed by an application of the uniqueness theorem. The method is simple; all stages of establishing the solution (with the exception of the proof) are carried through in detail.