bluuebunny/crossref_metadata_2025_split huggingface dataset:
INTRODUCTION TO THE INTERPRETATION OF RESISTIVITY MEASUREMENTS FOR COMPLICATED STRUCTURAL CONDITIONS*
Authors: ALFANO L. 
Published: April 2006

AbstractA study is made of the possibility of calculating electric potentials, and therefore of interpreting apparent resistivity measurements, when the ground presents structural conditions more complicated than plane, parallel stratification.For this work a schematic type of structure has been chosen, in which the discontinuity planes for electric resistivity are both parallel and perpendicular to the level of the ground.The problem has been examinated in its general aspect, and then some criteria for the numerical calculation have been indicated.Some calculated examples are presented, relevant to vertical electric soundings accomplished by conventional technique, for particular types of structure.
SOME OBSERVATIONS OF GAMMA RADIATION EMITTED BY A MINERAL SPRING IN JAMAICA
Authors: VINCENZ S. A. 
Published: April 2006

AbstractThe decay rate of gamma radiation emitted by a Jamaican mineral spring was measured using portable rate meters. The results of these experiments, supported by auxiliary tests, suggested that the main radioelement causing the radioactivity was radon 222. Fluctuations in the intensity of the radiation were studied in situ. An inverse relation between the intensity and the discharge rate of water was established and the effect of rainfall and of earthquakes was investigated. Some suggestions are made concerning the possible source of radon.
A NEW DEVICE FOR SEISMIC SURVEY EQUIPMENT *
Authors: MERLINI E. 
Published: April 2006

AbstractIn the laboratories of the agip mineraria a new apparatus has been developed which, utilizing reflected energy collected by several groups of seismometers, provides on a single trace an indication of the total energy level. This indication is controled in time according to an exponential characteristic, thus compensating for the attenuation which is effected in the subsurface. The apparatus enables indications of successive energy levels to be obtained for different shots, thus furnishing a time section even during the routine field work.
ON THE IDENTIFICATION AND CONSTRUCTION OF REFLECTED REFRACTIONS *
Authors: BORTFELD R. , HÜRTGEN H. 
Published: April 2006

AbstractReflected refractions are considered as the limiting case for ordinary steeply dipping reflections. Particularly, reflected refractions may be constructed (migrated) according to the same principles as ordinary reflections. In view of the inherent inaccuracy of the velocity data, there is no discrimination between reflected refractions and other steep events by methods of construction. Velocity determinations from reflection data also show a continuous transition from steep reflections to reflected refractions. I.e., it is impossible to discriminate by seismic ray methods between reflected refractions and other steep events.If disturbing, steep events may be attenuated to a great extent by special shot and geophone set‐ups. Also in this connection it is unnecessary to distinguish between reflected refractions proper and steep reflections.It seems to be more rational to consider steep events as ordinary steep reflections in the beginning of a survey, because otherwise real structural indications might possibly be thrown away.
MEASUREMENTS OF AMPLITUDES OF REFLECTED SEISMIC WAVES*
Authors: KOEFOED O. 
Published: April 2006

AbstractMeasurements have been made of amplitudes of reflected seismic waves, in order to investigate their change as a function of the shotpoint‐seismometer distance and of the position of the reflection point. The change with shotpoint‐seismometer distance, after correction for geometrical divergence, was usually small. This indicates either a rather strong difference between the values of Poisson's ratio for adjacent strata, or, more likely, a rather small value of the absorption coefficient. In one instance a very strong increase in amplitude with shotpoint‐seismometer distance was observed. This may be attributed to incidence near the critical angle. In another instance a pronounced increase in amplitude with the position of the reflection point was observed over a very short distance. This may be due to an elongated depression of the reflecting boundary.
WELL SURVEYS AND THE CALIBRATION OF VELOCITY LOGS*
Authors: SCHWAETZER T. 
Published: April 2006

AbstractIn the last two years several double‐receiver Velocity Logs (V‐Logs) have come into service. Theoretically, in this type of log the effect of the travel time in the mud and in the invaded or altered formations, responsible for the “Lag” (or delay times) in single receiver V‐Logs, could be eliminated. Thus the integration of the interval times would give the “real” vertical time as a function of depth. In practice, several authors have already noted that even for V‐logs with two receivers the integrated times differ from the results of the conventional well surveys.We consider here some of the geometrical, geological and instrumental factors that affect the time measurement of double receiver Velocity Logs, as well as the possibility that the discrepancy between the V‐logs and the conventional well survey could in some cases be due to faults, dip, folding, or the intrusion of high velocity layers near the well. Some examples are given, and the question of the polarity of first arrivals in well surveys is discussed.At present the discrepancies between the integrated times of even double receiver V‐Logs and the results of the well surveys remain too great to permit us the economy of eliminating the well survey. Furthermore, for the study of these discrepancies we must continue to shoot a considerable number of calibration points. We have, however, succeeded in reducing greatly the cost of the conventional survey by reorganising our well shooting methods. These methods, as well as the problems of surface corrections and the choice of datum plane they entail, are discussed.
COMPARATIVE CONSIDERATIONS ON THE ENERGY CONTENT OF SEISMIC WAVES IN CENTRAL AND LINEAR PATTERN SHOOTING*
Authors: PIERAU H. , ROSENBACH O. 
Published: April 2006

AbstractIn continuation of a publication by Pierau and Mueller (1960), theoretical and experimental comparisons are made about the energy content of seismic waves for central and linear shotpoint arrangements. The following results are obtained:Using shotpoint arrangements as chosen for the investigation, the energy content of deep reflections is greater in linear than in central pattern shooting, provided that the total quantity of charge is the same in both cases. Furthermore the seismograms obtained with linear shotpoint arrays are less disturbed by surface waves than those obtained in central pattern shooting. Both effects are superimposed and improve considerably the signal‐to‐noise ratio, thus explaining the improvement in the quality of deep reflections by uniformly linear shotpoint arrangements.ZUSAMMENFASSUNGIn Fortführung einer Publikation von Pierau und Müller (1960) werden theoretische und experimentelle Vergleiche über den Energiegehalt seismischer Wellen bei Zentralund Reihenschüssen durchgeführt, die folgendes Ergebnís liefern:Bei den gewählten Anordnungen der Schussbohrungen und unter der Voraussetzung gleicher Gesamtladungen sind die tiefen Reflexionen beim Reihenschuss energiereicher als beim Zentralschuss. Ausserdem sind die Seismogramme von Reihenschüssen weniger durch Oberflächenwellen gestöit als diejenigen von Zentralschüssen. Beide Effekte zusammen verbessern wesentlich das Verhältnis von Nutz‐ zu Stör‐Energie und erklären die Verbesserung der Qualität tiefer Reflexionen durch gleichmässig lineare Anordnung der Schussbohrungen.
ON THE SOLUTION OF ONE DIMENSIONAL ELASTIC WAVE PROPAGATION PROBLEMS IN STRATIFIED MEDIA BY THE METHOD OF CHARACTERISTICS
Authors: BLACK M. C. , CARPENTER E. W. , SPENCER A. J. M. 
Published: April 2006

AbstractThis paper describes a numerical method of solution for wave propagation in a medium whose elastic parameters and density vary with depth in any specified way. Results for a simple two layer problem are given to illustrate the method, and the extension to problems of current geophysical interest is briefly discussed.
SISMOGRAMMES SYNTHETIQUES; POSSIBILITES, TECHNIQUES DE REALISATION ET LIMITATIONS*.
Authors: BOIS P. , CHAUVEAU J. , GRAU G. , LAVERGNE M. 
Published: April 2006

Abstract1°– Synthetic seismograms have been computed with and without multiples by exact and by approximate methods. By means of these seismograms, some studies have been made on the various multiple reflections, the character of the films, the effect of the surface in the formation of multiples, as well as on the shape of the pulse and the spectra of seismograms. Refraction synthetic seismograms have also been realized on schematic examples with fault and pinch‐out.2°– Various techniques for synthesizing seismograms are described which make use of analogue computing equipment such as a bar with variable diameter, or of digital computers. The orders of magnitude of the prices of these various methods are shown.3°– Some of the limitations are described which are imposed on synthetic seismograms by the hypotheses and the inaccuracies of our knowledge of the conditions which prevail underground.
Ľ ANALYSE DES FILMS REELS ET LEUR COMPARAISON AVEC LES FILMS SYNTETIQUES
Authors: DELAPLANCHE J. , LEDOUX Y. 
Published: April 2006

AbstractThe practical use of synthetic records involves previous studies on field records from an original point of view; these studies consist essentially in analysing and cancelling noise, in bringing out the form of pulses and the character of seismic events, in detecting multiple arrivals. Various tools have been tested for this purpose: high multiplicity shooting, analysis of conventional well velocity surveys, mixing or selecting traces, varied filters; all these operations are facilitated by the use of magnetic recording.After several examples of these methods are given, it is shown how the results of such studies can help to make and discuss synthetic records with and without multiples. The share of multiple events and their effect on the efficiency of the later comparisons are especially treated.The authors finally present some specific examples of successful comparisons between synthetic records and field records treated beforehand. They insist on the discrepancies and on the importance of finding their origin, for the most tangible results in seismic interpretation generally appear during the analysis of such discrepancies.
EXPERIMENTS WITH STATIC‐RESISTANT BLASTING CAPS*
Authors: BANVILLE J. H. , RICHARD H. 
Published: April 2006

AbstractPremature detonation of seismic blasting‐caps may be caused by the accumulation of an electrostatic charge. This is especially true in desert areas where there are many sandstorms.Two makes of static resistant cap have been tested in the laboratory and the results compared with those for non‐resistant caps made by the same manufacturers. The full results are given in the table, the breakdown voltage for the resistant caps is in the range 20–30,000 volts as compared with the range 10–15,000 volts for the ordinary cap.It is strongly recommended the static resistant caps should always be used and that experiments on premature detonation from this cause should bemade in the field.In January 1960, 20 crews in the Sahara used a total of 146,150 static‐resistant blasting caps.
DEVELOPMENT OF NEW TECHNIQUES APPLIED TO THE SEARCH FOR STRATIGRAPHIC TRAPS*
Authors: CARISSIMO L. , D'AGOSTINO O. 
Published: April 2006

AbstractThe “Summarizer” is a new device designed and manufactured by the Agip Mineraria Electronic Laboratories which gives an output which is a function of the total energy detected by the geophone spread. This paper gives some examples of its use in stratigraphic mapping.Test surveys have been carried out in an area of the Po basin where the formations show many facies variations. Three gas fields of known geological features were considered. The usefulness of various methods of representation was evaluated as well as the contribution given by the new device. It was noticed that the results given by the “Summarizer”, when added to those obtained by standard and “variable area” sections, supply the interpreter with new useful elements. Lateral facies variations between gravels and shales have been recognized and localized.
PROBLEMES POSES A LA SISMIQUE DANS LA REGION PARISIENNE*
Authors: MILLOUET J. 
Published: April 2006

AbstractSeismic work near Paris first began in 1954. Two major difficulties characteristic of this region rapidly appeared:

The existence of silicified limestone beds in the plateaus: these high‐velocity beds, hard to drill, make it difficult to obtain surface corrections and carry strong “ground‐roll” noise waves.
The feeble structural variations call for a very accurate control of time measurements.

Drilling difficulties, and the need to eliminate parasite waves, have led to the adoption of pattern shooting from hammer‐drilled holes.The most effective elimination of ground roll has been obtained by shooting with a lateral offset of 600 m. This method has made it possible to work in regions where originally no reflections could be obtained.The difficulty of obtaining surface corrections has induced us to shoot up‐hole velocity surveys in deep holes at particularly important points. This work is done by a special crew. At other shot points, surface corrections are calculated from structural maps of surface strata and from velocity‐depth curves. The accuracy of these corrections, checked by drilling and velocity surveys, appears sufficient.The determination of lateral velocity variations by surface velocity shooting (X2/T2) is not feasible in this part of the Paris basin, as the accuracy of this method is insufficient.The control of reflection times must take into account the deformation of the signal as a function of the type of recording equipment and filters used, and also the modifications of the character of the reflection due to lateral stratigraphic variations. These variations can be observed by comparing the different velocity logs.
PROPAGATION OF WAVES IN INHOMOGENEOUS MEDIA
Authors: SCHOLTE J. G. J. 
Published: April 2006

AbstractA method is developed for determining the propagation of a wave of arbitrary shape in an inhomogeneous medium in which both the density and the velocity change with depth according to an arbitrary continuous function. The solution is obtained by means of successive approximations. The successive terms in this approximation correspond to the direct wave, single reflections and multiple reflections of successive order. The general formulae are then applied to three particular types of transition layer.
DEEP ORE EXPLORATION BY ELECTRICAL METHODS
Authors: BRAEKKEN H. 
Published: April 2006

AbstractIt has been found that ore prospecting by suitable electromagnetic and electrical methods may under favourable conditions—such as occur in parts of Norway—be carried out to greater depths than have so far been realized. By 500 c.p.s. electromagnetic measurements at the surface there was located a deep ore body, occurring in the continuation of, but separate from, an old ore body, which had been worked down to its end at a depth of some 500 m. The new ore body, starting at a depth of some 700 m and continuing downward with a slightly more dipping axis, has been traced over a considerable distance by further electromagnetic measurements at the surface, with the energizing current led directly to the ore in drill holes. Possibilities, problems and further improvements in deep E.M. techniques of measurement and interpretation are discussed. By D.C. equipotential mapping at the surface, with the current led directly to the ore, the location and direction of the deep ore body was established in agreement with the electromagnetic findings. Problems and developments in deep Charged Potential prospecting and interpretation are discussed. By 500 c.p.s. electromagnetic and D.C. potential measurements in drill holes essential information has been achieved both in locating ore formations beside a drill hole and in deciding whether ore formations in different drill holes are connected or not.
ATTENUATION DES ONDES SISMIQUES DANS LES SOLIDES*
Authors: LOEB J. 
Published: April 2006

AbstractFor the propagation of acoustic waves in formations, laboratory experiments yield an expression of the form:
image

in which A is the amplitude (strain or stress) A
0 some constant coefficient x the coordinate according to which propagation takes placeα the attenuation coefficient C velocityω the angular frequency of sinusoidal oscillation.No analogy between this law and that of electromagnetic waves can be made, since:

coefficient α is not independent of frequency: its expression is α=Kω (K constant);
however, with present recording technique, no noticeable dispersion can be found.

The present paper shows how results are compatible if losses of energy are accounted for by a hysteresis phenomenon that is analyzed (see Figure). Stress T is in abscissae, and strain δu/δx, multiplied by a coefficient E′ characteristic of the elastic properties of the solid, is in ordinates. The horizontal part of the curve is θ. It is supposed that the absorption properties of the ground are given by some dimensionless coefficientλ=θ/T−Then one getsα=ωλ/4CIf λ≪ 1, we get the propagation law
image

An attenuation takes place without phase shift, and consequently without dispersion.The author reverts to the inapplicability of the superposition principle, and foresees theoretically, for instance, that a strain T′ cos ω′t, where T′ > T and ω′ > ω, can completely cancel coefficient α.
EXACT EXPRESSIONS FOR THE GRAVITATIONAL ATTRACTION OF A CIRCULAR LAMINA AT ALL POINTS OF SPACE AND OF A RIGHT CIRCULAR VERTICAL CYLINDER AT POINTS EXTERNAL TO IT
Authors: PARASNIS D. S. 
Published: April 2006

AbstractThe gravitational attraction of a circular lamina and a right circular vertical cylinder at any axial point can be found by elementary methods. The attraction at a point P off the axis is usually estimated as follows. The attraction of a lamina, with the axis through P, touching the given lamina externally is subtracted from the attraction of a coaxial lamina which encloses the given lamina. The result is multiplied by the ratio of the area of the given lamina to the area of the annulus. The attraction of the cylinder is estimated by a closely analogous method. The answer is, however, valid only if P is a distant point.As a step towards calculating exactly the attraction of the cylinder at all points of the space external to it, the corresponding problem for the lamina is dealt with first. It is shown that the anomaly can be expressed as an infinite series in even powers of the horizontal distance of P. The coefficients of the powers consist of exact algebraic expressions containing simple terms of the form (1 +χ2)−n−1/2. These coefficients are determined by exactly summing certain infinite series involving the derivatives of the Legendre polynomials of odd order. The method of summation is believed to be of interest also in other problems where Legendre polynomials are encountered.The attraction of the cylinder is calculated by appropriately integrating the expression for the attraction of a lamina.Numerical calculations show that the approximate method everywhere underestimates the gravity anomaly of the lamina as well as of the cylinder. The error at distances one to two times the radius is upto 20 % for the lamina and 8.5 % for an infinitely long cylinder.
MODEL EXPERIMENTS AND SURVEY RESULTS FROM A WING‐TIP‐MOUNTED ELECTROMAGNETIC PROSPECTING SYSTEM*
Authors: BOYD D. , ROBERTS B. C. 
Published: April 2006

AbstractModel experiments at a scale of 1:200 were carried out in order to assess the performance of an E. M. system which was rigidly mounted on the wingtips of an aircraft. The experiments were performed over model conductors of various sizes, shapes and resistivities. From the results the detectability of various natural‐sized conductors was calculated. The results obtained over an unmined massive sulphide body in Cyprus are shown and a comparison made with the model results.
APPROXIMATIONS TO THE REFLECTION AND TRANSMISSION COEFFICIENTS OF PLANE LONGITUDINAL AND TRANSVERSE WAVES*
Authors: BORTFELD R. 
Published: April 2006

AbstractThe reflection and transmission coefficients for vertical incidence can be very closely approximated by computing the direct‐reflected and the direct‐transmitted portion for transition layers, and letting the thickness approach zero. The same procedure can then be applied to the general case of oblique incidence, which yields approximate values of the respective coefficients, including those of the converted waves. The approximate values compare well with the exact values calculated by Muskat and Meres (1940).These approximations might be adequate for all cases occurring in reflection seismic prospecting. They can also be used, possibly even more profitably, for the derivation of some rules governing the reflection process. The influence of Poisson's ratio can be read more or less directly from the approximate formulas. All converted waves depend primarily on the ratio of the shear velocities.
THE SIGNIFICANCE OF DIFFRACTION IN THE INVESTIGATION OF FAULTS*
Authors: KREY THEODOR 
Published: April 2006

AbstractSeismic reflection records taken across faults frequently show an overlapping of reflections from the displaced blocks. It is demonstrated that diffraction of seismic waves is a cause and the effect may be used in interpretation. Overlapping is increased if a seismic profile crosses a fault at an acute angle. Plotted dips will be inaccurate unless diffraction is taken into account. Further, the diffraction oscillation pattern will also be obtained if a reflection horizon terminates for a reason other than faulting, for example, at a wedgeout or reef edge, or at a sudden change of facies. The facts developed are demonstrated by practical examples in which attention is directed to the approximations involved in plotting the boundaries of discontinuities.
DEVELOPMENTS IN MARINE GRAVITY SURVEYING*
Authors: HOFMAN B. J. 
Published: April 2006

AbstractA description is given of the development, during the previous fifteen years, of gravity surveying methods in marshlands and marine areas. The methods described include the use of marshbuggies, weasels, helicopters, tripods, diving bells and remote control instruments. Special emphasis is placed on remote control instruments and a brief description of their construction is given. Finally, the corrections involved in marine gravity surveying are discussed, and the costs of the several methods are compared.
TOOLS FOR TOMORROW'S GEOPHYSICS *
Authors: DOBRIN MILTON B. , WARD STANLEY H. 
Published: April 2006

AbstractThe introduction of methods for recording and processing field data in digital form on magnetic tape for subsequent processing on electronic computers will result in major improvements in geophysical prospecting techniques. This offers great advantages over analogue recording such as increased dynamic range, greater filter flexibility, more convenience in processing by correlation techniques, freedom from distortion and noise, better adaptability to automatic plotting and contouring, and greater suitability for inverse convolution procedures. Digitally recorded seismic signals can be reliably transmitted long distances by telephone circuits to central data processing centers. Electronic computers facilitate processing of gravity, magnetic, and other potential field data. Smoothing, residual, correlation, and derivative techniques for handling data in digital form can enhance speed and flexibility of processing.