bluuebunny/crossref_metadata_2025_split huggingface dataset:
UTILISATION PRATIQUE DES FILMS SYNTHETIQUES DANS LE SAHARA NORD*
Authors: LAHERRERE J. 
Published: April 2006

AbstractThe object of this paper is to present 19 synthetic records recorded on 12 wells in the North Sahara by different methods.A comparaison is made of the synthetic records obtained by different methods:by analogy: United Geophysical Corporation Seismograph Service Corporationby computation: Institut Français du Pétrole Compagnie Générale de GéophysiqueThe method originated by Mr Baranov of the C.G.G. is studied in two cross sections: the first on four wells in the Hassai‐Messaoud field and the second on eight wells in the Anngueur region. The influence of internal and surface multiples on the correlations is very important and explains the reasons for marked variations in the quality of reflections. The problem of the origin of the basis of the stratigraphic correlations furnished by the geologists can be a source of errors.Finally, the comparison between the synthetic and field records indicates that the best results are not always obtained with a synthetic record including multiples.In conclusion, on the North Sahara, where the importance of multiples is preponderant and not readily apparent, and where interpretation is primarily based on continuity, the study of synthetic records including multiples on all exploration wells would appear to be indispensable.
AN EXPLANATION FOR THE HIGH ULTRASONIC VELOCITY IN INDIAN ROCKS*
Authors: HAYAKAWA M. , BALAKRISHNA S. 
Published: April 2006

AbstractIt has been observed in the course of a detailed investigation that Indian granites exhibit high ultrasonic velocities in contrast to the specimens obtained from other countries. An attempt has been made in this paper to offer an explanation of this peculiar behaviour. Firstly, the initial internal pressure and initial velocity at the time of formation of rocks are calculated by using the experimental results for the changes in velocity with pressure in Indian, American, Japanese and Russian rocks. Besides this, standard curves have been computed using the above named parameters. Also, their possible influence on the high velocity values of Indian rocks, even under atmospheric conditions is studied. The effect of time of the formation of rocks at specific depths is also calculated in detail. As one of the results of this investigation, it comes out that under high pressure (deeper depths) it requires longer time to complete the processes of formation of rocks than under low pressure (shallow depths) and under high pressure a lot of stress energy can be stored i.e., the initial velocity becomes high when the rock is formed at great depths while at shallow depths a less stress energy can be stored and consequently less velocity values. Thus the combined effect of time and physical conditions at the time of formation of rock on the velocity in the rock at a given time is investigated. It can be seen here that the elastic behaviour of rocks with pressure will provide a clue to the possible petrogenetic history and also the approximate age of the rock.
VERSUCHE ZUR AUSNUTZUNG VAGABUNDIERENDER STRÖME IN DER GEOPHYSIKALISCHEN PROSPEKTION.*
Authors: PORSTENDORFER G. 
Published: April 2006

AbstractThe experimental recording of the three components of the diurnal intensity of the stray currents in a mine shaft outside the region of mining activity of Freiberg has shown the uninterrupted presence of these currents with periods ranging from a few minutes to a few hours. It is demonstrated from theory and by model experiments that prospection by stray currents, utilizing telluric measuring methods, is feasible when the ratio between the distance to the sources of the stray currents and the size of the surveyed area exceeds a limiting value which depends on the accuracy of the measurements. To obtain an economic procedure it is necessary to replace the classical telluric technique by a vectorial recording method.From a field example in the vein deposit of Freiberg it is shown that stray currents of arbitrary direction, and also telluric currents, are canalized by veins of anomalous conductivity. Other examples are given of underground measurements of stray currents, which were carried out for studying conductivity anomalies.
THE INFLUENCE OF SURFACE FORMATIONS ON THE APPARENT RESISTIVITY VALUES IN ELECTRICAL PROSPECTING*
Authors: ALFANO L. 
Published: April 2006

AbstractThis second part deals with a subject analogous to the one developed in the first part, but related to surface irregularities with a non‐cylindrical structure. In this part we have taken into consideration both the effects due to potential electrodes and the effects due to current electrodes.The study of these cases has been made with the help of mathematical theory, but it has been necessary to extend this theory from the case of cylindrical bodies to the case of non‐cylindrical ones.Finally, as conclusion to both parts of the paper, some pages have been dedicated to the details of the calculation procedure, in order to demonstrate its practical htness for the study of this problem.
A DISCUSSION ON THE NATURE AND MAGNITUDE OF ELASTIC ABSORBTION IN SEISMIC PROSPECTING*
Authors: O'BRIEN P. N. S. 
Published: April 2006

AbstractLaboratory measurements indicate that seismic absorbtion in sedimentary rocks lies in the range 0.1 to 1.0 decibel per wavelength. Field measurements on the amplitude attenuation of direct, reflected and refracted pulses give values consistent with this.If the absorption is linear, dispersion must occur. If it occurs field measurements show that it must be less than 1% over the frequency range 20 c/s to 20 kc/s.Seismic pulses broaden so slowly with distance that, if the absorbtion is linear it must be less than that measured in the laboratory by a factor of at least ten. This is inconsistent with the amplitude measurements and would mean that emplaced rocks are more perfectly elastic than steel.Seismic absorbtion must therefore be non‐linear. It is assumed that, for large values of Q, the non‐linear equation of motion may be linearised (Knopoff and MacDonald, 1958) and Fourier synthesis used. If this is valid, then the attenuation per unit distance must be practically independent of frequency and dispersion must be negligible.Whatever mechanism is acting it must produce an attenuation of roughly one decibel per 1000 feet and a pulse broadening of about 1–2% in the same distance.It is extremely desirable to make more field and laboratory experiments to determine the physical mechanism by which absorbtion takes place.
CORRELATION A DISTANCE CONSTANTE EN SISMIQUE REFRACTION*
Authors: CLÉMENT A. , LAYAT C. 
Published: April 2006

The usual computation methods in refraction seismic in the Sahara often involve considerable shot distances. Therefore, in addition to a high consumption of explosives, difficulties of operation and interpretation arise.In order to cut down the shot distances, it was necessary to study with great care the refracted waves having the shortest possible traveling path along the marker. Such paths correspond to the zone of great relative energy resulting, on one hand, from the sudden increase of reflected energy beyond the critical angle (total reflection) and, on the other hand, from the sudden appearance of refracted energy. The proposed method is founded on correlations of traces located in this “critical zone” on the different records shot on a profile; in order to get around certain difficulties due to insufficient knowledge of the marker velocity, the interpreter is led to select a constant correlation distance, at least for sections of the profile.The paper describes in detail the setting up and utilization of the proposed method, analyses a few examples and gives an estimate of the advantages and the restrictions of this method.
ETUDE DES DIAPIRS EN ALSACE ET BADEN‐WURTEMBERG PAR LA METHODE DU RECTANGLE DE RESISTIVITE*
Authors: BREUSSE J. J. , ASTIER J.‐L. 
Published: April 2006

AbstractThe study of tectonics of salt and of diapirs in particular is an important problem in the mining field as well as in that of petroleum exploration. This paper describes surveys that were carried out, using the method of the rectangle of resistivities.After stating the principle of the method, the way it is carried out and its advantages, three examples are discussed: two in the Alsace plain (Hettenschlag‐Oberentzen and Blodelsheim), the third in Baden‐Wurtemberg (Weinstetten‐Heitersheim). Geological conditions are practically the same (resistive alluvia, very conductive marls and resistive salt series); the depth at which the top of the salt was found varied from 100 meters to more than 1000 meters. Maps of resistivities (with current electrode spacing of 6000 meters) and graphs of a few electrical soundings are presented, together with the results obtained under the form of isobath maps of the top of the salt series.The surveys lasted 26 months and covered 171 square kilometers. The work presented corresponds to three sections totalling 93 square kilometers and was chosen because of the diversity of the tectonics. Four drill holes have been carried out since then and have confirmed the results quite well.The method may be extended to the survey of the tectonics of a salt series or of a resistive substratum, for instance a limestone formation, that are deeper than the above cases (2000 meters or more), using current electrode spacing of 20 kilometers. Surveys of this type have already been realized in the field.
ETUDE STATISTIQUE DE SISMOGRAMMES*
Authors: AGARD J. , GRAU G. 
Published: April 2006

AbstractThe amplitudes of reflection coefficients as computed from well velocity logs are distributed according to approximately normal laws. The distribution in time of the reflection coefficients, the absolute value of which is greater than a certain threshold, is Poissonian. The amplitudes of real seismogram traces obey a normal law.The autocorrelation of a seismic trace is usually quite different from the autocorrelation of the corresponding impulse.
NOMOGRAMS FOR DETERMINING MAXIMUM ERRORS AND LIMITING CONDITIONS IN SEISMIC REFRACTION SURVEY WITH A BLIND‐ZONE PROBLEM
Authors: HAWKINS L. V. , MAGGS D. 
Published: April 2006

AbstractNomograms are presented for the determination of the blind‐zone in seismic refraction surveys. The nomograms are calculated for the case where an intermediate velocity is assumed within the blindzone of a recorded refractor which is overlain by a single recorded layer. The nomograms may be used with time‐term or critical distance calculations and yield the depth to the top of the blind‐zone, the thickness of the blind‐zone, and the corrected depth to the recorded refractor. These values represent the maximum or limiting conditions for a layer of the assumed velocity within the blind‐zone.
MESURES D'AMPLITUDE DES ONDES ULTRASONIQUES DANS LES SONDAGES*
Authors: MORLET J. , SCHWAETZER T. 
Published: April 2006

AbstractSince 1955, the continuous velocity measurements in bore holes, made with one, later with more receivers, have become indispensable for the geophysicist, and can be useful to the geologist and the production engineer. From the beginning we have found that the amplitudes of the signals received vary in the course of a single operation. The variations have for a long time been considered as a disturbing phenomenon. It was tried to suppress them by changing the instrument gain.With increasing precision of the velocity measurements we have sometimes observed anomalies that were hard to explain, discrepancies between the continuous velocity logs and the conventional well velocity survey, as well as between continuous velocity measurements made with different spacings. These phenomena could be observed in cased as well as in uncased holes. The first attempts to explain these phenomena by considering the velocities only, did not lead to an acceptable theory. A further study of these anomalies of the continuous velocity log has shown that in reality they were caused by strong variations of the amplitude which affected the velocity measurements. This result has led us to study the amplitude variations in open as well as in cased holes.Up to now, the characteristics of the apparatus used in France and in the Sahara have permitted amplitude measurements with a single receiver only. In addition to the “cement bond log” in cased holes, it seems that in open holes correlations can be observed between the measured amplitude and a) the lithology; b) the fluid contained in the pores; c) the continuity of the matrix or, conversely, the permeability. However, it is now certain that numerous factors affect the amplitudes of the signals simultaneously.In order to study the attenuation of ultrasonic waves in the different formations traversed by a deep well, we have studied the deformations of the signal in the course of its path in the mud and in the formation, restricting ourselves to the P waves. The factors to be taken in consideration are: a) the geometric energy dispersion, inversely proportional to the square of the distance from the source; b) attenuation by absorption and scattering in the mud and in the formation; c) the transmission coefficients at the transition from mud to formation and conversely, as well as at the transition between two formations having different velocities; d) phenomena of signal composition that are due to the fact that the receivers and the transmitters have a non‐infinitesimal length; these last mentioned phenomena have considerable influenc eon the amplitudes of the received signals.Finally, the practical method for obtaining an attenuation log in an open hole requires the measurement of the ratio of the amplitudes of the first arrivals at the two receivers. Some examples show the importance of amplitude measurements made with two receivers.
MODIFIED TRIPOTENTIAL PROSPECTING METHOD*
Authors: SARMA V. V. JAGANNADHA 
Published: April 2006

AbstractA modification to the tripotential method of Carpenter (1955) and Carpenter and Haberjam (1956) is suggested and its theoretical implications and practical advantages are discussed. A specially designed switchbox is described which enables model tank experiments to be made with the modified tripotential method and with conventional methods. The results broadly show that a horizontal distance of the configuration at which the γ—resistance becomes negative directly corresponds to the depth to the interface. Discrepancies between the observed and actual depths are due to the bottom and wall effects of the wooden tank.
EXPERIENCE WITH THE REFLECTION SEISMOGRAPH IN A MINE WITHIN A SALT‐PLUG *
Authors: WACHSMUTH GÜNTHER , SCHMIDT EDGAR 
Published: April 2006

AbstractTechnical development and the introduction of new construction procedures has increased the number of seismic surveys carried out underground. Interesting seismic records in three components are shown and discussed. A vertical section containing results of seismic research investigations and of drilling is shown.
REFLECTION AND REFRACTION OF SPHERICAL COMPRESSIONAL WAVES AT ARBITRARY PLANE INTERFACES *
Authors: BORTFELD R. 
Published: April 2006

AbstractThe exact expressions for the reflection and refraction of homogeneous spherical compressional waves at the plane contact between two semi‐infinite media are obtained by a new simple method. Whilst its general ideas were outlined in a previous paper (Bortfeld 1962) dealing with some special interfaces, this method is now applied to all kinds of contact (solid‐solid, solid‐fluid, fluid‐solid, solid‐free, fluid‐fluid, fluid‐free). By some improvements, the treatment of the general case is even more simple than the previous one of the special cases.Integrating the potentials for sinusoidal excitation over the circular frequency and adding the static potentials yields expressions for the step‐response which consist of (infinite) single integrals of elementary functions. By a single application of Cauchy's theorem, the complete set of wavefronts is obtained and the step‐response is put into forms suitable as a basis for numerical calculations. The responses for arbitrary source excitations are given in the usual way by superposition integrals.
SIMPLIFIED GRAVITY TERRAIN CORRECTIONS*
Authors: WINKLER H. A. 
Published: April 2006

AbstractThe method of Far Terrain Corrections is described which permits contouring of terrain effects for distant topography; near terrain effects must be computed separately.The method is only slightly less accurate than standard graphical techniques and saves computing time. It is most useful in medium size surveys involving 100 to 2,000 observation points where the application of electronic computers is uneconomic.
AIR WAVES IN ENGINEERING SEISMOLOGY
Authors: MOONEY HAROLD M. , KAASA ROBERT A. 
Published: April 2006

AbstractCertain travel time readings in shallow engineering seismology can be attributed to a seismic wave which has propagated through the air, but in which the energy has been transmitted into the ground before reaching the detector. Waveform evidence for this conclusion is presented, based upon the effects of altering the source conditions to delay the direct wave and of embedding the geophone in sound‐absorbent material. Erroneously large depths may be computed if these air wave readings are interpreted as readings produced by direct waves through the ground. Potential difficulty exists only if velocity in the near‐surface material is less than 330 meters/second (1100 feet/second).
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: TALWANI MANIK 
Published: April 2006

AbstractParasnis' method of obtaining the gravity anomaly of circular laminae can in some cases lead to large errors. The use of the solid angle chart given by Nettleton (1942) is suggested instead.
EFFET DE LA VITESSE ET DE LA CONSTANTE D'INTÉGRATION SUR LA FORME DES ANOMALIES AÉRORADIOMÉTRIQUES*
Authors: GIRET M. R. 
Published: April 2006

AbstractThe theoretical radiometric anomalies caused either by a pinpoint source or by a larger one, which could be detected 75 metres above the source by a mobile detector with a very low velocity and time constant, were treated by an analog simulator which gave the curves transformed by the effect of velocity and time constant. The characteristics of these curves are discussed.An actual airborne survey above a radioactive anomaly of small surface yielded results which are analyzed and compared with the previous theoretical data. The degree of agreement between theoretical and experimental results seems satisfactory.This study shows that the deformation of curves by velocity and time constant in most actual surveys is small enough when the product of velocity and time constant is less than 75 m for a flying altitude of 75 m.
A METHOD FOR QUANTITATIVE INTERPRETATION OF SELFPOTENTIAL MEASUREMENTS*
Authors: MEISER P. 
Published: April 2006

AbstractThe paper deals with the calculation of the potential distribution over various polarized bodies; the potential profiles are plotted on a double‐logarithmic net. For a quantitative evaluation the field graphs, plotted likewise in a logarithmic scale, are compared with model graphs. The method is explained by means of several examples, in which potential graphs of a single, as well as of several disturbing bodies lying close to each other, are interpreted. The practical examples have been derived from selfpotential measurements which were carried out above graphite deposits in the southern Bavarian woods.This method is generally valid for the interpretation of potential graphs of arbitrary dipoles. Therefore it can also be applied – in a slightly modified form – for the interpretation of magnetic measurements. An appropriate method of interpretation for this purpose is being prepared.
ELABORATION RAPIDE DE CARTES GRAVIMETRIQUES DEDUITES DE L'ANOMALIE DE BOUGUER A L'AIDE D'UNE CALCULATRICE ELECTRONIQUE*
Authors: LA PORTE M. 
Published: April 2006

AbstractA method is described in which various gravity maps (regional, residual, first and second derivatives, upward and downward continuation, etc….) may be quickly constructed, without manual plotting and visual interpolation, which are often a source of error. The coordinates and the g‐values (x, y and g) of the field stations are introduced into the electronic computer on perforated cards. The computations are carried out by means of a hexagonal network. The computed values and their respective positions on the network are plotted directly on a sheet of paper by the electronic computer. The map is obtained by assembling these sheets and contouring.
THE QUANTITATIVE RECORDING OF SEISMIC EVENTS WITH EXTREMELY LARGE AMPLITUDE VARIATIONS BY DISCONTINUOUS GAIN CONTROL*
Authors: ROSENBACH O. , SCHMITT O. , VEES R. 
Published: April 2006

AbstractA transistorized combination of multivibrators is described, by which the gain is set according to a time programme. This equipment allows quantitative recording of seismic events with extremely large amplitude variations. Some possible applications of this recording system to seismic research are discussed.
A STATISTICAL STUDY OF ISOSTASY*
Authors: NEIDELL NORMAN S. 
Published: April 2006

AbstractIsostasy was regarded as the impulse response to topographic loading, hence convolution with the topography should generate the observed gravity anomalies. Ordinate values of the impulse response were indeterminate but the zeroth, first and second moments were found to be significant. These could be interpreted as the degree of compensation, its spread, and the displacement with respect to the loading.
EVOLUTION DE L'ACTIVITE GEOPHYSIQUE DE SURFACE (PETROLE)*
Authors: DESAINT R. , RICHARD H. 
Published: April 2006

AbstractFrom data published in various journals, as for instance “Geophysics”, a lot of information can be gathered on the geophysical activity in the world. In this article the evolution of this activity is discussed, as far as it concerns the search for hydrocarbons.An interesting part of such a study consists of a comparison of the geophysical activity with the activity in drilling and the extent of the discovered reserves. In the USA in particular the amount of data available is sufficient to make a detailed analysis possible.
ETUDE STATISTIQUE DE LA CONTRIBUTION DES MULTIPLES AUX SISMOGRAMMES SYNTHETIQUES ET REELS*
Authors: BOIS P. , HEMON CH. 
Published: April 2006

RESUMEUne étude statistique par secteurs des coefficients de réflexion permet de préciser leur homogénéité et de donner des renseignements sur l'importance de la contribution des multiples et de l'atténuation due aux coefficients de transmission.Elle permet également de montrer que les multiples tendent à rendre normale la répartition des amplitudes des sismogrammes impulsionnels et que le filtrage par l'impulsion provoque le même phénomène sur les amplitudes des sismogrammes syntliétiques.
WAVE FRONT INVESTIGATIONS IN MODEL SEISsMOLOGY*
Authors: BERCKHEMER H. , ANSORGE J. 
Published: April 2006

AbstractA method is described which allows to measure the elastic wave motion in the “interior” of two‐dimensional solid models. It is based on the measurements of the lateral deformations of a plate that are related to the state of compression in the plane of the plate. A capacitive detector measuring the motion has been developed.Wave front studies have been carried out in a half space, in two half spaces in contact and in a single‐layered half space. The experimental results are compared with theory. Special attention has been paid to the head wave.