bluuebunny/crossref_metadata_2025_split huggingface dataset:
CONTRIBUTION A L'ETUDE DE LA DEFORMATION DU SIGNAL SISMIQUE. ANALOGIES. FILTRAGE EQUIVALENT *
Authors: CHAUVEAU J. 
Published: April 2006

SommaireCette publication débute par un essai de synthèse détudes antérieures relatives à la déformation d'un signal sismique, — déformation imputable, soit à la propagation dans les couches superficielles et les niveaux de transition, soit aux réverbérations d'une couche d'eau.On montre comment un modèle analogique convenable permet d'obtenir directement les réflexions et les transmissions d'une couche où la vitesse n'est pas uniforme. Les résultats obtenus sont comparés aux solutions exactes des équations de propagation et aux solutions qui résultent d'un échantillonnage de la distribution des vitesses dans la couche. Les filtres équivalents, à la propagation d'une part, et à léchantillonnage d'autre part, sont déduits de ces comparaisons.
ELASTIC BEHAVIOUR OF ROCKS AT LOW FREQUENCIES
Authors: USHER M. J. 
Published: April 2006

AbstractAn apparatus is described for the measurement of Young's modulus, E, and the energy loss per cycle, ΔW/W, of small beam‐shaped rock samples, over the frequency range 2 to 40 c/s. Results are given for seven sedimentary and two igneous types of rock. An increase of between 1 % and 3 % in E, and of up to 100 % in ΔW/W, occurred over this range. Experiments on rocks containing moisture showed a decrease in the magnitude of E (at 2 c/s), an increased frequency variation of E, and a greater and almost linear increase of ΔW/W with frequency. The effect of oil was similar except that the magnitude of E at 2 c/s was unaffected. It is suggested that the moisture and oil results are due to viscous movements of fluid through the pores in the rock, and that the changes in E and ΔW/W with frequency, in dry rocks, are due to a small viscous mechanism operative at low frequencies.
CONDITIONS D'EMPLOI DE LA GRAVIMETRIE EN EXPLORATION PETROLIERE*
Authors: CHEREAU J.‐Y. 
Published: April 2006

AbstractIn gravimetry the observer cannot exert any influence on the quantity he wants to measure, as he can in seismic exploration. This might easily tempt him to ascribe failures of the gravimetric method to natural causes outside his control.However, he keeps control of a sufficient number of factors to allow him to play a major part in a lot of cases. In this paper the conditions that govern the use of gravimetry are analyzed and subdivided into three classes, viz. natural, technical and economic conditions.
ÜBER DEN ZUSAMMENHANG ZWISCHEN SCHALLGESCHWINDIGKEIT UND POROSITÄT BEI ERDSCHICHTEN*
Authors: WACHHOLZ H. 
Published: April 2006

AbstractThere are various methods of measuring the porosity of rocks. The direct methods are based on the definition of the porosity ratio. The indirect procedures, which have often been adopted purely for economic reasons require interpretation methods that relate certain measured quantities to the porosity ratio.In the present article, the relationship between acoustic velocity and porosity will be examined. The interpretation method most commonly in use today is based on an approximative equation developed by Wyllie, Gregory and Gardner. This equation obtains the travel time of acoustic waves in a porous medium saturated with liquid by linear interpolation with respect to the porosity n between the travel time T0 in the compact medium (n= o) and the travel time T1 in the pure liquid (n= 1).As observed values of the travel time T differ from those that follow from this linear equation, it seems obvious to attempt a higher degree of approximation, e.g. by means of a polynomial of the third degree.Besides T0 and T1 other quantities are needed in order to obtain the coefficients of such a polynomial. These quantities must bear some relation to the physical constants of the rock. Only in the neighbourhood of n= o and n= 1 is it possible to make general statements concerning the behaviour of rocks and, in particular of the skeleton. Therefore, in the points n= o and n= i not only the values of the approximative function T=f(n) itself are given, but also those of its derivative with respect to n. The values of these derivatives ∂T/∂/Tn=0 and ∂T/∂/n‐1 depend on the properties of the material filling the pores and on data concerning the structure of the skeleton and the stresses in it. The considerations leading to a mathematical formulation of this dependence are dealt with in this article.The elastic constants of the skeleton were developed in Taylor series in n, that, for skeletons with low porosity were truncated after the linear term. The coefficients of n are functions of the constants of the material of the skeleton, the shape of the pores and the stresses in the skeleton. These functions were approximately computed for two limiting cases. For a more general application, it is useful to assume that these coefficients are the same for both Young's modulus and Poisson's ratio and then obtain the functional relation between the coefficient and the residual pressure from measurements performed in the laboratory with various kinds of rock. When this relation is established from such laboratory experiments, the cubic interpolation method can be applied.Whereas the linear interpolation method, as it has been in use up to now, presents a relation between porosity and acoustic velocity only, the cubic interpolation method makes it possible to determine the influence of pressure and the state of cementation of the rocks. Comparison with data obtained from direct measurements shows good agreement.
PRECISION DANS LES ETUDES MAGNETIQUES AERIENNES SON INCIDENCE SUR LA QUALITE DES RESULTATS*
Authors: GIRET RAOUL 
Published: April 2006

AbstractThe accuracy of an airborne magnetic survey is limited by the following factors:

Slow (diurnal) variations of the earth's field.
Fast variations of the earth's field (earth field “noise”).
Drift in measuring equipment.
Magnetometer “noise” (electronics, orientors …).
External disturbances, miscompensation.
Irregularities in flight altitude.
Location errors.

The relative importance of these different causes of errors is analyzed from two viewpoints:

Direct interpretation of anomalies on actual records,
Compilation of isogram maps and their quantitative interpretation (second derivative, reduction to the pole, …).

In conclusion, these errors do not affect the direct interpretation of profiles of standard quality. For instance, if the average altitude of the plane above the magnetic bodies is 1000 m, a variation of its flight level of about 100 m does not introduce serious errors in the interpretation.On the other hand, compilation of contoured isogam maps is often difficult, and compensation of the previous errors is not always possible except by approximate, rule‐of‐thumb methods. Furthermore, when the interval between lines is greater than the depth of magnetic masses below the plane of flight, the contours are interpolated and do not represent the magnetic field. Sometimes the contouring can offer different solutions, and the map is therefore not objective; this could then result in errors larger than those from the other causes.To evaluate the quality of the map and its interpretation we must know the location of flight lines and the compilation process employed. It is also wise to avoid quantitative interpretation of small anomalies and limit oneself to a qualitative interpretation.
A NOTE ON THE REFLECTION OF SEISMIC PULSES WITH APPLICATION TO SECOND EVENT REFRACTION SHOOTING*
Authors: O'BRIEN P. N. S. 
Published: April 2006

AbstractRichards (1961) and several others have shown that wide angle reflections may attain large amplitudes. This note extends the plane wave calculations of Richards to include the effect of the phase changes which occur at angles greater than critical. On seismic pulses this introduces a time lead of up to one half period and alters peak‐to‐peak amplitudes by up to 15‐20 %.It is pointed out that the plane wave reflection coefficient is not applicable at angles very close to critical where the true reflection coefficient is reduced by a factor depending on (R/λ) ¼ In ultrasonic experiments this factor reduced the reflection coefficient by between ½ and ⅓.Neither does the plane wave coefficient apply at grazing incidence, when it has to be reduced by a factor depending on (R/λ)1‐0.Graphs are given of the amplitudes of wide angle reflections and head waves for two cases and it is concluded that, except for shallow refractors and angles close to critical, the reflection is always significantly greater than the head wave.
LES FILTRES EN EVENTAIL*
Authors: FAIL J. P. , GRAU G. 
Published: April 2006

RESUMEOn étudie le principe de filtres séparateurs de vitesses apparentes ou filtres en éventail. L'opérateur de filtrage est déterminéà partir des caractéristiques spectrales bidimensionnelles (fréquence – nombre ?onde) de tels filtres.Les possibilités pratiques des filtres en éventail sont décrites en ce qui concerne l'amélioration du rapport signal/bruit. On évoque également les modifications éventuelles de la technique ?enregistrement sur le terrain qui pourraient être entraînées par l'utilisation systématique des filtres en éventail.
QUELQUES EXEMPLES D'ANALYSE D'ENREGISTREMENTS SISMIQUES*
Authors: KUNETZ G. 
Published: April 2006

RESUMECondition nécessaire et suffisante pour qu'un sismogramme obtenu à la surface ?un milieu stratifé puisse être considéré comme résultant de l'ensemble des réflexions, directes et multiples, subies par une onde plane de compression se propageant normalement aux strates, supposés parfaitement élastiques. Modification minimale à faire subir à un sismogramme donné pour qu'il satisfasse à cette condition.Possibilité, quand cette condition est satisfaite, de déduire du sismogramme la loi de variation de la vitesse des ondes élastiques dans le milieu considéré.Exposé détaillé du processus pratique sur un exemple et quelques autres résultats de son application.
SOME PHYSICAL ASPECTS OF SEISMIC SCALING LAWS FOR UNDERWATER EXPLOSIONS*
Authors: BURKHARDT H. 
Published: April 2006

AbstractThe paper deals with quantitative seismic measurements near underwater explosions. The blastings were carried out in an artificial small pond, the records were taken in adits, situated vertically below the charge. The range of charges extended from one detonator to 200 g of Ammon‐Gelit explosive.Conventional seismic scaling by comparing amplitude and size of charge does not yield a simple power law, the exponent being larger for smaller charges and vice versa. This result is due to the different frequency‐spectra of the seismic pulses, as shown by harmonic analysis. In contrast to this, the seismic energy as calculated from the records is directly proportional to the size of charge over the whole range.During the Lago Lagorai experiments in 1962 some quantitative seismic measurements near the shot point were also carried out. The relevant results are compared with the preceding ones and some differences are discussed.Some conclusions can be drawn:

The normal methodes, investigating the amplitude only, gives in many cases no clear description; this is especially true for nearby measurements with widely varying frequencies. Therefore it is suggested to extend conventional seismic scaling by including information on the frequency‐spectrum and the kinetic energy of the seismic signal.
In order to get clear experimental data for theoretical investigations, it is necessary to extend the recording over a half‐space, i.e. in adits or boreholes.
Influences of shape and size of the lake, in which the shots are fired, should be taken into account, too.
THE USE OF ISOCHRON CHARTS IN SEISMIC REFRACTION INTERPRETATION*
Authors: NEALE R. N. 
Published: April 2006

ABSTRACTA graphical method of interpreting refraction data is presented based upon wave front construction in which different overburden velocity distributions can be used. The wave fronts are constructed with the aid of an Isochron Chart. By using two or more Isochron Charts, the effect of velocity variations above the refractor of interest can be allowed for.
GENERALISATION DES OPERATEURS D'ANTI‐RESONANCE A UN NOMBRE QUELCONQUE DE REFLECTEURS*
Authors: KUNETZ G. 
Published: April 2006

RESUMEOn sait que l'effet perturbateur, sur une trace sismique, d'un fort réflecteur proche de la surface peut être en grande partie éliminé en convoluant la trace par un opérateur, dit “d'anti‐résonance”, très simple, puisqu'il ne comporte que trois termes.Nous nous proposons de montrer que pour éliminer, de la même manière, l'effet d'un nombre quelconque de réflecteurs, il existe également des opérateurs d' anti‐résonance à un nombre fini de termes, et nous donnerons les formules permettant de construire ces opérateurs.Les formules obtenues permettent également de vérifier qu'une trace sismique (symé‐trisée par rapport à l' origine) doit être une fonction d' auto‐corrélation, et fournissent, de plus, l'expression et l' interprétation physique d'une fonction dont la fonction d'auto‐corrélation donne la trace sismique.
REFRACTION SEISMICS WITH AN ANISOTROPIC OVERBURDEN: A GRAPHICAL METHOD OF INTERPRETATION*
Authors: HELBIG K. 
Published: April 2006

ABSTRACTAn analytical expression for the time‐distance curve of seismic waves travelling in a medium consisting of intrinsically anisotropic layers with arbitrarily dipping plane interfaces can be given in terms of the “co‐ordinates” of the interfaces (length h of the perpendicular from the shotpoint to the interface, strike ν and dip α of the interface) if for each layer the velocity is given as a function of the orientation of the wave normal. The interpretation of the time‐distance curve is understood as the inverse process, namely finding an expression for the co‐ordinates in terms of some characteristics of the time‐distance curve, e.g. intercept times and apparent velocities. In addition, it is useful to know where the “limiting ray”, which is the ray connecting shotpoint and last geophone, enters and leaves a specific layer, for it is only on the medium between these two points that information can be obtained by interpretation. As ray and wave normal do not generally coincide in anisotropic media, the location of these points cannot be calculated from the co‐ordinates and the direction of the wave normal without recourse to the functional dependence between the directions of ray and wave normal.An analytical solution of this problem would involve the solution of a number of equations, implicitly containing several parameters. Successive approximation would be rather cumbersome. Instead, a graphical method is proposed which yields all pertinent information without calculation.
CRITICAL‐ANGLE EFFECTS IN SEISMIC EXPLORATION*
Authors: POLEY J. PH. 
Published: April 2006

ABSTRACTIn the case where a medium of velocity α1 is underlain by a medium of higher velocity α2, no propagation of compressional elastic wave energy into the lower medium takes place at angles of incidence exceeding a certain critical value. This so‐called critical angle –which is a measure of the actual velocity‐contrast –is furthermore marked by a sharp increase in the amount of reflected compressional energy. An investigation has been made to find out whether this critical‐angle effect might be usable as a velocity‐contrast indicator in seismic exploration.Model experiments confirmed the expectation that this effect should be manifest at the surface under ideal conditions.Two small‐scale field set‐ups showed that the effect is actually measurable in the field (in one case after applying corrections for planting variations).Finally a seismic line along the shore of the North Sea provided the data for contrast analysis over a considerable distance along the base of the Tertiary. Comparison of the measured changes in contrast and subcrop velocities obtained at those locations where subsurface data from independent sources were available, showed good agreement.It is concluded that critical‐angle shooting may be used to indicate subcrop changes along a reflector, or even to obtain the same sub‐stratum velocity as is sought in conventional refraction work, at considerably shorter operating distances.
GEOPHYSIQUE ET VOLCANOLOGIE*
Authors: EVRARD PIERRE , JONES LOUIS 
Published: April 2006

AbstractThe authors present a review of the activities of the “Centre National de Volcanologie” (Belgium) in the field of the application of geophysical and geodesic techniques in the study of active volcanoes.The first region of interest is constituted by the African volcanoes: Nyiragongo and Nyamuragira, North of the Kivu lake; the second by the Etna in Sicily.The methods used were: volcano‐seismology, gravimetry, magnetism, underground clinometry and “tiltmetry”.The authors close with considerations on geothermic research, which is envisaged for future programmes.
SOME ELECTRONIC SIMULATORS OF GALVANOMETERS AND GEOPHONES, AND THEIR USE FOR INVERSE FILTERING*
Authors: HOSKEN J. W. J. 
Published: April 2006

AbstractElectronic circuits are described which simulate the effects of galvanometers and geophones. By placing these circuits in the feedback loop of an operational amplifier it is possible to obtain transfer functions which are the inverse of those of the transducers. That is, they will remove the distortion on the signal which was produced by the geophone or the galvanometer.Both a geophone simulator and its inverse filter have been built and used (O'Brien, 1965). The simulator is accurate over at least seven octaves and the inverse filter restores the ground signal to what it would have been if the recording geophone had had a natural frequency √n+1 times that of the actual geophone, where A is the gain of the operational amplifier used in the circuit.
ZUR ENTWICKLUNG EINES KOMPLEXEN ERDUNGSMESSERS*
Authors: ANDERS WILFRIED 
Published: April 2006

ABSTRACTAfter a brief reference to the various possibilities of measuring induced polarization, the experimental setup of a transistorized earth resistance meter is shown which allows one to measure the (real) resistance at the frequencies 9 cps and 1.5 cps. As a measure of the induced polarization, it supplies directly the resistivity percentage difference. The possibilities of its use are explained in detail and further development is considered.
A SIMPLE METHOD OF MAGNETOTELLURIC INTERPRETATION *
Authors: JAIN SUDHIR 
Published: April 2006

ABSTRACTA simple method of magnetotelluric interpretation is derived using the property that the earth currents flow in horizontal sheets. It is shown that when the depth is taken as two‐thirds of the Cagniard's depth of penetration (Cagniard, 1953), the mean resistivity‐over the depth is the same as the apparent resistivity of the medium. From a mean resistivity versus depth of penetration plot, resistivity can be easily computed at all depths of the sounding.This method gives satisfactory results in a short time and makes it possible to interpret the soundings over media of several layers. However, the results are inaccurate near maximum and minimum points of the plot as well as in the zone of thin layers.
POISSON'S CONSTANT WITH DRY SEDIMENTS AND WITH PACKINGS OF SPHERES*
Authors: WACHHOLZ H. 
Published: April 2006

ABSTRACTIn order to find a relation between Poisson's constant of dry sediments and the porosity, it is necessary to consider the elastic behavior of the sediment's initial state and the final state during the process of consolidation. Sand and other loose materials of more or less granular substances represent the initial state. As substitute for this zone, elastic constants of simple cubic and hexagonal packing are examined. Supposed is the adhesion for the planes of contact. Besides of Hertz's formula for the contact area of spheres, an elastic function of displacement due to a tangential force for the contact area of the spheres is used. This function has been derived. With the aid of these two. elements, the constants of the mentioned packing are calculated. Poisson's constant will then be calculated from the formula being valid for isotropic solids for three different directions of the sound. The mean value is lying at .With the known equation of Poisson's constant of rock having a small porosity, a third‐degree polynomial is formed. This polynomial agrees well with the average values of known measurements, and therefore can serve as a guide for the calculation of Poisson's constant of water‐saturated sediments.
PART I: THE SECTIONAL AUTO‐CORRELOGRAM
Authors: ANSTEY N. A. 
Published: April 2006

ABSTRACTThe auto‐correlation function of a seismic trace contains information on all the multiple reflection activity present in the trace.The interpretation of this information is facilitated by the arrangement of autocorrelation functions in cross‐sectional form, in the manner of a normal record section. This is the concept of the Sectional Auto‐Correlogram.Specifically, the Sectional Auto‐Correlogram will…Show if the record section does not include significant multiples, thus allowing confident picking of the primary reflections.Show if the record section does include significant multiples, giving their travel times and inclinations (and, under certain circumstances, their reflection coefficients).Indicate by what process the multiples should be treated.Yield an authoritative measure of the success of a multiple‐attenuating treatment.Delineate shallow horizons, even those whose primary reflections are too early to be recorded satisfactorily.Give the true travel time of a primary reflector, and the sign of its reflection coefficient.The Sectional Auto‐Correlogram allows the study of primary reflectors by consideration of the multiples generated by them, and in this sense may be said to turn multiple reflections to advantage. Thus a primary reflection at a certain time is defined if we find that every reflection on the record is followed by a multiple after this certain time. Alternatively, a primary reflection at a certain time is defined if, after that certain time, we can find a repetition of the entire record.The Sectional Auto‐Correlogram also has secondary uses in fault identification, crustal studies and weathering problems.