bluuebunny/crossref_metadata_2025 huggingface dataset:
ELIMINATION DE L'EFFET DES VAGABONDS INDUSTRIELS DANS UNE PROSPECTION PAR COURANTE TELLURIQUES*
Authors: KUNETZ G.
Published: April 2006

Abstract

Several 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

Abstract

A 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

Abstract

The 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

Abstract

A 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.
DÉCONVOLUTION DE TRACES RÉELLES*
Authors: D'HOERAENE J.
Published: April 2006

Abstract

The techniques of deconvolution have been formerly developped and tested on synthetic seismogramms.

They are in the present study applied to field records or play backs.

Three examples of the result of the deconvolution, i.e. of the reduction of filtering effects caused by the apparatus and the ground, are given.

They show that the deconvolution increases the power of resolution and emphasizes thereby the resemblances as well as the differences between traces; consequently it enriches the correlation and improves the picking of the reflections which have a permanent enough character.

Besides, it is shown that the comparison between deconvoluted traces and an impulsionnal synthetic seismogramm is, for the same reasons, more significant than between a field record and a filtered synthetic seismogramm.

Finally, a section of deconvoluted traces shows that it is possible to obtain a valuable increase of resolution using one and the same inverse filter for a group of field records obtained with the same filter setting, even in locations where subsurface conditions are somewhat variable.
COUPLAGE DES SISMOGRAPHES AVEC LE SOL*
Authors: FAIL J. P. , GRAU G. , LAVERGNE M.
Published: April 2006

Abstract

A series of laboratory and field experiments has proved the validity of theoretical formulae for the geophone‐to‐ground coupling characteristics. Soil properties and geo‐phone mass and size have been studied. It has been shown that soil properties in the immediate vicinity of the geophone determine the coupling, together with geophone mass and size.

Statistical studies of coupling characteristics have been conducted on various soils. In some cases the dispersion of resonance frequencies and damping constants is quite large, even when the geophones have been carefully planted.

As a rule, it may be said that geophone‐to‐ground coupling is not a source of trouble except ‐in high‐frequency studies. However, the filtering effect of multiple geophones may be affected by the statistical fluctuations of coupling on a given type of soil, even at usual frequencies.
SOME UNUSUAL LOW BOUGUER ANOMALIES OF SMALL EXTENT IN CENTRAL IRELAND AND THEIR CONNECTION WITH GEOLOGICAL STRUCTURE*
Authors: MURPHY T.
Published: April 2006

Abstract

During a regional gravity survey in Central Ireland a series of intense Bouguer anomalies of very limited extent was encountered. They are all negative, the largest being ‐6.4 mgal and each covers an area of the order of one square km. Gradients up to 9 mgal/km have been measured. The country rock is Carboniferous Limestone, density 2.7 g/cm3, but outcrops are scarce particularly in the region of the anomalies and the surface is in general covered by glacial gravels, drift and bog. Most of the anomalies lie on an approximate straight line running northeast‐southwest for a distance of 115 km.

An analysis indicates that the cause of each anomaly is a mass with a negative density contrast of at least 0.3 g/cm3, probably 0.5 g/cm3, and so positioned that its top is not deeper than 0.5 km from the surface.

As no rock with a density less than 2.5 g/cm3 is known to exist in the neighbourhood, it is postulated that the cause of the anomalies lies in a sequence of solution cavities in the limestone now filled with water or lightly packed rock debris and gravel aligned along a large fault. No such system has been known or suspected in Ireland.

The presence of such large faults would have serious consequences on the possibility of oil accumulation while the infillings of the cavities might have economic importance.
GEOELECTRICAL PROSPECTING WITH UNDERGROUNDELECTRODES*
Authors: ALFANO LUIGI
Published: April 2006

Abstract

In many situations, because of the great influence of a surface layer on apparent resistivity values, the interpretation of electrical soundings may be very indeterminate, according to the “equivalence principle”.

For these situations, an arrangement which includes an underground electrode has been proposed. With this method, the interpretative indeterminatecy may be often eliminated, as may be seen from the diagrams calculated for some typical situations.
REFLECTION AND TRANSMISSION COEFFICIENTS FOR PLANE LONGITUDINAL INCIDENT WAVES
Authors: KOEFOED O. ,   Institute for Applied Mathematics of the Technological University at Delft
Published: April 2006

Abstract

Tables are presented giving the two reflection coefficients and the two transmission coefficients resulting from the incidence of a plane longitudinal wave upon a plane boundary between two elastic media, for hundred different combinations of the elastic parameters and the density of the two media. The effect of these parameters upon the change of the reflection or transmission coefficient with the angle of incidence is discussed. For incidence beyond the critical angle the phase shift between the incident wave and the reflected or transmitted wave is also given.
DETERMINATION DE L'EPAISSEUR DES SEDIMENTS MEUBLES A L'AIDE DE LA METHODE DE STATISTIQUES DE ΔT*
Authors: LEENHARDT O.
Published: April 2006

Abstract

Offshore reflection records, even if they are of medium quality, can be used to determine the thickness of unconsolidated sediments. The method is described and its limits are specified. An example of application referring to the Gulf of Lyons is given.
ELASTISCHE ANISOTROPIE IN TEKTONISCH VERFORMTEN SEDIMENTGESTEINEN*
Authors: GIESEL W.
Published: April 2006

Abstract

Sedimentary rocks deformed by tectonic forces, especially sandstones, show anisotropy in their elastic behaviour. The velocity of longitudinal ultrasonic pulses in them varies with direction. In three directions perpendicular to each other, velocities are extreme. These directions are parallel to the tectonic axes.

In such rocks grains are arranged according to their shape. This special orientation developed during the tectonic deformation, which can also be recognized by deformed fossils.

A close relation exists between the anisotropy and the arrangement of the grains. A model of the sediment with grains arranged in a similar manner as in natural sandstones is tested mathematically for its elastic behaviour. Anisotropy similar to that of natural sandstones is exhibited by this model.
SURFACE‐SHIP GRAVITY MEASUREMENTS IN THE NORTH SEA*
Authors: FLEISCHER U.
Published: April 2006

Abstract

Modern marine gravimeters enable us to measure gravity at sea with a mean error of 2 to 5 mgals, depending on sea conditions and navigational accuracy.

Good results could be obtained, even in rough seas, by means of Graf's ASKANIA Sea Gravimeter mounted on an ANSCHÜTZ gyrostabilized platform.

When a DECCA Navigator System is used, the gravity measured at the points of intersection agrees within 5 mgals at wind‐force Beaufort 4 and vertical accelerations of about 60.000 mgals.

The southern North Sea has been surveyed with VFS “GAUSS”, the research vessel of the German Hydrographic Institute, Hamburg. Since 1959 about 4.000 miles of continuous gravity measurements combined with simultaneous magnetic measurements have been carried out in this area. Here nearly all remote‐control gravimeter stations of the Netherlands Geodetic Commission were passed once or several times. Hence they could be used as basic points. However, there are a few cases in which the Dutch data could not be confirmed.

The results are given as a free air isogam map covering the area between the meridian of Greenwich and 8° east, and between 54° and 56° latitude, with decreasing density of the measurements from east to west.
LA RECHERCHE DE PHOSPHATES PAR RADIOMETRIE AEROPORTEE*
Authors: BOLLO R. , JACQUEMIN M.
Published: April 2006

Abstract

As a rule, deposits of phosphates contain radioactive elements. Studies made in the laboratory of samples from North America and north Africa had shown that this radioactivity is due to the presence of uranium, and occasionally of thorium, either in the form of vaandate or in a diffuse state. Surface measurements carried out with a portable scintillometer had enabled some deposits to be outlined, but radiometric prospecting was only a supplementary method at this stage. From the results of these surface studies, it could be considered that the relations emitted by phosphates were sufficiently intense to be detected from a certain altitude.

Consequently, a scintillometer was installed aboard a helicopter, and experimental tests were carried out on the known deposit of Djebel Honk, Algeria. Three profiles, flown perpendicular to the existing layers at 45 metres, permitted us to ascertain the validity of the method, and to define the working standards. Despite the small width of these outcrops (30 metres at most), it was established that “helicopter radiometry” could be used for phosphate exploration.

Fourteen thousand kilometres of profiles were flown in northern Algeria. Since the phosphate deposits known in this area are located at the contact of the Cretaceous and Eocene (Dano‐Maestrichtian, Thanetian, Ypresian), a systematic coverage of these geological series was undertaken. It was then possible to draw up a rapid inventory of the series.

Airborne radiometry, and helicopter radiometry in particular, now seems to be the most efficient, quickest, and least expensive method that can be applied to systematic phosphate exploration.
CORRELATION TECHNIQUES –A REVIEW*
Authors: ANSTEY N. A.
Published: April 2006

Correlation techniques are in the process of passing from the research laboratory to the field. This paper seeks to aid the transition. The three main sections of the paper have these objects:

To state in words the basic principles on which correlation techniques are based, and the connection between these principles and more familiar concepts which are already among the tools of the exploration geophysicist.

To review briefly the published applications of correlation techniques in science generally.

To discuss some of the additional applications which are now emerging in exploration geophysics.

The treatment is graphical and illustrative, rather than rigorous. The paper is addressed to the practising exploration geoscientist and to the newcomer to correlation techniques. A list of about 150 references is given.
A NEW TECHNIQUE FOR THE MEASUREMENT OF GEOPHONE PARAMETERS UNDER FIELD CONDITIONS*
Authors: PALMER B. A.
Published: April 2006

Normally only operational checks are made on geophones in the field because of the lack of suitable test equipment. The test method described here was developed to enable accurate (better than 1 %) measurements to be made, in the field, of all geophones in common use which have natural frequencies of i c/s or greater.

The portable field instrument is simple to operate and can be used to test refraction and reflection geophones, either singly or in series strings.
CHARTS FOR DETERMINING THE GRAVITY EFFECT OF TWO‐ AND THREE‐DIMENSIONAL BODIES BOUNDED BY ARBITRARY POLYGONS*
Authors: COLLETTE B.J.
Published: April 2006

Charts are presented for the computation of the vertical component of the attraction of horizontal laminas and of horizontal cylinders bounded by irregular w‐sided polygons. Contrary to older methods no restricting conditions are made for the directions of the sides of the polygons.
A SIMPLE METHOD FOR THE CALCULATION OF STANDARD‐GRAPHS TO BE USED IN GEO ELECTRICAL PROSPECTING*
Authors: VAN DAM J. C.
Published: April 2006

The paper describes a new method for the calculation of standard‐graphs i.e. resistivity‐curves for assumed resistivity profiles. It starts from the integral of Stefanesco and arrives at a system of image poles, similar to, but simpler than earlier developed systems. The advantages of the new method are described, the accuracy is discussed and it is indicated how the accuracy can be improved by a simple artifice.
SYNTHETIC SEISMOGRAMS APPLIED TO THE SEISMIC INVESTIGATION OF A COAL BASIN*
Authors: VAN RIEL W. J.
Published: April 2006

In the present study an attempt is made to relate the general pattern of reflection seismograms obtained over a coal basin to the acoustical properties peculiar to the Coal Measures. The Carboniferous is characterized by a very rapid succession of distinct lithological units, resulting in a surprising variability in their physical properties. Coal seams in particular are conspicuous by their low density and velocity and they produce acoustical contrasts of 35–50 % with respect to country rock. The resulting heavy shielding action prevents the seismic energy from penetrating deeply into this type of formation.

With the aid of synthetic seismograms, arranged into synthetic profiles, it is shown that only a minor part of the Coal Measures reflections is of primary origin. The majority has a secondary character brought about by reverberations inside the weathering zone. Thus the conclusion is reached that reflection shooting allows of mapping only the structure of the top section of the Carboniferous, which is sufficient for the purposes of the coalmining industry.
ANALYTICAL AEROMAGNETIC INTERPRETATION THE INCLINED PRISM*
Authors: MOO J. K. C.
Published: April 2006

The problem of the magnetic anomaly due to the induced magnetisation, of a body‐having the form of an inclined prism is treated analytically. The formula for the total intensity anomaly is analysed to yield relations between parameters of the anomaly and the depth, width, and dip of the magnetic model. The treatment is extended to include the case of remanent magnetisation. The numerical results are presented as graphs prepared for use in the interpretation of measured anomalies.
CALCUL D'UN FILM SYNTHETIQUE A PARTIR D'UN TRES GRAND NOMBRE DE COUCHES*
Authors: DELAS C. , TARIEL P.
Published: April 2006

Abstract

It is considered it might be useful to test the validity of the theoretical study “Sur ľinfluence ?un empilement de couches minces en sismique” by Messrs. I. ?Erceville and G. Kunetz, Geophysical Prospecting, XI, No. 2, June 1963.

We chose a borehole of the Compagnie Française des Pétroles where the velocity logs frequently show fine interbedding. Two synthetic records were prepared:

a) For the first one, a large step (τ= 3 ms) was selected to preserve the general appearance of the field records (convolution by a Ricker wavelet with a pseudo‐period of 26.6 ms);

b) For the second one, a small step (τ= 0.5 ms) was taken, convoluted using the same Ricker wavelet.

We observed that the synthetic records without multiples are not dependent on the step taken for calculation, provided this step remains small in relation to the period of the convolution signal (τ, one‐way time, smaller than 1/8 of the period of the signal). Nevertheless, when a small step is used, the high frequencies may be better reflected on the synthetic record.

We also noticed that the direct wave attenuates rapidly with depth and is replaced by an accumulation of multiples that restore it exactly, but with a slight time‐lag. We termed this the “pseudo‐wave”. The above‐mentioned delay between the two synthetic records is in good agreement with the results published by Messrs. 1. ?Erceville and G. Kunetz.
SOME NOTES CONCERNING THE FREQUENCY ANALYSIS FOR GRAVITY INTERPRETATION*
Authors: MESKÓ A.
Published: April 2006

Abstract

One of the most important problems in the interpretation of gravity data is the separation of the data giving information characterizing the different geological structures. Various methods were elaborated to perform this separation (smoothing, removing of residuals, second derivatives, analytic continuation and others). For each operation various sets of coefficients were proposed. All these sets of coefficients may be considered as to provide linear filtering processes applied to the original map. The frequency response of the filter unambigously determines the method and gives good and clear information concerning their advantages (or disadvantages). The knowledge of frequency responses enables the choice of the most suitable method for the interpretation of a given map. Graphs are presented by the author showing:

the effect of radius used in the calculation of residuals

effect of the number of points used in averaging the data on a circle

the effect of the different systems of coefficients used in the various second derivative formulas.
ENERGY DENSITY SPECTRUM AND AUTOCORRELATION FUNCTION OF ANOMALIES DUE TO SIMPLE MAGNETIC MODELS*
Authors: SPECTOR A. , BHATTACHARYYA B. K.
Published: April 2006

Formulae of the energy spectrum and autocorrelation function have been derived for magnetic anomalies due to four classes of bodies which can be represented in turn by (a) poles, (b) line of poles, (c) dipoles and (d) line of dipoles. The effects of the depth and dimensions of the magnetized sources on the spectrum and the autocorrelation function have been studied. In the case of the dipole models, the orientation of the polarization vector casts a significant influence on the characteristics of the two functions. In all cases, however, the functions change in size and shape as the inclination and declination of the geomagnetic vector are varied.
NEW FILTERING METHODS WITH “VIBROSEIS”*
Authors: EDELMANN H.
Published: April 2006

In order to obtain high resolution correlograms, it is of importance amongst other things to get reflection signals with large bandwidth. An advantage of the VIBROSEIS*** method is that the frequencies radiated by the vibrators can be matched to the transmission response of the subsurface involved. By choosing the right frequency range, the highest possible amplitude and most favourable form may be given to the reflection signals.

In a reflection correlogram, individual signals cannot be considered in isolation. Signals of different origin are interfering with one another. They very often have different amplitudes, so that it may be desirable in many cases to filter out events of certain apparent velocity. With the VIBROSEIS method this may be achieved quite simply. All frequencies of the noise signal are uniformly suppressed. The advantage is that noise signals, e.g. refraction signals, which cannot be sufficiently attenuated by wavelength filtering, may be completely eliminated by this velocity filtering without affecting the bandwith of the desired signal. The total dynamic range of the tape recording can be used for the registration of wanted events. To perform this kind of filtering several vibrators are necessary in the field; each of them is controlled by an individual signal.

There is an unavoidable error of static and dynamic corrections which causes the results of reflection measurements to deteriorate when using multiple coverage. High frequency components especially are seriously affected by destructive interference. This difficulty can be avoided by using a VIBROSEIS signal with high frequency component amplitudes supported. For the probability of error of corrections a normal distribution is assumed. A smoothed amplitude characteristic may be achieved after stacking.

The amplitude characteristic of seismic devices is commonly reduced to about 100 cps bandwidth. For further improvement of resolution of VIBROSEIS correlograms it is necessary to apply special filtering methods. This is of particular interest when any kind of gain control is used to display weak events more clearly. With increasing amplification the sidelobes of the strong signals may reach the size of the weak events. In order to eliminate this effect, the amplitude characteristic of the VIBROSEIS signal is adjusted for optimum suppression of side‐lobes.
THE TERRAPAK *
Authors: PIEUCHOT M.
Published: April 2006

The Terrapak is a new seismic energy source of the surface energy source type. Essentially, the Terrapak consists of a compressed air piston which transmits a shock to the ground by means of a striker plate attached to the piston rod. The Terrapak is truck‐mounted together with its ancillary equipment. Shocks can be generated at 8 second intervals, and although the weight of the striker is relatively low (approximately 1400 Ibs) the impact velocity exceeds 66 ft/sec. The energy available is about 85,000 ft. lb., which is equivalent to that produced by conventional weight‐dropping methods. The power spectrum of the seismic wave produced by the Terrapak is spread out towards the higher frequencies because its impact velocity is greater than that of a dropping weight.

There is a noticeable difference between noise records made with the Terrapak and noise records made with a conventional weight‐dropping technique. The same noise frequencies are found in both cases, but low frequency noise is stronger with weight dropping than with the Terrapak, whereas the intermediate frequency reflections obtained using the Terrapak are more suitable for correlation.

The expansion of the compressed air generates a sound wave, the effects of which must be eliminated by the use of multiple geophone arrays. A spectrum analysis of the records has confirmed that the waves produced by the Terrapak are rich in intermediate frequency components. This facilitates the picking of reflections in normal areas where the apparent frequency of the reflections is about 30 to 35 c/s.
A DISCUSSION ON SEISMIC BINARY GAIN SWITCHING AMPLIFIERS *
Authors: SIEMS LEE , HEFER FRED W.
Published: April 2006

Geophysical field equipment has undergone rapid changes in the past decade; from simple AGC amplifiers and galvo cameras to binary gain switching amplifiers and digital recorders, all in an attempt to keep pace with the new geophysical interpretive methods developed, and the growing acceptance of the terminology, methods, and philosophy of communication theory.

The additional tools of the digital recorder and digital computer make it possible to utilize these new techniques in geophysical processing. Accomplishing these new techniques demands severe requirements on the digital field recording process in handling the decreasing energy return from the seismometer, and to fully realize the capabilities of digital techniques in reducing data. Simple automatic gain control may be used. However, in the more sophisticated interpretive methods, such as autoregression and deconvolution, it is necessary to reconstruct the actual energy levels in the computer. Recording the control signal used in master AGC or programmed gain control may prove satisfactory; however the accuracy of control versus gain is limited to I% for such analog instrumentation.

To utilize the computer to its fullest extent, and to accurately perform these new techniques, requires an accuracy of I% or better. This accuracy is obtainable by using a step gain control where the gain is increased by fixed steps in which each step represents a gain in amplification by a constant factor. The accuracy in this case can be made dependent only on the tolerance of resistors used as attenuators or feedback elements. Preferably the constant factor of gain steps should be a number easily handled by the computer. By using 6 db steps it becomes a simple matter to shift binary numbers, such as multiplying or dividing by 10 in the decimal system.

The requirements or parameters for such an amplifier system, and the elements of the amplifier necessary to achieve these requirements are presented.
THE USE OF THE CONTINUOUS SEISMIC PROFILER TO SOLVE HIDDEN LAYER PROBLEMS*
Authors: MORGAN N. A.
Published: April 2006

Integration of the continuous seismic reflection profiler with the marine refraction method on engineering surveys offers a solution to hidden layer problems, allowing both layer velocity and thickness to be computed.
TWO DIMENSIONAL STRAKHOV'S FILTER FOR EXTRACTION OF POTENTIAL FIELD SIGNAL*
Authors: NAIDU P. S.
Published: April 2006

A two dimensional linear filter operator based on Strakhov's method for the extraction of a potential field signal (gravity or magnetic) from a background of homogeneous random noise has been developed. An algorithm to solve for the coefficients of the operator is given together with the corresponding computer program in FORTRAN language. It may be used on any machine using FORTRAN IV. A few examples of the operator are also included.
RESPONSE OF A TWO‐LAYER GROUND TO AN INFINITE CABLE CARRYING ALTERNATING CURRENT WITH REFERENCE TO TURAM ANOMALIES *
Authors: DIZIOǴLU MEHMET Y.
Published: April 2006

A formula is developed for the vertical magnetic field due to an alternating current passing through a long horizontal cable placed on a two‐layer ground. The variations of the phase and amplitude ratio of the vertical field, along profiles perpendicular to the cable line are investigated. Within the limits encountered in practice, it is found that if the upper layer is conductive, as compared to the lower layer, the phase may vary appreciably whereas the amplitude ratio changes as in the case of vacuum.
EXPERIMENTELLE METHODEN UND EINE APPARATUR ZUR UNTERSUCHUNG DER BEZIEHUNGEN ZWISCHEN HYDRAU‐LISCHEN UND ELEKTRISCHEN EIGENSCHAFTEN LOSER UND KUNSTLICH VERFESTIGTER POROSER MEDIEN *
Authors: SCHOPPER JÜRGEN R.
Published: April 2006

In [50] and [51] a theory has been developed relating formation factor, permeability and porosity of porous sedimentary rock by means of statistical parameters of the pore system, and further, tying those statistical parameters to other macroscopically measurable quantities like capillarity, capillary retention, flow dispersion etc. This paper deals with experimental methods and apparatus for checking the theoretically derived relations using columns of packed loose or artificially consolidated sands or other granular matter. Some initial experiments, mainly intended for checking out equipment and methods are reported. The discussion of the results so far shows good agreement with the theory in most cases, except for the irreducible water saturation. However, for a definite statement on the general validity of the theory more data must be accumulated.
RESISTIVITY SOUNDING ON A TWO‐LAYER EARTH WITH TRANSITIONAL BOUNDARY*
Authors: MALLICK K. , ROY A.
Published: April 2006

A theoretical solution is obtained for the problem of a two‐layer earth with transitional boundary. In practice, the transition layer can stand for the weathered zone in hard rock areas where the degree of weathering diminishes with depth. Master curves and tables of data are presented for the case when the lower half‐space is infinitely resistive.
DEEP SEISMIC SOUNDING OF THE EARTH'S CRUST IN THE AREA OF THE DINARIDES AND THE ADRIATIC SEA*
Authors: DRAGAŠEVIÍ T. , ANDRIC B.
Published: April 2006

Deep seismic sounding was performed along two profiles which cross at the Dinarides area right angles. One of the profiles goes far into the Adriatic Sea.

Besides considerations on the lithophysical conditions, characteristics of the registered waves are analysed. The amplitude curves and curves of amplitude ratios are shown. Special attention was paid to the frequency of the registered waves.

In order to obtain a better knowledge of the registered wave pattern three‐component recordings of waves were carried out. The analysis of the records obtained is given, with particular regard to the possibility of creating converted waves.

The Earth's crust structure along the profiles II and III is given.
ANALYSIS OF GRAVITY ANOMALIES OF TWO‐DIMENSIONAL FAULTS USING FOURIER TRANSFORMS*
Authors: SHARMA BIJON , GELDART L. P.
Published: April 2006

The Fourier transform formula for a two‐dimensional fault truncating a horizontal bed at an arbitrary angle of inclination is derived. The amplitude spectrum of the Fourier transform is found to give information about the depth to the top of the upper part of the faulted bed and the inclination of the fault‐plane. Under suitable conditions the thickness and the displacement of the bed involved can be obtained. With actual field data, these transforms can be obtained at discrete points by a Fourier analysis of the gravity anomaly. A field example from the Logan fault area near Montreal, Que., Canada, is given.
TRANSIENTS AND FIELD BEHAVIOUR IN INDUCED POLARIZATION*
Authors: BERTIN J. , LOEB J.
Published: April 2006

This paper deals with electromagnetic fields in the so called “Transient Induced Polarization Technique”. Field equations are integrated in the case of a polarizable sphere inbedded in a sterile overburden. The existence of a remanent polarization vector P which slowly decays once the charging current has been cut off is taken as the initial condition. When the surface between the air and overburden is (as a first step) disregarded, the Laplace transform of the EM fields is given. The integral of the electric field (which is fairly often the result of prospection work) is independent of the various time constants related to electrochemical processes, but it stands as a good measurement of the total electrostatic dipole created by the charging current.

We investigate the geometrical circumstances that can bring negative values of I.P. signal. Such negative values can be found in two cases: 1. The discharge currents are. distorted by the ground surface. 2. The I.P. signal is picked up by electrodes inside the polarizable material.

The last part is dedicated to an account of experimental work performed on models and of an actual case history.

The mathematical derivations are included in an appendix.
QUELQUES APPLICATIONS DE LA THEORIE DE LA PREDICTION AU TRAITEMENT DES DONNEES SISMIQUES*
Authors: HEMON CH.
Published: April 2006

Abstract

In the case of simple time series it is shown that prediction operators can be considered as deconvolution operators which are easily obtained.

These operators possess the special feature of having a minimum phase, and their spectrum modulus represents, with a good dynamic range, the reciprocal of the square root of the modulus of the original autocorrelation spectrum.

A generalization of the simple time series theory to the functions of two independent variables is possible in as much as, on a given section, the application of the multiple time series method enables the function of time and distance variables to have well‐defined statistical properties; it is necessary, in particular, that the processes involved are stationary with respect to the two independent variables.

In the case of multiple time series the application of the Prediction Theory permits greater uniformity of the traces because it enhances the events which show a good correlation between traces and, on the other hand, tends to minimize the random events which cannot be correlated between traces. The signal‐to‐noise ratio is thus increased to a great extent.
THE ELECTRICAL CURRENT PATTERN INDUCED BY AN OSCILLATING MAGNETIC DIPOLE IN A SEMI INFINITE CONDUCTIVE THIN PLATE*
Authors: KOEFOED O. , STRUYK A. P.
Published: April 2006

Abstract

In a paper by Koefoed and Kegge (1968), which was based on previous work of Wesley (1958), the electrical current pattern has been derived that is induced by an oscillating magnetic dipole in a semi‐infinite thin plate of infinitesimal resistivity.

In the present paper, the range of validity of the assumptions, on which the work of Wesley is based, is subjected to a theoretical analysis. It is found that the decisive factor for the validity of Wesley's derivation is the quotient of the square of the penetration depth of the electrical current over the product of the thickness of the plate and a distance that is indicative of the size of the current loops in the plate. Wesley's derivation is shown to be valid only when this factor is negligible. It is also shown that in this condition the imaginary component of the anomaly must be negligible.

Model experiments are described in which the electrical current pattern is studied also in the range in which the derivation of Wesley is not valid. The procedure used in these model experiments was to measure the tangential component of the magnetic field strength very close to the metal plate that simulated the conductive dyke.

In order to express the results of the measurements in terms of the imaginary to real ratio, these results are compared with an interpretation graph for field measurements that was published by Hedström and Parasnis (1958). It is found that the current pattern in the plate is essentially the same as that which follows from Wesley's derivation, provided that the imaginary to real ratio is less than one third. The measurements do not permit to draw conclusions regarding the current pattern in the plate in conditions that correspond to larger values of the imaginary to real ratio.
THE DELINEATION OF THE BEDROCK CONFIGURATION OF PART OF PORT JACKSON, NEW SOUTH WALES, WITH A BOOMER SYSTEM*
Authors: EMERSON D. W. , PHIPPS C. V. G.
Published: April 2006

Abstract

A high resolution Boomer system was used to investigate the bedrock configuration of part of Port Jackson, New South Wales. The continuous reflection profiling technique was successful in delineating a channel incised in bedrock under a thickness of up to 60 m. of unconsolidated sediment covered by up to 20 m. of water.
REFLEXIONS SUR LES APPLICATIONS DE LA TRANSFORMEE DE FOURIER EN SISMIQUE ET EN GRAVIMETRIE*
Authors: JACQMIN A. , PEKAR L.
Published: April 2006

Resume

De nombreuses études ont été effectuées jusqu'à ce jour sur la Transformée de Fourier et ses applications en géophysique. En particulier, depuis ľavènement des ordinateurs qui ont entraîe la digitalisation de la principale méthode, sismique réflexion, les différentes techniques de traitement numérique ont fait ľobjet ?innombrables communications. La gravimétrie a toujours été une méthode numérique. Mais il est évident que pour elle également, de nouvellés possibilités se sont ouvertes. Aussi les gravimétriciens s'intéressent de plus en plus à la théorie et aux applications fondées sur ľétude des spectres en fréquences que permet la Transformée de Fourier. Depuis les travaux de C. A. Schwartz, W. Sokoloff et W. C. Dean, ?autres idées intéressantes, concernant le traitement de ľinformation gravimétrique, sont apparues: calcul du gradient vertical (V. Baronov), interprétation des anomalies à partir de leur spectre (M. E. Odegard et J. Berg Jr.), calcul des isopaques gravimétriques (J. L. Bible) etc….

Toutes ces idées, toutes ces techniques ont le même but: faciliter ľinterprétation. Mais tout en ayant le même but et ayant affaire au même genre de difficultiés, il semble que le gravimétricien et le sismicien se soient elabores, chacun de leur côté, des outils sans se soucier du fait que leurs méthodes, et plus spécialement leur méthode de traitement de mesures brutes, sont, sinon identiques, du moins très semblables et que par conséquent les perfectionnements atteints dans une méthode peuvent servir ľautre.

Ľobjet de la présente communication sera de repenser la philosophie des deux méthodes, sismique et gravimétrie, depuis ľexécution des mesures en passant par les principales méthodes de traitement, pour aboutir àľinterprétation, en se plaçant à deux points de vue complémentaires ?ailleurs:

– Bien que les traitements numériques se fassent le plus souvent dans le domaine fonctionnel par les convolutions, il est bien plus facile de comprendre et de concevoir ces traitements si ľon raisonne alternativement grâce à la Transformée de Fourier dans le domaine fonctionnel et dans le domaine spectral.

– En raisonnant en fréquences, il n'y a pas de différence de principe entre la sismique et la gravimétrie. Une courbe, graduée en milligals fonction de distance, et une trace sismique, représentant les variations de tension ?un galvanomètre en fonction du temps, sont, du point de vue de la Transformée de Fourier, identiques.

Dans cet esprit on abordera les sujets suivants:

– Signal sismique et signal gravimétrique

– Problème ?échantillonnage en gravimétrie (espacement de mesures variable)

– Filtrages.

•Présentation et commentaires de spectres de quelques exemple syntétiques et pratiques

•Filtrage en nombre ?onde

•Filtrage en fréquences.

•Problème de la fréquence o (dérivées horizontale et verticale)

– Autres applications de la Transformée de Fourier en gravimétrie.
REMARQUES SUR L'INTERPRETATION DES SONDAGES DE POLARISATION PROVOQUEE ESSAI DE THEORIE QUANTITATIVE *
Authors: VAN NGOC PHAM , ROUSSEL J. , TOURNIER Et D.
Published: April 2006

La polarisation provoquée (P.P.) est un phénomène particulièrement complexe non seulement du point de vue des mécanismes physiques qu'elle met en jeu, mais aussi du point de vue mathématique. A cause de ľanalogie que présentent les techniques expérimentales de sondage électrique classique de résistivité?une: part, et de sondage P.P. ?autre part, on éprouve une certaine tendance à interpréter les données du second à la manière du premier. C'est pourquoi il nous a semblé utile de calculer un modèle mathématique idéalisé et schématisé qui permette tout au moins de se rendre compte de ľallure générale du phénomène auquel on peut s'attendre. On s'est placé dans le cas le plus simple, celui ?une couche mince polarisable qui présenterait la même conductibilitéélectrique que le milieu dans lequel elle est intercalée. On se propose de fournir le résultat de ce calcul pour le cas simple ?une seule électrode ?injection et ?une seule électrode de mesure et, à partir de ces données, de calculer ľallure ?un sondage P.P. de type classique avec quadripôle Wenner.

On compare ensuite le diagramme calculé avec une courbe expérimentale obtenue sur un modèle figurant une couche mince de minerai disséminé II s'avère, en fin de compte, que ľallure générale du phénoméne fournit une base de contrôle solide àľexpérimentation sur modèles réduits.
THE CORRELATION OF SEISMIC VELOCITIES WITH FORMATIONS IN THE SOUTH‐WEST OF SCOTLAND *
Authors: HALL JEREMY
Published: April 2006

ABSTRaCT

In seismic studies being carried out to elucidate the structure at depth of the Midland Valley rift and the Tertiary igneous province in the West of Scotland, a lack of deep boreholes makes the collection of velocity data imperative for identification of seismic events and for determinations of depth. Three methods are used to investigate the correlation of seismic velocities and geological formations. The results show as strong a dependence of velocity on method of measurement as on lithology and the wide spread of values within a given formation makes the attribution of discrete velocity ranges to specific formations impossible. Changes of velocity are more significant than absolute values. The variations in both are discussed.
A STUDY ON THE DIRECT INTERPRETATION OF RESISTIVITY SOUNDING DATA MEASURED BY WENNER ELECTRODE CONFIGURATION*
Authors: CHAN SIEW HUNG
Published: April 2006

Abstract

This paper describes certain procedures for deriving from the apparent resistivity data as measured by the Wenner electrode configuration two functions, known as the kernel and the associated kernel respectively, both of which are functions dependent on the layer resistivities and thicknesses. It is shown that the solution of the integral equation for the Wenner electrode configuration leads directly to the associated kernel, from which an integral expression expressing the kernel explicitly in terms of the apparent resistivity function can be derived. The kernel is related to the associated kernel by a simple functional equation

image

where K1(λ) is the kernel and B1(λ) the associated kernel.

Composite numerical quadrature formulas and also integration formulas based on partial approximation of the integrand by a parabolic arc within a small interval are developed for the calculation of the kernel and the associated kernel from apparent resistivity data. Both techniques of integration require knowledge of the values of the apparent resistivity function at points lying between the input data points. It is shown that such unknown values of the apparent resistivity function can satisfactorily be obtained by interpolation using the least‐squares method. The least‐squares method involves the approximation of the observed set of apparent resistivity data by orthogonal polynomials generated by Forsythe's method (Forsythe 1956). Values of the kernel and of the associated kernel obtained by numerical integration compare favourably with the corresponding theoretical values of these functions.
NATURAL POTENTIAL ANOMALIES AS A QUANTITATIVE INDEX OF THE RATE OF SEEPAGE FROM WATER RESERVOIRS*
Authors: BOGOSLOVSKY V. A. , OGILVY A. A.
Published: April 2006

Abstract

Water seepage from reservoirs causes appreciable anomalies of natural electric fields. The possibility of mapping leakage places by means of the SP method has been discussed by the authors in an earlier report. Further work has shown that detailed measurements of the natural electric field allow to determine the seepage rates from individual areas of a water reservoir in relative units. If data on the total discharge from a water reservoir are available, the conventional seepage units can be converted into absolute ones. Using this technique on a water reservoir in Armenia has permitted to control the change of the leakage rate as hydroinsulation operations were in progress. It has been established that as a result of shielding the bottom with clay material leakage from the central part of the reservoir has stopped. On the other hand, construction of cement seepage‐proof protection has had so far no appreciable positive effect.
A TWO‐LAYER GROUND IN THE FIELD OF AN INFINITELY LONG CABLE*
Authors: BEZVODA V. , SEGETH K.
Published: April 2006

Abstract

When the fixed‐source electromagnetic method is applied the quantities measured are influenced by the resistivity of the whole environment. This occurs mostly in the cases of measurements in areas with prevailing high resistivities, and if a weathered layer with considerably lower resistivity than that of the original rock has been formed near the surface. For this reason it is important to be acquainted with the properties of the two‐layer ground with an overlying conductive layer.

In the present paper attention will be drawn to theoretical calculations connected with the field of the homogeneous ground and that of the two‐layer ground.
POINTE AUTOMATIQUE*
Authors: BOIS P. , LA PORTE M.
Published: April 2006

Abstract

The automatic picking of seismic sections replaces the slow and painstaking task of manual reflection plotting with rapid and economical processing by computer. Essentially, reflection picking is a decision‐making problem which also can be considered as a sort of filtering. Mathematically this means multiplying the seismic data matrix by a more or less complex decision operator.

For the sake of economy, we give an initial solution for simple cases which only require easily automatized decision‐making criteria.

We describe another more elaborate method for use in examining seismic phenomena which are more difficult to spot.

The process used is based on the recognition of shapes and consists first of all of determining a series of characteristics capable of identifying each reflection on each trace and then of comparing these different characteristics from trace to trace so as to be able to judge the continuity or discontinuity of the reflections.

Automatic picking thus leads to a schematic time‐section in which only the horizons found by calculation are retained. An automatic migration program then transforms this time‐section into a depth‐section.