bluuebunny/crossref_metadata_2025_split huggingface dataset:
A SURVEY OF HIGH RESOLUTION GEOMAGNETICS *
Authors: LANGAN LEE 
Published: April 2006

AbstractThe development of optically pumped and monitored “atomic” magnetometers has allowed the application of greater resolution in geomagnetic measurements for exploration purposes. This paper presents a survey of instrumentation in use, the variety of exploration techniques that are being used in practice, and an estimate of their state of development.Alkali metals (rubidium and cesium) and helium have been used as active elements to obtain the magnetic‐field dependent Larmor frequency. Each of these instruments is capable of obtaining high resolution data (data with sensitivity numerically smaller than one‐tenth gamma). They have been adapted for airborne, land, and marine usage.Such sensitivity has enabled the rapid development of geomagnetic gradiometers, high sensitivity aeromagnetics, diurnally reduced ground surveys, broad‐band magneto‐telluric surveys, susceptibility measurements, and convenient magnetic search and location techniques. Outlines of each procedure and an example of its application are given.ResumeEn détection des richesses du sol, “les magnétomètres atomiques” qui fonctionnent selon le principe ?un pompage optique ont permis ?obtenir des mesures plus sensibles. Sont décrits les appareillages actuellement utilisés, les méthodes de mesure différentes, ainsi que la situation technique récente.La génération de la fréquence Larmor qui dépend du champ magnétique s'obtient par les métaux alcalins (le rubidium, le césium) et par ľhélium. Chacun des instruments utilisés fournit des résultats de résolution fine, inférieure au dixième du gamma. Des équipements furent réalisés pour ľutilisation aéroportée, sur navire, ainsi que sur terre.De telles sensibilités élevées ont été rendues possibles grâce aux nouveaux gradio‐mètres, aux aéro‐magnétomètres extra‐sensibles, aux mesures des profils terrestres avec correction diurne, aux investigations magnéto‐telluriques large bande, aux mesures de susceptibilityé et aux méthodes pratiques de recherche magnétique.Le sommaire explique les principes à la base et les applications de tous ces proédés.
UNITS IN GEOPHYSICAL PROSPECTING*
Authors: KOEFOED O. 
Published: April 2006

ABSTRACTA system of geophysical units is proposed which is based on the International System of Units, using the meter, the kilogram, the second and the ampere as fundamental units. A historical introduction is given and the reasons for preferring the use of the International System of Units in exploration geophysics, are explained.At the meeting of the European Association of Exploration Geophysicists at Stockholm a resolution will be proposed recommending the use in exploration geophysics of the International System of Units.
MATHEMATICAL DENOTATION OF STANDARD‐GRAPHS FOR RESISTIVITY PROSPECTING IN VIEW OF THEIR CALCULATION BY MEANS OF A DIGITAL COMPUTER*
Authors: VAN DAM J. C. 
Published: April 2006

ABSTRACTThis paper is the follow‐up of an earlier paper by the same author on the calculation of standard‐graphs for horizontally stratified subsoils. The method which was developed in that earlier paper was destined for handwork; it was laid down in master‐tables. The present paper deals with the presentation of similar methods to the computer expert in purely mathematical denotation. Two different denotations are described for the calculation of the image pole strengths involved. The first denotation is an improved version of Watsons formulae; it gives the total strengths. The second denotation preserves the character of successive approximations as described in the previous paper. Both denotations have been worked out until a six layer resistivity profile, but actually there is no limitation to the number of layers. There is no restriction to the resistivities of any layer. The only condition is now that all interface depths must be integers.This paper is followed by a paper on the relevant computer program by Argelo in this same issue
TWO YEARS' SURVEY WITH CESIUM VAPOUR MAGNETOMETER*
Authors: ROYER G. 
Published: April 2006

ABSTRACTThe present paper shows that the techniques developed and exploited by qualified geophysicists have brought high sensitivity magnetic surveys to an industrial stage.It will appear that for most mining and oil problems, either on land or sea, the necessary modern equipment already exists without developing it further in the future. In particular, the digitalization of data is practically finished for the magnetometer itself as well as for some navigation techniques.
MEASUREMENTS OF THE VERTICAL GEOMAGNETIC FIELD GRADIENT BENEATH THE SURFACE OF THE ARCTIC OCEAN*
Authors: HEIRTZLER J. R. 
Published: April 2006

ABSTRACTSimultaneous measurements made on an ice island and about 1000 ft. below show that magnetic anomalies can be detected in the presence of large time variations of the magnetic field. Attenuation and phase lag of time variations at depth are measurable but do not limit the utilization of the vertical gradient of geomagnetic total intensity for defining crustal anomalies.
A 1,800 MILLIVOLT SELF‐POTENTIAL ANOMALY NEAR HUALGAYOC, PERU*
Authors: GAY S. PARKER 
Published: April 2006

ABSTRACTA large self‐potential anomaly was outlined in 1963–64 at Tantahuatay near Hualgayoc in the Andes of northern Peru. Peak value recorded was–1842 millivolts–thus making it one of the strongest, or perhaps the strongest, SP anomaly ever measured. A lack of detailed geological data precludes the formulation of an adequate explanation for the Tantahuatay anomaly, but geological and mineralogical similarities with the well‐documented Venencocha anomaly near Cerro de Pasco, Peru (Kruger and Lacy, 1949), suggest that the anomaly arises from sulfuric acid associated with the mineral alunite. The anomaly obviously cannot be explained by the half‐cell mechanism of Sato and Mooney (1960), who place a limit of 700 millivolts on self‐potential anomalies over sulfide bodies. Further study of the Tantahuatay anomaly would be of interest in understanding self‐potential mechanisms in general.
THE VERTICAL MAGNETIC FIELD OF AN ALTERNATING CURRENT DIPOLE FOR HORIZONTALLY STRATIFIED MEDIA *
Authors: MUNDRY E. 
Published: April 2006

ABSTRACTFor the computation of the vertical component Hz of the magnetic field of a horizontal A.C. dipole lying on the earth's surface, a recurrence formula is presented for a horizontally stratified half space, to obtain the (n+ 1)‐layer case from the w‐layer case.By means of several computed diagrams for the two‐layer case, Hz can be determined for different ratios of conductivity of the subsoil and that of the overburden. Thereby the distance from the dipole as well as the layer thickness h are expressed in terms of the wave length A of a plain wave in the overburden. Assuming a sufficiently large conductivity difference, the results show that evidence about the subsurface conditions can be obtained if the distance between the measuring coil and the dipole is of the order of A/3, and if the thickness h of the layer varies within the range A/100 < h < A/6.As an example for the 3‐layer case, a nonconducting intermediate layer is assumed.
TOPICS ON SEISMIC RESEARCH AT THE MONACO OCEANOGRAPHIC MUSEUM *
Authors: LEENHARDT OLIVIER 
Published: April 2006

ABSTRACTThe author comments the techniques and methods used in continuous seismic profiling by the Monaco Oceanographic Museum during the last five years.Pinger probe give informations on the Mud layering and thickness. On the shelf or in abyssal plains, boomer and sparker are employed and allow to rise various geological conclusions. South coast of France, continental shelf in the Gulf of Lion, abyssal plain of the Ligurian Sea and Lake of Geneva are the areas concerned to with the results.
CARACTERES DE ĽONDE ELECTROMAGNETIQUE DE SURFACE ENGENDREE PAR UN DIPOLE MAGNETIQUE *
Authors: DUROUX J. 
Published: April 2006

ABSTRACTThe electromagnetic field radiated from a magnetic dipole lying on the ground is considered, in the extremely low frequency range (DC to 20 000 Hertz).Theoretical and experimental data are given on the characteristics of the surface wave (vanishing wave) generated at the air‐ground interface, in the case of an homogeneous subsurface.The case of a subsurface with electrical resistivity varying with depth is considered.It is shown how the above‐mentioned characteristics may be applied in the quantitative investigation of the electrical resistivity of the subsurface as a function of depth, in a method using the measurements on the ground of all the components of the radiated field: horizontal electrical components, vertical and horizontal magnetic components.
EXPLORING DEEP INTERFACES BY SEISMIC WIDE ANGLE MEASUREMENTS*
Authors: MEISSNER R. 
Published: April 2006

ABSTRACTAmplitudes of the vertical ground motion are larger in the critical angle region than in the near vertical region, especially amplitudes coming from deeper boundaries or interfaces with small velocity contrast. Four basic boundary models are used to derive specific travel time patterns for first order and higher order interfaces. The transition from reflected waves to diving waves in the supercritical angle region is shown for the different models.Examples from wide angle surveys in Bavaria and in the Buchara region in the USSR have many characteristic similarities. Travel time patterns and asymptotic velocities are almost identical. The most important boundaries of the continental crust ‐ the Mohorovč Ić discontinuity and the top of the crystalline basement ‐ correspond to two boundary models mentioned before. Amplitude and frequency investigations have been used to derive items of the M‐discontinuity. It is certainly a gradient zone and seems to have a lenticular structure with material of stepwise different velocities.
ANALYSIS OF DIFFRACTION PATTERN FILTERING OF VARIABLY DENSITY AND VARIABLY AREA RECORDINGS
Authors: SCHEEN W. L. , VAN ASPEREN M. HOOGENDOORN 
Published: April 2006

ABSTRACTWhen a small, transparent replica of a seismic section is illuminated by a homogeneous beam of coherent, monochromatic parallel light a diffraction pattern is created that is representation of the double Fourier spectrum of the recorded seismic waves, i.e. their spectrum in terms of frequency, f, and apparent wave number, k.Masking selected parts of this diffraction pattern causes the spectrum to be filtered: the recomposition of the filtered spectrum then provides a filtered section.The ideal seismic section for this purpose would be a continuous variable density section obtained from recording made at every point of the seismic line. The light transmission coefficient (in terms of light amplitude) at each spot of the replica should be linearly related to the instantaneous seismic signal strength at the spot on the seismic section to which it refers.Unfortunately we cannot make recordings at every point of a seismic line and in our practically realisable recordings we have to be content with sampling in the direction of the location coordinate x. This means that with variable density recordings aliasing will be present and evident in the spectrum obtained in the direction of k; furthermore, the aliased spectrum is also multiplied by a sine function of k because the recording obtained at a given station is not presented on the seismic section as a single line along the time axis, but occupies the entire width of the trace.The diffraction patterns created by variable density recordings of dipping sine waves, including clipped recordings, and of the effect of dip filtering in such sections are discussed. The efficiency of dip rejection is shown to decrease with increasing dip.The diffraction pattern of a variable density recording is found to be characterised by a relationship between point pairs in the pattern.No such simple relationship has been found for the diffraction pattern of a variable area section; the spectra of such VAR sections belong to a very special class, because the amplitude transmission coefficient has only two values, viz. 0 and 1.Consequently, selective masking of the diffraction pattern of a VAR section may give rise to a filtered profile that does not look like a VAR section at all.General statements about the diffraction pattern of VAR sections are hard to give, because the transmission coefficient at a given point in the replica is not proportional to the signal level in the seismic section at the relevant point.In the case of VAR presentation of harmonic waves it was found that, as well as the aliasing effect in the k direction, higher harmonics of the frequency are also introduced.Some synthetic examples are given that show dip filtering to be less effective with VAR than with variable density recordings.Some arguments are advanced in favour of the opinion that high‐pass filtering of VAR sections will have less success than low‐pass filtering. This is demonstrated by two synthetic examples.
VERTICAL PROFILING OVER A MEDIUM OF CONTINUOUSLY VARYING RESISTIVITY*
Authors: UNZ M. 
Published: April 2006

ABSTRACTAn interpretation method is suggested for apparent resistivity profiles over a medium of continuously varying resistivity. The medium is replaced by an equivalent laminated system of constant resistivity in each layer and evaluated by superposition. The approximation facilitates detailed subsurface profiling as required for underground storage projects or water infiltration schemes.
MAGNETO‐TELLURIC MEASUREMENTS IN THE NORTH GERMAN BASIN*
Authors: VOZOFF K. , SWIFT C. M. 
Published: April 2006

ABSTRACTMagneto‐telluric measurements were carried out at a group of eight sites, from Braunschweig to Lübeck, to determine the resistivity values associated with the North German conductivity anomaly. The data were analyzed for scalar and tensor apparent resistivities over the period range 5–2000 seconds. The results in general indicate very conductive (˜I Ω‐m) sediments overlying a resistive basement which is strongly lineated.Interpreted basement depth (˜6 km) is compatible with published seismic refraction data. Principal conductivity axes in the basement appear to be directly related to trends of salt domes and major troughs. A major change in axis direction occurs near the center of the North German anomaly.
THE EAEG'S CHOICE OF UNITS*
Authors: GREEN R. 
Published: April 2006

ABSTRACTThe use of MKS system units in preference to the cgs system facilitates accurate numerical calculation in magnetostatic problems in geophysics and the practice of stating the precise dimensions of every unit guards against confusion. Suggestions are made for the unique definition of quantities such as magnetic potential, etc. for which the undesirable circumstance of arbitrary alternatives still persists.
PNEUMATIC ACOUSTIC ENERGY SOURCE*
Authors: GILES BEN F. 
Published: April 2006

ABSTRACTIn recent years considerable work has been done to devise a satisfactory non‐dynamite seismic system that would replace dynamite in offshore areas. Prior to the advent of digital recording and processing, the non‐dynamite sources have generally not provided the depth of penetration or the resolution required for satisfactory seismic interpretation.More recent developments in non‐dynamite offshore marine sources include adaptation of the Vibroseis from a land unit to a marine unit, and adaptation of the Dinoseis unit from a land to a marine unit. The SUE (Seismic Underwater Explorer) system is a thermodynamic non‐dynamite source utilizing a mixture of propane and oxygen detonated in a special chamber approximately 15 feet below the water surface. This source gives penetration to more than 4 sec in areas typified by Gulf of Mexico type geology and shows deeper penetration than had previously been obtained by dynamite along the western United States in areas with 20 lb charge limitations. A pneumatic source, the airgun, has been in production use in the United States since June 1966. This non‐dynamite source provides an intriguing amount of versatility and can be expanded to provide additional energy as necessary to obtain the penetration desired. Tests using systems comprised of from eight to twenty‐three airguns show penetration in excess of 5 seconds in many areas. Power spectra comparisons both in amplitude and frequency content demonstrate that this is a controlled source generating a controlled seismic wavelet and a controlled frequency spectrum that can be tailored to fit requirements of particular areas. Sample sections obtained in the Gulf of Mexico and the Pacific Ocean offshore California show adequate penetration to 5.0 seconds reflection time.Quantitative measurements with the airguns demonstrate the effect of:

Variation of the number of guns in the system;
Shaping the frequency spectrum by using different sizes of airguns in the system;
Effects on signal‐to‐noise ratios as a result of stacking several small energy sources together;
Reproducibility of the initial pulse wavelet from shot to shot.

The improvement in record quality as a result of advanced digital processing with non‐dynamite sources is comparable to that obtained with dynamite sources. Non‐dynamite sources make additional improvements possible where high source multiplicity is advantageous. Excellent dynamic correlations yield accurate velocity control as well as definitions of apparent velocities attributable to multiples and primary‐to‐multiple amplitude relationships.Non‐dynamite sources are being used more and more extensively in offshore exploration. The advent of digital recording and processing provides a means for improving depth of penetration and resolution of many non‐dynamite sources.
NOMOGRAMS FOR SOLVING EQUATIONS IN MULTILAYER AND DIPPING LAYER CASES*
Authors: CHAN SIEW HUNG 
Published: April 2006

AbstractNomograms for solving equations in multilayer and dipping layer cases are presented. The nomograms constructed are used to solve the following equations: I. Intercept‐time formula. 2. Critical distance formula. 3. Critical angle formula. 4. Critical angle and dip angle formula. 5. Vertical depth formula.
ESSAI DE FILTRAGE NON‐LINEAIRE APPLIQUE AUX PROFILS AEROMAGNETIQUES*
Authors: DREYER HENRI NAUDY ET HENRI 
Published: April 2006

ABSTRACTDigital aeromagnetic profiles recorded with a high accuracy can be filtered with an electronic computer. Linear filtering is not very efficient, because the frequency spectrum of a given anomaly is very wide. But other methods are possible which, through a step by step analysis of the profile, leave some categories of anomalies unaltered while they remove the others completely.Our method uses as a criterium the width of the anomalies; it distinguishes and processes differently “bell‐shaped” and “multi‐legged” anomalies. Some examples of the use of the method are shown.
AUTOMATED STATIC CORRECTIONS*
Authors: HILEMAN J. A. , EMBREE P. , PFLUEGER J. C. 
Published: April 2006

AbstractThe widespread use of common depth point techniques has emphasized the need for accurate static corrections. Manual interpretation methods can give excellent results, but a computer technique is desirable because of the great volumn of data recorded in common depth point shooting. The redundancy inherent in common depth point data may be used to compute a statistical estimate of the static corrections. The corrections are assumed to be time‐invarient, surface‐consistent, and independent of frequency. Surface consistency implies that all traces from a particular shot will receive the same shot static correction and all traces from a particular receiver position will receive the same receiver correction.Time shifts are computed for all input traces using crosscorrelation functions between common depth point traces. The time shift for each trace is composed of a shot static, a receiver static, residual normal moveout if present, and noise. Estimates of the shot and receiver static corrections are obtained by averaging different sets of the measured time shifts. Time shifts which are greatly in error are detected and removed from the computations.The method is useful for data which has a moderate to good signal to noise ratio. Residual normal moveout should be corrected before estimating the statics. The program estimates the statics for correctly stacking common depth point traces but it is not sensitive to constant or very slowly changing static errors.
PROTEE A SELF‐ADAPTING DECONVOLUTION AND DERINGING PROGRAM*
Authors: D'HOERAENE J. , WLODARCZAK R. 
Published: April 2006

ABSTRACTDeconvolution and deringing are well known subjects and it is not necessary to state again their objectives nor the basical methods used to reach them. Let us just remember that, generally, among many others, the two following assumptions are made for simplification purposes:

—for deconvolution, it is assumed that the recorded seismic signal is constant, meaning that its shape is the same all along the time interval during which the trace is to be deconvolved;
—for de‐ringing, it is assumed that the ringing period is constant and that the intensity of the ringing phenomenon is independant of the time.

With these two assumptions, a single constant operator can be applied for deconvolving, deringing or both. In most cases, the time variations of the signal or of the ringing are small enough and the error resulting of the application of a constant operator is acceptable. It results into a slight increase of the noise level or into a small residual ringing in the processed trace.When this noise or the residual ringing are too important, the assumption of a constant signal and ringing period must be rejected. This is the case that is examined here according to the following steps:

—short definition of the problem;
—fast evaluation of some possible solutions;
—the selected solution: resulting approximations and how to obviate them, computing method and a remark about the operators;
—theoretical example: the efficiency of the process used is evaluated on data in which the results aimed at are known; the influence of the selection of numerical values to be assigned to the parameters is examined;
—real cases: comparison of results obtained with the Protee process and with more conventional processes assuming a time invariance or including a weighted composition of several conventional processes each with a different operator.
INTERPRETATION OF REFRACTED‐DIFFRACTED WAVES DUE TO DYKES*
Authors: FACSINAY LÁSZLÓ , SÁGHY GYÖRGY 
Published: April 2006

ABSTRACTThis paper gives an interpretation of a specific type of refracted‐diffracted waves. The solution is supported by the good accord of data in seismic and magnetic interpretation. Beyond solving the problem of the phenomenon, the interpretation of such events shows that in the exploration of dykes and intruded formations the refracted‐diffracted waves can—under favourable conditions—also render some useful information.
SEISMIC REFRACTION MEASUREMENTS IN THE BALTIC SEA*
Authors: BUNCE ELIZABETH T. 
Published: April 2006

AbstractSeismic refraction measurements were made in two areas of the Baltic Sea in June 1967. The refraction data were obtained in the course of the transmission measurements program of Operation MILOC BALTIC 67.Three profile pairs were obtained, two in the area south of Öland Island, Sweden, the third to the east, north of the peninsula of Hel, Poland. The water depths vary from 60 to 90 meters between the areas.The receiving positions for the two profiles south of Oland Island are only 46 km apart but the structures differ markedly. The northern section, only 500 m thick, shows a rather thin sedimentary cover above 350 m of 3.7 km/sec material that in turn overlies 5.6 ‐ 5.9 km/sec velocity material. The southern section, almost 2 km thick, has an equivalent amount of low velocity material, and a layer about 1 km thick having velocity 4.8 km/sec that overlies 6.0 km/sec velocity material. The eastern profile shows high velocity material, 5.6 km/sec, at 2.5 km depth.Correlation of the layers determined by seismic refraction with nearby geology suggests that the structural change south of Öland Island may represent the boundary of the Sarmatian Shield in this region.