ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1969.tb02080.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1969.tb02081.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe paper presents a discussion of some of the noise features of the VIBROSEIS SYSTEM***and their bearing on the determination of the optimally weighted stack.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1969.tb02082.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractA 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.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1969.tb02083.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractLaboratory measurements, and a fewin situobservations, show that saturated marine sediments have interdependent mechanical and acoustical properties, Acoustically, of particular importance are the acoustic impedance, velocity of sound and the sound attenuation coefficient of the sediment. The first two properties can be measured relatively easily from a surface ship; the measurement of attenuation however, is more problematical. It is suggested that this can be achieved by a quantitative treatment of the acoustic data collected during routine sub‐bottom profiling over a variable thickness of superficial sediments. In the assessment of four different sediment locations in the Irish Sea it was found that quantitative treatment of the acoustic signals yielded both a value of the attenuation coefficient as well as a measure of the frequency dependence of the attenuation. In addition a statistical analysis of the signal intensities seems to provide an indication of the relative roughness of the bottom and sub‐bottom interfaces. From the wide range of information provided the mechanical properties of the sea‐floor sediment may be esti

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1969.tb02084.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

SummaryOne of the main objectives of seismic digital processing is the improvement of the signal‐to‐noise ratio in the recorded data. Wiener filters have been successfully applied in this capacity, but alternate filtering devices also merit our attention. Two such systems are the matched filter and the output energy filter. The former is better known to geophysicists as the crosscorrelation filter, and has seen widespread use for the processing of vibratory source data, while the latter is. much less familiar in seismic work.The matched filter is designed such that ideally the presence of a given signal is indicated by a single large deflection in the output. The output energy filter ideally reveals the presence of such a signal by producing a longer burst of energy in the time interval where the signal occurs. The received seismic trace is assumed to be an additive mixture of signal and noise. The shape of the signal must be known in order to design the matched filter, but only the autocorrelation function of this signal need be known to obtain the output energy filter. The derivation of these filters differs according to whether the noise is white or colored. In the former case the noise autocorrelation function consists of only a single spike at lag zero, while in the latter the shape of this noise autocorrelation function is arbitrary.We propose a novel version of the matched filter. Its memory function is given by the minimum‐delay wavelet whose autocorrelation function is computed from selected gates of an actual seismic trace. For this reason explicit knowledge of the signal shape is not required for its design; nevertheless, its performance level is not much below that achievable with ordinary matched filters. We call this new filter the “mini‐matched” filter.With digital computation in mind, the design criteria are formulated and optimized with time as a discrete variable. We illustrate the techniques with simple numerical examples, and discuss many of the interesting properties that these filt

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1969.tb02085.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

ResumeDe 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 fr

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1969.tb02086.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractA mathematical analysis is given of the phenomenon of equivalence in resistivity sounding, which is based upon the properties of the raised kernel function. Analysis of this function instead of the apparent resistivity function is justified because, as has been shown in a previous publication, variations in the apparent resistivity function lead to variations in the raised kernel function with relative values of the same order of magnitude The expression for the raised kernel function is expanded into a Mac Laurin series. Equivalence can occur only if the second order term of this series is negligible. The coefficient of the first order term depends on the resistivity and the thickness of the layer under consideration. There is an infinite set of combinations of values for these two quantities, for which the coefficient of the first order term has the same value. All these combinations represent equivalent layer distributions.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1969.tb02087.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractTotal gamma airborne radiometric survey of El Alamein area in the Western Desert has been carried out by the Atomic Energy Establishment. The flight lines are directed north‐south with 500 m spacing, while the ground clearance is about 50 m. Superimposition of the radioactivity profiles over El Alamein Oilfield shows a general decrease of gamma radiation in the central part of the structure framed by zones of relatively higher values. The aerial radioactivity of El Alamein Oilfield is described and it is correlated with some reported radiometric characteristics of other oil bearing structures. The distribution of aeroradiometric measurements over El Alamein Oilfield and its environment has been found to be lognorma

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1969.tb02088.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractAn efficient method of computing spectrum and cross‐spectrum of large scale aero‐magnetic field (or of any other two‐dimensional field) has been developed and programmed for a digital computer. The method uses fast Fourier transform techniques. Briefly, the method is as follows: a digitized aeromagnetic map is divided into a number of rectangular blocks. Fourier transforms of these blocks are computed using a two‐dimensional fast Fourier transform method. Finally, the amplitude of the Fourier transforms is averaged to give the desired spectrum. Computation of cross‐spectrum follows the same lines. In fact, the same programme may be used to a compute the spectrum as well as cross‐spectrum. The method has a number of computational advantages, in particular it reduces greatly computational time and storage requirements. The programme has been tested on synthetic data as well as on real aeromagnetic data. It took less than 30 seconds on an IBM 360/50 computer to compute the spectrum of an aeromagnetic map covering an area of approximately 4500 s

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1969.tb02089.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY