摘要:

ABSTRACTThe use of MKS system units in preference to the cgs system facilitates accurate numerical calculation in magnetostatic problems in geophysics and the practice ofstatingthe 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.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1968.tb01957.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

ABSTRACTDetermining the shape of a pulse generated by an explosion solely from the data provided by the recorded seismic trace is a difficult and even ambitious task.Knowledge of parameters such as length and number of “arches” of the pulse under study is, in fact, indispensable in solving this problem.These parameters cannot be found directly in the seismic trace, which nevertheless contains a great amount of information. Autocorrelation, with its mathematical and statistical properties, is an efficient way of making the best of this information.We compute all the autocorrelations of reflections having a given number of arches which fulfil certain conditions determined in advance. Then, after statistical testing of some parameters pertaining to the autocorrelations (abcissae of zeros, of extrema …), we select only those with a maximum likelihood. It is sufficient to consider only the reflections whose autocorrelations have been selected and to arrange them in groups according to their shape and arch number in order to obtain average pulses.In so doing several solutions are arrived at, but when considering a given number of traces, a single record for instance, it is possible by comparing these results with each other to considerably reduce their number.In the last part of the paper the nature of the impulse obtained with our method is examined in order to find out whether it is “minimum phase” for carrying out decon

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1968.tb01958.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

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:1Variation of the number of guns in the system;2Shaping the frequency spectrum by using different sizes of airguns in the system;3Effects on signal‐to‐noise ratios as a result of stacking several small energy sources together;4Reproducibility 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

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1968.tb01959.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractDeep 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 give

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1968.tb01960.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

ABSTRACTThe 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 gi

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1968.tb01961.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

ABSTRACTThe accuracy of the magnetic registrations of a new field station constructed at Niemegk Observatory is described. The most important aspects for the construction were good mechanical stability, a good constancy of all physical data and the fact, that the station is ready in the field for solid registration ere long. The apparatus was proved during geomagnetic survey in the field, especially in view of the variability of the geomagnetic variations. The results obtained by field work and by comparison at observatories are good. It is planned to enlarge the registrations by means of photocellcompensators.Der Plan zur Konstruktion einer transportablen und schnell aufstellbaren geomagnetischen Feldregistrierstation geht schon auf das Jahr 1939 zurück. In diesem Jahr wurde von Fanselau ein Plan für eine solche Station den Askania‐Werken in Berlin‐Friedenau unterbreitet und zur Konstruktion empfohlen. Der Krieg verhinderte eine rasche Durchführung der Fertigungsarbeiten, so daß erst nach Beendigung des Krieges die Askania‐Werke den auf diesen Vorschlägen beruhenden Magnetographen fertigen konnten. Am Adolf‐Schmidt‐Observatorium für Erdmagnetismus in Niemegk wurden dann weitere geomagnetische Feldregistrierstationen entwickelt [1, 2, 3]. Bei der Konstruktion des Gerätes wurde bewußt auf Robustheit und Stabilität Wert gelegt, während der Gesichtspunkt, ein möglichst leichtes und kleines Gerät zu haben, nicht so sehr im Vordergrund stand. Von dem neuen Typ der Station sind inzwischen schon eine ganze Reihe von Exemplaren in Betrieb genommen worden, so daß es an der Zeit ist, einige Bemerkungen über Zuverlässigkeit in der Konstanz der Skalen‐ und Basiswerte sowie über andere instrumentelle Daten der Geräte zu machen. Auf Grund eingehender Messungen am Observatorium und im Gelände liegt genügend umfangreiches Material vor, um diese Frage

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1968.tb01962.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

ZUSAMMENFASSUNGDie Interpretation magnetischer Anomalien durch Modellkörper geschieht bevorzugt nach der indirekten Methode (trial und error). Dieses von Hand aufwendige Verfahren läβt sich mit Hilfe der Ausgleichsrechnung nach der Methode der kleinsten Quadrate Rechenautomaten übertragen.Die allgemeinen Grundlagen des Verfahrens werden beschrieben. Wesentliche Voraus‐setzungen sind:1)die Annahme bestimmter Körperformen2)das Vorhandensein von Näherungswerten der Unbekannten (Lage, Magnetisierung etc.)3)eine genügend groβe Anzahl von Meβwerten, um den Ausgleichsprozeβ durchführen zu können.Die Vorteile der Methode sind:1)weitgehende Automatisierung und schnelle Arbeitsweise bei Verwendung von Rechenautomaten2)Ermittlung der Fehler der UnbekanntenDie Methode wurde angewandt auf die Interpretation 2‐dimensionaler ΔZ‐ und ΔT‐Anomalien. Drei Körpertypen werden dem Rechenprogramm zugrunde gelegt, und zwar die unendliche und endliche diinne Platte und der Kreiszylinder. In die Maschine ein‐gegeben werden nur die Meβwerte. Die Interpretation erfolgt im einzelnen in folgenden Schritten:1)Ermittlung von Näherungswerten2)Bestimmung der Körper bester Annäherung3)Iteration für den Körper bester Annäherung.Die Maschine gibt die Endwerte der Unbekannten (Lage, Einfallen, Magnetisierung etc.) mit Angabe der mittleren Fehler sowie die hierzu gehörigen Modellanomalien aus. Diese Endwerte werden einem Zeichenautomaten übergeben, der die gemessene Kurve, die theoretische Kurve und die gesuchten Modellkorper zeichnet.Interpret

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1968.tb01963.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

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 formul

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1968.tb01964.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

ABSTRACTSeveral papers have been published in which the electromagnetic anomalies are described that are produced by conductive ore bodies of different shapes. No publications are available, however, in which the electrical current pattern is described that is induced in these ore bodies. Yet an insight in this electrical current pattern would be valuable in order to assess the possibilities of different electromagnetic techniques, for instance with regard to the determination of the dip and of the depth extent of plate shaped ore bodies.In the present paper computations are given of the electrical current pattern induced by an oscillating magnetic dipole in a semi infinite plate shaped orebody of infinitesimal thickness, in which the penetration depth of the current is infinitesimal to a higher order than the thickness of the plate. The computations are based upon an equation derived by Wesley for the magnetic field produced in these conditions, combined with the relation between the electrical current density in a laminar sheet and the magnetic field produced by this current at the surface of the sheet.The results of the computations show that, if the horizontal distance between the dipole source and the sheet is sufficiently small, the maximum current density of the return current may occur at a depth below the upper edge of the sheet which is appreciably smaller than the depth of the upper edge of the sheet below the surface. The depth of the return current becomes large when the horizontal distance between the source and the sheet is large.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1968.tb01965.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1968.tb01966.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY