摘要:

ABSTRACTThe basic principles of remanent magnetization are stated, and possible applications are discussed in the fields of age determination of rocks, the study of relative movements of continents, and investigation of the thermal history of rocks.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01406.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

ABSTRACTAn attempt is made to interpret some magnetic anomalies in Denmark and Northern Holland. As the thickness of the nonmagnetic sediments in the areas is large, the interpretation must depend mainly on computational procedures, i.e. a combined analysis of gravimetric and magnetic anomalies, assuming that the two kinds of anomalies originate in the same body.The mathematic basis of these computations is presented, and from this conclusions are drawn about both direction and intensity of the magnetism in the underlying rocks.On this basis, the magnetic declination in these rocks appears to be westerly for all the areas considered. This declination is, of course, a combined effect of induced and remanent magnetization. The corresponding magnetic inclination is smaller than the inclination existing at the surface, and in several cases the magnetic inclination in the rocks is clearly negative, i.e. directed upwards.Both the declination and the inclination in the rocks vary considerally from one locality to another. However, if we assume that these varying results are caused mainly by different ratios of the strengths of induced and remanent magnetism, the directions of remanent magnetism group themselves around a fixed declination, about ‐160°, and a fixed inclination, about ‐60°.Estimates of the magnitude of both induced and remanent intensities of magnetization are contained in these conclusions. In both cases the magnitude may be of the order 10‐2cgs units.The hypothetical geomagnetic poles corresponding to this direction of natural remanence are situated near the central part of the northern Siberian coast and near that part of the Antarctic coast just south of South

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01407.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

AbstractA special method is described for calculating the terrain correction of the observed gravity data. The ground around each station is divided into a certain number of sectors and a special integral of the topographical section is calculated along each dividing radius.A computation chart has been constructed, by means of which the integration is reduced to the measurement of an area or of the first moment of an area. A planimeter or alternatively an integrator have to be used for this measurement.The article shows how to trace the computation chart for the use of the first moment method.This method has been extensively tested by the author and on the basis of this experience it has been found that the method affords a considerable speeding up of the calculation and is, in this respect, superior to the other methods that have been used so far for calculating the terrain correction.The problem of the accuracy of the integrator is also discussed in this paper.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01408.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

ABSTRACTThe electrical resistivity of 60 pyrite, 31 chalcopyrite, 42 pyrrhotite, 8 arsenopyrite and löllingite, 6 cobaltite, 15 galena, 13 zincblende, 26 haematite, 46 magnetite, 16 various manganese minerals, 23 complex ores and 7 graphitic shale samples (mostly from Swedish localities) was measured by the four point method. The method and the precautions needed in its application are briefly discussed. The results are presented in the form of a table which also gives other relevant data on the samples (e.g. percentage of ore in a given sample). The results are believed to be of interest to geophysicists engaged in prospecting for ore by electrical methods.The following can be mentioned among the main conclusions. The electrical resistivity of ore samples varies “locally” on a single sample often by factors of 10–100 but usually within about ± 30% and it often varies by much greater amounts (factors of 100–10000) from one sample to another. The possible causes of such variation are mentioned. The resistivity of pyrite, haematite and magnetite ore samples does not show any significant correlation with the ore content for the samples investigated. There is furthermore no correlation between the standard deviation of the resistivity on a single sample on the one hand and sample resistivity or ore content on the other hand. In the case of chalcopyrite and pyrrhotite the observations suggested the following relations:For chalcopyrite:log10(resistivity in ohmcm) = (6.2±4.2)/(vol. %CuFeS2) – (I‐39 ± o.38)For pyrrhotite:log10(resistivity in ohmcm) = (73 ± 19) / (vol. %FeS) – (3.26 ± o.31)The paper concludes by giving the approximate limits within which the electrical resistivity of the various ores investigated appreas to lie. The feasibility of detecting these ores by electrical operations i

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01409.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

ABSTRACTDuring the last two years the Exploration and Production Research Laboratory, Shell Development Company, Houston, Texas, had occasion to evaluate a number of seismic amplifier channels submitted by various seismic contractors and manufacturers. From this study, material for the present paper has been collected.The modern trends to be found in the electrical design of up‐to‐date equipment are reviewed, and opinions of the E&P Research Laboratory, not necessarily shared by the industry, are expressed. No specific designs are mentioned, the material being presented in a general way.The over‐all elementary channel is discussed briefly and the various components are described functionally.Filtering is mentioned from a point of view of minimum requirements for an average reflection survey, and absolute sensitivity, minimum useful signal voltage from a geo‐phone, and noise are discussed.Gain control is treated in two regions–the automatic control region and the initial control region. For the former, static and dynamic control characteristics are discussed, and the factors influencing the control range are brought out. For the latter, it is pointed out when a system is said to require obligatory or optional initial suppression.Harmonic distortion, originating in the inductive components of the input circuit due to low‐frequency roller energy, is presented in a manner facilitating understanding of the distribution of low‐frequency filtering alon

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01410.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

ABSTRACTIt is proved that horizontally stratified media, the various materials of which do not differ in their Poisson number, can be considered as isotropic for reflections of a small dip when taking into account quasi‐longitudinal waves which have to be reckoned with in practice. Approximating the surface of the wave by an ellipsoid would, however, result in considerable errors.Moreover, curves are presented allowing practical calculations for steeper dips to be mad

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01411.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

ABSTRACTSince harmonic analysis of seismograms seems to become more familiar in the interpretation of seismic data, the author presents the results of a thorough check analysis. Following a fixed scheme, one seismogram is analysed by means of a mechanical analyser (system Mader‐Ott). Standard deviation of Fourier coefficients is examined, and scattering in phase values is discussed. At the best, in the range of maximum amplitudes of the spectrum, the method yields 6% in phase scattering. At the worst, on either side of the spectrum, 13 % are obtained. Generally 8 % have to be taken in account. (Percentages in periods of partial‐waves of the analysis). The results are in accordance with former routine analysis (Korschunow, 19

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01412.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY