ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1963.tb02055.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

AbstractA method is found for programming the calculation of gravity and magnetic profiles across two‐dimensional bodies of arbitrary cross‐section for high‐speed computers. It is based upon an idea applied recently by Worzel, Landisman and Talwani, of approximating the cross‐section with an n‐sided polygon. The gravity and magnetic formulae are functions of the coordinates of the vertices. A profile of each kind takes only a few seconds to compute, and the accuracy appears to be at least as good as that of g

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1963.tb02020.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

AbstractThe theoretical aspects of a general configuration of the tripotential prospecting method are described while particular cases of the method were described by Carpenter and Haberjam (1956) and Sarma (1961).

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1963.tb02021.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

AbstractThe accuracy of an airborne magnetic survey is limited by the following factors:1Slow (diurnal) variations of the earth's field.2Fast variations of the earth's field (earth field “noise”).3Drift in measuring equipment.4Magnetometer “noise” (electronics, orientors …).5External disturbances, miscompensation.6Irregularities in flight altitude.7Location errors.The relative importance of these different causes of errors is analyzed from two viewpoints:a)Direct interpretation of anomalies on actual records,b)Compilation of isogram maps and their quantitative interpretation (second derivative, reduction to the pole, …).In conclusion, these errors do not affect the direct interpretation of profiles of standard quality. For instance, if the average altitude of the plane above the magnetic bodies is 1000 m, a variation of its flight level of about 100 m does not introduce serious errors in the interpretation.On the other hand, compilation of contoured isogam maps is often difficult, and compensation of the previous errors is not always possible except by approximate, rule‐of‐thumb methods. Furthermore, when the interval between lines is greater than the depth of magnetic masses below the plane of flight, the contours are interpolated and do not represent the magnetic field. Sometimes the contouring can offer different solutions, and the map is therefore not objective; this could then result in errors larger than those from the other causes.To evaluate the quality of the map and its interpretation we must know the location of flight lines and the compilation process employed. It is also wise to avoid quantitative interpretation of small anomalies and limit oneself to a qualitative

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1963.tb02022.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

AbstractWhen inspecting maps that were obtained a few years ago as a result of the interpretation of aeromagnetic surveys, one is divided between feelings of satisfaction about well confirmed predictions, of regret about unfortunate choices or errors that could have been avoided by present experience and of confusion in regard to certain still poorly understood phenomena.Some documents of the Bureau de Recherches de Pétrole have been examined in order to evaluate the precision of aeromagnetic interpretations and to find possible sources of the observed discrepancies

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1963.tb02023.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYThe normal procedure in calculating the effective induced magnetisation of bodies is to introduce the demagnetisation factor. The theory of calculating the demagnetisation factor is however restricted to bodies of 2nd degree surface lying in a homogeneous field i.e. homogeneously magnetised bodies. All other bodies have to be approximated.Here, the method is based on iterative calculation of magnetisation fields, which makes it possible to calculate the effective magnetisation of any bodies, when the distribution of the inducing field and susceptibility are known.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1963.tb02024.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

AbstractRichards (1961) and several others have shown that wide angle reflections may attain large amplitudes. This note extends the plane wave calculations of Richards to include the effect of the phase changes which occur at angles greater than critical. On seismic pulses this introduces a time lead of up to one half period and alters peak‐to‐peak amplitudes by up to 15‐20 %.It is pointed out that the plane wave reflection coefficient is not applicable at angles very close to critical where the true reflection coefficient is reduced by a factor depending on (R/λ) ¼ In ultrasonic experiments this factor reduced the reflection coefficient by between ½ and ⅓.Neither does the plane wave coefficient apply at grazing incidence, when it has to be reduced by a factor depending on (R/λ)1‐0.Graphs are given of the amplitudes of wide angle reflections and head waves for two cases and it is concluded that, except for shallow refractors and angles close to critical, the reflection is always significantly greater than

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1963.tb02025.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

AbstractThe present work was initiated by an account given by Messrs. Kunetz and ?Erceville. It is greatly inspired by the article of G. W. Postma: Wave propagation in a stratified medium. There a construction of the “wave front” is given, starting from the surface of the velocities. This latter surface is the pedal of the wavefront. This theory is based on a certain section of Love's Treatise on the Mathematical Theory of Elasticity (Ch. XIII, sect. 209). However, no proof of this theory has been provided, neither in Postma's article nor in Love's work.It is the intention of this article to supply such a proof. Also the construction is proved to be valid only for distances from the point source which are large compared with the wavelen

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1963.tb02026.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1963.tb02027.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

Books reviewed in this article:Geomagnetismus und Aeronomie, Vol. II, Edited by Prof. Dr. G. Fanselau“Geomagnetic instruments and measuring methods” (Geomagnetische Instrumente und Meßmethoden) by Dr. H. Wiese, Dr. H. Schmidt, Dr. O. Lucre, Dr. Dr. F. FrölichLehrbuch der Angewandten Geologie(Textbook for applied geology). Edited by Prof. Dr. A. BentzBand I: Allgemeine Methoden, Kartierung, Petrographie, Paläontologie, Geophysik, Bodenkunde, written by well known authoritiesContinental Drift,edited by S. K.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1963.tb02028.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY