ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1970.tb02114.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1970.tb02115.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractWhen the fixed‐source electromagnetic method is applied the quantities measured are influenced by the resistivity of the whole environment. This occurs mostly in the cases of measurements in areas with prevailing high resistivities, and if a weathered layer with considerably lower resistivity than that of the original rock has been formed near the surface. For this reason it is important to be acquainted with the properties of the two‐layer ground with an overlying conductive layer.In the present paper attention will be drawn to theoretical calculations connected with the field of the homogeneous ground and that of the two‐layer g

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1970.tb02116.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThree common expressions for the normal moveout of recorded seismic events are investigated by numerical simulation procedures for accuracy in predicting the root‐mean‐squared (RMS) or mean, as the case may be, subsurface velocity function from seismic data. The principal investigation, for which detailed error curves are shown, was derived for a stochastic subsurface model composed of strata with thicknesses ranging up to 91.4 m (300 ft) and boundary velocity contrasts ranging up to 45.7 m/sec (150 ft/sec); there was a 95 percent chance of velocity increase with increased depth. The effects of changes in the basic statistical subsurface model are discussed.The results appear to confirm the judiciousness of the choices oftoand (x/z') as plotting parameters to be used with the respective percent errors in the three expressions, where are, respectively, the zero‐offset arrival time of, the offset distance of, and the mean‐squared velocity encountered by a seismic ray. Out of the three normal‐moveout expressions examined, the “straight‐raypath” expression with the RMS velocity substituted as its velocity term proved to be the most accurate in the determinatio

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1970.tb02117.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractDespite the use of CDP and digital methods the Zechstein base is still the deepest horizon in the vast salt‐dome basin of Central Europe for which continuous information can be obtained by reflection seismics. Thus in North‐western Germany, in addition to reflection seismics, the refraction seismic method has been increasingly used for a reliable survey of deeper horizons.The first part of the paper deals with the investigation of the various possibilities and limitations of refraction seismics with regard to the investigation of Pre‐Zechstein layers in a basin with a tectonically very complicated overburden. The recording techniques specially developed for continuous profiling of the desired refraction seismic arrivals and the data processing methods are described.The main problems of interpretation are then discussed, in particular with regard to depth representation. The advantages and disadvantages of the various methods, e.g. Gardner's, Hales' and Wyrobek's, and of the wave‐front method, are compared. On account of the tectonically complicated overburden Thornburgh's wave‐front method proved to be the most useful.In a further section the various possibilities for velocity determinations are mentioned, e.g. Wyrobek's determination of the overburden velocity, for which the wave‐front method automatically furnishes the necessary corrections to a deep datum.Finally, some examples are given for the results obtained, including some incidental information on the d

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1970.tb02118.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

ResumeLes étinceleurs àélectrodes multiples, permettent ?améliorer considérablement la finesse de la sismique à haute resolution.Un pouvoir séparateur de ľordre de 2 mètres peut être obtenu jusqu'à une profondeur de l'ordre de 150 mètres avec des étinceleurs à 1000 joules, comportant quelques centaines ?électrodes. Plusieurs enregistrements

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1970.tb02119.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractA two‐coil induction logging system in an infinite homogeneous medium has been theoretically analysed for the relative contributions of various ground elements to the total signal at the receiver. Unlike an earlier approximate treatment by Doll (1949), the present analysis takes skin effect into account (while neglecting displacement currents). Contour diagrams depicting relative contributions from every ground point and diagrams for vertical and radial/lateral investigation characteristics are presented. The results differ significantly from Doll's in the following points:1The relative contribution is frequency and conductivity dependent;2It does not show symmetry with respect to the center of coil system;3It alternates between positive and negative values with distance;4Real and imaginary contributions for a given conductivity and frequency are different from each other.The possibilities of a horizontal‐horizontal sonde is briefly examined and found to be inferior to the usual sonde because of its higher sensitivity to the mud column and the invaded z

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1970.tb02120.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe results of geophysical surveys carried out in the Kopili Hydel Project site in the United North Cachar and Mikir Hills district, Assam, to locate and trace underground caverns in limestone are presented. Electrical resistivity observations over known limestone caverns showed significant anomalies (high resistivity). In the course of the systematic electrical resistivity survey conducted at the eastern fringe of the Umrong basin to study the competency of the proposed reservoir, a number of indications of possible caverns in limestone were obtained and a few of them have been verified by drilling. An analysis of the electrical resistivity data also suggests that the deep seated caverns are aligned along an axis trending NNW‐SSE, which may represent a zone of weakness– presumably a fault–that has influenced the formation of the caverns in preferred direction. Drilling over a few of the geophysical indications have corroborated the presence of a fault along the eastern fringe of the Umrong

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1970.tb02121.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe digital computer technique described for interpreting resistivity soundings over a horizontally stratified earth requires two steps. First, the kernel function is evaluated numerically from the inverse Hankel transform of the observed apparent resistivity curve. Special attention is given to the inversion of resistivity data recorded over a section with a resistant basement. The second step consists in the least‐squares estimation of layer resistivities and thicknesses from the kernel function. For the case of S or T‐equivalent beds only one layer‐parameter can be obtained, either the longitudinal conductance, or the transverse resistance respectively.Two examples given in the paper show that a wide tolerance is permitted for Choosing the starting values of the layering parameters in the successive approximation procedure. Another important feature for practical applications is good convergence of the iterations. The method is probably best suited for interpreting profiles of electrical soundings with the purpose of mapping approximately horizontal interfaces at

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1970.tb02122.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

RésuméAprès avoir essayé?analyser, par voie optique, ľeffet de la réflexion fantôme sur des enregistrements sismiques, on montre ľapplication de deux méthodes de filtrage de ce fantôme sur des exemples réels.La première méthode utilise là mise à feu séquentielle de charges situées à différentes profondeurs dans un même trou; il s'agit ?un filtrage réalisé sur le terrain. Le deuxième procédé consiste à filtrer, au central, des enregistrements réalisés à des profondeurs de tir dif

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1970.tb02123.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY