摘要:

AbstractComputations have been made for the effect of ground slope in combination with transmitter coil misorientation on different electromagnetic depth sounding systems and sets of frequency sounding master curves are presented for different angles. The effect of a thin air layer due to the elevation of coils above ground surface has been studied for different systems. Also discussed are the effects due to an error in transmitter‐receiver coil separatio

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1973.tb00011.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractAttention is given in this paper to the display of intensive seismic refraction information in a convenient form similar to spatial display techniques being developed for resistivity methods.An observational space for first arrivals is defined and illustrated with respect to some simple structures and the possible use of such a representation in diagnosis is discussed.The spatial display is suitable both for steeply dipping and gently dipping structures. In the latter case, the low relief space may be subjected to further operations to produce apparent velocity distributions and values simply related to plus times.A practical example of the latter process and the subsequent interpretation is given.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1973.tb00012.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractIn the region of Paktia (SE Afghanistan) geoelectrical resistivity measurements and airborne‐magnetic surveys were carried out. Although the aims of the two investigation methods were different, it was possible to draw new conclusions by combining the results obtained so far. The problems were: 1. Location of aquifers and determination of their structural position. 2. General survey to determine the crystalline basement as a basis for oil exploration.Using geoelectrical methods, the depths of magnetic bodies were determined precisely, whereas the combination with airborne‐magnetic methods enabled an extrapolation of the geoelectrical results from profiles to the subsurface. By geoelectrical means the fill of intermontane basins was classified and sedimentary thicknesses of at least 1400 m were identified.The magnetic anomalies are divided into both broad anomalies with small amplitude, caused by the crystalline basement, and narrow anomalies with large amplitude, caused by basic volcanics (ophiolites). The magnetic anomalies show that the occurrence of ophiolites is restricted to faults. The upper surface of the magnetized crystalline basement rises from 3000 m b.s.l. in the W to o m in the E. Thus, the concept of the geological structure of this region (trough to the W, swell to the E) is confirmed.ZUSAMMENFASSUNGIm Gebiet von Paktia (SE‐Afghanistan) wurden geoelektrische Widerstandsmessungen und airbornemagnetische Messungen durchgeführt. Obwohl die Fragestellung für beide Untersuchungsmethoden unterschiedlich war (einmal: Ortung von Grundwasserleitern und Klärung ihrer strukturellen Lage, zum andern: Übersichtsvermessung zum Nachweis des Kristallins als Grundlage der Erdölexploration), konnten durch eine Kombination der Ergebnisse neue Aussagen gewonnen werden.Mit Hilfe der Geoelektrik wurde die Tiefenlage der magnetischen Störkörper präzisiert, umgekehrt erlaubte die Verbindung mit der Airbornemagnetik die Ausdehnung der Geoelektrik‐Ergebnisse von Profilen in den räumlichen Untergrund. Durch die Geoelektrik wurden die Füllungen der intromontanen Becken gegliedert und Sedimentmächtigkeiten von wenigstens 1400 m nachgewiesen.Die magnetischen Anomalien gliedern sich in breite großräumige Anomalien mit geringer Amplitude, deren Ursache im kristallinen Basement, und engräumige Anomalien mit großer Amplitude, deren Ursache in basischen Vulkaniten (Ophioliten) zu suchen ist. Die magnetischen Anomalien zeigen, daß die Ophiolithe an Störungen gebunden sind. Die Oberfläche des magnetischen Kristallins steigt von 3000 m b.s.l. im W auf o m.s.l. im E an und bestätigt damit die Vorstellung vom geologischen Bau des Gebietes

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1973.tb00013.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractThe use of arctangents rather than arcsines in the expression for the gravitational attraction of a homogeneous rectangular prism reduces computational difficulties. Once a subroutine is available to compute one component of attraction in a Cartesian coordinate system, the other components may be obtained by cyclic permutation of the field point and body coordinate parameters. This technique also readily provides derivatives of the gravitational attraction and hence forms a compact method for the calculation of a magnetic anomaly due to a homogeneous rectangular magnetic prism.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1973.tb00014.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractThe values of the filter coefficients used for the computation of electromagnetic sounding curves are studied in conjunction with the values of the input function to the filter, or the range of values which the input function may assume, and the filters are broken off at such a place that the error in the sum of the products of filter coefficient and input function does not exceed a prescribed value. This analysis is carried out for the horizontal coils system, the perpendicular coils system, and the vertical coplanar coils system. The lengths of the filters so derived depend on the layer parameters, the frequency and the coil spacing. Even in the most unfavourable cases the filters are shorter than the filters published by Koefoed, Ghosh, and Polman (1972).

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1973.tb00015.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractTo specify intelligently a nondynamite source in a marine seismic data‐collection system, it is important to use all known parameters of the system—source, receiver, and recording‐system characteristics. A technique has been developed to design the far‐field pressure pulse of an air‐gun array by taking these parameters into account.Important source variables to consider are interaction among guns in the array and the depth of the array. Near‐field pressure signatures of individual guns, which are relatively unaffected by boundaries, have been used to‘construct’the far‐field pressure pulse of the array by considering these variables. Comparison between constructed pulses and measured far‐field pulses shows substantial agreement.Streamer depth and recording‐system bandpass should also be considered when designing an air‐gun array. Comparison of far‐field pressure pulses for several bandpasses clearly shows the importance of considering this variable; e.g., the initial pulse is severely attenuated when a high‐cut filter is used. Likewise, an additional filtering effect due to the streamer's proximity to the surface should be taken into account.Design of an air‐gun array using the principles just outlined

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1973.tb00016.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractWith the help of the principle of superposition the Input response of a conducting infinite horizontal homogeneous cylinder is synthesised from its step‐function response. The variation of transient peaks and the time lag between the secondary and primary fields with the cylinder constitution parameter are illustrate

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1973.tb00017.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractMany practical energy sources are available for land use and likewise a goodly number for marine operations. However, the transitional region between navigable water and negotiable land is poorly served. The vehicles that are capable of operating amphibiously are limited in the pay‐load they can transport, and in the bulk of apparatus that can be operated from the space available. The Flex‐O‐Gun (Trademark of Geo Space Corporation) is a new, lightweight gas exploder designed to meet the requirements for operation in rivers, bays, and marsh areas not generally accessible to the larger, heavier systems such as the Dinoseis (Trademark of Atlantic Richfield Company), Vibrator and Air Guns. Weighing less than 70 kilograms, the Flex‐O‐Gun requires only modest sources of oxygen and propane and the associated firing equipment for operation.The gun delivers energy by the sudden introduction into the water of high pressure gases resulting from detonation. The device is unique in that the underwater gun assembly contains no gas mixing or firing elements. A flexible, metallic hose conveys the charge of mixed gases and subsequent detonating flame to the gun from control and firing mechanisms located above the surface. With its small weight and total space requirements, the Flex‐O‐Gun can be operated from small boats, buggies, or trucks, and is easily transported.In this paper the features of the gun are described and the results given of tests of its operations. An implanting device is also discussed which extends its application to viscous formations. The device employs water jets mounted below the gun to wash down a hole and insure placement of the gun at depths to obtain maximum

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1973.tb00018.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractDividing a vertical conducting vein into horizontal strips, response of each of them is obtained for various transmitter receiver orientations.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1973.tb00019.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractThe geophysicist involved in the analysis of two‐dimensional data should have an understanding of the two‐dimensional finite Fourier transform and the mechanics of two‐dimensional filtering. Frequency aliasing must be considered when working with sampled data. In two dimensions it is advantageous to consider aliasing in terms of the overlap of the repeating spectra inherent in the finite Fourier transform. Two‐dimensional filtering can be performed as a transient convolution in the space domain, as cyclic convolution utilizing the frequency domain or as the multiplication of polynomials using thez‐transform. If the “edge” effects are removed, the results of the three methods

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1973.tb00020.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY