ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1978.tb01610.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1978.tb01611.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractA finite realization of a discrete random noise process may be considered as a one‐sided energy signal. Its phase property can then be described by means of the center position. The samples of such a realization are the components of a random signal vector and the center position is therefore a random variable. A statistical analysis shows that the expected value of the center position equals half the time duration of the realization. This implies that theZ‐transform of the realization may be expected to have an equal number of poles and zeros inside and outside the unit circle. The standard deviation from the expected value of the center position is shown to depend on the time duration of the realization and on the autocorrelation of the process. It follows that, for processes that can be described by the convolution of a white series and a disturbance wavelet, the center position is independent of the phase property of the wavelet. A conclusion based on these results is that the homomorphic technique of wavelet estimation through cepstrum stacking must give questionable outcomes. Another conclusion is that the super‐position of a realization of random noise on a minimum phase wavelet will in general give a mixed phase resulting signal. It is pointed out that schemes for the derivation of deconvolution filters do not take account of this pheno

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1978.tb01612.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractIn western Canada, the near surface weathered zone has variable velocity and is underlain by more uniform subweathering material. The uphole time is often used to compensate for the weathered zone, but there are limitations to its use.A method is proposed using the refraction delay time which is exactly proportional to the weathering correction time for several commonly assumed weathering velocity functions. The method does not require accurate determination of velocities or weathering depth nor even the depth of shot, yet is theoretically exact. A strip off timetris used to replace the weathered zone mathematically with high velocity material wheretr= zD/F, whereDis the delay time andFthe Blondeau factor.An algorithm using first break times is proposed that is amenable to computer use for determiningDfor each geophone point.Fmight be constant in some areas but is more likely a variable to be solved in an automatic static program. Thus, structure and residual statics can be handled at once.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1978.tb01613.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractIt is well known that the application of the “bright spot’ technique has been more successful in marine prospecting than in land prospecting. This is due partly to the problem of distortion of the seismic signal caused by the geophone‐ground coupling, especially when carrying out high resolution, shallow seismic surveys in swampy terrain.The effect of geophone‐ground coupling on the response of a single geophone to the incident compressional waves has been treated by several authors. However, they have always neglected the influence of mutual interaction between an array of geophones on the response of each geophone forming the array. We show that mutual interaction, which results from the re‐radiation of the incident compressional waves by the geophones forming the array, can have considerable effect on the response of each geophone.The effect of the geophone‐ground coupling on the response of a seismic channel is considered in the absence and presence of mutual interaction between a group of geophones for the case when the shear wave velocity of the soil varies by a fact

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1978.tb01614.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractExpressions for the I. P. activity coefficient for an inhomogeneous sphere with the conductivity increasing/decreasing from the core towards the periphery according to a power law have been derived.In certain geometrical situations of the electrode configurations a negative I. P. signal is obtained. The negative I. P. may be understood as due to modifications in the discharge current from the polarized medium during the discharge process.The results of the investigation may be useful for more accurate interpretation of I. P. anomalies due to isometric inhomogeneous bodies.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1978.tb01615.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractMagneto‐telluric experiments were performed in August 1974 in the Muhos Jotnian sedimentary formation and the Koillismaa Precambrian basement complex by the Centre de Recherches Géophysiques, Garchy, and the Department of Geophysics, University of Oulu, employing the “Résistivimètre magnéto‐tellurique”, an instrument which permits apparent resistivity values to be observed at eight pre‐selected frequencies between 8–1700 Hz.Preliminary soundings were made on the Muhos formation and on its surroundings, after which a magneto‐telluric profile was measured involving eleven sites on a line 13 km long extending across the formation. Some further soundings were made at certain sites of known stratigraphy. The resistivity values in the sedimentary formation were found to vary between 10 ωm and 200 ωm, while those in the basement were markedly higher. This resistivity contrast suggests that the method seems to be suitable for delimiting the sedimentary formation.Soundings made on the basement at Koillismaa show apparent resistivity values in the range 1000–20000 ωm. The interpretation of these soundings was in agreement with other, independently obtain

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1978.tb01616.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe conventional methods of magnetic interpretation consider in general the induced magnetization only. However, in a computer oriented inverse method, the direction of magnetization can be taken as arbitrary. Following this procedure, this study aims to present a realistic interpretation of an aeromagnetic anomaly from Chitaldrug Schist belt (Mysore, India) assuming a three‐dimensional configuration of the causative source possessing remanent magnetization. It further provides the direction of remanent magnetization of the source rock as obtained from the analysis of the magnetic anomaly. The total intensity map obtained delineates the surface and sub‐surface structures in the region and provides informations regarding the characteristics of primordial cr

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1978.tb01617.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractFor a thin highly‐conducting layer with given longitudinal conductance the recurrence formulae for ann‐fold horizontally stratified subsoil are established for d.c. resistivity and magnetotelluric soundings. Similarly, a thin low conductivity layer with given transverse resistance is treated in the d.c. case and a non‐conducting intermediate bed in magnetotellurics. Model curves for a thin high‐ or low‐conductivity intermediate layer in the three‐layer case have been carried out, which may serve as an extension of the well‐known three‐layer diagrams for a Schlumberger configuration. The corresponding model curves in magnetotellurics are given.By numerical comparison of these curves with real three‐layer curves some diagrams have been developed to show the allowed thicknesses of the intermediate layer in the Schlumberger case and in the case of magneto

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1978.tb01618.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe minimum distance criterion of Backus and Gilbert is used to determine the depths of line masses approximating the subsurface two dimensional distribution of density differences responsible for the observed residual Bouguer anomaly values. The quantity minimized is the sum of the squared differences between the starting trial depths and the desired final depths of line masses. The search for the desired depths is limited to preset depth ranges.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1978.tb01619.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY