bluuebunny/crossref_metadata_2025_split huggingface dataset:
ON THE PROPAGATION OF SEISMIC WAVES IN A SOLID BODY WITH ELASTIC AFTERWORKING*
Authors: MENZEL H. 
Published: April 2006

AbstractThe different equations of elasticity concerning the departure of the behaviour of rocks from perfect elasticity are discussed. The theory of elastic afterworking and its significance for the propagation of elastic waves is studied in detail. It is found that this theory does not explain the observations on seismic waves in exploration geophysics so well as the theory of viscoelasticity suggested by Ricker.
SUR UNE METHODE ANALYTIQUE DE CALCUL DE L'ANOMALIE REGIONALE*
Authors: BARANOV V. 
Published: April 2006

AbstractThe common notion, that the regional anomaly must be as regular as possible, can be translated into mathematical language by requiring that the regional anomaly shall be represented, over a not too large area, by a surface of the second or of the third degree. The residual anomaly is commonly defined by the requirement that its horizontal dimensions must be as small as possible. This implies that also its amplitude should be small. This requirement may be moulded into a mathematical form by stating that the square of the difference between the Bouguer anomaly and the regional anomaly, integrated over a certain area, must be a minimum. On these two definitions an analytic method is based for deriving the regional anomaly. Practical computation procedures are presented.
A TEST ON ELASTIC ANISOTROPY MEASUREMENT AT BERRIANE (North Sahara)*
Authors: CHOLET JACQUES , RICHARD HENRI 
Published: April 2006

AbstractThe geophysicists who attempted to evaluate elastic anisotropy of some bedded formations most often gave but little information about recording and interpretating the measurements.May be they did not lay enough stress on the fact that any determination of the anisotropy factor is a critical operation and that, to have some certainty. it must be made under good conditions and then discussed.Due to the very favourable conditions offered: undisturbed tectonics and topography, relatively regular series the Berriane district in Northern Sahara, is rather well suited to accurate measurements and to an anisotropy study down to 1,250 meters. Since measurements have been carried out in the wildcat drilled at Berriane by S. N. Repal, it seems interesting to communicate the results obtained and to discuss them according to the influence of high velocity layers.It can be noted that in the clay and sand series which have been investigated, anisotropy coefficient amounts to 1.09 or so.To conclude, it seems desirable that determinations made by numerous operators should allow a more accurate knowledge of the anisotropy factor in the main types of rocks.
A RATIONAL APPROACH TO THE DESIGN OF ELECTRICAL FILTERS AND OF SHOT‐HOLE AND GEOPHONE PATTERNS IN SEISMIC REFLECTION PROSPECTING*
Authors: MUIR F. , HALES F. W. 
Published: April 2006

ABSTRACTThe authors develop an optimum filtering theory for seismic reflection recording. A criterion of record improvement is applied to a mathematical model consisting of a set of wavelets superimposed on a random noise backgruond. This leads to the design of electrical filters and geophone and shot‐hole patterns with optimum filtering characteristics.
GRAVITY VARIATIONS IN SURVEYS ACROSS GEOLOGICAL BOUNDARIES *
Authors: COL‐L‐EY G. C. 
Published: April 2006

ABSTRACTThe paper discusses the variations of Elevation Correction Factors (E.C.F.) across various stratigraphical and structural occurrences with particular reference to the dipping bed, fault and horst. Graphs are prepared giving E.C.F. variations for various angles of dip and a method is suggested for application in the field. Errors in the linear variation that is commonly used for small angles of dip are discussed.The second part of the paper consists of the application to interpretation of (I) Change of gravity dip and (2) The gravity inversion. It is shown how from a gravity map the dip, position of outcrop and thickness of a dipping bed can be determined. The last part shows how anticlines can give rise to negative anomalies and that in the direction of dip similar structures can at one point have no surface expression and afterwards invert to positive anomalies. The danger of attempting to predict the size of structures in such areas is emphasised.
A RAPID METHOD OF DETERMINING THE FORM OF A SEISMIC*
Authors: TARRANT L. H. 
Published: April 2006

ABSTRACTA set of refraction line arrival times can be readily converted into a set of delay‐times providing the refractor velocity is known. If we then subtract the delay‐time at the shot‐point end, we arrive at a set of delay‐times representing the refractor depths at the receiving end. This paper is concerned with the conversion of such a set of delay‐times into a profile of the refractor.The method is semi‐graphical and very easy to apply. For each geophone station an arc of a circle is constructed, such that the envelope of the series of arcs represents the surface of the refractor. While the method is not quite exact, especially when the dips are large, it is of particular value in allowing for the effects of varying dips upon the offset distance. The method treats the overburden above the refractor as if it were of uniform velocity.
THE USE OF INTEGRATORS HELPS COMPUTING TERRAIN CORRECTIONS IN GRAVIMETRY*
Authors: MONNET C. 
Published: April 2006

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.
THE ELECTRICAL RESISTIVITY OF SOME SULPHIDE AND OXIDE MINERALS AND THEIR ORES*
Authors: PARASNIS D. S. 
Published: April 2006

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 is briefly discussed.
ON THE RELIABILITY OF HARMONIC ANALYSIS OF SEISMOGRAMS
Authors: KORSCHUNOW A. 
Published: April 2006

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, 1955).
THE TECHNICAL‐ECONOMIC ASPECTS OF AUTOMATIC DATA REDUCTION*
Authors: OLSON ROBERT W. 
Published: April 2006

AbstractThe background of automatic data processing as well as other improvements in prospecting methods is almost certainly economic. Consciously and intentionally or intuitively and even subconsciously, economic forces are the drive for improvements.Automatic processing can contribute to the increasing utility of seismic data. Reduction in the amount of routine work will permit talented people to utilize their time creatively on the more difficult problems. At the same time automatic reduction will provide for a greater volume of work. These two aspects will probably provide the first effective pressure for a high degree of automation.It is to be expected, however, that the ultimate and greatest value will be better interpretation; possibly more detail, possibly clearer more definitive interpretation, possibly both.Time concepts in the processing of seismic data are, of course, vital; either in simple time corrections of either static or dynamic nature or in treatment of signals in the time domain.Much development work is needed before these advantages can be realized. Principal development needed is an increase in dynamic range in the overall system.
THEORETISCHE FRAGEN ÜBER BÜNDELUNG VON GEOPHONEN BEI UNTERTAGE‐MESSUNGEN*)
Authors: CELMI?Š AIVARS 
Published: April 2006

AbstractThe arrays of multiple geophones used in underground seismic prospecting must satisfy two conditions:1) In each group only a few geophones can be used.2) The array must work in a rather wide frequency band.In the present paper the effect of the 3 parameters (geophone spacing, sensitivity and time shift) of a linear array is investigated in order to improve the directional sensitivity of the array.Necessary conditions which are independent of the frequencies are found for the optimum sensitivities of the geophones in a linear array.The optimum values of the parameters mentioned above are calculated for arrays of 2 and 3 geophones and for a frequency band width which may be used in underground seismic prospecting.
REPRESENTATION OF DEPTH‐CONTOUR MAPS OF ARBITRARILY CURVED REFLECTION HORIZONS, INCLUDING REFRACTION OF RAYS, THREE‐DIMENSIONAL CASE*
Authors: GRAESER E. , LODE W. , POTT G. 
Published: April 2006

ABSTRACTA method of constructing depth contour maps of arbitrarily curved horizons obtained from seismic reflection surveys is discussed. This method takes into account three dimensional refraction, avoiding the construction of seismic cross sections of any kind. It requires little work even if refraction at several horizons is taken into account. The multiple layer problem is traced back to the single layer case. Discontinuities in velocity are also taken into account.
TECHNIQUE NOUVELLE DE MODÈLES RÉDUITS POUR LA PROSPECTION ÉLECTRIQUE
Authors: CAGNIARD L. , NEALE R. N. 
Published: April 2006

AbstractThe use of small scale models in the interpretation of results of electric prospecting involves two majors difficulties: (1) the dimensions of the models and of the tanks in which the experiment is performed must be of unwieldy large sizes if one wants to be quite free from side effects; (2) the precise geometrical relation, in respect to the model, of the successive points where the interesting data are measured, requires an intricate installation, and is costly in both time and money.The technique which is described in this paper eliminates these difficulties as well as some others. The surface of the ground is represented by the lower face of a thick horizontal plate of plexiglas which is laid at the surface of the liquid filling the tank. This plate is pierced by a great number of small holes whose coordinates have been measured initially with the necessary precision. The electrodes are then introduced into these holes without creating any perturbation in the distribution of the lines of current flow. A solution of copper sulphate is used as the liquid in conjunction with copper electrodes. In this way, a D.C. excitation is possible, combining precision with convenience.
SOME PROBLEMS OF THE AEROMAGNETIC SURVEYS1)
Authors: DOMZALSKI W. 
Published: April 2006

ABSTRACTA brief description of the procedure usually adopted for ascertaining the accuracy o aeromagnetic data is given as a background to the discussion of factors which affect this accuracy. These factors fall mainly into two groups: spatial positioning, i.e. relation to the ground surface, and effects contributing to the observed relative magnetic values. The evaluation of the observed anomalies in terms of the most probable causes and the anomalies themselves are directly influenced by the amount of the available control of factors mentioned above. The effects of various factors, such as plan positioning, height keeping, diurnal drift, are discussed, the arguments being based on theoretical and practical premises.
ÉTUDE DE DÖMES DE SEL AU GABON *)
Authors: REYRE D. , VALLET J. M. 
Published: April 2006

AbstractThe present development of exploration in Gabon and the latest successes obtained by drilling have led the authors to publish a historical account of the geological and geophysical research concerning two particularly typical salt domes: those of N'Daminzé and Ozouri.Both of them are located in the western basin of Gabon: the first one in the zone of the savannahs, the second being a part of a series of salt domes in the delta of Ogooué.The western basin of Gabon forms, as a whole, a huge westward‐inclined monocline and is characterized by a general phenomenon of diapirism the type of which, in the delta of Ogooué, greatly differs from that of the savannahs zone.Because of the scarcity of outcrops in these zones geophysical exploration has been of valuable help.
RESULTS OF SUBSURFACE INVESTIGATIONS USING SEISMIC DETECTORS AND DEEP BORE HOLES*
Authors: BREWER H. L. , HOLTZSCHERER J. 
Published: April 2006

abstractThe wells Parentis 10 and 12 which are located on the eastern edge of the Parentis anticline were found to be considerably lower at the top of the reservoir series than had been expected.Unfortunately the village of Parentis is located in this important zone and no more seismic results could be obtained which might help locate faults and give a better picture of the area. To help in our understanding of the area, we attempted to investigate the subsurface conditions surrounding the wells by shooting shaped charges or primacord in the well and recording the returning seismic energy along profiles located on the surface. Thus far, we have used this method in three wells: Parentis 10, Parentis 12 and Lugos 2.With the data given by a velocity survey in each well, time‐distance curves have been calculated for several typical possibilities: horizontal layers, dipping layers and the effect of a fault. A comparison of the calculated and experimental curves shows anomalies which correspond to a change of the average velocity along the travel path, which can correspond to geological changes such as: a sudden change of dip, a fault or a thickening of the section.The anomalies have been studied on the different profiles from each well and a possible interpretation of the subsurface conditions has been given. The directions of the major accidents determined by this method are in general agreement with those found by the regular seismic shooting.
ĽENREGISTREMENT ÉLECTRONIQUE SIMULTANÉ DE PLUSIEURS COURBES DANS LES OPÉRATIONSDECAROTTAGE*
Authors: MURATORI G. , MANARA G. , CHIZZONI G. 
Published: April 2006

AbstractElectronic recorders have been used for recording borehole logs since several years.Some difficulties are however experienced in recording more than two curves at the same time.An experimental 4 curves electronic recorder has been constructed using up to date miniaturized servomechanism components.A general description together with performance data is given; applications of the same construction principles to pen recorders with a greater number of curves and to photographic recorders are also discussed.
IMPÉDANCES ET MATRICES CARACTÉRISTIQUES EN PROSPECTION ÉLECTROMAGNÉTIQUE*
Authors: LOEB J. 
Published: April 2006

AbstractAn analogy is established between the propagation of an electromagnetic field in a horizontally stratified conductive medium and that of currents in a linear electric network. This analogy will allow us to know in which case measurements executed at the surface of the ground can provide information about the properties of deeper layers. The situation is the same as when one tries, by means of impedance measurements at the input terminals, to know the properties of electric lines or lumped networks.A symmetrical linear network establishes between:Voltages V1 and V2 (respectively at input and output terminals)Currents I1 and I2 (respectively at input and output terminals), the relationship
image
is called the “phase constant” and Z the characteristic impedance The table
image
is called “characteristic matrix”If one then takes the horizontal components of an electromagnetic field, one can compare the voltage V with the horizontal electric field E (in volts m‐1) and the current I with the horizontal magnetic field H (in Amp m−1)For plane waves in vacuum, one gets (Schelkunoff) Z=C (velocity of light)A layer whose thickness is D has a phase constant⌈= 2 πD/λ (λ= wavelength)For plane waves in a conductive, non magnetic medium whose conductivity is δ, one gets
image
For the system of waves created by a point‐source one expresses the solution, since it is classical, as a sum or integral of different modes. For each of these modes, one can still write a bilinear relationship similar to (1), and calculate Z and ⌈.A generalization of this result is given.Boundary conditions that exist at the surfaces of separation are met by writing the continuity of E and H. This condition exactly corresponds to the fact that there one V and one I at the junctions of various sections of lines, or networks.The characteristic matrix of a cascade of networks‐or here that of a horizontally stratified ground– is the product of the matrixes of each network. If, in addition, one knows the end impedance–here the conductivity λn of the last layer, supposed to be infinite–one can compute the input impedance Re of the whole system. In electromagnetic prospecting, it is Re that conditions the observable field.Inversely, if measurements were infinitely accurate, the. knowledge of the surface field would give all the thicknesses D and conductivities δ of intermediate layers, in the same way that impedance measurements at the input terminals of a cable would allow to locate any failure. The imperfection of measurements causes the elements located too far away (from the point of view of wave attenuation) to escape detection.
DIFFERENTIAL ELECTRIC LOG*
Authors: COLOMBO U. , SALIMBENI G. , SIRONI G. , VENEZIANI I. 
Published: April 2006

ABSTRACTA new logging method, which makes use of specific chemical reactions to locate petroleum or other minerals has been developed. The method has been named “Differential Electric Log” (CED).In this paper the application to the CED method of redox (reduction/oxidation) reactions is discussed. A series of organic oxidants was found, capable of undergoing reaction with crude oil, sulphur, mineral sulphides, lignite. A small amount of an oxidant of this type is added to the drilling fluid and pumped into the borehole where reaction takes place in correspondence with layers containing oxidizable minerals. Two SP logs, recorded before and after the oxidation, are compared and the presence of such minerals is thus detected.A theoretical hypothesis explaining the mechanism of the potential change due to the chemical reaction is proposed both in the case of electronically conducting and non conducting minerals. The influence of redox potential on SP is discussed.The results of laboratory experiments on several different oxidizable ores and those of field tests performed on pyrite, lignite, and oil wells are reported on and discussed on the basis of the theoretical hypothesis proposed.
VARIATION OF THE WORDEN GRAVIMETER SMALL DIAL SCALE FACTOR WITH TIME*
Authors: SAXOV S. 
Published: April 2006

AbstractA series of repeat observations during a period of 5 years reveal a variation with time of the Worden gravimeter No. 142 small dial spring system. A possible change in the gravity difference concerned is ruled out. It is shown that the small dial scale factor has diminished by about 0.25 % within the last two years against about 0.5 % four to five years ago. The ratio of L.D. to S.D. has been analysed and the results obtained show confirmation of the change in the small dial system and prove a consistency in the large dial system.
PROBLEMS AND RESULTS WITH REFRACTION SEISMICS IN BOREHOLES
Authors: HOLSTE W. 
Published: April 2006

AbstractRecently, quite good determinations of interfaces have been made by means of seismic well surveys. These were carried out for various oil companies in Northwest Germany, especially on salt‐domes, and in Southern Germany, and in the area of the Upper Rhine Valley. It was the purpose to determine the configuration and position of salt‐flanks and important planes of stratification in the neighbourhood of deep wells, and thus to reduce the risk of expensive wells.For the delineation of the boundary surfaces the method described by Gardner in “Geophysics 1949” was applied.The problems arising and the results obtained are discussed in connection with some interesting examples. From them we see, above all, that a knowledge as precise as possible of the seismic velocities of all media involved in the measurement is very important. A good idea of the general stratification in the area of deep wells seismically surveyed will make possible a rational and adequate planning of the survey program and will facilitate the interpretation.
RESULTS OF SURFACE REFLECTION SEISMIC MEASUREMENTS IN THE SIDERITE DISTRICT OF THE SIEGERLAND*
Authors: REICHENBACH R. , SCHMIDT G. 
Published: April 2006

AbstractThe iron ores of the Siegerland‐district are found in lodes occurring in schists of Lower Devonian age. In the course of the geophysical exploration for these ores, an attempt was also made to clarify the structure and the tectonics of the substratum of the sedimentary rock formations by seismic reflection measurements from the surface. Reflections were recorded in great numbers from layers of Silurian and Devonian age. The form of the folding of the strata derived therefrom corresponds well with that deduced from geological investigations. Beyond that, correlatable reflections were recorded from horizons down to a depth of nearly 25 000 m. It turned out that the iron ore lodes known from the mine workings occur almost vertically above those places where greater dislocations appear in the deepest substratum, and which geologically could be interpreted as fracture zones. The results so far obtained seem to be indicative of the fact that the tectonics of the deepest substratum and the occurrence of ore deposits are related to each other.