bluuebunny/crossref_metadata_2025_split huggingface dataset:
FIVE‐LAYER MASTER CURVES FOR THE HYDROGEOLOGICAL INTERPRETATION OF GEOELECTRICAL RESISTIVITY MEASUREMENTS ABOVE A TWO‐STOREY AQUIFER*
Authors: FLATHE H. 
Published: April 2006

AbstractOne of the main tasks of geoelectrical techniques in their application to hydrogeological objects is the detection of aquifers with fresh water and the delimitation of such aquifers from impermeable or salt‐water‐bearing beds. In practice it frequently occurs that intercalated clay horizons divide an aquifer into several “storeys” of various thicknesses.The present paper deals with an aquifer consisting of two storeys (sand and gravel), above a substratum of good electrical conductivity (clay, salt water). By means of a set of 72 computed master curves, the possibilities of interpretation of geo‐electrical measurements above such a substratum are examined with respect to the specific resistivities of the overburden and the intercalated clay horizon. Different thicknesses of the two groundwater storeys are considered. The result gives an idea of the extent to which geoelectrical measurements may help to elucidate hydrogeological conditions; it also provides the geophysicist with practical hints for the performance and the interpretation of such measurements.
EXAMPLES OF SYNTHETIC REFRACTION ARRIVALS AND WIDE‐ANGLE REFLECTIONS*
Authors: BORTFELD R. 
Published: April 2006

AbstractThe exact responses of plane interfaces to incident spherical compressional waves are calculated by an electronic computer. The reflected part of the response is shown for various positions of the ‘shot’ and of the ‘receiver’ as well as for various velocity contrasts. This makes it possible to study some features of the reflection process, especially the behaviour beyond the critical angle.
SERIES FOR THREE‐DIMENSIONAL MIGRATION IN REFLECTION SEISMIC INTERPRETATION*
Authors: SATTLEGGER JOHANN 
Published: April 2006

ABSTRACTThe problem of three‐dimensional migration is solved for arbitrary, three‐dimensional, continuously differentiable velocity functions v=v (x4) by means of series.The derived formulae are applied to numerical examples.The possibility of approximating real, discontinuous velocity distributions by continuous functions is mentioned and illustrated by an example.The application of electronic computers, which is necessary due to the complexity of the formulas, is discussed.
DESIGN OF SUB‐OPTIMUM FILTER SYSTEMS FOR MULTI‐TRACE SEISMIC DATA PROCESSING*
Authors: FOSTER M. R. , SENGBUSH R. L. , WATSON R. J. 
Published: April 2006

ABSTRACTUsing optimum filter theory as a starting point, we describe a method for the design of practical multi‐trace seismic data processing systems. We assume the inputs to be the superposition of signal, coherent noise, and incoherent noise. The signal and coherent noise moveouts are described statistically by their probability densities. Our approach is to split the system into two stages. The first stage achieves optimum noise suppression but distorts the signal. The signal distortion is reduced in the second stage by an optimum finite memory inverse filter.The system that is obtained using our method of design depends upon the form of the probability density functions. We show two examples, ghost suppression and velocity filtering. In ghost suppression we choose a model with moveouts known exactly, which corresponds to delta functions for the probability densities. In velocity filtering the signal and coherent noise moveouts are equally probable within non‐overlapping ranges.The resulting system in each case is both simple and effective. In ghost suppression a simple shift and subtract cancels the coherent noise. The signal distortion is reduced by an inverse filter. The velocity filter system consists of differentiated moving averages applied to each trace, followed by a 90° phase shift and a low pass filter.
THE KÖNIGSBERGER RATIO AND THE DIPPING‐DYKE EQUATION*
Authors: HOOD PETER 
Published: April 2006

ABSTRACTThis article deals with the effect that the Königsberger ratio, the ratio of remanent to induced magnetization, has in modifying the dipping‐dyke equation. Many reversed dykes are found on aeromagnetic maps and their presence indicates that remanent magnetism must often play a significant part in the magnetic expression of normally‐polarized dykes. The methods for the measurement of remanent magnetization and susceptibility (k) are outlined, and the relationship between k and volume % magnetite (V) is discussed. It is proposed that a good approximation is k= 0.15 (x−1 ‐ x), where x=1‐V/100. The general equation for the dipping dyke, which includes the contribution of remanent magnetization, is given. A method of obtaining k from the magnetic map is also derived.
SUR LA DEFINITION DE L'ANOMALIE DE BOUGUER ET SES CONSEQUENCES PRATIQUES*
Authors: NAUDY H. , NEUMANN R. 
Published: April 2006

ABSTRACTWhen interpreting Bouguer Anomalies, it is important that the location of the point to which the corrected measurement is related, is correctly defined: the station itself or its projection on the datum plane. The consequences of this choice are not negligeable when the topography is rough.
LE MAGNETOMETRE AEROPORTE MP 121 SUD‐AVIATION
Authors: THOMAS J. 
Published: April 2006

AbstractProton precession magnetometers usually operate discontinuously since thy rely one intermittent impulses. The aerial versions of these magnetometers suffer from relatively high background noise. The type of magnetometer discussed in this paper has solved the two problems of discontinuity of measurements and reduced sensitivity due to background noise.Comparative texts with an established flux‐gate apparatus have given significant and convincing results.
SPONTANEOUS POLARIZATION STUDIES*
Authors: BECKER ALEX , TELFORD W. M. 
Published: April 2006

ABSTRACTSelf potential measurements, both in drill holes and on surface, have been made in and around sulphide mineralization. Similar measurements were carried out on small scale laboratory models. The potential and current configurations around theoretical sulphide bodies are also described. Results of the model and field work seem to verify, in a qualitative manner, the electrochemical mechanism of spontaneous polarization proposed by Sato and Mooney. Possible causes are suggested for the abnormally large surface anomalies frequently found in the field.
GEOPHONE DISTORTION OF SEISMIC PULSES AND ITS COMPENSATION*
Authors: O'BRIEN P. N. S. 
Published: April 2006

ABSTRACTAn electronic analogue was used to obtain geophone distortion of typical seismic pulses. Some of the results were checked by computation and in all cases agreement was extremely close. For late arrival events estimates of attenuation and phase shift may be made from the steady‐state response curves. It is explained why these curves are not applicable to the first peak, for which one must use the results in Table III.Ground‐geophone coupling introduces the same distortion as a very lightly damped galvanometer with a natural frequency usually in the range 100c/s—200c/s. In swampy terrain this frequency may reduce to 30c/s—40c/s and coupling effects may be severe.An electronic unit whose characteristics are the inverse of those of a geophone has been used to improve the first peak amplitude of a seismic refraction record. Since 1c/s geophones are often desirable in refraction survey it may well be more economic to use higher frequency geophones followed by their inverse filter.
MEASUREMENTS ON THE ARRIVAL REFRACTED FROM A THIN HIGH SPEED LAYER*
Authors: DONATO R. J. 
Published: April 2006

AbstractA theory is developed to predict the amplitude and velocity of the first arrival produced by a thin solid refractor embedded in a solid environment. Laboratory experiments on a three dimensional model substantially confirm the theory. The essential conclusion may be found in Figure 8 where it is shown that for a constant wavelength, and for thicknesses up to about one half a wavelength, the attenuation per unit distance decreases monotonically with increase of refractor thickness.The assumption is made that the amplitude, A, attenuates as (x)‐n exp(‐βx), where x is horizontal distance and n and β are constants. It is emphasised that it is difficult to obtain reliable values for n and β from the initial amplitude measurements.
ETUDE DU “POINT BRILLANT” SUR MODELES SISMIQUES*
Authors: COURONEAU JEAN 
Published: April 2006

AbstractThe technique of two‐dimensional seismic models offers a simple solution to the problem of pulse reflection at the interface of two solids. Particular attention is paid to the existence and character of the amplitude increase in the interference zone between PP and PPP. The following points are discussed:

– the considerable deformation of the pulse when such an increase exists.
– the desagreement existing in the neighborhood of the critical points between the amplitude calculated by plane wave theory and the amplitude observed for cylindrical or spherical waves.
– the nonexistence of such an increase when velocity or density contrasts are too great.
– the presence, in the case of very large velocity contrasts, of an increase of the amplitude in the zone of interference, between PP and PSP‐waves.
– the considerable importance of conversion arrivals (PS+SP).
– the necessity of taking into account the emission of distorsional waves so that the observed arrivals of conversion waves can be explained.
P – AND SV – WAVES FROM UPHOLE SHOOTING*
Authors: MEISSNER R. 
Published: April 2006

AbstractUphole recordings in sediments very often reveal shear waves. With their velocity and that of the P‐waves Poisson's ratio may be determined, this usually has unexpectedly high values.A number of up‐hole shots were recorded with a linear spread of geophones and with constant gain amplifiers. Calculations were made to show the effect of the free surface and ray divergence (the spread factor). The theoretical, relative amplitudes of the ground motion were plotted together with the observed values. In general, there is good agreement between theory and observation which is better for the P‐waves than for the S‐waves. The reasons for this difference are discussed.Finally, an absorption coefficient is calculated from the amplitudes measured at the surface.
METHODE DE CALCUL DE LA DERIVEE SECONDE VERTICALE DU CHAMP GRAVIFIQUE OU DU CHAMP MAGNETIQUE UTILISANT ĽINTERVALLE DES ISOGAMMES*
Authors: VAN NGOC PHAM 
Published: April 2006

ABSTRACTThis new method of calculation, of the second vertical derivative of gravity or magnetic fields is appreciably different from the classical methods because it is based upon the variations of the distance between the isogams rather than a regular grid with “constant spacing”. In a certain way, it is a method of “constant interval”. A number of practical advantages are inherent to the method, among these, the possibility to use the cartesian charts with bi‐logarithmic scales which make the calculation much easier, and the creating of iso‐error maps which are indispensable for the interpretation of the derivative maps. Three examples of practical application are given, two of them pertain to gravimetry, the third to aeromagnetism. These results are compared with second derivative maps obtained with other methods.
MULTIPLE EVENTS IN REFRACTION SHOOTING*
Authors: MEISSNER R. 
Published: April 2006

ABSTRACTA description and classification is given for those later events in seismograms of refraction–and wide angle reflection shooting which travel nearly parallel and at constant time intervals behind the first arrivals and which are frequently observed in field surveys. Multiple events with the velocity V1 of the uppermost layer may be caused by multiple P‐reflections and certain velocity conditions or by PS‐conversions. In addition to these types multiple events with the velocity V2 or Vn may be caused by reflected refractions or by reflected diving waves. The different types will be distinguished mainly by means of travel time–and amplitude‐considerations.
MODEL SEISMIC INVESTIGATIONS ON REFRACTED WAVES*
Authors: GUHA S. 
Published: April 2006

ABSTRACTThe headwave system for an incident P‐wave in a two‐layer case has been traced in the ‘inside’ of a two‐dimensional model and it is found that the measured fronts do not coincide with the wavefronts constructed according to the Huygen's principle. A refraction profile indicates different velocities near the critical distance but shows the true value for the higher velocity medium at greater distances. An error in the intercept time, which is about 6 % too high in the example, should, however, always be present even if extrapolation is done from the region where the profile shows the true velocity of the medium.
RAPID COMPUTATION OF THE GRAVITATION ATTRACTION OF TOPOGRAPHY ON A SPHERICAL EARTH*
Authors: TAKIN MANOUTCHEHR , TALWANI MANIK 
Published: April 2006

ABSTRACTA brief review of the existing methods of gravity reduction is given and a new method suitable for use on high speed digital computers is described. The method is based on the formula for the gravitational attraction of a frustum of a cone. The topographic contours are represented by polygons and the x and y coordinates of corners of the polygons constitute the input to the computer. The vertical component of the gravitational attraction is calculated by evaluating the cone formula for a number of vertical sections of the topography. Each vertical section is simplified by adopting a procedure of grouping and averaging for the distant points of the section. The effect of the earth's sphericity is taken into account by lowering the distant points of the sections by amounts determined by the curvature. The computations include the area close to the point at which the attraction is required and may be limited to an area defined by a circle centered at this point. The method is therefore compatible with the conventional zone chart methods.As an illustration of the method the gravitational attraction of Caryn Seamount in the Atlantic Ocean is computed. The total Bouguer correction and the Terrain correction are also computed for an area in northwestern South America and comparisons are made with hand computations by a zone chart method. As an example, for work at sea, the Bouguer corrections for an area near the Island of Mauritius in the Indian Ocean are computed and the effects of sphericity and three‐dimensionality are calculated.The gravitational attraction of two‐dimensional bodies can be computed in a very similar manner. The attraction of the Puerto Rico Trench model is computed and the results are compared with other methods. The effects of sphericity and assumptions involved in extending the models to infinity are discussed.
AN EVALUATION METHOD FOR GEOMAGNETIC DEEP SOUNDING, ITS DERIVATION AND PRACTICAL USE*
Authors: SCHEUBE H. G. 
Published: April 2006

ABSTRACTThe derivation and application of a new method of geomagnetic deep sounding, that is exploring for underground electrical conductivity anomalies by means of temporal variations of the earth's magnetic field, is presented.The problem is restricted to two dimensions (horizontal and vertical) and for the case of a nearly homogeneous horizontal component of the disturbance vector as compared with the vertical over the area in question.The basis of the method is a relationship between both components of the disturbance vector. The first step is a period analysis of the records and from this the construction of so called “characteristic functions”, one for each station, these functions being determined by the conductivity distribution of the earth's interior. The second step consists of a model interpretation of these functions.The method is applied to simultaneous records from five stations (U. Schmucker, 1959) within the region of the conductivity‐anomaly of Northern Germany. A preliminary model of this anomaly is given.
A PORTABLE PROTON PRECESSION MAGNETOMETER*
Authors: SARMA D. GUPTA , BISWAS S. K. 
Published: April 2006

ABSTRACTThe paper describes a transistorised, portable proton precession magnetometer constructed for surface geophysical prospecting. Constructional and circuit details are furnished. The readout of the instrument is digital. The accuracy of measurement is ± 1 part in 20,000. The maximum gradient of the total field under which a satisfactory measurement can be made is about 1 gamma/cm. The sensing head uses a single coil system with distilled water as the proton sample.
PART II: THE SECTIONAL RETRO‐CORRELOGRAM
Authors: ANSTEY N. A. , NEWMAN P. 
Published: April 2006

ABSTRACTThe retro‐correlation function (or auto‐convolution) of a seismic trace is obtained by correlating the trace against a time‐reversed version, of itself. The Sectional Retro‐Correlogram is obtained by the arrangement of retro‐correlation functions in sectional form, in the manner of the Sectional Auto‐Correlogram.During the process of retro‐correlation, each primary event on the seismic trace interacts with each primary event on the time‐reversed seismic trace to generate a first‐order surface multiple event. Similarly each primary interacts with each multiple, and each multiple with each multiple, to generate higher‐order surface multiple events. Thus the final appearance of the Sectional Retro‐Correlogram is that of a record section which contains no primary reflections.The travel‐time and sign of the events displayed on the Sectional Retro‐Correlogram are correct, but the amplitudes of the higher‐order multiples are exaggerated. Nevertheless there is often a remarkable correspondence between the Sectional Retro‐Correlogram and the later parts of the record section from which it was derived.
ω‐k FILTER DESIGN*
Authors: WIGGINS RALPH A. 
Published: April 2006

AbstractTwo‐dimensional band‐pass filters can be constructed by a simple extension of the theory of one‐dimensional band‐pass filters. Similarly to the one‐dimensional analogue the shape of the two‐dimensional filter is important in determining its effectiveness. The band‐pass filter formulation can be further refined so that the filter will concentrate its rejection energies in certain areas of the ω, k plane. Such band‐pass, band‐reject filters are found by solving a set of simultaneous equations.
REFRACTION LE LONG DES BANCS MINCES RAPIDES ET EFFET D'ECRAN POUR LES MARQUEURS PROFONDS *
Authors: LAVERGNE M. 
Published: April 2006

ABSTRACTRefraction along thin high velocity layers and along basement is investigated in two cases.a) high velocity layer just on the basement.b) high velocity layer higher above.Period and attenuation of refracted waves are givers as a function of the layer thickness H. Refracted arrivals along thin high velocity layers are visible at significant distances if the layer thickness is not smaller than A/6, where A is the longitudinal wavelength in high velocity medium. The pseudoperiod is proportional to the layer thickness H. The attenuation at large distance follows an x‐ne‐k1x law, where n is close to I and k1 is inversely proportional to H.Refracted arrivals along the basement are observable even in the case of thin high velocity layers situated in the overburden; their intensity is smaller and their pseudo‐period larger than when no layer exists in the overburden. The intensity of the basement arrival decreases and the pseudoperiod increases with increasing layer thickness.The pseudoperiod and the attenuation of refracted arrivals along high velocity layers and along the basement are also highly dependent on acoustic contrasts.Both arrivals from a high velocity layer and from the basement can be recorded simultaneously, provided the frequency spectrum of the seismic chain is sufficiently broad. In all cases layer arrivals show a character very different from basement arrivals.
ON THE ELECTROMAGNETIC RESPONSE OF CONDUCTORS IN THE INDUCTIVE METHOD OF PROSPECTING (MODEL STUDIES)*
Authors: PODDAR M. , BHATTACHARYA P. K. 
Published: April 2006

ABSTRACTIn the inductive method of prospecting, information on conductivity and size of conducting ore‐bodies located in non‐conducting host rocks, can be conveniently obtained by studying amplitude‐frequency relation or amplitude‐phase relation of their response with the help of suitable Master‐curves. Experiments carried out in the laboratory on the scale‐model method show these Master‐curves to be different depending on the type of primary excitation and the shape of conductor. Cases of sphere, plate and disc in uniform field, field of line source and dipole field have been studied with an Amplitude‐Phase Meter specially constructed in the laboratory for this purpose.
REFRACTION LE LONG DES BANCS MINCES RAPIDES ET EFFET D'ECRAN POUR LES MARQUEURS PROFONDS*
Authors: Lavergne M 
Published: April 2006

ABSTRACTRefraction along thin high velocity layers and along basement is investigated in two cases.a) high velocity layer just on the basement.b) high velocity layer higher above.Period and attenuation of refracted waves are given as a function of the layer thickness H. Refracted arrivals along thin high velocity layers are visible at significant distances if the layer thickness is not smaller than A/6, where A is the longitudinal wavelength in high velocity medium. the pseudoperiod is proportional to the layer thickness H. The attenuation at large distance follows an x−n e−k1x law, where n is close to I and R1 is inversely proportional to H.Refracted arrivals along the basement are observable even in the case of thin high velocity layers situated in the overburden; their intensity is smaller and their pseudoperiod larger than when no layer exists in the overburden. The intensity of the basement arrival decreases and the pseudoperiod increases with increasing laer thickness.The pseudoperiod and the attenuation of refracted arrival along high velocity layers and along the basement are also highly dependent on acoustic contrasts.Both arrivals from a high velocity layer and from the basement can be recorded simultaneously, provided the frequency spectrum of the seismic cbain is sufficiently broad. IN all cases layer arrivals show a character very different from basement arrivals.RESUMELa refraction le long des bancs minces rapides et du socle moins rapide sous‐jacent, est etudiee sur modeles dans deux cas:a) banc rapide reposant directement sur le socle;b) banc rapide situe plus haut dans le recouvrement.La period et l'attenuation des ondes rerractees sont donnees en fonction den l'epaisseur H du banc rapide. Les arrivees refractees le long des bancs rapides ne sont pas visibles sur une distance importante si l'espaisseur de ces bancs est inferieure a A/6 A designant la longueur d'onde longitudinale dans le milieu rapide. La pseudoperiode est proportionnelle a l'epaisseur H du banc. L'attenuation a grande distance suit une loi eb x−n e−k1x avec n voisin de l et k1 inversement proportionnel a H.Les arrivees refractees le long du socle sont observables en presence de bancs minces rapides dans le recouvrement, mais avec des internsites plus faibles que dans le cas d'unrecouvrement homogene. La pseudoperiode des impulsions refractees du socle augmente avec l'epaisseur H du banc rapide. L'attenuation en fonction de la distance est superieure a l'attenuation observee pour un recouvrement homogene, et elle croit avec H.La pseudo‐periode et l'attenuation des arrivees refractees le long des bancs rapides et des marqueurs sous‐jacents sont largement fonction des impedances acoustiques des milieux en presence.Les arrivees d'un banc mince rapide et socle peuvent etre observees simultanement a condition que la chaine d'enregistrement ait un spectre en frequence suffisamment large. On constate dans tous les cas que le caractere des arrivees des bancs est tres different du caractere des arrivees du socle.