bluuebunny/crossref_metadata_2025_split huggingface dataset:
RELATIVE DETERMINATION OF THE DENSITY OF SURFACE ROCKS AND THE MEAN DENSITY OF THE EARTH FROM VERTICAL GRAVITY MEASUREMENTS*
Authors: DOMZALSKI W. 
Published: April 2006

AbstractThe gravity difference between two stations, one at the surface and the other underground vertically below the former and at a given distance from it, depends on the mean density of the earth, σm as well as on the density of the layer of rock contained between the two stations. When one of these densities is known, the other can be computed from this gravity difference. The reliability of this determination depends on the relative accuracies with which σm and σ can be obtained.These accuracies are discussed in the paper. The mean density of. the earth has been determined with an accuracy of approximately 0.01 gr/cm3. The determination of the density of a layer of rock depends on density determinations of rock samples which are not representative of the layer as a whole. Thus the accuracy of the value of σ based on a number of sample determinations will depend on many factors, including the method of averaging the density values obtained from the samples and the degree of uniformity in the geology.To investigate the problem discussed above, three sets of gravity measurements were made under differing conditions. In each instance a number of pairs of stations vertically above each other were occupied on the surface and underground. The results computed from the data on each pair of stations in a set of measurements were considered as repeated measurements of the same quantity, and the most probable value was calculated.The results demonstrated that the accuracy varied with the conditions prevailing in the area where the observations were made. In Godstone Quarries the dip of the strata was negligible, the rocks fairly uniform and structural conditions undisturbed. Consequently, although the rock layer between the surface and underground stations was only of the order of a hundred feet, the mean density of the earth computed from the average density of the rock samples, was very close to the accepted standard value of 5.52 gr./cm3. This agreement, however, was easily upset when only one random sample density was assumed as representative of a given formation.In a different locality in Cumberland the observations were made in a mine and on the surface. The rock layer between the surface and the underground stations was approximately a thousand feet thick. One set of measurements followed a line parallel to a fault, the other a line crossing this fault. The results differed appreciably from the standard value of σm, particularly in the latter case.It is concluded that the gravity difference between a surface and an underground station can be used satisfactorily to determine the average density of a rock layer in situ and en bloc, using the standard value for the mean Earth density.
UN INTÉGRATEUR POUR LE CALCUL DES CORRECTIONS TOPOGRAPHIQUES*
Authors: BOLLO R. , GOGUEL J. 
Published: April 2006

AbstractWhen gravimetric prospecting is concerned with a region featuring broken relief the calculation of topographical corrections becomes vitally important, for these rectify apparent anomalies completely. It is essential that they should be calculated as exactly as possible. By the classic method this takes an extremely long time and may in the long run involve an outlay actually higher than that expended on operations on the terrain.It has thus been felt necessary to seek methods which would speed up calculation, and, bearing that in mind, the use of a polar integrator has been envisaged. With this the contour lines of a map can be followed between two fixed radii, the pole corresponding to the location of the position. Two integrator roulettes will give the values of the first two terms of the expansion in terms of the quotient of the height divided by the distance, the second of the terms resulting from the curvature of the earth. Unless there are escarpments very close to the position, the use of these two terms will be sufficient.Polar integration will deal successively with different contour lines and a subsidiary graph will be plotted, giving the value of each of the integrals in terms of the height. By means of this subsidiary graph the values of the corrections will be obtained with a planimeter and a moment integrator. It is envisaged that the same operation could be repeated in the case of two maps with different scales, for instance, 1–20,000 and 1–200,000 the effect of the areas in the immediate neighbourhood of the position being taken into account by the observer. It is hoped that in this way the calculation of topographical corrections will be made quicker, more exact and less laborious.
ETUDE THEORIQUE DE LA VITESSE DES ONDES DE COMPRESSION DANS LES VASES*
Authors: D'ERCEVILLE I. 
Published: April 2006

AbstractIt has been noted that in water‐saturated silt, the velocity of propagation of longitudinal waves is very low. The purpose of this paper is to suggest a theoretical explanation for this phenomenon.The medium under study is assumed to consist of identical solid spheres piled one upon the other in a regular array, with the fluid filling the interstices. First the velocity of propagation is calculated for the system of the solid particles alone; then, utilizing the results obtained for this case, the velocities for the solid‐fluid system are calculated. Two velocities are obtained, one of them being higher and the other lower than in the case where no fluid is present.
TEMPLATES FOR FITTING SMOOTH VELOCITY FUNCTIONS TO SEISMIC REFRACTION AND REFLECTION DATA*
Authors: HAGEDOORN J. G. 
Published: April 2006

ABSTRACTVelocity functions can be grouped into families, any One of which results, in seismic pictures differing among themselves only in their scales of time and distance but similar in all other respects. For any one of these families it follows that curves drawn on logarithmic scales of time and distance to represent a particular relationship between seismic quantities will be similar in shape. This leads to the use of templates with logarithmic scales for fitting a smooth velocity function to a set of seismic data. Suitable templates for fitting refraction and reflection data to velocity distributions linear with either depth or vertical time are presented. An insight into the uncertainties involved is obtained with the aid of numerical examples.
THREE DIMENSIONAL GRAVITY SURVEY*
Authors: DOMZALSKI W. 
Published: April 2006

ABSTRACTThe paper describes and discusses the results of an experimental gravity survey which was carried out underground on different levels of a mine, in the mine shafts, and on the surface above the mine workings.The paper is composed of three complementing sections. The part dealing with gravity measurements in the shafts gives also attention to the particular problem of the terrain corrections underground, due to the surface topography. The interval densities from gravity measurements in the shafts are computed and adjusted in accordance with known geology and compared with the stratigraphical columns of the shafts. The effect of the ore body on the stations in the shaft is derived theoretically and compared with the observed one.The gravity contours are constructed on different levels in the mine workings and discussed in relation to the known extent of the ore body. The gravity profile across a fault underground is presented and discussed. Another gravity profile was run underground in the same plan position as a surface traverse 1000 feet above it. The line of boreholes along this traverse gives good account of geology which includes step‐faulting. This known geology is compared with the deductions based on the gravity results. This is also done in the case of another gravity profile run over a known geological section. A number of gravity measurements were also taken in the same plan position, separated by the vertical distance of 800–1,100 feet. These points were placed by the boreholes previously drilled in the area. Attempt in correlation of these and gravity results is made.The densities computed from the gravity measurements are compared with the laboratory determinations of the densities, carried out on samples from different parts of the mine.The contours on the top of the base formation are constructed from the information obtained from the boreholes, and are compared with the gravity contours on the surface above.A simple method of computation of the effects of slabs and blocks is presented as applied to the calculation of the corrections for underground drifts and faults. A table is appended for use with this method.
THE RELATION BETWEEN SIZE OF CHARGE AND AMPLITUDE OF REFRACTED WAVE*
Authors: GASKELL T. F. 
Published: April 2006

AbstractExperiments carried out using charges of up to 200 lbs. at a distance of about 20,000 ft. from the geophones suggest that the amplitude of the refracted wave ground motion is roughly proportional to the weight of charge. Simple energy considerations lead one to expect a relation of a form in which velocity amplitude is proportional to W.An explanation of the observed relation may be based on a theory according to which the efficiency of the explosion increases with the source size, that is the distance from the source at which the pressure wave of the explosion ceases to cause permanent deformation of the surrounding medium.The above theory was further confirmed by measurements of the radius of the cavity produced by explosions of charges of different size in clay. Also, explosion of charges in artificial water‐filled cavities were found to give seismic wave amplitudes three or four times greater than those produced by the same charge in a narrow hole. It is possible that these observations explain in part why the charges required in marine refraction experiments are very much smaller than those needed in refraction work on land, but additional reasons for this difference are also discussed.
PURPOSE OF ACCIDENT REPORTS AND STATISTICS*
Authors: RICHARD H. 
Published: April 2006

ABSTRACTThe President of the E.A.E.G. Safety Committee has stated that European geophysicists fail to attach sufficient importance to accident statistics. Nevertheless these statistics are the best means at our disposal for the study of the factors influencing the number and severity of accidents.It appears essential that two points should be stressed, firstly that the accident reports must be completed correctly, and secondly that the interpretation of each report and of the statistical data must be done systematically.If these conditions are fulfilled it should be possible to create, at all levels, a technical and psychological atmosphere which would do much to protect geophysicists against accidents.
EINIGE NEUERUNGEN AN DEN GEOMAGNETISCHEN FELDWAAGEN*
Authors: FANSELAU G. 
Published: April 2006

ABSTRACTAt the Niemegk Observatory geomagnetic balances with torsion ribbons have been constructed since a few years. They have well known advantages over balances resting on knife edges: greater stability of the zero position, ease of enlarging the measuring range by torsion, no serious damage when the instrument is not clamped. Both H‐ and Z‐ balances have proved highly satisfactory. Also a combined H‐and Z‐balance has been developed. To a certain extent, the torsion ribbon balances can be made insensitive to levelling errors. Torsion wire balances used as zero instruments have not been considered for field measurements for reasons of time saving, They are however being made for laboratory measurements.
PRINZIPIELLE BEMERKUNGEN ZU THEORIE UND PRAXIS DER METHODE DER ZWEITEN ABLEITUNG BEI DER INTERPRETATION GRAVIMETRISCHER MESSERGEBNISSE
Authors: ROSENBACH OTTO 
Published: April 2006

ABSTRACTThe first part of the paper deals with theoretical considerations concerning the arithmetic mean of gravity values and its use with regard to the derivation of approximation formulae for the second derivative. In order to calculate the second derivative in practice the arithmetic mean. ḡ(r) of a continuum of gravity values on a circle of radius r is approximated by a Taylor polynomial and then replaced by the arithmetic mean gn(r) of n discrete gravity values. Because of the invariance of ġ(r) with regard to rotations of the coordinate system in the horizontal datum plane there exists a lower limit for the number n; this lower limit depends on the degree of the Taylor polynomial used in the formula for gzz.The general results of the first part yield routine formulae for the special case of a regular hexagonal grid; these formulae are given and discussed in the second part of the paper. Three formulae are applied to the gravity data of the Los Angeles Basin. Some remarks concerning the comparability of different approximation formulae and some hints with regard to routine calculations conclude the paper.
ON THE BEHAVIOUR OF A WORDEN GRAVIMETER FOR PERIODICAL VARIATIONS IN EXTERNAL TEMPERATURE AND RAPID VARIATIONS OF PRESSURE *)
Authors: CAPUTO MICHELE 
Published: April 2006

ABSTRACT1. A Worden gravity meter has been tested for sinusoidal variations in the external temperature, by determining simultaneously the corresponding variations of temperature inside the Dewar vacuum bottle, and the variations in the readings.A second Worden gravimeter has been tested for rapid variations in external pressure.
THE VARIATION WITH DISTANCE OF THE AMPLITUDE OF CRITICALLY REFRACTED WAVES *)
Authors: O'BRIEN P. N. S. 
Published: April 2006

AbstractAmplitude measurements have been made of the height of the first peak of an arrival refracted from a shallow refractor. If the amplitude is assumed to decay as the inverse mth power of the distance, the least squares value for m is found to be 2.16 ± .04. Because of this value and because of the character of the recorded event it is concluded that the arrival is a simple critical refraction. After applying the theoretical ‘spread’ factor for critical refraction there remains a residual attenuation of 1.96 ± 0.28 decibels per 1000 feet. The predominant frequency in the pulse is about 20 c.p.s. and this attenuation agrees with the losses found for such a frequency by extrapolation of the published results of other workers. Although no evidence could be seen on the records for a change of pulse frequency with distance, the quoted result would be consistent with a dependence of residual attenuation on the first power of the frequency, and would be inconsistent with a dependence on the second power of the frequency.It is concluded that studies of the amplitudes of refracted events will give useful estimates of the attenuation factors of rocks.
QUELQUES EXEMPLES DE DIFFRACTIONS EN SISMIQUE‐REFRACTION ET LEUR APPLICATION A LA DETERMINATION DES VITESSES VERTICALES*
Authors: LEDOUX Y. 
Published: April 2006

ABSTRACTThe progress in the registration of refraction shots obtained in the last years permits a more systematic study of the secondary arrivals. In zones with disturbed tectonics, a noticeable portion of the received energy derives from diffraction phenomena caused by velocity anomalies in the marker bed or in the overburden (faults, local heterogeneities). Some characteristic examples are presented and schematically explained.A more advanced analysis of the branches of the travel time curve caused by diffraction leads, in favourable cases, to a new method of calculating the offsets and the vertical velocities, independent of the usual methods for the determination of these parameters.
DENSITY DETERMINATION ON NEAR‐SURFACE LAYERS BY GAMMA ABSORPTION*)
Authors: HOMILIUS J. , LORCH S. 
Published: April 2006

ABSTRACTFrom gamma ray absorption the density of soil to a depth of i m. can be determined in situ, without taking samples, by a method which has been described in a previous paper (Wendt 1954) and which has been checked with satisfactory results (mean error about 1%). A nearly vertical steel rod with a gamma ray source at its lower end is pushed into the ground, and the gamma radiation is measured at the surface with two counters placed symmetrically with respect to the rod.As a first step in interpreting the observed effects, the assumption had been made that counters are infinitesimally small. This paper shows how a theory can be developed without this assumption, the finite dimensions of the counters being taken into account by an integral expression. For this purpose a determination of the dependence of the counting rate on the angle of incidence of the gamma rays is required. A comparison of the experimental results with the theoretical ones demonstrates that the integral expression is correct.The influence of deviations from the normal geometry of the arrangement (e.g. caused by bending of the probe) on the results is investigated, as well as the influence of variations of the density with depth.The treatment of the basic problems has been carried through in such a manner that the results obtained can be applied to other absorption methods as well.
THEORETISCHE UNTERSUCHUNG ÜBER DIE MEHRFACHAUFSTELLUNG VON GEOPHONEN*
Authors: KÜPPER FRANZ JOSEF 
Published: April 2006

ABSTRACTThe receiving of seismic waves by multiple geophones (geophone‐group) is described by a system of coupled differential equations considering only effective resistances. For so‐called symmetrical connections of the geophone‐group which are used in practice nearly in all cases, a method can be given for solving this system of differential equations. The solutions so derived are valid for seismic waves of any shape. The calculation takes into account the coupling of the geophones as well as the building‐up transient oscillations.A suitable measure of superposition is defined, based on the energy transferred during the receiving of the seismic waves. By this means effects similar to interference are investigated which occur at the geophone‐group. As a numerical example calculation is carried out for a geophone‐group consisting of three geophones which is excited by impulse‐shaped waves of the form of a damped sinusoidal oscillation. The occurring effect of superposition and its dependence on direction are discussed. In the appendix formulae are presented for investigation of further numerical examples.
AN ACCURATE GRAPHICAL METHOD FOR INTERPRETING SEISMIC REFRACTION LINES*
Authors: HALES F. W. 
Published: April 2006

ABSTRACTA method of refraction computing is described which establishes the two points of incidence at the surface of the ray‐paths from any point on the refractor when observed from opposing directions. The distance between these points is used to determine the radius and the centre of a circle to which the refractor must be tangential. The matching of forward and reverse data is intrinsic in the method so that the resulting profile is automatically positioned in depth. It is shown that if the effects of dip are neglected, errors are introduced in the derived radius and also in the position of the centre but these errors are shown to cancel each other almost exactly.
THE CAUSES OF GEOPHYSICAL ACCIDENTS*
Authors: RICHARD H. 
Published: April 2006

AbstractThe attention of everyone has already been drawn to the part which accident reports must play (Geophysical Prospecting, March, 1957, PP‐ 1 to 8). We intend to show here, with supporting examples, that the systematic analysis of the causes, does allow one to obtain practical conclusions.To begin with, it is advisable to widen the notion of geophysical accident as much as possible. This being done, about 200 reports distributed over a long period and a sufficient number of parties, are dealt with. The collected reports are sufficiently numerous to draw conclusions in a general way bearing on the headings: drilling, transport, outbreaks of fire, explosives, falls, stings, shocks, miscellaneous causes.All the quoted figures are referred to the number of accidents reported. Action must be taken to encourage european geophysicists to study accident reports and to analyse the causes. This may be done in such a way that secret information, such as whereabouts of their personnel, is not disclosed.Efforts to promote “Security” must in the first place bear on the quest for the causes, the definitions of ‘accident’ and of ‘geophysicist’ being taken at their widest possible meaning.
THE INFLUENCE OF A LAYER COMPLYING WITH A LINEAR VELOCITY LAW ON THE SHAPE OF SEISMIC PULSES
Authors: MENZEL H. , ROSENBACH O. 
Published: April 2006

ABSTRACTA layer with parallel plane boundaries is assumed to have a constant density and exhibit a velocity of propagation of seismic waves which increases linearly with the distance from one boundary plane. The influence of this layer on the shape of seismic pulses is investigated in two different cases, in which:1. The layer is embedded between two media each of which has a constant density and velocity of propagation.2. The layer is adjacent to one medium of constant density and velocity; i.e. one boundary plane of the layer is the free surface of a two‐layered elastic half space.Through one medium with constant velocity a plane compressional wave impinges at normal incidence on the layer complying with the linear velocity law. The incident seismic pulse is therefore split up into reflected and transmitted parts, the elastic motions of which are studied in the neighbourhood of the layer. The mathematical solution can be deduced for a general pulse by using the Laplace‐Transformation. The general solution reveals that the layer following the linear velocity law influences the shape of the reflected and transmitted pulses. This influence is discussed in detail by demonstrating some numerical examples.
CHANGES OF SHAPE OF SEISMIC IMPULSES IN HOMOGENEOUS VISCOELASTIC MEDIA
Authors: POSTMA G. W. 
Published: April 2006

ABSTRACTChanges of shape of seismic waves provide information on the properties of the material in which the waves propagate. Ricker (1953) has attempted to explain the changes of shape on the basis of a simple viscoelastic theory. His conclusions are at variance with those of others who find a dependence of the attenuation on frequency which could be explained only by a much more complicated linear theory or by nonlinear theories.To provide a basis for discussion, the essentials of the theory of viscoelasticity are briefly reviewed. If a relaxation spectrum, rather than one or very few relaxation times, is admitted, a great variety of experimental results can be described by the linear theory of viscoelasticity. A linear theory is indicated when no obvious violations of the principle of superposition occur.Ricker's theory is presented with some modifications which allow for a finite duration of the initial pulse and for the approximate character of his basic assumptions. There do not appear to be serious discrepancies between his theory and his experimental results. Some of the objections to his theory can be met by assuming a finite duration of the initial pulse. However, more direct measurements made under similar circumstances by McDonal et al. (1958) at the same location lead to a conclusion on the nature of the material not in accordance with Ricker's. This casts doubt on the sensitivity of his method.Laboratory measurements usually yield results which are not explainable in terms of simple viscoelastic models. Whether a linear theory with a relaxation spectrum or a nonlinear theory should apply depends much on the experimental conditions. We must also consider the possibility of nonlinear mechanisms which are active at small amplitudes. No stand is taken in this controversy, but it is pointed out that the question linear or nonlinear could be decided experimentally without considering the details of the theories.