bluuebunny/crossref_metadata_2025_split huggingface dataset:
COMBINED ANALYSIS OF GRAVIMETRIC AND MAGNETIC ANOMALIES AND SOME PALAEOMAGNETIC RESULTS*
Authors: LUNDBAK ASGER 
Published: April 2006

ABSTRACTAn attempt is made to interpret some magnetic anomalies in Denmark and Northern Holland. As the thickness of the nonmagnetic sediments in the areas is large, the interpretation must depend mainly on computational procedures, i.e. a combined analysis of gravimetric and magnetic anomalies, assuming that the two kinds of anomalies originate in the same body.The mathematic basis of these computations is presented, and from this conclusions are drawn about both direction and intensity of the magnetism in the underlying rocks.On this basis, the magnetic declination in these rocks appears to be westerly for all the areas considered. This declination is, of course, a combined effect of induced and remanent magnetization. The corresponding magnetic inclination is smaller than the inclination existing at the surface, and in several cases the magnetic inclination in the rocks is clearly negative, i.e. directed upwards.Both the declination and the inclination in the rocks vary considerally from one locality to another. However, if we assume that these varying results are caused mainly by different ratios of the strengths of induced and remanent magnetism, the directions of remanent magnetism group themselves around a fixed declination, about ‐160°, and a fixed inclination, about ‐60°.Estimates of the magnitude of both induced and remanent intensities of magnetization are contained in these conclusions. In both cases the magnitude may be of the order 10‐2 cgs units.The hypothetical geomagnetic poles corresponding to this direction of natural remanence are situated near the central part of the northern Siberian coast and near that part of the Antarctic coast just south of South America.
A THEOREM CONCERNING ANISOTROPY OF STRATIFIED MEDIA AND ITS SIGNIFICANCE FOR REFLECTION SEISMICS*
Authors: KREY Th. , HELBIG K. 
Published: April 2006

ABSTRACTIt is proved that horizontally stratified media, the various materials of which do not differ in their Poisson number, can be considered as isotropic for reflections of a small dip when taking into account quasi‐longitudinal waves which have to be reckoned with in practice. Approximating the surface of the wave by an ellipsoid would, however, result in considerable errors.Moreover, curves are presented allowing practical calculations for steeper dips to be made.
A SMALL‐SCALE FIELD INVESTIGATION OF MOTION NEAR THE SOURCE *)
Authors: MASON R. G. 
Published: April 2006

ABSTRACTA seismic field investigation on a reduced scale is described. A falling weight was used as the source of energy, with a recording system which permitted the display on a cathode ray oscillograph of two dimensional pictures of ground displacement in the vertical plane containing the source. These permit a quantitative study of the magnitude and direction of displacement and of the instantaneous velocity of motion.
THE USE OF NEAR SURFACE TEMPERATURE MEASUREMENTS FOR DISCOVERING ANOMALIES DUE TO CAUSES AT DEPTHS*
Authors: KAPPELMEYER O. 
Published: April 2006

AbstractIn this paper an attempt has been made to evaluate the possibilities of determining subsurface features from temperature measurements made at shallow depths. The temperatures at the observation depth used are subject to seasonable variations. The amount of this variation differs, and these differences have been attributed to structural features. Local differences in temperature are also caused by surface factors such as the thermal conductivity of the soil, the vegetation and the micro‐climate. The differences in temperature due to surface factors are so great that the variation in heat flow caused by differing thermal conductivities of the rocks at depth cannot be detected at the surface. It is not possible therefore to use this method to determine the position of subsurface structures such as domes, anticlines or horsts.It is also shown that concentrations of radioactive elements in the rocks do not provide any measurable heating.The method has been successfully applied to the problem of finding fissures, cracks and similar features provided that convective heat transport from depth to the surface has taken place along these features. In order to compute the area through which a given amount of water at a given depth must pass to give a specific temperature increase a model has been considered. From the shape of the temperature anomaly above a fissure carrying such heated water, the places at which the rising water enters the groundwater stream can be seen immediately. It is possible to estimate the amount of rising water by computing the amount of heat energy transferred to the surface.The method is particularly suitable for determining the position of steam deposits in regions of recent vulcanicity. In such a region a location, hitherto unknown, was found where steam rising from depth condenses beneath the surface.The area and form of the anomaly indicate the extent in depth of this steam bearing zone. By means of observations made at the individual points, it was also possible to compute approximately the energy being released at the surface. This value can give an indication of the extent to which the steam deposits regenerate themselves.Finally it has been shown that percolating canal water can be detected thermally near the canal banks. Such anomalies are dependent on the season.
MULTIPLY REFLECTED REFRACTIONS IN A SHALLOW LAYER.
Authors: O'BRIEN P. N. S. 
Published: April 2006

AbstractA strong late arrival, with several cycles, has been observed in line refraction shooting, for distances ranging from 5000 to 30,000 feet. Using equations given by Officer (1953) it has been possible to establish that this event is a multiply reflected refraction. The conclusive factor was its very large amplitude which was about 60 times that expected for the simple head wave, at the distances involved. The wave‐guide was bounded by the surface of the earth and by the base of the Low Velocity layer, at a depth of about 80 feet.An earlier paper (O'Brien, 1957a) gave a study of the head wave pulse refracted from this interface and the conclusions in the two papers are altogether compatible.
ON THE THEORY OF GAMMA RAY SCATTERING IN BOREHOLES*
Authors: HOMILIUS J. , LORCH S. 
Published: April 2006

ABSTRACTThis paper deals with the theory of the gamma ray scattering method, which is applied in determinations of density, mainly in boreholes. In this method, the gamma radiation from a radioactive source is scattered round the borehole, and recorded by a detector which is protected against direct radiation by lead.The theory is based on the scattering and absorption properties of matter with regard to gamma radiation, as described by the Klein‐Nishina formula in terms of the quantum theory. The single scattered portion of radiation, which is of particular importance, is calculated. In doing this an absorption dependent on the scattering angle, and a counter efficiency dependent on the energy of radiation and the angle of incidence, are taken into account. The range of the detector can also be considered.For homogeneous soil, the dependence of the counting rate on the distance between source and detector, on the density, and on the screening of radiation by the lead absorber, is investigated.Furthermore, the scattering range for various soil densities and distances between source and detector is also determined. The existence of a substantial degree of agreement between theory and experimental findings is demonstrated. Results are compared with those of the Djadkin diffusion theory, and are illustrated by means of examples of the gamma gamma probe and the gamma density meter for surface measurements.
THE PLUS‐MINUS METHOD OF INTERPRETING SEISMIC REFRACTION SECTIONS*
Authors: HAGEDOORN J. G. 
Published: April 2006

AbstractThe elastic impulse‐from an explosion is propagated through the earth as an expanding shell bounded by the wavefront. This wavefront and its motion are a physical reality while rays or trajectories are much less sharply defined and cannot actually be observed because the wavelengths involved in seismic processes are too long. This means that the visualization and the interpretation of seismic processes can be carried out in a more satisfactory, simple and comprehensible way with wavefronts than with rays.H. R. Thornburgh (1930) introduced the very lucid and simple method of interpreting seismic refraction sections, using Huygen's principle to construct wavefronts from two symmetrical shotpoints by working back from their observed arrival times at the surface. The depths are found first with only a knowledge of the velocities down to the refractor and after that the velocities in the refractor can be determined.The pattern of the two wavefronts at equal time intervals, obtained when carrying out Thornburgh's construction, leads to the very simple, approximative “Plus‐Minus” method. The additions of the travel times from two symmetrical shotpoints to‐each geophone give the relative depths and their subtractions give the velocities of the refractor. The method extrapolates exact quantities from the refractor boundary up to the surface by the “Plus”‐ and “Minus” lines. This extrapolation introduces errors that can, more or less, be corrected for. A number of hypothetical cases are presented to give an insight into the applicability and reliability of the “Plus‐Minus” method. Its main applications are for fairly shallow refraction investigations and for determining weathering corrections for refraction and reflection work.
DIRECTION SHOOTING*
Authors: BORTFELD R. , HÜRTGEN H. , KOPPEL H. 
Published: April 2006

AbstractBy direction shooting is understood a method of continuous seismic profiling with shots distributed along the total length of the geophone spread, the shots being fired either with time delays in the field, or, recorded singly on magnetizable material and composited with time‐delays. Therewith, the subsurface can be probed in any desired direction, enhancing reflections from these directions and attenuating or eliminating events from all other directions. For each reflection, the correct delay can be found by a simple procedure from a single trial record.A complete description of the method is given, inclusive of all procedures and proofs pertaining to it. Synthetic examples and field examples illustrate the efficiency of the method and its resolving power.
CONTRIBUTION DES ABAQUES BILOGARITHMIQUES A L'INTERPRETATION GRAVIMETRIQUE*
Authors: NAUDY H. 
Published: April 2006

AbstractAmong the means of comparing experimental anomalies with theoretical ones, logarithmic master curves constitute a very practical procedure. Theoretical anomalies for a large number of simple structures have been calculated once for all and drawn on logarithmic scale, in a condensed and handy way. The experimental anomalies are all represented in the same manner, and comparison with the master curves reveals one or several gravimetrically valid structures. If many master curves are available, various hypotheses can be put to the test.Logarithmic master curves have the advantage of taking into account the whole of the anomaly to be interpreted. For each structure they furnish all parameters defining it: depth, dimensions, density contrast. As master curves can be used very quickly, several hypotheses for each anomaly can be tried out in a very short time, so as to associate a group of possible structures with the anomaly. This seems to be the best way of coping with the indeterminateness of the gravimetric method.
A LABORATORY INVESTIGATION INTO THE ELASTIC PROPERTIES OF LIMESTONES*
Authors: KOEFOED O. , OOSTERVELD M. M. , ALONS I. J. G. 
Published: April 2006

AbstractMeasurements have been made by the resonance method of the longitudinal bar velocities and the transverse velocities of 29 chemically pure limestones of varying porosity. The elastic anisotropy factors of the limestones were found to vary over a wide range. For the isotropic limestones, both the longitudinal and the transverse velocity decrease in general with increasing porosity, but this decrease is somewhat irregular. The irregularities in the velocity were found to correlate with the irregularities in the electrical resistivity of the samples when saturated with a standard salt solution, and with those in their tensile strength. This correlation indicates an influence on the velocity of the geometry of the pore space of the rock and of its counterpart: the geometry of the matrix. Indications have been obtained that a condition akin to weathering may be partly responsible for the irregularities in the velocities.Saturating the samples with water was found to result in a decrease of their velocities. An investigation of the available literature, combined with measurements made in our laboratory with a low frequency pulse method, indicate that water saturation results in a decrease of the velocity at low frequencies and in an increase of the velocity at high frequencies.Since other investigators have shown that the velocities of dry rock are hardly effected by the frequency, one must conclude that the velocities of water saturated rock do change appreciably with frequency.The values of Poisson's ratio were found to decrease with increasing porosity, but more so for the dry samples than for the water saturated samples. A possible explanation is that the cross‐contraction and cross‐dilatation is partly consumed in changing the diameters of the pores, thus reducing the effect on the outer diameter of the sample; this mechanism would be partly resisted by water filling the pores.
THE INTERPRETATION OF MAGNETIC ANOMALIES DUE TO DYKES*
Authors: BRUCKSHAW J. M. , KUNARATNAM K. 
Published: April 2006

AbstractBased on simple scaling laws, a method is developed for the routine interpretation of magnetic anomalies arising from uniformly magnetised dykes. The method can be applied to any observed component of the field, i.e. the vertical, horizontal or the total field anomaly and it is applicable for any resultant direction of magnetisation of the dyke itself and for any strike direction. The necessary data for the interpretation are given in the form of curves covering a range from o up to 15 for the ratio of the thickness of the dyke to the depth to its top. It is also shown that, by integrating in a suitable manner the observed anomaly due to inclined bodies having a horizontal upper surface and enclosed by two pairs of parallel and inclined planes, a curve is obtained which corresponds to a dyke anomaly and which can be interpreted by the same technique.
EINIGE ERGEBNISSE DER VIBRATORTECHNIK IN DER INGENIEURGEOPHYSIK*
Authors: MILITZER H. 
Published: April 2006

ZUSAMMENFASSUNGNach einer kurzen Einführung über das Prinzip der Vibratortechnik werden Ergebnisse vibratorseismischer Arbeiten auf Platten (Eis, Betonplatten, Straßendecken) mitgeteilt. Der Auswertung wurden Biegewellen zugrunde gelegt und die ermittelten experimentellen Ergebnisse mit theoretischen Dispersionskurven verglichen.
A RAPID METHOD OF DETERMINING DIP OR MAGNETIZATION INCLINATION FROM MAGNETIC ANOMALIES DUE TO DYKE‐LIKE BODIES*
Authors: POWELL D.W. 
Published: April 2006

ABSTRACTAnomalies due to igneous dykes or layering within metamorphic rocks often approximate to those calculated for geometric dyke models. In aeromagnetic surveys over outcrops of these rocks, where the ‘depth’ is generally the flying height, the ratio in which two geometric functions combine to produce such anomalies can be determined from profiles. This ratio is influenced by geomagnetic latitude, the strike and dip of the ‘dyke’ and its direction of magnetization. It is practicable to solve for either unknown, i.e. dip or magnetization inclination if the other is assumed. Since igneous dykes tend to be vertical and metamorphic rocks are generally inductively magnetized it is geologically valid to make these assumptions.
A GENERALIZED FORM OF NETTLETON'S DENSITY DETERMINATION*
Authors: LINSSER HELMUT 
Published: April 2006

ABSTRACTThe formula for the Bouguer anomaly contains the density of the masses above the datum plane. If we use a wrong value for the density we obtain on the Bouguer map additional anomalies which coincide with the topographic features.If we do not know the Bouguer density we can compute several Bouguer maps based on different arbitrary densities. Then we select that map which shows the least correlation with the topography and obtain in this way a reasonable value for the density. This method has been found by Nettleton.Several authors have formulated this process mathematically and have elaborated numerical methods. This paper will present such a method. It differs from the former methods by the following:

A general formula for the Bouguer density is presented, using a non‐specified linear operator. By choosing special definition for this operator, we can obtain the formulae of several of the known methods.
It is shown that the determination of the density by “Nettleton Profiles” gives less reliable results than the statistical investigation of the whole area covered by the gravity survey.
The known methods do not consider the variations of the vertical gradient. It is shown that in areas with a regional gravity anomaly or an extended topographic feature the known methods yield poor results.
It is shown that the vertical gradient of gravity used as operator gives a most exact and simple formula.
It is shown how the electronic computer—after reading the Bouguer values based on an arbitrary initial density—can compute the residuals, derivatives etc., which are based on the corrected Bouguer density.
A METHOD OF COMPUTING TRUE INTERVAL VELOCITIES FROM EXPANDING SPREAD DATA IN THE CASE OF ARBITRARY LONG SPREADS AND ARBITRARILY DIPPING PLANE INTERFACES*
Authors: SATTLEGGER JOHANN 
Published: April 2006

ABSTRACTThe method presented takes the influence of refraction rigidly into account. All travel‐times available are used in an application of the method of least squares. The solution is illustrated by a computer flow diagram.
FIELD CONTINUATION AND THE STEP MODEL IN AEROMAGNETIC INTERPRETATION*
Authors: HENDERSON ROLAND G. 
Published: April 2006

ABSTRACTDownward continuation of the field in the neighborhood of a singularity of a magnetic anomaly is used to render the anomaly more two‐dimensional, to make the bottom of the causal body more remote, and to obtain an auxiliary function, φ (O, z), by means of which the anomaly may be interpreted in terms of an equivalent vertical contact or step model. The concept of “apparent depth” is introduced and used in studying depth extent and susceptibility. The methods are illustrated with theoretical and practical examples.
THE REDUCTION OF LATERAL EFFECTS IN RESISTIVITY PROBING*
Authors: HABBERJAM G. M. , WATKINS G. E. 
Published: April 2006

AbstractTo be able to make use of all existing probe interpretation techniques, it is desirable that field resistivity observations be conducted in such a way that it is possible to construct an equivalent curve for the surface variation of potential about a point source. Further, the usual parallel layer interpretation will only be justified in as much as the observed potential curve is compatible with such a subsurface geometry. Thus, whilst a potential curve may be constructed from suitable finite potential differences obtained using a Wenner configuration of electrodes, it can be shown, using the tri‐potential technique of measurements, that these potential differences may arise partly from lateral resistivity variations.In this paper, a ladder network technique is employed to display these lateral effects and an adjustment method proposed to reduce them. The adjusted potential differences obtained form a consecutive series suitable for summation to give the potential function. These values are subject to further minimum adjustments required for them to comply with slope and curvature conditions for a layered medium. After forming the potential curve by summation, a final numerical smoothing process is carried out. From this smoothed potential curve, corresponding Wenner and Schlumberger curves can readily be derived for interpretation.The method proposed thus attempts to extract from the observed data the maximum part which can be reconciled with a purely depth variation of resistivity. A method is also proposed for compounding the ‘errors of closure’ of the network to provide a Lateral Inhomogeneity Index which gives a measure of the departure of the observed data from the basic interpretation requirements.The method involves no great labour, but can readily be programmed for a computer if desired. Examples are given of the application of the method to field observations. In the interest of objectivity, the final smoothing has been confined to a single stage but in certain very extreme examples a further stage may prove desirable.
THREE‐DIMENSIONAL ELECTRIC MISE‐A‐LA‐MASSE SURVEY OF AN IRREGULAR LEAD‐ZINC‐COPPER DEPOSIT IN CENTRAL SWEDEN *
Authors: PARASNIS D. S. 
Published: April 2006

ABSTRACTThe principle of the mise‐á‐la‐masse method is to earth one current electrode of a pair in a conducting mineral show (in a borehole, in an outcrop etc.) and measure the resulting distribution of electric potentials. The distribution will, to some extent, reflect the geometry of the ore mass of which the mineral show forms a part.In a mise‐á‐la‐masse survey of a lead‐zinc deposit in Central Sweden electric potentials were measured on the surface of the ground as well as in some 25 drillholes, in either case with earthings (successively) in three different parts of the irregular ore deposit. Besides this, measurements were made in drillholes with earthings in two further drillholes.Geologic correlation between the drillholes is difficult in the present case on account of the irregular geometry of the ore deposit. However, the mise‐á‐la‐masse measurements clearly showed the dip and the pitch of the ore body, established connections between the different ore widths encountered in the various holes, and yielded information about the shape of the ore mass.In particular, the survey showed that the ore lenses must be crescent‐shaped rather than tabular, and the dip was indicated to be westerly, instead of easterly as originally presumed.Three‐dimensional models of equipotential surfaces were constructed from the observed drillhole and surface potentials (using transparent plastic sheets and thin copper wire) and these helped to elucidate the mass geometry further.The surface and underground potential data collected in the present case should be of nterest to geophysicists working on analytic continuation problems.