bluuebunny/crossref_metadata_2025_split huggingface dataset:
SIGNIFICANCE AND IMPLICATIONS OF SHINGLING IN REFRACTION RECORDS *
Authors: CASSINIS R. , BORGONOVI L. 
Published: April 2006

ABSTRACTThe occurrence of shingling in. long range refraction records often makes the task of the seismic interpreter heavier, especially when several refractors are encountered and the velocity contrasts are small.The explanation of the phenomenon given by the existing literature is examined and the theoretical results are compared with the observed data on field records.In field seismograms shingling must be separated from the effect of geological structures or lateral discontinuities.If an appropriate analysis of shingling is possible, this phenomenon can be related to the type of refracting layer, being a useful tool to a qualitative approach.On the other hand the implications of shingling are examined on the side of the geometrical interpretation
SPECIFICATION OF TWO MODULI OF A VISCOELASTIC MATERIAL *
Authors: THOMSON KER C. 
Published: April 2006

AbstractIn order to adequately understand the complicated, anelastic processes governing wave propagation in soils or highly weathered rock it seems desirable first to have available a convenient laboratory material for such propagation studies the frequency dependent rheological parameters of which are known beforehand. A property measurement program has been conducted to determine the complex Young's modulus and the complex shear modulus of a commercially available viscoelastic material over a broad spectral region.
SOME RESULTS OF THE GEO‐ELECTRICAL RESISTIVITY METHOD IN GROUND WATER INVESTIGATIONS IN THE NETHERLANDS*
Authors: VAN DAM J. C. , MEULENKAMP J. J. 
Published: April 2006

AbstractIn the year 1958 the Service for Water Management of the „Rijkswaterstaat” started its program of geo‐electrical resistivity prospecting in the western part of the Netherlands. The aim of this program was to obtain data on the salinity distribution of the ground water.The ground water regime in this part of the Netherlands is most intricate. This is due to the geological and geo‐hydrological conditions and to the low elevation of the land. Many reclaimed areas are up to several metres below mean sea level.The resistivity data obtained are closely related to the salinity of the ground water. On the basis of bore hole data it was even possible to arrive at calibration curves for the salinity of the ground water in sand deposits. Under special conditions it was also possible to draw conclusions with respect to the presence of less permeable formations as e.g. clay layers.Some remarks are given on the practical performance and the interpretation of the measurements.A review is given of the work done until now. Some results are shown by means of maps of the salinity distribution of the ground water in the western and northern parts of the Netherlands.Two examples are described of the use of the data obtained during the survey in the province of Zuid‐Holland.Another two examples are presented of detailed investigations for special purposes in relatively small areas.
TOPOGRAPHIC AND ISOSTATIC CORRECTIONS TO GRAVITY SURVEYS IN MOUNTAINOUS AREAS*
Authors: JOHN V. P. st , GREEN RONALD 
Published: April 2006

ABSTRACTIn mountainous areas it is an inadequate procedure to reduce gravity observations by merely subtracting the effect of an infinite flat slab of material between the station and sea‐level, and adding a terrain correction. A programme is described which directly computes the effect of masses above sea‐level, and mass‐deficiencies below it; as well as the effect of compensating masses under the Pratt and Airy isostatic systems. As an example, the method has been applied to a regional gravity survey of Papua and New Guinea where it is seen to remove the usually high correlation of the Bouguer anomaly with local topography.
GRAPHICAL EVALUATION OF MAGNETIC AND GRAVITY ATTRACTION OF THREE‐DIMENSIONAL BODIES*
Authors: SHARMA P. VALLABH 
Published: April 2006

ABSTRACTA nomogram is presented which enables evaluation of the components of magnetic attraction of a homogeneous finite rectangular prism, and of gravitational attraction due to a uniform rectangular lamina.In practice any three‐dimensional body could be approximated by a number of right rectangular prisms of varying dimensions governed by the shape of the body. The magnetic attraction of the whole body is then obtained by numerical summation of the effects of the constituent prisms.For evaluating the gravitational effect, the cross‐section of the body corresponding to each elevation contour is approximated by a number of rectangular laminae (or by a stepping polygon) the attraction of which can be determined with the aid of the same nomogram. The total gravitational attraction of the body is obtained by a process of graphical integration along the vertical axis.
THE ANALYSIS AND DESIGN OF TWO‐DIMENSIONAL FILTERS FOR TWO‐DIMENSIONAL DATA *
Authors: DARBY E. K. , DAVIES E. B. 
Published: April 2006

ABSTRACTSome of the methods such as regional removal and second derivative calculations which can be used to outline anomalies on potential data maps can be thought of as a filtering operation. The analysis and design of such two‐dimensional filters by means of direct and inverse two‐dimensional Fourier transforms have been considered.An analysis of several published sets of second derivative coefficient sets indicates that, in general, they are not a good approximation to the theoretical second derivative filter. Alternate methods of designing regional removal and second derivative filters are discussed. The properties of various two‐dimensional filters are further illustrated by means of maps obtained from the convolution of several of these filters with a set of observed field data. These maps show the large changes in anomaly shape which can result from the inclusion or rejection of various wavelength components.
SHIP‐TOWED MAGNETICS IN PETROLEUM EXPLORATION*
Authors: PRINDLE ROBERT O. 
Published: April 2006

AbstractIn one geophysical survey over a salt dome in the Gulf of Mexico, data taken from a single magnetic and seismic shipborne traverse demonstrated significantly the importance of magnetic measurements. The reduced magnetic and seismic profiles were integrated with gravity measurements from an earlier survey demonstrating the value of obtaining simultaneous geophysical data. The traverse was approximately 25 miles in length, 135 miles southeast of Galveston, Texas. The observed gradient averaged approximately 2 gammas per 1000 feet and crosses the southwest corner of a large shallow salt dome called the Way Dome. The recorded magnetic profile over the salt dome shows a negative magnetic anomaly extending for approximately 12 miles with a maximum amplitude of approximately 20 gammas. This negatively anomaly is due to the negative susceptibility contrast between the salt and cap rock that truncates the surrounding parent sediments. The shape of the negative anomaly correlates well with the continous seismic record and clearly delineates the topographical and structural features of the salt dome. The recorded analog magnetic profile was replotted, with both the regional gradient and time variations removed, which makes the observed anomaly much sharper than is noticeable on the original recorded strip chart record. A theoretical magnetic anomaly was calculated using a computer program for comparison to the observed anomaly. The results showed good correlation.
BEDROCK DEPTH FROM SURFACE POTENTIAL MEASUREMENTS*
Authors: ROY AMALENDU 
Published: April 2006

ABSTRACTWhen, in a two‐layer earth, the substratum is insulating or infinitely conducting, the thickness of the top layer can be determined from surface potential measurements along a radius from a single point power electrode. The observed potential needs to be numerically integrated in a direction perpendicular to the said radius, and Figure 4 can then be used to find the thickness. A field example is included.
DETERMINATION DE L'IMPULSION SISMIQUE*
Authors: BOIS P. 
Published: April 2006

ABSTRACTDetermining the shape of a pulse generated by an explosion solely from the data provided by the recorded seismic trace is a difficult and even ambitious task.Knowledge of parameters such as length and number of “arches” of the pulse under study is, in fact, indispensable in solving this problem.These parameters cannot be found directly in the seismic trace, which nevertheless contains a great amount of information. Autocorrelation, with its mathematical and statistical properties, is an efficient way of making the best of this information.We compute all the autocorrelations of reflections having a given number of arches which fulfil certain conditions determined in advance. Then, after statistical testing of some parameters pertaining to the autocorrelations (abcissae of zeros, of extrema …), we select only those with a maximum likelihood. It is sufficient to consider only the reflections whose autocorrelations have been selected and to arrange them in groups according to their shape and arch number in order to obtain average pulses.In so doing several solutions are arrived at, but when considering a given number of traces, a single record for instance, it is possible by comparing these results with each other to considerably reduce their number.In the last part of the paper the nature of the impulse obtained with our method is examined in order to find out whether it is “minimum phase” for carrying out deconvolutions.
ÜBER DIE GENAUIGKEIT GEOMAGNETISCHER FELDREGISTRIERSTATIONEN*
Authors: FANSELAU G. , RITTER E. , WOLTER H. 
Published: April 2006

ABSTRACTThe accuracy of the magnetic registrations of a new field station constructed at Niemegk Observatory is described. The most important aspects for the construction were good mechanical stability, a good constancy of all physical data and the fact, that the station is ready in the field for solid registration ere long. The apparatus was proved during geomagnetic survey in the field, especially in view of the variability of the geomagnetic variations. The results obtained by field work and by comparison at observatories are good. It is planned to enlarge the registrations by means of photocellcompensators.Der Plan zur Konstruktion einer transportablen und schnell aufstellbaren geomagnetischen Feldregistrierstation geht schon auf das Jahr 1939 zurück. In diesem Jahr wurde von Fanselau ein Plan für eine solche Station den Askania‐Werken in Berlin‐Friedenau unterbreitet und zur Konstruktion empfohlen. Der Krieg verhinderte eine rasche Durchführung der Fertigungsarbeiten, so daß erst nach Beendigung des Krieges die Askania‐Werke den auf diesen Vorschlägen beruhenden Magnetographen fertigen konnten. Am Adolf‐Schmidt‐Observatorium für Erdmagnetismus in Niemegk wurden dann weitere geomagnetische Feldregistrierstationen entwickelt [1, 2, 3]. Bei der Konstruktion des Gerätes wurde bewußt auf Robustheit und Stabilität Wert gelegt, während der Gesichtspunkt, ein möglichst leichtes und kleines Gerät zu haben, nicht so sehr im Vordergrund stand. Von dem neuen Typ der Station sind inzwischen schon eine ganze Reihe von Exemplaren in Betrieb genommen worden, so daß es an der Zeit ist, einige Bemerkungen über Zuverlässigkeit in der Konstanz der Skalen‐ und Basiswerte sowie über andere instrumentelle Daten der Geräte zu machen. Auf Grund eingehender Messungen am Observatorium und im Gelände liegt genügend umfangreiches Material vor, um diese Fragen sicher beantworten zu können.
EIN AUTOMATISCHES VERFAHREN ZUR INTERPRETATION MAGNETISCHER ANOMALIEN NACH DER METHODE DER KLEINSTEN QUADRATE*
Authors: BOSUM W. 
Published: April 2006

ZUSAMMENFASSUNGDie Interpretation magnetischer Anomalien durch Modellkörper geschieht bevorzugt nach der indirekten Methode (trial und error). Dieses von Hand aufwendige Verfahren läβt sich mit Hilfe der Ausgleichsrechnung nach der Methode der kleinsten Quadrate Rechenautomaten übertragen.Die allgemeinen Grundlagen des Verfahrens werden beschrieben. Wesentliche Voraus‐setzungen sind:

die Annahme bestimmter Körperformen
das Vorhandensein von Näherungswerten der Unbekannten (Lage, Magnetisierung etc.)
eine genügend groβe Anzahl von Meβwerten, um den Ausgleichsprozeβ durchführen zu können.

Die Vorteile der Methode sind:

weitgehende Automatisierung und schnelle Arbeitsweise bei Verwendung von Rechenautomaten
Ermittlung der Fehler der Unbekannten

Die Methode wurde angewandt auf die Interpretation 2‐dimensionaler ΔZ‐ und ΔT‐Anomalien. Drei Körpertypen werden dem Rechenprogramm zugrunde gelegt, und zwar die unendliche und endliche diinne Platte und der Kreiszylinder. In die Maschine ein‐gegeben werden nur die Meβwerte. Die Interpretation erfolgt im einzelnen in folgenden Schritten:

Ermittlung von Näherungswerten
Bestimmung der Körper bester Annäherung
Iteration für den Körper bester Annäherung.

Die Maschine gibt die Endwerte der Unbekannten (Lage, Einfallen, Magnetisierung etc.) mit Angabe der mittleren Fehler sowie die hierzu gehörigen Modellanomalien aus. Diese Endwerte werden einem Zeichenautomaten übergeben, der die gemessene Kurve, die theoretische Kurve und die gesuchten Modellkorper zeichnet.Interpretationsbeispiele werden vorgeführt.
A POSSIBLE WAY OF TRACING GROUNDWATER FLOWS IN KARST*
Authors: ARANDJELOVI DUŠAN 
Published: April 2006

ABSTRACTIn designing as well as in the construction of hydro‐electric power plants and water‐supply projects in karst, the knowledge of the location of groundwater flows is invaluable. Attempts made so far in this direction have not produced the desired results and all the methods known so far have shown to be more or less ineffective, especially with respect to deep‐seated underground flows.An interesting suggestion on the possible determination of the groundwater flow location by using a specific geophysical prospecting procedure is based on the studies and knowledge of groundwater flows in the karstland of Yugoslavia. The procedure is as follows: a time‐bomb thrown down a swallow‐hole travels down to the groundwater flow and explodes at a predetermined moment. Elastic waves generated by the explosion propagate reaching the surface, where they are detected by properly arranged geophones that are connected with a standard seismic apparatus. By a specific graphical or arithmetical method the coordinates of the epicentre and hypocentre of the underground explosion can be worked out, and thus the location of the groundwater flow determined. By successive repetition of the experiment, i.e. by different time activation of underground explosion of the time‐bomb, the location of the groundwater flow can be defined over longer paths.The success of the experiment depends upon a number of factors all of which must be met. If only one of them is overlooked, the experiment will not succeed. All this calls for great care both in preliminary work and in the course of the experiment. Substantial funds invested in and considerable time required in executing the experiment are multiply recompensed by the success of the experiment. The information obtained about the location of groundwater flows will directly affect the maximum operating pool adopted for hydro‐electric power projects and the most favourable point in cutting off groundwater flows and bringing them to the surface for water‐supply purposes.
GEOELECTRICAL INVESTIGATIONS IN EAST AFGHANISTAN*
Authors: HOMILIUS J. 
Published: April 2006

ABSTRACTDuring the years from 1965 until 1967, a German/Afghan team carried out a number of geoelectrical resistivity measurements according to the “Four‐Point‐Method” within the framework of Technical Assistance to Afghanistan.On two selected objects of investigation, i.e. Kabul (69°10 E, 34°30′N) and Zarkašan (67°40′E, 32° 54.5′N), the possibilities and limits of the resistivity method in the exploration of useful groundwater resources, of the geological structure, and in the treatment of problems pertaining to mineral deposits in Afghanistan are demonstrated. In connection with geological mapping these geophysical investigations provided certain conceptions on the structure and the stratigraphy of the intramontane basins in the region south of the Hindukush mountains. Field interpretations are checked by boreholes and by computed model graphs.
SOME EXPERIMENTS CONCERNING THE PRIMARY SEISMIC PULSE*
Authors: O'BRIEN P. N. S. 
Published: April 2006

ABSTRACTRecordings were made with three types of detector of the primary compressional (P) and shear (S) wave pulses generated by explosions in boreholes. Charge weights varied from 0.08 kg to 9.5 kg and detector distances varied from about 3 m to about 80 m. Scaling by the simple factor W1/3 where W is the charge weight, enabled observations from different sized charges to be fitted to a single expression.Experiments were carried out in the Bunter sandstone and the London clay and both fluid and solid tamping were used. This variation in tamping had no significant effect on the P‐waves but it may have affected the generation of SV‐waves. In both media the P‐wave energy carried at 30 m from the shot by frequencies less than 100 Hz decreased rapidly with depth and was usually 1–2 % of the available chemical energy for a shot depth of 15 m. The S‐wave energy was much less than this, but was highly directional.The P‐wave pulse had the appearance of a damped sinusoid in very good agreement with the predictions of the ‘equivalent radiator’ hypothesis. However, the surface of this radiator should be identified not with the blown cavity but with the surface at which the tensile stresses associated with the stress wave become less than the tensile strength of the rock.The predominant frequency for a 1 kg charge at a depth of 15 m was 24 Hz in the clay and 52 Hz in the sandstone. In these and similar media, therefore, an effort should be made to keep individual charges less than 1 kg in reflection shooting and less than 10 kg in refraction shooting.The value of Q was about 50 in clay and about 25 in the sandstone. These estimates are rather uncertain because of the small distances over which the pulses were observed.The Z‐transforms of the sampled pulses indicated that they were all of minimum phase, or very near to it.
UNE METHODE D'ANALYSE FINE DES PROFILS AEROMAGNETIQUES *
Authors: NAUDY HENRI 
Published: April 2006

ABSTRACTA method to analyse aeromagnetic profiles is proposed: several horizontal (width‐) and vertical (amplitude‐) parameters are deduced from the anomalies. These parameters are then compared with diagrams drawn on a logarithmic scale. The comparison yields depth and magnetization of the causative bodies.The method lends itself equally well to a quick estimate and to a thorough interpretation, depending on the number of parameters deduced and on the number of diagrams. It can be applied also to the anomalies of the total field and its vertical gradient.
CENTRAL FREQUENCY SOUNDING IN SHALLOW ENGINEERING AND HYDRO‐GEOLOGICAL PROBLEMS*
Authors: PATRA H. P. 
Published: April 2006

AbstractThe paper deals with the early stages of development of a convenient form of electromagnetic induction method of sounding referred to as ‘Central Frequency Sounding’ and abbreviated as CFS. The method is introduced as a rapid and useful technique for investigation of shallow engineering and hydro‐geological problems. Sets of theoretical two‐layer master curves, suitable for interpretation of field data involving measurement of the vertical magnetic component of the field induced at the center of a loop placed on a two‐layer earth, have been presented.The approximate but reasonably accurate solutions for a two‐layer earth of any arbitrary resistivity contrast have been considered for the purpose and expressed in a form suitable for computation. The computed results have been presented in sets of curves useful for interpretation of field data.
APPLICATION OF REFRACTION SEISMICS TO SUBSALT TECTONIC PROBLEMS IN A DEEP SALTDOME BASIN*
Authors: KREY TH. , NODOP I. 
Published: April 2006

AbstractDespite the use of CDP and digital methods the Zechstein base is still the deepest horizon in the vast salt‐dome basin of Central Europe for which continuous information can be obtained by reflection seismics. Thus in North‐western Germany, in addition to reflection seismics, the refraction seismic method has been increasingly used for a reliable survey of deeper horizons.The first part of the paper deals with the investigation of the various possibilities and limitations of refraction seismics with regard to the investigation of Pre‐Zechstein layers in a basin with a tectonically very complicated overburden. The recording techniques specially developed for continuous profiling of the desired refraction seismic arrivals and the data processing methods are described.The main problems of interpretation are then discussed, in particular with regard to depth representation. The advantages and disadvantages of the various methods, e.g. Gardner's, Hales' and Wyrobek's, and of the wave‐front method, are compared. On account of the tectonically complicated overburden Thornburgh's wave‐front method proved to be the most useful.In a further section the various possibilities for velocity determinations are mentioned, e.g. Wyrobek's determination of the overburden velocity, for which the wave‐front method automatically furnishes the necessary corrections to a deep datum.Finally, some examples are given for the results obtained, including some incidental information on the deeper crust.
RELATIVE CONTRIBUTION TO SIGNAL BY GROUND ELEMENTS IN TWO‐COIL INDUCTION LOGGING SYSTEM*
Authors: ROY A. , DHAR R. L. 
Published: April 2006

AbstractA two‐coil induction logging system in an infinite homogeneous medium has been theoretically analysed for the relative contributions of various ground elements to the total signal at the receiver. Unlike an earlier approximate treatment by Doll (1949), the present analysis takes skin effect into account (while neglecting displacement currents). Contour diagrams depicting relative contributions from every ground point and diagrams for vertical and radial/lateral investigation characteristics are presented. The results differ significantly from Doll's in the following points:

The relative contribution is frequency and conductivity dependent;
It does not show symmetry with respect to the center of coil system;
It alternates between positive and negative values with distance;
Real and imaginary contributions for a given conductivity and frequency are different from each other.

The possibilities of a horizontal‐horizontal sonde is briefly examined and found to be inferior to the usual sonde because of its higher sensitivity to the mud column and the invaded zone.
DETECTION OF SOLUTION CHANNELS IN LIMESTONE BY ELECTRICAL RESISTIVITY METHOD*
Authors: DUTTA N. P. , BOSE R. N. , SAIKIA B. C. 
Published: April 2006

AbstractThe results of geophysical surveys carried out in the Kopili Hydel Project site in the United North Cachar and Mikir Hills district, Assam, to locate and trace underground caverns in limestone are presented. Electrical resistivity observations over known limestone caverns showed significant anomalies (high resistivity). In the course of the systematic electrical resistivity survey conducted at the eastern fringe of the Umrong basin to study the competency of the proposed reservoir, a number of indications of possible caverns in limestone were obtained and a few of them have been verified by drilling. An analysis of the electrical resistivity data also suggests that the deep seated caverns are aligned along an axis trending NNW‐SSE, which may represent a zone of weakness– presumably a fault–that has influenced the formation of the caverns in preferred direction. Drilling over a few of the geophysical indications have corroborated the presence of a fault along the eastern fringe of the Umrong basin.