bluuebunny/crossref_metadata_2025 huggingface dataset:
QUANTITATIVE INTERPRETATION OF GAMMA‐RAY LOGS
Authors: Scott J. H. , Dodd P. H. , Droullard R. F. , Mudra P. J.
Published: October 2002

A quantitative method for determining the concentration of gamma‐ray emitting elements in layered rock penetrated by boreholes has been developed by the U. S. Atomic Energy Commission. It is based on the relationship [Formula: see text] where [Formula: see text] is the mean thickness T, k is a constant of proportionality, and I is the intensity of the gamma‐ray field along the borehole axis at a distance z from a fixed point of reference on the axis. This relationship has been confirmed theoretically and empirically. In application, the grade‐thickness product of a mineralized zone intersected in the borehole is determined by multiplying the area under the gamma‐ray log curve by a constant of proportionality. The mean grade of the zone is determined by dividing the grade‐thickness product by the zone thickness. Corrections applied for nonstandard conditions in the borehole reduce the data to equivalence with standard calibration conditions. Because the volume sampled in this logging method is significantly larger than that of core samples, the resulting data are more representative than data from chemically‐assayed core.
THE RESPONSE OF A DISK IN A DIPOLE FIELD
Authors: Douloff Artel A.
Published: October 2002

Electromagnetic type curves are basic tools in mining geophysics in reducing ambiguity of interpretation. To this end, a mathematical solution is given for the quasi‐static response of an infinitely conducting disk in a dipolar magnetic field. The solution, which emerges as a series solution of Laplace’s equation in oblate spheroidal co‐ordinates, converges rapidly enough only in certain ranges of radii of the disk. Sommerfeld’s image method leads to an alternate solution that is exact. For finite conductivity, the mathematics becomes rather unwieldy, so experimental modelling produced the type curves in this range. By using high frequencies and aluminum disks, “infinitely” conducting models were constructed to check the theoretical solutions. All computation was done on an IBM 650 digital computer.
NOTES ON THE SESSION ON GOVERNMENT SCIENCE AT THE SEG CONVENTION IN GALVESTON, TEXAS, NOVEMBER 1960
Authors: Van Melle F. A.
Published: October 2002

The history of the attempts at seismic control of nuclear tests shows that even before the discovery of decoupling or muffling—known in seismic exploration from shooting in a dry cavity—of explosions, the state of the art favored the cheating nation. With muffling, detection lags concealment of small nuclear tests by a factor in excess of one hundred. Technical and political considerations cannot be separated. A multibillion dollar effort such as the 180 seismic‐station Geneva system should not be undertaken without virtual certainty of adequate detection. If delays in construction, operation, and in situ inspection rendered the program ineffective within Russia and China after the free world had spent billions on the network in other parts of the world; the West would have suffered a sensitive cold war defeat and incurred the resentment of the underdeveloped nations. It would face frustration and loss of confidence at home. A fraction of the number of Geneva stations within the U.S.S.R., supplemented by a world‐wide net of seismological observatories of universities and other bodies with standard modern equipment and exchange of personnel and data, would have all the indirect advantages claimed by Dr. H. Bethe for the full Geneva system. A break‐through in research to advance detection by a factor in excess of one hundred is needed before an effort of DEW line magnitude appears justified. The probability of radical break‐throughs in research is never large. This diminishes the importance of attempts to improve detection by factors of two or three and of auxiliary development projects, such as those connected with on‐site inspection which presuppose effective seismic detection by a world‐wide net of stations.
REFRACTION AND REFLECTION OF SONIC ENERGY IN VELOCITY LOGGING
Authors: Tuman V. S.
Published: October 2002

In this paper we have questioned the present accepted concept of straight‐line path of the refracted beam (in velocity logging) as the source of energy for the first arrivals recorded by the receivers. The energy considerations and the field data indicate that possibly we are looking at the curved paths, an idea which so far has not been discussed thoroughly in the literature. Equations are developed for this curve path which are based on Pickett’s empirical relation. Some specific cases were analyzed using the IBM 650. It is evident that these curved paths could be utilized in some cases to yield information about the permeability in situ. In general it is concluded that the field of velocity logging has tremendous potentialities, and there is plenty of room for further research in this area. For example, the development of sonic logging to yield porosity and permeability of the formation in situ is very intriguing. The ideas presented in this paper, after further experimental verification, can also be applied to surface seismic prospecting.
RADIATION RESISTANCE OF A VERTICAL MAGNETIC DIPOLE OVER AN INHOMOGENEOUS EARTH
Authors: Negi Janardan G.
Published: October 2002

The expressions for the energy radiated per second from an oscillating vertical magnetic dipole situated above a two‐layer earth are derived. Of the three important cases to which particular attention has been given, the first and the second involve the presence of a conducting and insulating substratum, respectively. The third deals with a dipole placed over a thin conducting sheet of infinite extent. Appropriate approximations have been made such that the results may be useful for geoelectrical exploration.
EXCERPTS FROM AN ADDRESS GIVEN BEFORE THE ANNUAL CONFERENCE OF THE DIVISION OF EARTH SCIENCES, NATIONAL RESEARCH COUNCIL.
Authors: Bates Charles C.
Published: October 2002

It is a striking fact that this country has no single major center, governmental, industrial, or academic, possessing the breadth required for handling all the concurrent work needed in Vela Uniform. As a result, the Advanced Research Projects Agency (ARPA) has several agents handling the forty major contracts in the Vela Uniform program, each agent being assigned a specific technical area. For those of you not familiar with the ARPA concept, the actual management mechanism includes the following.
WAVE‐FRONT CHARTS AND THREE DIMENSIONAL MIGRATIONS
Authors: Musgrave Albert W.
Published: October 2002

A computer is required to calculate the complex wave‐front charts which are needed in many areas. On a medium size computer wave‐front charts can be constructed using up to 40 layers. Each layer can be a constant velocity or can start with any velocity and have an increase in velocity with vertical time. These wave‐front charts may be automatically plotted for use in migration in a vertical plane. At the same time that the wave‐front chart is being obtained, a list may be made which shows the depth and offset for each reflection time and stepout value. This migration list may be used to migrate values from time maps in three dimensions. Before migrating, these time maps should have contours of all time values even though overlapping occurs as on buried foci of sharp synclines. Thus, it is a simple matter to make a migrated depth map from any time map regardless of the crookedness and discontinuity of the profiles or the lack of cross‐line control.
THE SEISMIC PROPERTIES OF LAKE MARACAIBO
Authors: Levin Franklyn K.
Published: October 2002

The seismic properties of Lake Maracaibo were investigated in an extensive experimental program. The controlling factor was found to be extremely low mud velocities produced by free gas in the bottom mud. The most important seismic phenomenon was singing, and its characteristics were investigated in detail. Deviations from the behavior expected from a simple theory were found. A strong, low‐frequency mud wave was present. Where the mud was not too thick, normal dispersion occurred.
ENGINEERING SEISMOLOGY APPLICATIONS IN METROPOLITAN AREAS
Authors: Linehan D. , Murphy V. J.
Published: October 2002

Seismic refraction investigations in two “noisy” areas differing in geologic environment and field conditions indicate the reliability of such a technique for foundation engineering problems. Shothole conditions and generating media are of great importance. Dense media, clay, and materials within the water‐table are most favorable; fill debris is the least suitable. Seismic noise in the city, usually transient in character, is not an insurmountable problem; a patient instrument operator is a key to success. Several shot locations along an individual spread and a geophone spacing not to exceed 50 ft are standard field procedure for achieving a maximum amount of data.
On: RIGASSI’S NOTE ON “FAULTS AND EARTH TIDES,” (GEOPHYSICS, OCTOBER, 1961, P. 643).
Authors: Mandelbaum Hugo
Published: October 2002

Danilo A. Rigassi reported an experiment measuring, with a theodolite, elevations across a vertical fault. The elevation difference across the fault was measured hourly from 4:25 A.M. to 20:00 P.M. on June 8, 1960. It varied from a low of 99.311m at 6:00 A.M. to 99.324m at 20:00 P.M. Rigassi attributes this variation to differential tidal motion of the denser Cretaceous horst against the surrounding Oligocene region.
A SIMPLE CRITERION FOR INTERPRETING NEGATIVE GRAVITY ANOMALIES
Authors: Bott M. H. P.
Published: October 2002

The second derivative of gravity across a profile above a two‐dimensional semi‐infinite horizontal slab with a sloping edge has two turning values. Their relative magnitudes provide a simple criterion for determining the direction of the slope. Since the boundary between sedimentary basins and the underlying denser basement rocks characteristically slopes inwards towards the basin, and the contacts of granite batholiths usually slope outwards, this simple criterion provides a means for distinguishing between buried granites and sedimentary basins from their gravity anomalies. The reliability of the criterion is confirmed for observed gravity profiles in Great Britain.
THE EFFECT OF A FAULT ON THE EARTH’S NATURAL ELECTROMAGNETIC FIELD
Authors: d’ Erceville I. , Kunetz G.
Published: October 2002

The main purpose of this paper is to study the effect on a natural electromagnetic field of a lateral variation in the physical properties of the ground. An exact mathematical solution is given for two media of different resistivities in contact along a vertical plane (fault) overlying a horizontal basement that is taken as being either infinitely resistive or infinitely conductive, or at infinite depth. Results are given in the form of curves along profiles perpendicular to the fault. Some practical inferences are drawn from the shape of the curves and from their comparison.
HEAD WAVES FROM A BED OF FINITE THICKNESS
Authors: Levin Franklyn K. , Ingram John D.
Published: October 2002

The behavior of the head wave from a high‐speed layer embedded in a low‐speed half‐space has been investigated with two‐dimensional seismic models. Twelve layer thicknesses ranging from four wavelengths to one‐tenth wavelength were used. A simple theory based on interference between the head wave and the reflections from the bottom of the layer gave amplitude‐distance values which agreed with the observations for layer thicknesses down to about one‐third of a wavelength. For thick layers, the experimental amplitude dependence on distance was different from the theoretical law (−3/2 power of the distance). The velocity minimum for thin layers discovered by Lavergne was confirmed and a possible slight velocity maximum at intermediate layer thicknesses noted. The velocity for zero layer thickness appeared to be greater than the free bar velocity. Systematic variations of head‐wave spectra with layer thickness occurred.
CONTINUOUS SEISMIC PROFILING WITH MATCHED FILTER DETECTOR
Authors: Clay C. S. , Liang W. L.
Published: October 2002

These experiments were made to study the application of pulse compression and continuous profiling techniques to deep‐sea geophysical research. Tests were made in several areas with low‐ and high‐frequency sources. Reflection profiles with a 125‐cps source were made in the Straits of Florida. The receiving hydrophone was towed behind the ship. The hydrophone consisted of a 75‐ft long array of 25 equally‐spaced acceleration‐balanced barium titanate elements inside an oil‐filled hose. The source transmitted either a ping or a chirp coded ping. The receiver included a shift‐register type of matched filter. Profiles were taken with both short pings and with chirp pings. The signal‐to‐noise gain of the chirping matched filter system was at least 12 db. Profiles were taken with a 400‐cps source and the low‐frequency source in Long Island Sound to compare operations with different source frequencies. The 400‐cps source did not penetrate beneath consolidated sediments whereas the low‐frequency source did. The 400‐cps source was used to study the reflections from the 15,500‐ft deep bottom in the basin near Eleuthera, B.W.I. Reflections at subbottom depths of about 75, 300, and 800 ft were observed. The shallow reflector was irregular in depth and appearance.
GEOPHYSICAL ACTIVITY IN 1961
Authors: Smith Neal J.
Published: October 2002

Combined Petroleum Geophysical Activity.—Petroleum geophysical exploration in the Free World, consisting of seismic, gravity, ground magnetic, and other nonairborne geophysical methods, declined 3.1 percent, to 10,203 crew‐months in 1961 for a net loss of 323 crew‐months. This is 24 percent below the peak year of 1956. Airborne magnetometer activity was down from its high of 556,652 line‐miles in 1960 to 347,841 line‐miles, a drop of 37.5 percent.
REPLY BY AUTHOR TO DISCUSSION BY CARL KISSLINGER
Authors: Adams WM. Mansfield
Published: October 2002

I agree completely with the cogent discussion of Professor Carl Kisslinger. Since the slope of the empirical curve in Figure 11 of Nicholls is altered by the one point, the evaluation of the possibility that our results might be reversed should definitely await further investigation.
A LOW‐FREQUENCY GEOPHONE FOR BOREHOLE USE
Authors: Lynn Ralph D.
Published: October 2002

Design and performance features of a moving‐coil geophone for borehole used are described. The natural frequency is 1.2 cps and the sensitivity is 50 volts/cm/sec. Including the amplifier, the line output sensitivity is 17,000 volts/cm/sec. The input noise level of the amplifier is about 0.2 microvolt which corresponds to ground motion of about [Formula: see text] at one cps. A ball‐drop method of geophone calibration is described.
LOVE WAVES IN A NONHOMOGENEOUS INTERNAL STRATUM LYING BETWEEN TWO SEMI‐INFINITE ISOTROPIC MEDIA
Authors: Dutta Subhas
Published: October 2002

This paper studies the possibility of propagation of Love waves in a nonhomogeneous internal stratum of finite depth lying between two semi‐infinite isotropic media in two different cases. In one case the rigidity and density vary as [Formula: see text] and in the other case as [Formula: see text], where λ is a constant and z is the depth measured from the common interface of the upper medium and the internal stratum.
STANDARD CURVES FOR INTERPRETATION OF MAGNETIC ANOMALIES OVER LONG TABULAR BODIES
Authors: Gay S. Parker
Published: October 2002

The magnetic anomalies in vertical, horizontal, and total intensity for the thin infinite dike are shown to belong to a single mathematical family of curves for all values of dip and strike of the dike and all values of inclination of the magnetizing field. The complete family of standard curves has been constructed and is incorporated into an interpretational scheme based on superposition with observed magnetic profiles. This technique should give more reliable interpretations than methods based on only a few isolated points of a profile curve. By integration of the general thin‐dike response a general expression of similar form has been derived for thick dikes, and ten sheets of curves for dikes of varying width indices have been constructed. By employing the method of subtraction of curves these serve for constructing anomaly profiles over bodies of finite depth extent. Additionally, for thin dikes the much‐neglected demagnetization corrections have been incorporated in the interpretational method following verification by model studies. One important disclosure of this work is that the depth and location of the apex of an infinite tabular body may be determined without knowing the intensity or direction of magnetization within the body, assuming only that these quantities are constant throughout.
REPLY by P. L. GOUPILLAUD WITH THE APPROVAL OF H. R. PRESCOTT
Authors: Goupillaud P. L.
Published: October 2002

Mr. A. T. Dennison’s remarks are essentially correct, more particularly with regards to the assumed initial conditions. Mr. Prescott’s solution would correspond to a set of very special initial conditions in which the receptor mass would be passing, at the instant of arrival of the sine wave, through its equilibrium position with an initial momentum such that the initial amplitude of the transient term be equal to the amplitude of the steady‐state term. It is clear that such initial conditions have little or no real physical significance.
UNIPOLE METHOD OF ELECTRICAL PROFILING
Authors: Gupta Ravindra N. , Bhattacharya P. K.
Published: October 2002

In the unipole method of resistivity prospecting, an electrode arrangement AMNA′ with a third common electrode at infinity, is used as against the arrangement AMNB in the conventional bipole method. The electrodes A and A′ are connected to one and the same pole of electric current. In the case of the unipole method, field intensity at the center of the spread is zero for a homogeneous ground. This results in a pure‐anomaly method, increasing the depth of investigation and the sensitivity of field measurements considerably. The percentage of total current entering the deeper regions is larger in the unipole method than in the bipole method. The difference is further increased if a less resistive layer is present near the surface of the earth. Sensitivity of the unipole method to the near‐surface inhomogeneities is less than that of the bipole method. But the unipole method is more sensitive to the deeper inhomogeneities of interest. The unipole arrangement introduces some focusing of the current within a particular range of the depth which can be controlled by altering the spacing between the current electrodes. In general, response curves for the unipole method are less complicated and admit more controls for interpretation than those for the bipole method. A theoretical and experimental comparison of the unipole method with the conventional bipole method shows that the former method is more effective than the latter in certain applications. The field instruments used at present for the bipolar measurements can be very easily adapted to the unipole method.
On: “TERRAIN CORRECTION TABLES FOR GRAVITY” BY JOHN L. BIBLE (GEOPHYSICS, OCTOBER 1962, PP. 715–718)
Authors: Thyssen‐Bornemisza Stephen , Stackler W. F.
Published: October 2002

The expanded tables of Bible are very useful for gravity meter work, especially in rugged territory, but it appears regrettable that in the interest of simplicity Zones B and C have been somewhat neglected. It is true that, in standard surveys, high correction accuracy is not needed for these zones, but surveys with very close spacing of stations are gaining interest and an appropriate subdivision may seem advisable.
AN APPROXIMATE SOLUTION OF THE PROBLEM OF MAXIMUM DEPTH IN GRAVITY INTERPRETATION
Authors: Skeels D. C.
Published: October 2002

It is assumed that the maximum depth for the mass responsible for a given gravity anomaly is closely approximated by the depth to the top of the vertical‐sided mass (prism or cylinder, as the case may be) whose calculated anomaly gives the closest fit to the observed anomaly, and whose density contrast is the maximum permitted from geological considerations. A set of charts is presented by means of which the depth and dimensions of the prism (or cylinder) of “best fit” can be determined quickly from the amplitude, half‐maximum, and three‐quarter maximum widths of the anomaly, together with the assumed density contrast. Four examples are given of the use of the method with actual data.
INTERPRETATION OF GEOPHYSICAL PROFILES BETWEEN SINGAPORE AND LABUAN, NORTH BORNEO
Authors: Isaacs Kalman N.
Published: October 2002

An interpretation is given of an airborne magnetometer profile from Singapore to Labuan, North Borneo, coupled with a gravity profile which partially covered the same path. The interpretation indicates a shallow basement along the western half of the profile, except for a minor sedimentary basin about 50 miles west of the Tambelan Islands, and another minor sedimentary basin in western Borneo. East of Kuching, Sarawak, the geophysical profiles apparently impinge on a major basin, with sedimentary thickness of the order of 10,000 ft.
THE CALCULATION OF TOTAL‐INTENSITY MAGNETIC ANOMALIES FOR CERTAIN BODIES BY DIGITAL COMPUTER
Authors: Hughson James T.
Published: October 2002

A method has been devised for calculating total‐intensity magnetic anomalies caused by bodies of finite and infinite thickness. It involves the computer summation of point‐function‐cell area products. Magnetic effects for differently‐shaped bodies are computed by ordering appropriate changes in component cell configurations.
MOTION PRODUCT SEISMOGRAMS
Authors: White J. E.
Published: October 2002

This paper describes a means of combining the voltages from a three‐component seismometer so as to suppress noise waves arriving randomly from all directions and to indicate the direction of arrival of any particular wave‐train, such as might be caused by an earthquake, explosion, or moving vehicle. Each of the horizontal components of motion is electronically multiplied by the vertical component, with or without phase shift, and the two resulting products are displayed as a vector pointing to the source of seismic waves. The equipment assembled to perform these operations is referred to as the Motion Product Detector. Mathematical analysis and small‐scale tests of the Motion Product Detector on the Research Center grounds look promising.
THE RESPONSE OF AN ELASTIC PLATE SUBMERGED IN A LIQUID HALF‐SPACE TO EXPLOSIVE SOUND
Authors: Rosenbaum J. H.
Published: October 2002

A mathematical analysis is presented for the case of a point‐source explosion in the liquid layer above an elastic plate of infinite horizontal extent immersed in a liquid half‐space parallel to the free surface of the liquid. An asymptotic solution, valid for long times after the explosion, is derived; it expresses the pressure response in the liquid layer in terms of characteristic vibrations of the layered medium. Trapped and exponentially decaying modes have been investigated numerically for the Lucite plate in water. Special emphasis is placed on the description of sustained reverberations (singing). This phenomenon is described in terms of complex modes, where some energy travels back radially towards the source. At long times, singing can be described in terms of “standing” waves of nonvanishing horizontal wave number. It is also closely connected with a type of trapped wave in the liquid layer‐plate combination whose horizontal phase velocity is greater than the velocity of sound in the fluid, but which is completely decoupled from the liquid half‐space below the plate. At very long times, however, the strongest signal is associated with an almost completely decoupled shear motion of the plate, and the horizontal wave number approaches zero. A brief discussion of the total transmission of plane harmonic sound waves through a Lucite plate in water is given. The total transmission curves are used to show qualitatively that singing often may not be observed in connection with the above‐mentioned trapped waves.
EXPRESSION OF E‐W FRACTURES IN MAGNETIC SURVEYS IN PARTS OF THE U.S.A.
Authors: Fuller M. D.
Published: October 2002

Continental magnetic anomaly patterns are interrupted by east‐west features similar to, though less obvious than, those found in the East Pacific. The distribution of these east‐west interruptions in aeromagnetic surveys of parts of the U.S.A. has been analyzed quantitatively. Evidence of persistence of E‐W interruptions across individual surveys for distances of more than 100 miles is presented. By comparing surveys at different longitudes but at the same latitude, it is shown that certain interruptions continue for greater distances. For example, the Mendocino feature of the East Pacific can be traced unmistakably through surveys in California to eastern Nevada, and appears to be present in eastern Colorado. By analogy with the East Pacific studies, the magnetic features are interpreted as the expression of a pattern of fractures. However, there is no evidence of consistent offset comparable with that found in the East Pacific. The fractures are considered to be deep and partly decoupled from the upper reaches of the crust, so that they are clearly recognized in the thin oceanic crust but are partly masked by local shallow complexities in the continental crust.
WIDE‐BAND EXTRACTION OF MANTLE P WAVES FROM AMBIENT NOISE
Authors: Backus Milo , Burg John , Baldwin Dick , Bryan Ed
Published: October 2002

The spatial correlation characteristics of ambient short‐period (0.5 to 5 cps) noise at Ft. Sill, Oklahoma, and on the Cumberland Plateau in Tennessee were investigated on “permanent” arrays with 3–4 kilometer diameter. Dominant ambient noise at the two locations is spatially organized, and to first order may be treated as a combination of seismic propagating wave trains. At the Tennessee location noise energy above one cps is dominantly propagating with velocities from 3.5 to 4.5 km/sec, and must be carried in deeply trapped, high‐order modes. Generalized multichannel filtering (Burg) can be used to preserve a large class of mantle P‐wave signals, wide‐band, in a single output trace, while at the same time specifically rejecting ambient noise on the basis of its organization. Results of generalized multichannel filtering applied on‐line at the nineteen‐element array in Tennessee and applied off‐line are discussed.
CONVERTED WAVES IN REFRACTION SURVEYS OVER MARKERS WITH VARIABLE DEPTH
Authors: Hall D. H.
Published: October 2002

Converted head waves are observed sufficiently often in crustal and other refraction surveys to raise interesting questions as to their possibilities in interpretation. Some simple cases are examined in which sequences of P, S, and converted head waves are assumed to be observed over a two‐ and a three‐layer medium. Investigation is made of the theoretical requirements in terms of numbers of shot and recording points, and the number of members in the sequence, to allow calculation of layer velocities and thicknesses when there is low to moderate structure on the interfaces. It is found that as few as a single shot and a single recording point, and two, three, or four members of a sequence are sufficient to allow determination of some or all of the P and S velocities in the layers, and the depths to the layers below shot and recording point. How far these possibilities can be realized in practice is dependent on the development of techniques to produce and observe converted waves consistently in refraction surveys. To what extent this can be done is at present little known, and is a matter for future research. If converted waves can be used regularly in refraction work, some operational advantages might result as follows. Because of the decrease in the number of shot and recording points necessary to derive velocities and depths when sequences of head waves are observed, it is possible either to gather usable data with minimum effort, or, if a more elaborate array of points is used, to achieve greater detail regarding the lateral variation in velocity and depth over what would have been obtained from a single wave type.
BOREHOLE GRAVITY METER AND ITS APPLICATION
Authors: Goodell R. R. , Fay C. H.
Published: October 2002

The Shell Development borehole gravimeter is an instrument which utilizes as a measure of gravity the frequency of a chosen mode of vibration of a string supporting a freely suspended mass. The instrument, which is capable of determining differences in gravity between stations to one milligal or better, has been in semiroutine use by Shell for over two years. The most common application of such a meter, the determination of average densities for intervals of the order of one thousand feet, is illustrated by data from several wells.
ELECTROMAGNETIC FIELDS OF A SMALL LOOP ANTENNA ON THE SURFACE OF A POLARIZABLE MEDIUM
Authors: Bhattacharyya B. K.
Published: October 2002

Studies are made in this paper on the characteristics of the electromagnetic fields produced by a small loop antenna placed on the surface of a medium which exhibits induced‐polarization effects. An approximate expression for the effective impedance of a polarizable medium is used for this purpose. Both the real and imaginary parts of the impedance are appreciably frequency‐dependent. Different expressions suitable for specific ranges of time and specific values of the characteristic parameter of the medium are obtained for the fields when the antenna is excited by a step‐function current source. The step‐function responses show marked differences in characteristics as the parameter of the medium is increased from very small values, typical of membrane polarization, to very large values corresponding to electrode polarization. The rate at which the magnitude of the transients decays with time is highly dependent on this parameter. The rate of decay in the initial small part of the transient curve increases, whereas in the remaining major part the rate decreases with rise in the value of the parameter.
Introduction to Theoretical Seismology, Part I, Geodynamics. J. B. Macelwane, S. J., John Wiley & Sons, New York, 1936. x+366 pp., $6.00.
Authors: Slotnick M. M.
Published: October 2002

The volume is a companion to another characterized as Part II and entitled Seismometry by F. W. Sohon, S. J. The present volume is a source of a great deal of valuable information, especially for one interested in beginning a study of earthquake lore and eager to form a foundation in that field. Of particular value in this connection is the completeness of the bibliography.
ON THE EXTENSION OF TWO‐LAYER METHODS OF INTERPRETATION OF EARTH RESISTIVITY DATA TO THREE AND MORE LAYERS
Authors: Watson Robert J. , Johnson James F.
Published: October 2002

The two‐layer problem has been solved completely. Considerable success with the three‐layer problem has been attained by the extension of the two‐layer methods of Tagg and Roman making use of the principle established by Hummel. Some of the limitations of these methods are examined by the comparison of theoretical curves for various values of [Formula: see text], [Formula: see text], and [Formula: see text] with help‐curves computed using Hummel’s principle. In general it is found that the three‐layer problem of the type where a good conductor lies between two relatively poor conductors is more favorable for interpretation by the extension methods than is the opposite case where a poor conductor lies between two good conductors. The disadvantage in the latter case is that the field measurements must be carried to very much larger electrode spacings compared to the depth investigated. In all three‐layer problems where [Formula: see text], a good interpretation for [Formula: see text] is difficult. The four‐layer problem is much more difficult and only very special types lend themselves to the extension methods. The use of a large number of theoretical curves for curve matching is advocated both as a supplement to the extension methods and as a more powerful but slower method for the less favorable three‐layer problems as well as for problems of four or more layers.
DETERMINATION OF THE POTENTIAL PRODUCTIVITY OF OIL‐BEARING FORMATIONS BY RESISTIVITY MEASUREMENTS
Authors: Martin M. , Murray G. H. , Gillingham W. J.
Published: October 2002

Electrical logging is now almost universally applied in oil and gas fields throughout the world. The usual practice is to record the self‐potential and resistivity curves which, together, reveal the location and thickness of strata penetrated by the drill and a great deal as to their lithology and fluid content. The resistivity log thus obtained serves very well to disclose in detail formations penetrated and to distinguish between oil and water. With the device used for ordinary electrical logging purposes, the true resistivity of the formation is not measured. The recorded resistivity is only an apparent value which is governed by several influencing factors, besides the true resistivity of the formation and its fluid content. As applied to the oil content of a formation, it is a qualitative measurement, merely showing the vertical extent of the oil accumulation. Experience has shown that the electrical conductance of oil sands is due to connate water held by molecular forces to the sand grains. Research has disclosed a definite mathematical relationship between the true resistivity of an oil sand and the ratio of its oil and connate water. This leads the way to a new practical application of electrical logging. By using a suitable combination of measuring devices, the true resistivity of an oil sand may be measured in an oil well. The true resistivity measurement, used in conjunction with other field and laboratory data, may in certain cases be used quantitatively to make a determination of the net oil content of a productive layer. The method by which these measurements are obtained is described and actual examples are cited.
SCATTERING OF SHEAR WAVES BY SMALL TRANSEISMIC OBSTACLES
Authors: Schwab Fred
Published: October 2002

Using spherical vector wave functions, the general problem of the scattering of plane transverse waves by a transeismic sphere is formulated. The far‐field result for a small sphere is presented. One part of the scattered field arises from the density contrast between the sphere and the external medium, and another part arises from the rigidity contrast. Each contrast results in a scattered compressional wave having radial displacements, and a transverse wave having displacements parallel to the sphere’s surface. The four fields are represented graphically. The density contrast produces a dipolar compressional field and a toroidal transverse field. The displacements of both are symmetric about a line in the direction of polarization of the incident wave, and are otherwise independent of the direction of incidence. The rigidity contrast produces a quadrupolar compressional field, and a transverse field for which the directivity pattern is given. A model is presented which gives the relative displacement directions of this last field. The scattered fields due to the density contrast behave as though they were due to a pure displacement oscillation of the sphere, and those due to the rigidity contrast as though they were due to a pure distortional oscillation.
PHASE‐DISTORTIONLESS FILTERING
Authors: Domenico S. N.
Published: October 2002

Phase‐distortionless filtering is accomplished readily in a magnetic delay‐line filter. The necessary and sufficient condition for the elimination of phase distortion is a symmetrical unit‐impulse response or operator. Three‐, six‐, nine‐, and twelve‐point operators were selected from an analytical filter for which the unit‐impulse response is symmetrical. These were applied in a delay‐line filter achieved in conventional magnetic‐tape playback equipment. Advantages of phase‐distortionless filtering demonstrated here are (1) elimination of frequency‐dependent time lags and (2) identification of time‐invariant points of seismic events on a multifiltered seismogram display. The latter should faciliate the correlation of reflections between seismometer group positions and interlocking seismograms. Filtering with each of the above four operators demonstrated that the three‐point operator performs nearly as effectively as the six‐, nine‐, and twelve‐point operators.
DEEP SEISMIC REFRACTION INVESTIGATION IN THE CANADIAN ARCTIC ARCHIPELAGO
Authors: Sander G. W. , Overton A.
Published: October 2002

During 1962 and 1963, the Dominion Observatory conducted refraction seismic surveys in the islands north of the Canadian mainland. These surveys are part of a project of the Government of Canada to explore the Polar Continental Shelf. The operation consisted of three stationary recording units and a shooting party which traversed the frozen sea in a tractor train. Three refraction‐seismic profiles form a continous section from the Canadian Shield through the Franklinian Geosyncline and the Sverdrup Basin to the Arctic Ocean. Post Devonian sediments in the Sverdrup Basin were found to be 10 km thick. The lower, basic portion of the crust is indicated by a velocity of 7.3 km/sec at a depth of 24 km and the base of the crust at 38 km.
THE PHYSICAL FOUNDATIONS OF FORMATION DENSITY LOGGING (GAMMA‐GAMMA)
Authors: Tittman J. , Wahl J. S.
Published: October 2002

The principal modes of interaction between gamma rays and atoms are reviewed. Special attention is paid to the need for using only Compton scattering in order to determine the electron density of a sample or earth formation and for eliminating chemical composition effects arising from low‐energy photoelectric absorption. The nature of the so‐called Z/A effect is discussed in relation to the conversion of electron density, the immediately measured quantity, into bulk density. Since gamma‐ray diffusion results from repeated scattering in the formation, the Boltzmann transport equation is used as the framework for understanding empirical observations. The method‐of‐moments solution provides both an understanding of the spatial variation of the gamma‐ray energy spectrum and also a basis for reducing the Boltzmann equation to the simple diffusion equation. A discussion is presented comparing experimental results with the diffusion solution for the point‐source‐at‐plane‐interface problem. The comparison confirms the validity of the mathematical and physical approximations made.
LONG‐TIME RESPONSE PREDICTED BY EXACT ELASTIC RAY THEORY
Authors: Spencer T. W.
Published: October 2002

The formal solution for an axially symmetric radiation field in a multilayered, elastic system can be expanded in an infinite series. Each term in the series is associated with a particular raypath. It is shown that in the long‐time limit the individual response functions produced by a step input in particle velocity are given by polynomials in odd powers of the time. For rays which suffer m reflections, the degree of the polynomials is 2m+1. The total response is obtained by summing all rays which contribute in a specified time interval. When the rays are selected indiscriminately, the difference between the magnitude of the partial sum at an intermediate stage of computation and the magnitude of the correct total sum may be greater than the number of significant figures carried by the computer. A prescription is stated for arranging the rays into groups. Each group response function varies linearly in the long‐time limit and goes to zero when convolved with a physically realizable source function.
GRADIENT MEASUREMENTS IN GROUND MAGNETIC PROSPECTING
Authors: Hood Peter , McClure D. J.
Published: October 2002

The development of electronic magnetometers, i.e., the proton‐precession and fluxgate instruments, for use in ground magnetic surveys has permitted the measurement of the first‐vertical derivative of the total field, or of the vertical component of that field, with negligible addition to the total cost of the survey. The gain in information is, however, significant. Curves for the vertical gradient over a vertical contact, point pole, and finite dipole are presented. The vertical contact is outlined by the zero contour for the vertical gradient of the vertical component, and the depth of burial is half the horizontal distance between the positive and negative maxima. The depth of burial of the point pole and finite dipole is approximately equal to the horizontal distance between the negative half‐maximum points on the vertical‐gradient curves.
GRAVITY INTERPRETATION USING THE FOURIER INTEGRAL
Authors: Odegard Mark E. , Berg Joseph W.
Published: October 2002

The gravitational anomalies of simple bodies (sphere, cylinder, and fault) were used to develop methods for analyzing gravity data in the frequency domain. The Fourier transforms of the functional representations of the theoretical gravitational anomalies of these bodies were obtained. Mathematical relations were formulated between the transform‐versus‐frequency relationships and the depths and sizes of the bodies. Compound gravity anomalies (multiple cylinders, fault, and cylinder) were analyzed, and the transforms were reduced to transforms of anomalies due to individual simple bodies. These methods of analysis were applied to theoretical anomalies using numerical techniques, and the accuracy of both depth and size determinations was within a few percent in all cases.
SHORT CONVERSION TABLES BETWEEN ENGLISH AND METRIC SYSTEMS OF UNITS
Authors: Thomson Ken
Published: October 2002

In February, 1964, the National Bureau of Standards announced its adoption of the Intertional System of Units (abbreviated SI for Système International d’Unités). The Bureau proposes to use this system in all of its publications except where its use would impair communication or usefulness.
SEISMIC MAPPING OF UNDERGROUND CAVITIES USING REFLECTION AMPLITUDES
Authors: Cook John C.
Published: October 2002

Underground cavities (and similar marked lateral changes in seismic impedance) having dimensions of tens to hundreds of meters should markedly reflect artificial seismic waves and locally obstruct reflections from deeper horizons. This should be especially true for liquid‐filled cavities if shear waves are employed. Attempts have been made to apply these principles in delineating solution‐mined cavities in bedded salt. In one seismically reverberant area, results from a brine‐filled cavity 300 m below the surface were unclear. Strong seismic “shadows” were found, however, in a seismic reflection survey of solution cavities 500 m below the surface, in a seismically favorable area. At present, the method requires good reflecting horizons both above and below the stratum to be explored. The amplitude ratio of the two reflections is used to represent the seismic “opacity” of the stratum between, normalized for the effect of varying seismic efficiencies at the shots and detectors. Among other applications, the method should be useful in mapping natural caverns and nuclear‐blast cavities.
COMPUTATION WITH THE HELP OF A DIGITAL COMPUTER OF MAGNETIC ANOMALIES CAUSED BY BODIES OF ARBITRARY SHAPE
Authors: Talwani Manik
Published: October 2002

Formulas are derived for the magnetic anomalies caused by irregular polygonal laminas. These are used to obtain the three components of the magnetic anomalies caused by a finite homogeneously magnetized body of arbitrary shape. There is no restriction to the direction of magnetization; in general, it may not be the same as that of the earth’s field. Total‐intensity anomalies are also obtained. Use of these formulas in a computer program is discussed and illustrated by computing the anomaly caused by Caryn Seamount. Simplified, formulas are presented for the anomalies caused by finite rectangular laminas. In addition to bodies of complex shape, the computer program can also be profitably used for computing the magnetic anomalies caused by bodies of relatively simple geometry. The second derivatives of the gravitational potential of a massive body, that is, quantities familiarly known as gradient and curvature in torsion‐balance work and the first vertical derivative in gravity work are also obtained by this method.
GEOPHYSICAL HISTORY, BREHM FIELD, PRATT COUNTY, KANSAS
Authors: Bird W. E.
Published: October 2002

The Brehm field, Pratt County, Kansas, was discovered in October, 1961, after a detailed seismic survey following a subsurface lead. Developed production is from the Arbuckle, Simpson, and Lansing. Production to date is about three hundred thousand bbl of oil plus about one billion cu ft of gas. Estimated reserves are four to six million bbl of oil.
CRUSTAL STRUCTURE FROM CONVERTED HEAD WAVES IN CENTRAL WESTERN MANITOBA
Authors: Hall D. H. , Brisbin W. C.
Published: October 2002

Deep seismic sounding of the earth’s crust was conducted along a line of seven recording sites running from Flin Flon to Mafeking, Manitoba. Two interfaces, the Conrad and the Mohorovičić discontinuities, were distinguished. The following head‐wave types were observed: P*, SPP, SPS, S*, [Formula: see text], PSPSP, SSPSS, SPPPS, SSPPS, and PSPSS. Even though only a single shotpoint was used, it was found possible to determine velocities, layer thicknesses, and structure, using the interpretational possibilities of converted head waves. Discontinuities were determined as follows: Conrad—rises from 15.5±1‐km depth near Flin Flon to something just under 10‐km depth near Mafeking; Mohorovičić—rises from 34±1‐km depth near Flin Flon to 31±1‐km depth near Mafeking. Velocities are as follows upper layer—[Formula: see text], [Formula: see text]; intermediate layer—[Formula: see text], [Formula: see text]; lower layer—[Formula: see text]. Ratio of vertical to horizontal radial displacement was experimented with as a method of identifying converted head waves, and was found to be definitive for head waves arriving from the Mohorovičić as an S wave. Traveltime was found to be effective in wave identification. Comparison of the observed gravity curve with the curve computed for the seismic model indicates that depths and densities related to the model do not totally explain the observed gravity. There is reason to believe that masses of anomalous density within the granite layer are responsible for the disagreement.
CASE HISTORY OF THE LEA FIELD, LEA COUNTY, NEW MEXICO
Authors: Franklin D. W. , McFarlane J. F.
Published: October 2002

A reconnaissance seismograph survey was conducted during 1958 in the relatively unexplored north flank of the Delaware Basin, south‐central Lea County, New Mexico. Conventional methods were employed, single shotholes and multiple geophones. Mapping was based mainly on character correlation. Data quality was fair. Interpretation was complicated by facies changes in relationship to Permian reefing, and sufficient deep‐well and velocity data control were not available to evaluate satisfactorily the effects of these changes. The seismic map showed approximately 450 ft of overall closure with fault along east flank. Subsequent drilling checked the seismic map closely. The Lea field, discovered in 1960, covers approximately 2,280 acres and produces from three zones. The discovery well was drilled as a unit operation with Marathon Oil Company being the operator.