bluuebunny/crossref_metadata_2025 huggingface dataset:
THE VELOCITY AND RAY PATHS OF SOUND WAVES IN DEEP SEA WATER
Authors: Dyk Karl , Swainson O. W.
Published: October 2002

Basic experiments conducted by the U. S. Coast and Geodetic Survey in 1933 and 1934 to determine the ray paths of sound in sea water are reported. Time‐distance, frequency, and amplitude measurements were obtained both in deep sea and shallow waters off the California coast. The mean velocity from a depth of 30 fathoms to a depth of about 1000 fathoms agreed with predictions within a few meters per second. The data indicate a velocity of 1,580 meters per second in the mud‐floor at the experimental site. A high velocity near the source was indicated and the underwater explosion acted as a multiple source. A maximum of five reflections was observed, and diffraction was a factor in the observance of reflections beyond certain critical distances as a result of ray curvature. Direct paths along the surface were also limited by ray curvature. Direct transmission along a narrow (nearly) constant velocity layer at a depth of 100 fathoms was found, but direct transmission along the 400‐fathom velocity inversion could not be definitely established although it seemed highly probable. The direction of first motion associated with several ray paths showed a gradual change of sign with increasing distance.
THE GEOPHYSICAL DISCOVERY AND DEVELOPMENT OF THE BAYOU COUBA DOME
Authors: Melchior Louis F.
Published: October 2002

This case history of the Bayou Couba Dome, St. Charles Parish, Louisiana, reports the results of seismic refraction, seismic reflection, and gravity exploration leading to the discovery of the dome. These data, together with the results of additional exploration done to define the dome, compare favorably with the actual dome shape to the extent it is determined by drilling.
GEOPHYSICAL ACTIVITY IN 1952
Authors: Eckhardt E. A.
Published: October 2002

Geophysical activity during 1952 reached a new all‐time high: On the basis of incomplete reports, the full time services of 948 crews were utilized the world over last year, an increase of 157 crews over 1951. The 9,801 crew‐months of seismograph work in the U. S. and Canada alone exceeded the 9,549 crew‐month world total of such work in 1951. There was a slight decrease in gravity operations from 1,526 crew‐months in 1951 to 1,502 crew‐months in 1952. The reports received on magnetometer activity seem to be neither complete nor reliable, and no attempt to estimate a trend seems justified.
RESIDUAL ANOMALIES AND DEPTH ESTIMATION
Authors: Saxov Svend , Nygaard Kurt
Published: October 2002

The residual gravity anomaly at a point is defined as the difference between the average anomalies along two concentric circles whose center is at the point, divided by the difference between the two radii or [Formula: see text] It is shown that the residual anomalies previously determined by the average circle or the average polygon method (Griffin, 1949) are included in the present definition. The second vertical derivative of g and, to some extent, the fourth vertical derivative of g (Peters, 1949) are also included. The relation between the residual anomalies and the depth of the subterranean masses is examined. It has been pointed out that the gravitational effect originating from a body with mass m is clearly apparent when the center of mass of the body has the depth [Formula: see text]. The influence from masses at a greater or lesser depth is almost eliminated. By avoiding the use of the center point in the figuring of the residual anomalies the influence of random errors is minimized.
THE CORRELATION BETWEEN PRE‐CAMBRIAN ROCK DENSITIES AND BOUGUER GRAVITY ANOMALIES NEAR PARRY SOUND, ONTARIO
Authors: Oldham C. H. G.
Published: October 2002

A gravity survey and a survey of rock densities have been carried out over an area of two thousand square miles near Parry Sound. A closed positive Bouguer gravity anomaly of thirty milligals was delineated, and a considerable variation was found to exist in the densities of pre‐Cambrian gneisses. In most previous interpretations of gravity over the Canadian Shield the gneisses have been assumed to possess a uniform density and anomalies have been attributed to changes in the thickness of horizontal crustal layers. In this paper it is shown that the Parry Sound anomaly can be explained in terms of structures within the crust taking the form of projections downward of the density variations found at the surface. The postulated structure is a nearly circular basin of dense gneisses. The shape is reasonable and agrees with such geological evidence as is available.
GRAVITY MAXIMA CORRESPONDING WITH SEDIMENTARY BASINS
Authors: Martin Rodolfo
Published: October 2002

Gravity work in Argentina has shown maximal values over the deepest part of some sedimentary basins. It is suggested that this unexpected result may be explained as a case of imperfect isostatic adjustment and may be of general interest in the interpretation of gravimetric surveys. It is also suggested that Airy’s theory gives a better explanation of isostatic compensation over moderately large areas while the Pratt theory is applicable to enormous regions, of continental extent.
OUR EXPANDING HORIZONS
Authors: Lay Roy L.
Published: October 2002

Exploration assignments today are more challenging than ever before. The emphasis is on smaller structures and more accurate and deeper interpretations. Many of the more difficult areas, formerly not considered amenable to geophysical exploration, reveal a similarity of problems in widely separated geological and geographical provinces. Geologists and geophysicists are continually broadening their viewpoints because they realize more and more that few areas are unique. Geophysics has made and is continuously making substantial contributions to basic geology. Exploration thinking is broadening steadily toward more definite evaluation of the many types of oil‐bearing traps. Explorationists are learning the principles of sound business risk and thereby expanding their horizons by becoming good businessmen as well as highly trained specialists. The opportunity to expand our horizons further was never more promising than at the present.
A THREE‐DIMENSIONAL SEISMIC WAVE MODEL WITH BOTH ELECTRICAL AND VISUAL OBSERVATION OF WAVES
Authors: Evans J. F. , Hadley C. F. , Eisler J. D. , Silverman D.
Published: October 2002

The short wave lengths required in a seismic model to give wave‐front patterns geometrically similar to those in a large prototype (the earth) can only be obtained by using high frequency sound waves. As sources and detectors of such high frequency waves, piezoelectric crystals are used, primarily because under identical stimuli they are capable of almost perfect duplication. Such duplication is made use of in displaying on an oscilloscope stationary patterns which are characteristic of transient particle motion at a point in the model. Also, it has made possible the direct visual observation of transient wave fronts in transparent models, techniques for which are described, and sample photographs given. As an example of quantitative use of the described model techniques, the results are presented showing symmetric and anti‐symmetric wave propagation in a free elastic plate. Good agreement is found between many features of the experimental record and theoretical predictions.
A GEOLOGICAL AND GEOPHYSICAL STUDY OF PILOT KNOB (SOUTH), TRAVIS COUNTY, TEXAS
Authors: Romberg Frederick , Barnes Virgil E.
Published: October 2002

Pilot Knob is an exhumed volcano of Cretaceous age, composed of “serpentinized” pyroclastics and minor amounts of basalt in both intrusive and extrusive masses. The geology of Pilot Knob was re‐examined, and gravity and magnetic observations made and interpreted, in order to present a complete picture of the feature itself, its history, its relation to the region and area surrounding it, and the resemblances between it and the serpentine plugs in the neighborhood, to which it is geologically related. Some of these plugs have been discovered by geophysical means, and some so discovered have produced oil; the application of gravity and magnetic data to such discoveries is analyzed. The extrusive masses are here reported for the first time, and other evidence is given for the age and volcanic nature of Pilot Knob. The observations reveal 1) strong gravity and magnetic anomalies over the central basalt mass, 2) a pattern of weaker anomalies probably caused by flows and dikes and suggesting that Pilot Knob is situated near the intersection of two sets of fractures, and 3) evidence that “serpentinized” pyroclastics show weak magnetic anomalies and (in the local setting) no visible gravity anomalies.
CROSS‐CORRELATION FILTERING
Authors: Jones Hal J. , Morrison John A.
Published: October 2002

Correlation analysis techniques may be applied to seismic data already subjected to standard recording and analysis procedure in an effort to extract additional information, or to raw data as an alternative filtering method. These techniques involve determination of certain parameters which provide a quantitative measure of the correlation between two sets of data. Among the most useful of these parameters are the auto‐ and cross‐correlation coefficients and functions long used by statisticians in time series analysis and recently applied to filtering and prediction problems in the field of communications. This paper discusses some applications of correlation analysis in interpretation of seismograms. The use of cross‐correlation analysis to identify weak reflections masked by high noise is illustrated for several problems. Equivalence of correlation analysis procedures to filtering operations is stressed. Special analog computing equipment facilitating computation of correlation coefficients and power spectra directly from oscillograms or graphs is described. A brief discussion of modern optimum filter theory is presented.
THE EFFECT OF MOISTURE ON THE DIRECT CURRENT RESISTIVITIES OF OIL SANDS AND ROCKS
Authors: Jakosky J. J. , Hopper R. H.
Published: October 2002

This paper contains the results of detailed research study to determine the factors which govern the electrical conductivities of oil sands and rocks. The experimental work shows the electrical resistivity to be an inverse function of the percentage of conductive water present in any rock type. It was found that the resistivity‐moisture curve of both petroliferous and non‐petroliferous rock are of a general hyperbolic form. For the higher values of moisture content, the curves rapidly approached the conductivity of the electrolyte contained within the rock or oil sands, while for the lower values of moisture content the resistivity values are high and governed by the properties of the rock. Rocks containing soluble salts have critical points on their resistivity‐moisture curves, with the greatest change occurring in the neighborhood of ten per cent moisture content. Rocks containing fresh water have relatively high resistance values which change fairly uniformly with the variations in moisture content. The research work indicates that the presence of oil does not appreciably effect electrical resistance of the rock. Since the resistivity values are dependent upon the electrolytic effect, the work indicates that resistivity values alone are not a reliable criterion for predicting the presence or absence of an oil sand. The work explains further why high electrical resistivity values are not to be expected when applying electrical geophysical methods for mapping subsurface structure.
FUNDAMENTAL RELATIONS IN SEISMOMETRY
Authors: Scherbatskoy S. A. , Neufeld J.
Published: October 2002

The equations for dynamical equilibrium of a geophone are derived by means of the Lagrange method and applied to the particular cases of a moving armature geophone, moving conductor geophone, and electrostatic geophone. The galvanometer for seismic recording is usually of the moving coil type and its equations are similar to those of a moving conductor geophone. The magnetic type geophone as well as the galvanometer consist essentially of two dynamical systems characterized by an asymmetric coupling: “the transducing resistance.” A brief analysis is given of the problem of determining the response of a seismograph to a given earth motion.
EXPERIMENTAL DETERMINATION OF THE TRANSIENT CHARACTERISTICS OF SEISMOGRAPH APPARATUS
Authors: Washburn Harold W.
Published: October 2002

A method of experimentally determining the transient response of seismometer, amplifier, and oscillograph is described. In the apparatus employed the earth motion is replaced by a transient wave generator and the seismometer by an equivalent electrical circuit. Comparison of these laboratory data with field records has shown that accurate predictions can be made from laboratory tests.
A NEW SOURCE OF DAMPED WAVE TRAINS SUITABLE FOR THE TESTING OF GEOPHYSICAL APPARATUS
Authors: Hare D. G. C.
Published: October 2002

A newly developed electric circuit is described, by means of which electrical transients of nearly any desired characteristics may be conveniently produced. The circuit is particularly adapted for use with a cathode ray oscilloscope, in that no auxiliary synchronization is necessary. A typical use in the testing of geophysical circuit elements is illustrated, and a novel method of making rough phase‐shift measurements is described.
A SET OF CURVES TO ASSIST IN THE INTERPRETATION OF THE THREE LAYER RESISTIVITY PROBLEM
Authors: Wetzel W. W. , McMurry Howard V.
Published: October 2002

A set of apparent resistivity curves for the Wenner electrode configuration is given. This set covers a wide range of variations of layer thickness and resistivity for the three‐layer earth. A method for interpretation of field data is outlined.
APPARENT RESISTIVITY FOR DIPPING BEDS—A DISCUSSION
Authors: Van Nostrand Robert G. , Cook Kenneth L.
Published: October 2002

Two groups of workers, here designated the “image school” and the “harmonic school” respectively, have attacked the problem of the interpretation of resistivity data over a dipping bed or dipping fault. The earlier attempts were made by the image school; but the more successful attempts have been made only recently by the harmonic school. The most successful work prior to that presented in the foregoing paper by Maeda has been done by the Russians, whose papers in their English translation are probably available to few American geophysicists. The purpose of this discussion is to appraise the relative merits of various prior solutions to the dipping bed problem in the light of the exact solution to the problem, which is given by Maeda. The terminology and symbols used herein are identical to those used by Maeda in his paper.
INSTRUMENTATION FOR A NEW ELECTROMAGNETIC GEOPHYSICAL FIELD TECHNIQUE, AS APPLIED IN SOUTH AFRICA
Authors: Bellairs G. ff.
Published: October 2002

The carrying out of rapid geophysical surveys by the electromagnetic method has been facilitated by the development of new apparatus, which enables the field intensity at any point to be read directly from the scale of a portable instrument.
ENERGY DISTRIBUTION IN EXPLOSION‐GENERATED SEISMIC PULSES
Authors: Howell B. F. , Budenstein D.
Published: October 2002

Three separate pulses were recognized on seismograms of ground motion resulting from explosions measured at distances ranging from 10 to 1,172 ft from the shotpoint. It is believed that the first pulse represents primarily body waves, the second pulse coupled waves, and the third pulse Rayleigh and Love waves arriving simultaneously. The ratios of the energies of the various pulses are given for several distances. The rates of attenuation of the three pulses are expressed as exponential functions and also as inverse power functions.
A NEW ELECTROMAGNETIC FIELD TECHNIQUE
Authors: Enslin J. F.
Published: October 2002

A technique has been developed for accurate location of narrow vertical or inclined structures such as joints, fault planes, mineralized fissures, and weathered dykes. An alternating current of audio‐frequency is introduced conductively into the ground at a center‐point. Relative or absolute measurements of the tangential component of the resultant horizontal electromagnetic field are made at stations on concentric circles around the center‐point. Curves of the amplitudes, in decibels, are plotted as ordinates against the station positions. These are called the [Formula: see text]. The locations of peaks occurring vertically above current concentrations in narrow conducting zones are plotted on a map of the area and corresponding peaks are easily joined up to delineate such structures. Phase measurements have proved to be of minor importance for the location of geologic structures.
AN EDUCATIONAL PROGRAM IN GEOPHYSICS
Authors: Woollard G. P.
Published: October 2002

The problem of organizing an adequate, balanced training program for a career in geophysics has been the subject of several studies and investigations, the most comprehensive being that conducted by the American Institute of Mining and Metallurgical Engineers’ special committee on Geophysical Education in collaboration with the American Association of Petroleum Geologists and the American Geophysical Union. The results of such studies have invariably indicated that the ideal geophysics curriculum should stress the fundamentals of physics, mathematics, and geology with a minimum amount of work in geophysics as such for coordinating the more basic sciences. The ideal undergraduate curriculum would include course coverage along the following lines: (a) basic geology with advanced work in stratigraphy, structural geology, mineral deposits and petrology, (b) basic physics with advanced work in electricity and magnetism, optics, light and sound, and instrumentation techniques, and (c) basic mathematics with advanced work in calculus, differential equations, potential theory, and vector analysis.
GRAVITY INVESTIGATIONS IN THE HOCKLEY SALT DOME, HARRIS COUNTY, TEXAS
Authors: Allen W. E. , Caillouet H. J. , Stanley L.
Published: October 2002

Gravity measurements at the surface, in the shaft, and in the drifts of the United Salt Company’s mine at the Hockley salt dome have been analyzed to determine densities of sediments, cap rock, and salt rock. The curve derived from the gravity changes indicates the presence of lithologic breaks that correspond with the known geology of the shaft. The density values computed from this curve correspond closely with acceded values for near‐surface clastic sediments, limestone, gypsum rock, anhydrite rock, and salt rock.
THE APPLICATION OF A THREE‐ELEMENT MODEL TO THE S.P. AND RESISTIVITY PHENOMENA EVINCED BY DIRTY SANDS
Authors: McKelvey J. G. , Southwick P. F. , Spiegler K. S. , Wyllie M. R. J.
Published: October 2002

A simple resistor model consisting of three elements in parallel and representing (a) an element of solution and conducting solid particles in series, (b) an element of the solid particles only, and (c) an element of solution only, explains satisfactorily the experimental relationship between the conductivities of solutions used to saturate synthetic dirty sands and the conductivities of the saturated sands. The synthetic dirty sands consist of beds of ion‐exchange particles. The same model is applied to give a theoretical explanation of the potential differences between two different solutions when these meet in the interstices of a synthetic dirty sand; excellent agreement is observed between theory and experiment. It is found that both potentials and resistivities depend on the same geometrical parameters. Hence they can be related to each other. The relationship is derived between the self‐potential deflection and the resistivities of rock and invaded zone. It is compared to various formulae proposed by other investigators for interpreting logs in dirty sands. Conductivities and potential differences across plugs of “synthetic dirty sands” containing oil have been measured. At high oil saturations the potential differences are almost as high as those across a solid membrane containing the same ion‐exchange resin.
LETTER TO THE EDITOR
Authors: de Bremaecker J. Cl.
Published: October 2002

Considering that all the fundamental work in physics is done in the metric system, and that it is important that results obtained in the U. S. be readily comparable with those obtained elsewhere, I think it would be desirable that the authors of papers to be published in Geophysics be asked to give their measurements also (or only, if they prefer) in the metric system. For instance: “The velocity is 3,500 ft/sec (1.067 km/sec).”
A RESONANT CHAMBER METHOD FOR SOUND VELOCITY AND ATTENUATION MEASUREMENTS IN SEDIMENTS
Authors: Shumway George
Published: October 2002

Sound velocity and attenuation measurements in unconsolidated marine sediments have been made by a resonance method which utilizes a thin‐walled plastic cylinder as a pressure‐release container to hold samples. Velocities were determined from resonant frequencies which lay between 23 and 36 kc/sec for the 2 inch diameter by 4 inch long cylindrical container used. Attenuation was determined from the sharpness of the resonant modes. Relatively undisturbed sediment samples were obtained by diver, in shallow water, using the same plastic containers in which the acoustic measurements are made. Deep sea samples were obtained by cutting sections from cores which were taken in plastic tubes. Velocities for shallow water sediments in the San Diego area ranged from 4,840 ft/sec (0.978 times sea water velocity) for fine silt to 5,680 ft/sec (1.147 times sea water velocity) for medium sand, measured at 60°F. and atmospheric pressure. Velocities in deep‐sea red clay samples ranged between 0.980 and 1.040 times the sea water velocity, at 60°F. and atmospheric pressure. Attenuation coefficients for shallow‐water San Diego sediments varied from about 1 to 4 db/ft for silts, to about 3 to 8 db/ft for sand.
A PRELIMINARY EVALUATION OF THE SHALLOW REFLECTION SEISMOGRAPH
Authors: Pakiser L. C. , Warrick R. E.
Published: October 2002

Following successful tests of a specially constructed shallow reflection seismograph in early 1954, new experimental work has been conducted on the Colorado Plateau, in the Upper Mississippi Valley zinc‐lead district, and in Portage County, Ohio. Although reflections were recorded in all of these areas, they were not continuous and correlatable on the Colorado Plateau and in the Upper Mississippi Valley. In Ohio, on the other hand, reflections were recorded from horizons within the Pleistocene overburden as well as from bedrock and horizons within the consolidated rock section. Conditions favoring good reflections are similar for both shallow‐ and deep‐reflection work; they differ only in scale.
SEISMIC WAVE PROPAGATION IN POROUS GRANULAR MEDIA
Authors: Paterson Norman R.
Published: October 2002

Theoretical and experimental studies have been made of the manner in which sound waves are propagated in porous granular aggregates. A cylindrical piezo‐electric source is used and this simulates the explosion of a charge in a seismic shot‐hole. It is found that in general two waves of volume expansion are propagated and that these involve coupled displacements of both constituents of the media. The waves are termed frame‐waves, air‐waves or liquid‐waves depending upon the nature of the pore‐filler and the relative displacements of the constituents. The frame‐wave velocity is dependent upon the strength of the frame, the densities of solid and pore‐filling materials and the texture of the medium. Air‐ and liquid‐wave velocities are related to the texture of the medium and to the density and viscosity of the pore‐filler. Frame‐strength is important to a lesser degree. Waves are dispersive only in the case of media of very low permeability. Attenuation is related to viscosity, texture and frequency. Scattering is probably important only at the highest frequencies and largest particle diameters used in the experiments. It is shown that porosity and permeability of a beach sand can be inferred from velocity measurements. These properties provide information regarding grain‐size, sorting and the nature of the pore‐filler.
SEISMIC WAVES FROM A HORIZONTAL FORCE
Authors: White J. E. , Heaps S. N. , Lawrence P. L.
Published: October 2002

As part of a program of fundamental research on seismic waves, a generator was built for applying a transient horizontal force at the surface of the ground and the resulting seismic waves were observed in some detail. The force is applied when a mass swinging through an arc strikes a target anchored to the earth. Surface geophones along a line in the direction of the force register vertically polarized shear waves refracted back up to the surface, whereas geophones on a line perpendicular to the force register horizontally polarized shear waves. The speeds of the two types of shear waves are often different, indicating anisotropy. Geophones buried below the target show a down‐going shear wave. Variation of amplitude with angle, and other features, are in qualitative agreement with the results given by Rayleigh and others for the waves due to a force at a point in an infinite solid. Love waves and other surface waves were observed, which of course would not be expected from an nterior force.
GEOPHYSICAL HISTORY OF PARENTIS OIL FIELD, FRANCE
Authors: Vajk Raoul , Walton George
Published: October 2002

In 1951, the French Government granted an exclusive exploration permit to the Esso R.E.P. (a Standard Oil Company affiliate) over an area of 4,357,980 acres around Bordeaux in the northern part of the Aquitaine Basin, France. This area was investigated first by surface geology; then it was surveyed by the gravity meter. In checking the gravity anomalies by the reflection seismograph, a subsurface structure was found at Parentis in 1953, which was drilled in 1954, and was proved to be oil bearing. The Parentis oil field is the most important oil field, not only in France, but in all Europe outside the Iron Curtain. Gravity map, seismograph map, seismic profiles, telluric map and geological contour maps, and cross sections of the Parentis structure are presented.
GEOPHYSICAL STUDIES IN THE INTERMONTANE BASINS IN SOUTHERN CALIFORNIA
Authors: Mabey Don R.
Published: October 2002

Geophysical surveys were made by the U. S. Geological Survey in Searles Lake basin and in the Mojave Desert near Barstow, California to test the application of geophysical exploration to the study of the geologic problems associated with the intermontane basins of southern California. In Searles Lake basin a coordinated gravity and seismic reflection and refraction survey indicated that the fill in the basin is about 3,300 feet thick with the greatest thickness occurring east of the center of the basin. The regional gravity data from the area near Barstow can be used to estimate the thickness and extent of the Tertiary and Quaternary deposits.
GEOPHYSICAL ACTIVITY IN 1956 INTERIM REPORT TO MIDYEAR
Authors: Patrick Homer G.
Published: October 2002

World‐wide activity in geophysical explorations by the petroleum industry, after reaching a record high in 1955, declined by approximately 2 percent in the first six months of 1956. An average of 1098 geophysical crews of all types were employed in the first half of 1956 compared to the 1955 average of 1119 crews. The decline in global activity can be attributed to reductions in the use of the three principal geophysics methods, seismic, gravity and magnetic in the western hemisphere. Increased use of all methods, except magnetic which showed a small decline, was reported in the eastern hemisphere.
EXPLORING FOR ANCIENT CHANNELS WITH THE REFRACTION SEISMOGRAPH
Authors: Pakiser L. C. , Black R. A.
Published: October 2002

In the Monument Valley of Arizona and Utah, uranium ore has been found in ancient channel deposits, primarily in the Shinarump member of the Chinle formation of Late Triassic age. The seismic velocity in the Shinarump member is substantially less than that in the Moenkopi formation of Early and Middle(?) Triassic age, which unconformably underlies the Shinarump. Therefore, the ancient channels can be located by using the refraction seismograph. Because the erosion surface of the Moenkopi in channel areas is curved. a delay‐time method of analysis is used to determine the position in depth of the Shinarump and Moenkopi contact. The problem of velocity variations within the Shinarump can be largely overcome by careful interpretation supported by drill‐hole and velocity control.
A GRAVITY MAXIMUM IN THE GREAT VALLEY OF CALIFORNIA DUE TO THE ISOSTATIC EFFECT OF THE SIERRA NEVADA
Authors: Ivanhoe L. F.
Published: October 2002

A gravity maximum extends along the full length of the Great Valley of California. This feature is believed to represent the western limit of the gravity effect due to the adjustment of the Sierra Nevada isostatic block. Recognition that such a maximum with a sedimentary basin may be due to isostasy rather than to shallow geologic features assists in the interpretation of gravity data.
A SEISMIC MODEL STUDY OF THE PHASE VELOCITY METHOD OF EXPLORATION
Authors: Press Frank
Published: October 2002

Variations in the phase velocity of earthquake‐generated surface waves have been used to determine local variations in the thickness of the earth’s crust. It is of interest to determine whether this method can be used to delineate structures encountered by the exploration geophysicist. A seismic model study of the effect of thickness changes, lithology changes, faults and scarps, on the phase velocity of surface waves was carried out. It is demonstrated that all of these structures produce measurable variations in the phase velocity of surface waves. Additional information is required, however, to give a unique interpretation of a given phase velocity variation in terms of a particular structure. Some remarks on the phenomenon of returning ground roll are made.
THE GULF SEISMIC PROFILE PRINTER
Authors: Palmer E. M.
Published: October 2002

A seismic recording system has been developed in which seismic sections, printed photographically in variable‐density form, simulate geologic cross‐sections. The seismic signals recorded from geophone stations arranged for continuous reflection center‐point control are presented in a sequence of vertical tracks. The tracks are adjusted for known corrections and reproduced at a selected horizontal scale. Prints of the variable‐density section exhibit all events and their interrelationships for ready recognition and appraisal. The printer mechanism reduces seismic information to a uniform time basis, with weathering and elevation corrections to datum, and with stepout corrections in which account is taken of changing wave‐front velocity with vertical travel‐path time. The original field records comprise variable‐density tracks on strips of 70‐mm film. In the printer, individual record tracks are successively scanned and transferred to a continuous sheet of film by contact printing. Punched cards supply correction data to mechanisms which displace each record track according to the desired corrections. Normal and special printing functions are automatically performed.
A PROBLEM IN THE ANALYSIS OF GEOPHYSICAL DATA
Authors: Grant Fraser
Published: October 2002

The problem is to analyze mapped data into components which may be termed “trend” and “residual.” The approach used is polynomial fitting by least squares, following the method of DeLury when the data are evenly distributed (or sampled), and of Kendall when they are not. The DeLury method, however, is extended somewhat in scope to include missing values. A number of statistical tests are discussed which should assist in determining the optimum amount of complexity to ascribe to “trend.” The attitude taken throughout this paper is unbiased in the sense that positive and negative residuals are held a priori to be equally likely. An example is given of the regional correction of a gravity survey designed to explore for sulphides near Val d’Or, Quebec. In conclusion, a brief discussion is given of the advantages of polynomial fitting over smoothing and “gridding” methods from the point of view of labour and costs.
SURFACE AMPLITUDES OF REFLECTED BODY WAVES
Authors: Knopoff L. , Fredricks R. W. , Gangi A. F. , Porter L. D.
Published: October 2002

The components of the surface motions of a plane free surface are computed for the incidence of plane body waves.
RESPONSE OF THIN DYKE TO OSCILLATING DIPOLE
Authors: Wesley James Paul
Published: October 2002

A dyke of sulfide ore may be geophysically prospected by observing its response to a slowly oscillating magnetic dipole source. To a first approximation the field produced by a thin dyke is given by a dyke of infinite conductivity and vanishing thickness in a vacuum (Wesley, 1958, Geophysics, v. 23, p. 128). In order to identify the ore and to estimate the size of the deposit, it is necessary to consider further approximations involving the conductivity and thickness of the dyke. By a type of analytical continuation an approximation is found which agrees both with the exact solution for a dyke of infinite conductivity and vanishing thickness and with the exact solution (approximated only for ωσ large and also for σ small) for an infinite slab of finite conductivity and nonvanishing thickness, the dyke appearing as an infinite slab when both source and observer are near the dyke but far removed from the edge. The solution is very good provided the dyke is geometrically thin.
A REVIEW OF METHODS OF FILTERING SEISMIC DATA
Authors: Smith Mark K.
Published: October 2002

Filtering in its general sense represents an important phase of data processing. In recent years such new methods as delay line filtering and digital filtering as well as conventional seismic filtering have been described in the literature. The purpose of this paper is to clarify the relationship between these methods of filtering and to compare design criteria such as cross‐correlation filtering and zero‐phase filtering. Synthetic records as well as field records are used to illustrate the effects of the various filtering techniques.
AN EXPERIMENTAL INVESTIGATION OF FACTORS AFFECTING ELASTIC WAVE VELOCITIES IN POROUS MEDIA
Authors: Wyllie M. R. J. , Gregory A. R. , Gardner G. H. F.
Published: October 2002

An experimental investigation has been made of the factors which affect the velocity of vibratory signals in porous media. It is shown from the results of experiments carried out on appropriate natural and synthetic porous systems that the time‐average formula previously suggested by Wyllie, Gregory, and L. W. Gardner is of considerable utility. This formula states that [Formula: see text] where [Formula: see text] measured, [Formula: see text] in saturating liquid, [Formula: see text] in rock solid, and ϕ=volumetric porosity fraction. The effects are examined of differential compacting pressures on the applicability of this formula to consolidated and unconsolidated rocks. It is shown that the time‐average relationship cannot be applied to determine the total volumetric porosity of carbonate rocks which are vugular and fractured. In such rocks, paradoxically, this circumstance may be advantageous because of the lithological information that may be obtained from an appropriate combination of velocity and nuclear log data. The effects of oil and gas saturation on velocity have been examined experimentally and are found to be comparatively minor. The combination of velocity data with information from electric logs in order to locate zones of oil and gas saturation is shown to be generally valuable; this is particularly so when holes are drilled with oil‐base mud. Some discussion is given of the possible effects on velocity measurements of the relative wettability of rock surfaces by various liquids. Owing to instrumental limitations, it cannot necessarily be assumed that measurements made in the laboratory are directly applicable to the interpretation of velocity data obtained under field conditions.
KEY VARIABLES OF GRAVITY
Authors: Romberg Frederick E.
Published: October 2002

There is an inherent difficulty in converting gravity data into geologic information because the problems have to be solved indirectly. This difficulty has given rise to an intellectual gap between people who interpret gravity data and those who apply the results. With a view to bridging this gap, a check list of variables important to the correlation of gravity and geology is offered. This should help the non‐specialist to obtain a better idea of where gravity will give him useful information. Remarks are made on the role each variable plays in the interpretation process and on the accuracy with which each may be used in computations. The effect of target depth on residual and derivative interpretation methods is examined. Examples are given showing the extent to which information about geologic structures can be got from gravity.
RESIDUAL AND SECOND DERIVATIVE OF GRAVITY AND MAGNETIC MAPS
Authors: Roy Amalendu
Published: October 2002

There has been considerable discussion regarding the merits and demerits of the “smoothers” and the “gridders” in preparation of residual and second derivative maps. The controversy is probably unnecessary, as it appears that, basically speaking, the “smoothers” determine or tend to determine the residual, whereas the “gridders” aim at the second derivative. Following are the reasons for this statement.
SCATTERING OF SHEAR WAVES BY SPHERICAL OBSTACLES
Authors: Knopoff Leon
Published: October 2002

The problem of the scattering of plane S waves by a perfectly rigid, infinitely dense sphere is formulated. Calculations are made for the case in which the medium outside the sphere has a Poisson’s ratio of [Formula: see text]. The range of sizes of obstacles used in the calculations includes radii very small compared with the wave length and radii comparable to the wave length. The scattered wave motions include a P mode and two S modes. One of the S modes has a formal correspondence to the SH mode of plane seismology; the other corresponds to the SV mode. At large distances from the obstacle the scattered P and S fields are computed together with the phase shifts in time occurring in all the components. For small obstacles, the scattered azimuthal S component is circularly symmetric; the scattered meridional S component diffraction pattern is generally elongated in the direction of propagation; the scattered P component is generally broadside to the direction of propagation.
OPTIMUM PROSPECTING PLANS IN MINING EXPLORATION
Authors: Ellis R. M. , Blackwell J. H.
Published: October 2002

The method of L. B. Slichter (1955) for optimizing prospecting plans in cases where geological information is meager has been extended to take account of a number of additional factors. These include non‐random distribution of ore in plan, non‐random distribution in depth and finite thickness of ore bodies. Involved is the problem of overlap of ore bodies which appears to be of minor importance in most practical circumstances. Evaluation of maximum profit ratios (or net profits) indicate that the new factors make significant changes from the results predicted by the simpler treatment and thereby justify the additional complication. It appears that in many practical problems digital computing facilities could be used to advantage to accelerate problem solution.
DISCUSSION ON: LATERAL VELOCITY VARIATIONS NEAR BOREHOLES
Authors: Brooks J. A.
Published: October 2002

The requirement that integrated vertical times from a continuous velocity log check to within some small percent the vertical times computed from the observed travel times of a geophone survey in the same borehole is to me unreasonable. Although we geophysicists know that there are inherent errors in the results of geophone surveys because of possible errors in weathering velocity corrections, datum velocity corrections, depth of shot corrections, and especially seismic travel‐path assumptions, we have presumed the cumulative error in all but unusual surveys to be within the limits of accuracy of reflection seismograph interpretation. The usual seismic travel path assumption, particularly in areas of high velocity stringers or velocity inversions, can be very treacherous in the computation of vertical times. Consequently, I cannot understand why some of our colleagues insist that the log results are incorrect unless they check very closely with the computed vertical shot times. Maybe the computed times are wrong!
ELECTRICAL PROPERTIES OF SYNTHETIC METALLIFEROUS ORE
Authors: McEuen Robert B. , Berg Joseph W. , Cook Kenneth L.
Published: October 2002

Ninety small cores of synthetic metalliferous ore were constructed from solid glass spheres averaging 0.5 mm in diameter, lead spheres 1.0 mm in diameter, and refractory cement. The lead content of the cores varied from zero to 50 percent by frame volume. The effective porosity was controlled by the manufacturing pressure and ranged from 10 to 20 percent. The cores were saturated with NaCl solution. The apparent impedance of the cores was measured with a modified Wheatstone bridge as a function of frequency and current density. The low‐frequency effects of induced polarization were separated from the over‐all decrease of impedance with increase of frequency by taking advantage of the dependence of these effects upon current density. The over‐all decrease of the impedance with frequency and the polarization effects were found dependent upon the effective porosity and the lead content. Both the polarization effects and the over‐all decrease of the impedance with frequency increased with decreasing porosity. The induced polarization effects at 10 cps attained a maximum at approximately 15 percent lead content. The impedance of a synthetic ore with a small lead content was found to be larger than that of corresponding cores barren of lead.
EXACT TRUE DIP FOR A SINGLE CONSTANT‐VELOCITY REFLECTOR
Authors: Kirby Calvin
Published: October 2002

Methods of determining the true dip, or velocity, or both when the velocity is constant are described in the literature. When the sines of the angles of dip are known for two spreads in line with the shotpoint, and at right angles, the true dip can be found exactly (Nettleton, 1940; p. 294–295; and others). An exact extension of this result to two spreads not at right angles is simple, although apparently the equations have not been published. A slightly more general case in which at least two detectors are assumed to be in line with the shotpoint can also be solved exactly by elementary means. The general case in which no two detectors are in line with the shotpoint has apparently not been published. For the special cases mentioned, the present treatment is of greater generality, since the detectors here are not required to be in a level plane, which seems to be a requirement of previous methods. The present work is general in part through being three‐dimensional and including the dip. The wave front is not assumed to be planar.
A REVIEW OF GEOPHYSICAL INSTRUMENTATION
Authors: Born W. T.
Published: October 2002

This paper is a historical review of the development of instrumentation used in all phases of geophysical prospecting, including well logging. Particular reference is made to pertinent papers published in Geophysics and its predecessor publications.
APPLICATION OF SEISMIC METHODS TO A GROUND‐WATER PROBLEM IN NORTHEASTERN OHIO
Authors: Warrick R. E. , Winslow J. D.
Published: October 2002

Valleys cut in the bedrock in northeastern Ohio by Tertiary and Pleistocene streams have been filled by Pleistocene glacial drift so that there is little surface evidence of their existence. Some of these buried valleys are good sources of ground water, so information regarding the location, depth, and cross‐section of the buried valleys is important in water‐supply investigations. Detailed knowledge of the configuration of the buried valleys is useful also in interpreting the glacial history of the region. Test surveys in Portage and Summit Counties, Ohio, by the U.S. Geological Survey indicate that seismic methods can be used to determine depth to bedrock and thus to be applicable to the study of the buried valleys.
OPERATIONS RESEARCH—A TOOL IN OIL EXPLORATION
Authors: Cobb Howard
Published: October 2002

Operations Research is a tool which may be used by the exploration man to help in planning exploration activities and in making decisions. Electronic computers and mechanized data handling may be used in the analyses which are a part of Operations Research. Various types of exploration data which we put on punch cards are readily available for Operations Research studies. Mathematical models of various activities play a large role. They are often built up from data of past experience. Thus, statistics and probability theory are important to the studies. Other techniques commonly associated with Operations Research studies are Linear Programming, Game Theory, Queueing Theory, Monte Carlo, and Search Theory. Operations Research has been defined as quantitative common sense. It is probably the cheapest and one of the more effective of our exploration tools. We use it when we plan optimum control for a geophysical survey. We use it when we analyze the future of a frontier oil province.
USES OF THE GAMMA‐RAY SPECTROMETER IN MINERAL EXPLORATION
Authors: Mero John L.
Published: October 2002

Gamma‐ray spectroscopy offers a rapid and reliable radiometric method of analysis of uranium and/or thorium ores. Methods of ore analysis are described and experimental results are presented. The uranium‐thorium ratios of rocks, which are important in strata recognition and correlation studies, can be determined directly by gamma‐ray spectroscopy without the necessity of making individual uranium or thorium assays. Analysis of potash ores is facilitated with a gamma‐ray spectrometer. Erratic behavior of gamma‐ray well logs can often be resolved by studying the gamma‐ray spectra of these logs. Neutron‐activation, followed by gamma‐ray spectral analysis, of common earth materials offers a method of borehole rock analysis for elements such as calcium, hydrogen, chlorine, sulphur and magnesium. Data in studies employing radioactive tracers can often be enhanced through use of a gamma‐ray spectrometer. Other present and potential applications of the gamma‐ray spectrometer in mineral exploration are also discussed.
GEOPHYSICAL ACTIVITY IN 1959
Authors: Patrick Homer G.
Published: October 2002

Geophysical activity by the petroleum industry in 1959 was reduced in all the major areas of the free world except in the Far East where a small over‐all gain was reported. An average of 957 geophysical crews of all types operated in world‐wide exploration during the year. In 1956, a record high year, the world‐wide average was 1,136 crews.
PROPAGATION EFFECTS IN INDUCTION LOGGING
Authors: Duesterhoeft W. C.
Published: October 2002

Induction logging utilizes the component of induced receiver coil voltage that is in phase with transmitter coil current as a measure of the conductivity of material surrounding the coils. This paper considers the problem of the field of a vertical magnetic dipole in a horizontally stratified, isotropic conductive formation and shows the receiver coil voltage can be considered as composed of responses due to electromagnetic waves in the formation. These waves which experience attenuation and phase shift as they propagate in the formation are reflected at each interface encountered, and a component of receiver coil voltage is induced for each passage of a wave. The relation of the receiver coil voltage components to the geometric factor of previous analysis is discussed. Universal curves that are useful in determining the response due to unreflected primary and reflected secondary waves are presented Example induction log system responses based on the analysis of the present paper are presented.