bluuebunny/crossref_metadata_2025 huggingface dataset:
SEISMIC WAVES FROM A TRANSDUCER AT THE SURFACE OF STRATIFIED GROUND
Authors: Evison F. F.
Published: October 2002

Vibration impulses of variable frequency and duration have been generated by means of an electrically excited vibrator and the resulting seismic waves recorded at the ground surface along a 200‐ft traverse. The first arrivals were refractions from the water table and a deeper clay‐siltstone interface, and these checked with the results of a standard refraction survey. The amplitudes of displacement of the refracted waves varied in each case with approximately the inverse square of distance; the critical distance was marked by a discontinuity of amplitude. Two later impulsive arrivals recorded within 50 msec of the first were interpreted respectively as a transformed reflection from 85 ft depth and an ordinary compressional reflection from 200 ft depth. A dispersive Rayleigh wave gave an independent estimate of the shear velocity and thickness of the surface layer. Air‐coupled waves of frequencies 70.8 cps and 330 cps were recorded and have been related to the first‐ and third‐mode Rayleigh waves respectively.
THE STRUCTURE OF THE NOISE BACKGROUND OF A SEISMOGRAM II
Authors: Horton C. W.
Published: October 2002

One second samples of two seismogram traces are analyzed statistically. The traces represent the outputs of two geophones at depths 75 and 125 feet which were part of a vertical spread. The first four moments and the first four semi‐invariants and the standard deviation are computed for the first and second halves of a one second sample from each trace. These quantities are used to compute the distribution functions of the amplitudes of the seismogram traces. The resulting curves agree very closely with the distribution functions determined directly from the seismogram trace. The number of zeros per second are computed from a theoretical formula developed by Rice (1945). It is shown that the observed number of zeros per second agrees with the predicted value, but the agreement is limited by the small number of zeros that occur in a one second sample. Some general conclusions regarding the statistical behavior of the noise background of a seismogram are offered.
SUBMARINE GRAVITY DETAILING, SAN LUIS PASS DOME, BRAZORIA COUNTY, TEXAS
Authors: Nettleton L. L.
Published: October 2002

The San Luis Pass shallow salt dome lies about 7 miles offshore from the Texas coast under about 50 feet of water. A detailed submarine gravity survey was made to determine the outline, thickness and depth of caprock as a guide for test drilling for the evaluation of the dome as a sulphur prospect. There were no drilling contacts on the dome when the work was done. Seventeen test wells were subsequently drilled within the shallow dome outline as estimated from analysis of the gravity results. The caprock found was slightly smaller in area, considerably shallower in depth and of substantially the same thickness as predicted. The caprock material is nearly all gypsum.
A THEORETICAL STUDY OF INDUCED ELECTRICAL POLARIZATION
Authors: Frische Richard H. , von Buttlar Haro
Published: October 2002

A mathematical solution is obtained and numerically evaluated for determining the depth to a saturated aquifer when prospecting for ground water by induced electrical polarization. In a horizontally stratified earth model consisting of a nonpolarizable overburden and an underlying, infinitely deep polarizable layer, the induced‐polarization potential difference for a Wenner electrode configuration is nearly independent of the resistivity contrast. The computation agrees with results from a laboratory model tank and with a field curve. This justifies confidence in the validity of the results obtained from the model tank on earth models too complex for computation.
GRAPHICAL CALCULATION OF TOTAL‐INTENSITY ANOMALIES OF THREE‐DIMENSIONAL BODIES
Authors: Henderson Roland G. , Zietz Isidore
Published: October 2002

Calculation of the total‐intensity anomaly of a three‐dimensional body of arbitrary shape is greatly facilitated by the orthographic projection of a topographic map of the body onto a plane normal to the inducing field. The graphical integration is then effected by a modified Gassmann integration process. Applications to theoretical and laboratory models establish the relative accuracy of the method. Examples are given of applications to observed anomalies over two laccoliths, Round Butte and Square Butte, in Montana.
REFLECTIONS FROM MULTIPLE TRANSITION LAYERS PART I—THEORETICAL RESULTS
Authors: Berryman L. H. , Goupillaud P. L. , Waters K. H.
Published: October 2002

Continuous velocity logs may be approximated by a series of zones in which the velocity is a linear function of the depth. The reflection response of a series of transition layers may be calculated from an iterative type formula, developed in this paper, which is well suited to digital computer use. This solution takes into account multiple reflections between layers. The reflection output for any input wave shape may be calculated. In this paper a Gram Charlier series pulse having a spectrum peaked at 40 cps is used throughout to facilitate comparison of results. The dependence of the reflection response of single and double layers on frequency and the reflections for the standard input pulse are illustrated. It is shown that 1. Symmetrical double transition layers give an appreciable reflection output even for a base thickness as low as 10 ft. 2. The upper layers of a multilayer group may influence considerably the reflection character from the lower layers.
RESEARCH AND PROGRESS IN EXPLORATION
Authors: Dunlap Henry F. , Johnson Curtis H.
Published: October 2002

This is a general review of new developments in geophysical exploration in 1957. In the Eastern Hemisphere, the strong emphasis on the use of refined seismograph techniques in virgin territories despite extreme operating problems is a development of primary importance. In mining geophysics a new Swedish development employs a rotary electromagnetic field and two‐plane operation to improve substantially the economy and effectiveness of reconnaissance for conductive ore‐bodies. In the United States new developments include work on a method of seismic exploration using continuous waves rather than pulses, the incorporation of transistors into seismic units, a trend toward simplified equipment for plotting seismic record sections, an electrical prospecting method which permits detection of near surface structures in water‐covered areas, and the increased use of continuous velocity logs. Other developments have occurred in the field of chemical logging, including the use of mass spectrometers, infrared analyzers, and gas chromatographic columns. Academic research into techniques for dating feldspar‐bearing rocks has advanced spectacularly. It is now possible to obtain dates on certain kinds of rocks extending from a few thousand years to a few billion years in age.
VERTICAL GRADIENT OF GRAVITY
Authors: Thyssen‐Bornemisza Stephen
Published: October 2002

As the co‐author of the paper “Observation of the Vertical Gradient of Gravity in the Field” which appeared in Vol. 21 (1956) of Geophysics, I should like to add some comments.
RESULTS FOR A GRAVITY CONTROL NETWORK AT AIRPORTS IN THE UNITED STATES
Authors: Woollard G. P.
Published: October 2002

Results are presented for a network of gravity control bases located at the major airports throughout the United States. This network of bases was established as a means of integrating existing gravity surveys into a unified whole. It provides not only control of data but also a means of checking and adjusting calibration differences to a common standard. The gravity standard used is that determined by measurements with the Gulf compound quartz pendulum apparatus at a series of sites covering a range of 4,800 mgals between Fairbanks, Alaska, and Mexico City, D. F., Mexico. The accuracy of the individual measurements on an absolute basis is believed to be within 0.3 mgal using a Potsdam datum value of g equal to 980.1190 gals taken at floor level in the United States Coast and Geodetic Survey gravity vault in the Commerce Building, Washington, D. C. Observation sites are described with sufficient detail to permit reoccupation within 5 to 6 feet.
COMMENTS ON “THE MOVEOUT FILTER”
Authors: Lawrence P. L.
Published: October 2002

The casual reader may draw erroneous conclusions from this paper. In particular, I would like to comment on three points: 1. The apparent great difference between the results of Parr and Mayne (P & M) and Savit, Brustad, and Sider (S B & S) shown here. 2. The importance of length as well as number of elements in a pattern. 3. The importance of an “optimum” rejection filter.
NUMERICAL SOLUTIONS FOR LOVE WAVE DISPERSION ON A HALF‐SPACE WITH DOUBLE SURFACE LAYER
Authors: Dorman James
Published: October 2002

The IBM 650 computer of the Watson Scientific Computing Laboratory, Columbia University, was programmed to obtain numerical solutions for the period equation for Love waves on a half‐space with a double surface layer. Solutions including higher modes for seven models of the continental crust‐mantle system are presented. This group of related cases shows that certain properties of the solutions are diagnostic of crustal structure. These relationships are illustrated graphically.
SOME UNORTHODOX PETROLEUM EXPLORATION METHODS
Authors: Cook John C.
Published: October 2002

Over a period of three years, more than a hundred new or little‐known methods of seeking underground petroleum deposits were impartially evaluated. Most of these methods were the products of independent inventors. A large proportion of the methods proved to have little or no scientific foundation; nevertheless, the protagonists were afforded ample opportunity to prove the value of the methods by field performance. The results with every such method on which adequate data were accumulated were either negative or inconclusive. The methods which possessed some degree of technical merit included a few worthy of careful scientific study. These belonged to the general fields of seismic improvements, geochemical and radioactivity techniques, and electrical techniques. Some of these methods have received a degree of attention from laboratories of major oil‐producing companies. Several examples of unorthodox methods are described. Scientifically trained persons can often detect fallacious methods by the protagonists’ gross misuse of technical language. However, a study of the principles involved and statistically valid field testing are more conclusive.
CATION EXCHANGE AND INDUCED ELECTRICAL POLARIZATION
Authors: Schufle J. A.
Published: October 2002

A report has been made by Vacquier et al. (1957) on the detection of ground water by induced electrical polarization (I.P.). Direct current is introduced into the ground at two points for a short period of time. The current is then interrupted and a small induced voltage, which may take several minutes to decay, appears between another pair of electrodes. Vacquier suggested that the I.P. might be pictured as being due to local electrodialysis of the clay across semi‐permeable membranes formed by adjacent sand grains. When the current is shut off, the induced potential dies away as the exchangeable ions slowly redistribute themselves along the clay.
ELECTROMAGNETIC FIELDS OF A TRANSIENT MAGNETIC DIPOLE ON THE EARTH’S SURFACE
Authors: Bhattacharyya Bimal Krishna
Published: October 2002

Transient electric and magnetic fields close to the surface of the earth, as developed by a step‐function current flowing in a circular loop of wire, have been determined. The effect of the insulating air region is fully taken into account. It is observed that the air region has an appreciable influence on the fields over the surface of the earth. The effect of displacement current within the earth has also been considered. Expressions of electric and magnetic fields have been utilized to determine (a) the mutual impedance function between the primary loop and a small length of wire and (b) the voltage induced in a secondary loop. Both these functions are found to have appreciable magnitudes only during the time interval between the arrival of the wave travelling through air and that of the wave via the conducting medium. From a study of this duration and the initial amplitude of either of the two functions, it is possible to obtain values of conductivity and permittivity of the earth. Curves have been plotted to depict the nature of variation of these functions with time for different values of the electric constants of the earth.
OFFSHORE SINGING—FIELD EXPERIMENTS AND THEORETICAL INTERPRETATION
Authors: Werth G. C. , Liu D. T. , Trorey A. W.
Published: October 2002

At some locations offshore, seismic records degenerate into nearly sinusoidal waves or simple combinations of nearly sinusoidal waves despite the fact that the recording may be made with little or no seismic filtering. Results from field experiments indicate that this “singing” phenomenon is caused by the reflections themselves exciting an acoustic resonant layer formed by the ocean surface and bottom. A simple theoretical model predicts the mode of excitation and the frequency, depth, and range dependence which are verified by controlled field experiments.
INTERNAL FRICTION OF FINE‐GRAINED LIMESTONES AT ULTRASONIC FREQUENCIES
Authors: Peselnick Louis , Zietz Isidore
Published: October 2002

Ultrasonic pulse measurements in the 3 to 10 mc/sec frequency range were made of shear and dilatational absorption and velocity for three samples of fine grained, homogeneous, and well compacted limestones at atmospheric conditions. The complex moduli of elasticity were calculated for two limestone specimens of different grain size and porosity. A “hysteresis” or “solid‐friction” type of loss for waves of dilatation was found in all three limestone specimens. Shear measurements made in one of the limestones also show a “hysteresis” type of loss. Comparison of the dilatational loss in a single crystal of calcite to the dilatational loss in the limestones indicates that the internal friction for the limestone specimens probably occurs at the grain boundaries.
COMMENTS ON “INTERRELATIONSHIPS BETWEEN MAGNETIC ANOMALY COMPONENTS”
Authors: Celmins Aivars
Published: October 2002

On page 748 of the above named paper, Affleck (1958) mentions an interesting behavior of magnetic anomalies which are caused by homogeneous magnetized two‐dimensional bodies. He states that in these cases the airborne magnetometer anomaly can be treated as either the vertical or horizontal component anomaly if the true magnetization is replaced by a pseudo‐magnetization of other direction and intensity. It may be of some interest to formulate this behavior more precisely, so much the more as the interdependence between the magnetization directions and the direction of a normal magnetic field can be expressed by a rather simple formula.
BROADSIDE REFRACTION SHOOTING
Authors: Richards T. C.
Published: October 2002

The three‐dimensional refraction trajectories and travel times in seismic broadside refraction shooting across simple steeply dipping or faulted hypothetical structures are determined when the shotpoint is displaced from the axis. No curved surfaces are assumed and the diffractions to be expected from the structural discontinuities are evaluated. An approximate method for correcting arc time measurements taken over the opposite side to that of the shotpoint is investigated while the conversion of times to dip is discussed. Discussion is also given to the differences in the diffraction time curves caused by changing the shotpoint from the up to the down side of a fault and the relationship these curves have with the refraction time curves in both arc and broadside shooting. The results of these studies indicate the care that should be taken in distinguishing between refracted and diffracted events, and in relating a measured broadside time to a particular point on the refractor. The latter may lead to significant error when simple mid‐point depth computations, often resorted to in field work, are employed.
SEISMIC DATA ENHANCEMENT—A CASE HISTORY
Authors: Graebner R. J.
Published: October 2002

The theory relating to many methods—for example, multiple seismometer techniques—which the geophysicist may control to improve record quality is well known. However, its application has not been fully exploited. An example of the reduction of theory to practice in one area characterized by poor records is presented. It comprises a series of analytical tests designed to discover the cause of poor records, to examine the effect of each variable on the signal‐to‐noise ratio, and to evaluate the solutions predicted by theory. The tests showed that the poor record quality was attributable chiefly to relatively strong surface and near‐surface waves propagating outward from the shot. Wave length filtering by means of suitable shot and seismometer patterns, and compositing through data processing methods, greatly improved record quality and permitted magnetic recording of reflected signals over a broad frequency range. The tests established, in the allotted time, that the quality of the data would meet clearly specified standards of performance. Experience has shown that better seismic data can generally be obtained when the design of techniques is based on the special character of the signal and noise determined from simple tests rather than when the design is based on general assumptions.
COMMENTS ON “FREQUENCY ANALYSIS OF SEISMIC PULSES,” SECTION I (THEORY)
Authors: Sengbush R. L.
Published: October 2002

It is amazing that Fourier analysis is still misunderstood 137 years after Fourier. The periodic time‐waveform and its frequency spectrum are not too troublesome. It is in going from the periodic to the transient that causes the difficulty. At the risk of being obvious, let me outline the basis of the analysis.
WIDE ANGLE REFLECTIONS AND THEIR APPLICATION TO FINDING LIMESTONE STRUCTURES IN THE FOOTHILLS OF WESTERN CANADA
Authors: Richards T. C.
Published: October 2002

Experimental and theoretical evidence is presented to show that a strong seismic event, occurring late in a record and at distances beyond the critical distance, is a wide angle reflection: and not a refraction from a high velocity limestone formation. The evidence includes studies of the effects of anisotropy on the velocities along reflected and refracted paths and of the variation of amplitude of the event with distance. The paper also describes how the results of broadside wide angle reflection shooting may be combined with normal reflection shooting to map strongly dipping limestone structures. An application to a profile through a foothills well in Western Canada is included.
AIRBORNE RADIOACTIVITY SURVEYS IN GEOLOGIC EXPLORATION
Authors: Moxham R. M.
Published: October 2002

The value of airborne radioactivity surveys in guiding uranium exploration has been well established. Improved circuitry and development of semiquantitative analytical techniques now permit examination of more complex geologic problems. It is shown that the airborne technique can be used in exploration for thorium‐bearing heavy mineral deposits and for uraniferous phosphorites. The observed radiation intensity and configuration of the gamma radiation field may be used to approximate the equivalent uranium content and extent of the surficial part of such deposits. The equivalent uranium content of infinite sources can probably be determined within a few thousandths of a percent and the boundaries fixed within a few hundred feet. As the areal extent of the source decreases, the accuracy of the analytical results likewise decreases.
EFFECT OF PORE FLUIDS ON THE ELASTIC PROPERTIES OF SANDSTONE
Authors: Mann R. L. , Fatt I.
Published: October 2002

Bulk compressibility, Young’s modulus, and Poisson’s ratio were measured on three sandstones. Measurements were made on both dry and water saturated samples. Several runs were made on each sandstone to establish the statistical validity of the differences observed between the wet and dry samples. Bulk compressibility of wet sandstone was 10 to 30 percent greater than for dry. Young’s modulus was 8 to 20 percent less for wet sandstone, and Poisson’s ratio was 100 percent greater on one type of sandstone when wet and only slightly greater or about the same on wet samples of the others. A high clay content is believed to lead to a large effect of water on the elastic moduli of sandstone.
GEOPHYSICAL CASE HISTORY OF THE HORSE CREEK FIELD, LARAMIE COUNTY, WYOMING
Authors: Peters Jack W.
Published: October 2002

The Horse Creek field located in Laramie County, Wyoming, was discovered and developed by the General Petroleum Corporation following a reconnaissance gravity survey and preliminary and detail seismic surveys. The gravity survey, made during 1940, delineated a strong maximum gravity anomaly having a magnitude of about 5 mg. Limited seismic work was then conducted in the area during 1941 and 1942 and mapped a prominent anticline having some 2,000 ft of closure. In September, 1942, General Petroleum Corporation spudded in their No. 78-31-G well, located on the apex of the structure. This well was completed as the discovery for the field, producing from the lower Cretaceous‐Lakota sand. The second well, No. 74-6-P, was completed in April, 1943, as the lower Cretaceous‐Muddy sand discovery for the field. Further seismic work was done during 1944 and 1945 to detail and refine the structural picture. Subsequent drilling developed the Muddy sand as the primary producing zone in this field. A total of 32 producing wells has been drilled on this structure and to August, 1958, the total cumulative production from the field was 3,519,000 barrels of oil.
ACCURATE DEPTH DETERMINATION OF THE VELOCITY SURVEY WELL PHONE
Authors: Nolting R. P.
Published: October 2002

Many velocity surveys have been shot in which the actual depth of the well phone was in question at one or more of the levels shot in the borehole. The computed time to the questioned level would not fit the other data obtained from the velocity survey, i.e., the data from the questioned level would not fit the time‐depth curve within reason or, more recently, it could not properly be fitted to the corrected continuous velocity log data. If the “first break” of the questioned level could not be repicked to conform to the other data, a notation was made in the velocity survey report that the depth of the well phone was probably in error. Although this assumption was correct in many cases, there are various other reasons why data from one check level should not fit the rest of the data.
To: NOMOGRAMS TO SPEED UP SEISMIC REFRACTION COMPUTATIONS, GEOPHYSICS, OCTOBER, 1960.
Authors: Meidav Tsvi
Published: October 2002

The last sentence in the paper “Nomograms . . . ,” p. 1045 should read: “Pass a line through i and Z and read off X, the offset distance.” Also, a regrettable typist omission is present in the paper “An Electrical Resistivity Survey for Ground Water,” and was not captured in reading the typed manuscript. The sentence before last on p. 1093 should read: “The project was later concluded under the auspices of the Missouri Geological Survey, with the active help of Dr. H. C. Spicer of the U.S.G.S. who spent much time in instructing the author in both field techniques and interpretation.”
INTERPRETATION OF SYNTHETIC SEISMOGRAMS
Authors: Sengbush R. L. , Lawrence P. L. , McDonal F. J.
Published: October 2002

A linear filter model of the complicated seismic process can be formulated by assuming that (1) the layering of the earth is described by the continuous velocity log, (2) the shot pulse is time‐invariant and propagates as a plane wave with normal incidence, and (3) all multiples, ghosts, and other noise are negligible. Then, the model earth with discrete layers can be considered a filter whose impulse response is the set of reflection coefficients. The set of reflection coefficients becomes the reflectivity function when the model earth has a continuously varying velocity. By definition, the reflectivity function is the derivative of the logarithm of velocity, where both are functions of two‐way travel time. The input to this filter is the time‐invariant shot pulse. The output is a synthetic seismogram that contains the reflectivity function filtered by the shot pulse; in other words, it consists of primary reflections only. Since the filter is linear, the input and the filter may be interchanged, the reflectivity function becoming the input and the shot pulse becoming the filter. A non‐mathematical discussion of the reflections from simple, ideal velocity layering shows that: (1) The reflection from a step velocity function is the shot pulse itself. (2) Thin beds produce a differentiated shot pulse. (3) Beds which approximate a square pulse in velocity produce a pair of shot pulses, with the second delayed in time and reversed in phase with respect to the first. The composite reflection has its greatest amplitude when the layer thickness (in two‐way travel time) is one‐half the basic period of the shot pulse. This situation is called “tuning.” The strongest reflections on field records result when the shot pulse is tuned to the velocity layering. (4) Ramp‐transition zones (linear increase in the logarithm of velocity) produce integrated shot pulses at the changes in slope of the velocity function. A correspondence can be established between the velocity function and the synthetic seismogram by shifting the velocity function later in time. The shift is required because of “filter delay.” The amount of filter delay is related to the impulse response waveform, which, in the case of the synthetic seismogram, is given by the reflection from a step velocity function.
SOME ASPECTS OF ELASTIC WAVE PROPAGATION IN FLUID‐SATURATED POROUS SOLIDS
Authors: Geertsma J. , Smit D. C.
Published: October 2002

Biot’s equations for the propagation of dilatational waves in fluid‐saturated porous solids in the low‐frequency range are analyzed for the purpose of application in geophysical research. The deformation constants of the system are unraveled in terms of compressibilities and porosity, and suitable approximate solutions for wave velocity and attenuation of the waves of both the first and the second kind are obtained. A saturated elastic porous solid is found to behave, as far as the wave of the first kind is concerned, approximately as a standard element. The wave of the second kind rapidly dies out with increasing distance from the source and consequently one might infer that in seismic studies only the wave of the first kind needs consideration. It is shown, however, that its presence has an effect upon the reflection and absorption at any interface between two different fluid‐saturated porous solids. At such an interface a wave of the second kind is again generated. General formulae for the reflection and absorption for normal incidence at the interface are obtained, which include the effect of second‐wave generation. Additional results of the investigation are the following: A rather simple formula for the speed of sound in sedimentary rocks (the wave of the first kind) is obtained, which has to replace the so‐called “time‐average relation” now sometimes used. A comparison between the results obtained here and published results on wave propagation in simpler fluid‐solid systems, such as, for instance, suspensions, showed some weak points in the older theories. Suggestions for possible improvements are given.
MOTION OF THE GROUND ON ARRIVAL OF REFLECTED LONGlTUDlNAL AND TRANSVERSE WAVES AT WlDE‐ANGLE REFLECTlON DlSTANCES
Authors: Richards T. C.
Published: October 2002

The horizontal and vertical motions of the surface of the ground on the arrival of reflected longitudinal and transverse waves from an elastic discontinuity are determined theoretically, with special reference to those parameters encountered in exploring for limestone structures in the foothills of Western Canada by wide‐angle reflection techniques. The results, which cover a wide range of possible overburden velocities, are expressed by means of curves from which the displacement for any practical elastic contrast, depth and observation distance may be readily determined. Properties of these curves are examined empirically. The theory assumes plane waves in determining the amplitude ratios at the structural or free surface discontinuities and spherical waves in deriving spread factors. Corrections to the curves on account of a non‐uniform overburden velocity are considered in the case of a typical central foothills well. The evidence for PP and PS in model, and to a less extent in field work and the significance of phase changes on reflection are discussed. It is concluded that the horizontal geophone should prove to be a useful additional tool in wide‐angle reflection surveys in disturbed foothills zones. Here, it could confirm or refute the arrival of a reflection registered by the vertical geophones in the many cases where doubt exists.
SALT BED IDENTIFICATION FROM UNFOCUSED RESISTIVITY LOGS
Authors: Lishman J. R.
Published: October 2002

Salt beds have almost infinite electrical resistivity. They differ from other infinitely resistive beds in that they are usually soluble in drilling fluids, and give rise to enlarged boreholes. An infinitely resistive bed lying between shales may be recognized from the characteristic shape of the electric log resistivity curves, and the ratios of their readings. Any one of the curves may then be used to compute the borehole diameter, and hence decide whether the bed is salt. Where a washed out salt bed is adjacent to another infinitely resistive bed in which the borehole is to gauge, the configuration of the curves is very characteristic. Apparent resistivity ratios again help to identify the salt.
THEORETICAL HORIZONTAL RESISTIVITY PROFILES OVER HEMISPHERICAL SINKS
Authors: Cook Kenneth L. , Gray Russel L.
Published: October 2002

An album of 40 sets (about 200 different curves) of theoretical horizontal resistivity profiles over and near outcropping hemispherical sinks shows the effects of sink diameter, reflection factor k, and distance of the traverse from the center of the sink upon the magnitude and shape of the apparent resistivity curves. Curves for sink diameters of 16a, 8a, 6a, 4a, 2a, a, and 0.5a, and reflection factors k of ±0.8, ±0.6, ±0.4, and ±0.2 are included. The values of apparent resistivity for both the Lee and Wenner configurations were computed using a digital computer. In general, the larger the sink, the larger the magnitude of the apparent resistivity anomaly up to a sink diameter of about 8a, for which the apparent resistivity over the central part of the sink is essentially equal to the resistivity of the sink, irrespective of the reflection factor. For sink diameters equal to the electrode separation a, large apparent resistivity anomalies result from “pseudo‐focusing” effects. The major peaks of the apparent resistivity curves, which lie outside the edges of the sink for negative reflection factors and inside for positive reflection factors, can be used to detect the edges of the sinks. The album of curves provides a general utility for the qualitative interpretation of apparent resistivity anomalies over features other than hemispherical sinks, such as faults (for large sinks), dikes, grabens, and similar features.
CURRENT AND FUTURE PARAMETERS IN GEOPHYSICS
Authors: Baile Richard A.
Published: October 2002

A seeming paradox of our time is the continued decline in use of geophysical effort while constant and steady improvement of the tool is being achieved. Seismic crew effort in the United States declined from an all time high of 710 in 1952 to 395 in the fall of 1958—a 44 percent decline! Patrick (1960). In 1958 for the first time the United States used less than 50 percent of the world effort.
TERRAIN CORRECTIONS FOR AIRBORNE GRAVITY GRADIENT MEASUREMENTS
Authors: Chinnery M. A.
Published: October 2002

A method is given for the calculation of terrain corrections for airborne measurements of the vertical gradient of gravity. This includes a short account of the theory concerned, a description of the practical procedure, a complete set of numerical tables, and some examples of their application. The method described is shown to be very flexible, both with regard to aircraft height and to complexity of topography. Some discussion is also given of the magnitude of topographic effects on the gravity gradient, and it is shown that terrain corrections are in general more important here than in normal gravity work.
VELA UNIFORM, THE NATION’S QUEST FOR BETTER DETECTION OF UNDERGROUND NUCLEAR EXPLOSIONS
Authors: Bates Charles C.
Published: October 2002

Negotiations between the United States, the United Kingdom, and the USSR have been underway since October 31, 1958, a period of over two years, in an effort to reach agreement on a treaty for cessation of nuclear weapons’ testing. It is United States policy to enter into such a treaty only if there is an effective control system policing such a ban. This paper provides a résumé of key technical events that have occurred with reference to the creation of such a control system, capable of detecting and identifying underground nuclear explosions. The paper also describes the VELA UNIFORM program, a widespread research and development effort under the over‐all management of the Advanced Research Projects Agency, that is designed to improve markedly the state of the art in this particular technical field over the next two to three years.
PROPOSED STANDARDS FOR SEISMIC AMPLIFIERS . . . AND WHAT THEY MEAN TO FIELD RECORDS
Authors: McManis Louis B.
Published: October 2002

Seismic amplifier performance may be categorized broadly into AGC action, filtering, and distortion (including noise). Eight specifications can define the characteristics of each as follows: AGC— 1. Steady‐state AGC including “burst‐out”, 2. AGC control vs frequency, 3. Dynamic AGC action, 4. AGC distortion effects; Filtering— 5. Amplitude response, 6. Phase response; Noise and 7. Pre‐filter distortion; Distortion—8. Internal amplifier noise. These eight specifications allow a user to predict, and consequently allow for, amplifier action—both desirable and deleterious—in obtaining field records. The author proposes that these specifications, coupled with the usual “external” specifications, be considered as a starting point for establishing a standardized method of specifying seismic amplifier characteristics similar to the SEG “Standard Methods of Specifying Performance” for magnetic recording.
FAULTS AND EARTH TIDES
Authors: Rigassi Danilo A.
Published: October 2002

It can be assumed that the effect of luni‐solar attraction depends, to a certain extent, upon the geological structure. For instance, this effect should not be equal on the two sides of a fault separating rocks of different densities and competencies. If, on two geologically different blocks separated by a fault, two different values of the earth tidal motion can be measured, there is an earth tidal anomaly evidencing the presence of the fault. In other words, measuring and comparing earth tidal motions can be considered as a new geophysical prospecting method.
CASE HISTORY—DESERT SPRINGS GAS FIELD SWEETWATER COUNTY, WYOMING
Authors: Earl John H. , Dahm John N.
Published: October 2002

Desert Springs Area is located in central Sweetwater County, Wyoming, on the west flank of the Red Desert Basin, with the Rock Springs uplift to the west and the Wamsutter arch to the south. The producing reservoirs are in the Upper Cretaceous Lewis and Almond formations, with the Almond being the uppermost formation of the Mesaverde Group in the area. Petty Geophysical Engineering Company was contracted to conduct a seismic survey over the area. Work was initiated on April 3, 1956 and completed July 24, 1956. Fault evidence was noted in the area, based on discontinuity of seismic events and change of reflection characteristics. On the basis of this fault evidence, El Paso Natural Gas Company drilled the Desert Springs No. 1 well which potentialed for 7.7 million cubic feet of gas per day. This led to additional drilling; and, as of January 1959, eight wells have found production at an average depth of 6,100 ft, having potentials from 7.7 million cubic ft of gas per day with some distillate. A detailed study of stratigraphy, lithology, and sedimentation, along with a detailed review of the seismic data utilizing the velocity survey in Desert Springs No. 1 well, was undertaken. The final analysis revealed that the phenomena originally mapped as a fault is in reality a series of facies changes. Three main stratigraphic type traps: offshore bar, lateral facies change, and wedge‐out below an unconformity; are believed to be present in this area, thus making an integrated and coordinated exploration program between the geologists and the geophysicist necessary if we expect to find additional oil and gas reservoirs of this nature.
INVERSE CONVOLUTION FILTERS
Authors: Rice R. B.
Published: October 2002

The difficult problem of trying to locate stratigraphic traps with the reflection seismograph would be simplified (at least in good record areas) if it were possible to perform the inverse of the reflection process, i.e., to “divide out” the reflection wavelet of which the record is composed, leaving only the impulses representing the reflection coefficients. This process has been discussed by Robinson under the title “predictive decomposition,” but his approach requires that the basic composition wavelet be a one‐sided, damped, minimum‐phase time function. Most seismic wavelets which we observe or are accustomed to working with (e.g. the symmetric Ricker wavelet) are not of this class. The purpose of this paper is to discuss a digital computer approach to the problem. Finite, bounded inverse filter functions are obtained which will reduce seismic wave forms to best approximations to the unit impulse in the least squares sense. The degree of approximation obtained depends upon the time length of the inverse filter. Inverse filter functions of moderate length produce approximate unit impulses whose breadths are 50 percent or less than those of the original wavelets. Hence, these filters will increase resolution well beyond the practical limits of instrumental filters. Their effectiveness is more or less sensitive to variations in the peak frequency and shape of the composition wavelet, and to interference, depending upon individual conditions. Although this sensitivity problem can be solved to some extent through the proper design of the inverse filter, it is aggravated by the usual lack of knowledge about the form of the composition wavelet.
RECENT TECHNIQUES FOR DETERMINATION OF “IN‐SITU” ELASTIC PROPERTIES AND MEASUREMENT OF MOTION AMPLIFICATION IN LAYERED MEDIA
Authors: Swain R. J.
Published: October 2002

Determination of the elastic properties of earth materials by laboratory means is subject to sizable errors. These errors may be serious in spite of the large safety factors normally used in engineering design, particularly if the structure must withstand severe dynamic loads. Means of obtaining elastic constants “in‐situ” are described. Further, the phenomenon of displacement multiplication between the underlying competent rock and overlying alluvium or fill is reviewed and the first instrumentation system designed specifically to measure this relationship for engineering purposes is described.
On: RIGASSI’S NOTE ON “FAULTS AND EARTH TIDES,” (GEOPHYSICS, OCTOBER, 1961, P. 643).
Authors: Gillett M. F.
Published: October 2002

The comments that Mr. Rigassi made in his discussion of Faults and Earth Tides are significant and suggest an extensive examination of earth tides or gravity variations (with time) as related to geophysical prospecting. Mr. Rigassi should be complimented for making and reporting his experiment.
ULTRASONIC SHEAR‐WAVE VELOCITIES IN ROCKS SUBJECTED TO SIMULATED OVERBURDEN PRESSURE
Authors: King M. S. , Fatt I.
Published: October 2002

Ultrasonic equipment has been developed to measure shear‐wave velocities in small rock samples at hydrostatic pressures up to 2,400 psi. Under certain optimum conditions dilatational wave velocities can also be determined. The method employs a beam of ultrasonic energy passing through a liquid in which a quarter‐inch‐thick parallel‐sided sample of rock is rotated. From the laws of classical optics for the refraction and reflection of waves at boundaries between dissimilar media and the known velocity of sound in the liquid, the velocities in the sample may be calculated from a record of ultrasonic energy transmitted through the sample as a function of angle between the sample and the ultrasonic beam. Results obtained with this apparatus from samples of materials for which the velocity of waves has been published show good agreement with the latter. The variation of the velocity of shear waves in dry rocks with applied hydrostatic pressures up to 2,400 psi have been measured for seven sandstones, a chalk, and a limestone. The shear‐wave velocities were found to increase with an increase of the applied pressure. For five of the sandstones the increase in velocity at high pressures approached the one‐sixth power of the applied hydrostatic pressure predicted theoretically for a sphere pack model.
BROOMSTICK DISTRIBUTED CHARGE
Authors: Martner S. T. , Silverman D.
Published: October 2002

A new, practical distributed charge, called the “Broomstick” Distributed Charge, has been developed. The underlying principle is one of the first to be applied to distributed charges, and has been used for many years in experimental work. It comprises an explosive charge in the form of a length of Primacord wound in a helix around a long slender mandrel. In the Broomstick Charge the mandrel is a wooden rod 5 ft long and approximately [Formula: see text] inches in diameter with helical groove throughout its length in which the Primacord is wound. The pitch of the helix is chosen to produce the required detonation velocity along the axis of the rod. The rods are joined by threaded couplings that permit the Primacord detonation to pass from one rod to the next. A 50‐ft long Broomstick Distributed Charge can be made with a total explosive weight as small as [Formula: see text] lb, which is of distinct advantage for obtaining high‐resolution in many areas. If larger charge weights are desired, concentrated charges (canned explosive primers) can be coupled between adjacent rods. The charges can be assembled rapidly, are rugged enough to withstand poling into the hole, and leave a fairly clean hole when detonated.
THUMPING TECHNIQUE USING FULL SPREAD OF GEOPHONES
Authors: Peacock Robert B. , Nash D. M.
Published: October 2002

During recent years the use of a heavy weight hitting the earth as a source of energy in reflection seismograph work has increased considerably, particularly in the Delaware and Val Verde Basins of West Texas and New Mexico. The thumping procedure allows the replacement of shotholes, drill bits, and explosives with a weight‐drop truck, thereby allowing a saving of up to several thousand dollars per month over conventional pattern shooting. One thumping technique that can be used involves a procedure in which each drop in a thump pattern is recorded into a full spread of geophones. A modified FM tape recording truck of the type normally used on pattern shooting crews is employed to record the weight‐drop energies. Raw field tapes are composited and corrected for weathering, elevation, and normal moveout in a playback center. Comparisons of pattern shooting and thumping in the Delaware and Val Verde Basins verify that in most areas of the two basins the thumping technique does provide data that is as usable as shooting data. Examples of data obtained by using the procedure described in this paper are presented, showing a regional line, a fault crossing, and steeply‐dipping horizons.
APPLICATIONS OF THE EXPANDING REFLECTION SPREAD
Authors: Musgrave A. W.
Published: October 2002

Techniques have been developed for the usefulness of the expanding reflection profile whose basic elements were described by Dix in 1955. Procedures have been established which make the shooting and interpretation of these expanding reflection spreads simpler and more reliable. Special presentations have been developed for the displaying of these profiles on record sections, and nonlinear paper has been designed for plotting the time‐squared versus distance‐squared graphs. The expanding spread is a valuable seismic tool and has numerous applications. It may be used for the identification of reflections and multiples. From the true reflections, calculations can be made to present the normal velocity survey information, i.e., time, average velocity, and interval velocity versus depth. Among other uses is the determination of the normal moveout curve. Various types of presentations are used to display expanding spreads in record section form. Also, various noise and multiple problems are exhibited.
On: “RECENT TECHNIQUES FOR DETERMINATION OF IN SITU ELASTIC PROPERTIES AND MEASUREMENT OF MOTION AMPLIFICATION IN LAYERED MEDIA,” BY R. J. SWAIN (GEOPHYSICS, APRIL, 1962, PP. 237–241).
Authors: Meidav Tsvi
Published: October 2002

Swain points out that seismic techniques have been used for determination of elastic parameters in unconsolidated materials as well as in consolidated ones. It must be pointed out that relationships between elastic moduli and longitudinal and shear velocities are not entirely valid for soil or other unconsolidated matter, as those are not truly elastic. An exception to this statement may be made with a small error when it is desirable to determine the dynamic elastic properties of the material at the frequency of the seismic wave. Such a determination might be useful in testing a foundation for a vibrating machinery or a runway.
REPLY BY AUTHOR TO DISCUSSIONS BY TSVI MEIDAV AND H. R. NICHOLLS
Authors: Swain R. J.
Published: October 2002

I am pleased to know of the additional theoretical and practical activities in this area of engineering geophysics and of the interest which my paper has generated.
On: “VARIATION OF ELECTRICAL RESISTIVITY OF RIVER SANDS, CALCITE, AND QUARTZ POWDERS WITH WATER CONTENT” BY V. V. J. SARMA AND V. B. RAO (GEOPHYSICS, AUGUST, 1962, PP. 470–479)
Authors: Higdon W. T.
Published: October 2002

The paper on the electrical resistivity of river sands by Sarma and Rao is misleading on several important points. One of the assertions of the introduction is that “The electrical resistivity of a geological formation is a function of … (1) the amount of moisture and consequently of porosity; (2) salinity of the moisture; and (3) grain size of the formation.” With the first two of these factors there can be no quarrel, but Sarma and Rao fail to show that the third factor, i.e., the grain size of the formation, is a determinant of its resistivity. To demonstrate the lack of effect of grain size it is necessary to sort out the effect of grain size from that of water salinity and porosity in Sarma’s and Rao’s data. This is difficult and involves some assumptions in the absence of data. The porosities of the loosely packed sands will not vary widely since theoretically the porosities of packs of spheres are independent of the size of the spheres. Particularly for coarse, well‐sorted, rounded sands this should be a valid assumption. Since the river sands here studied classify as upper medium grain size or greater, and should be well sorted and rounded by the action of the river in depositing them, they may reasonably be expected to fulfill the conditions for uniform porosities for the several packings reported. To eliminate the salinity effect, the data may be normalized by the standard practice of taking the ratio of the resistivity of the sand pack containing water to that of the water itself, defined as the apparent formation resistivity factor (FRF) in logging literature.