bluuebunny/crossref_metadata_2025 huggingface dataset:
GEOPHYSICAL HISTORY OF MAMOU FIELD, EVANGELINE PARISH, LOUISIANA
Authors: Dobyns D. Ray , Roper W. B.
Published: October 2002

This paper presents a chronological historical record of the geophysical activity in the area near the town of Mamou, Louisiana which subsequently led to the discovery of the Mamou Oil Field. The successive stages of geophysical exploration were: 1. Mechanical seismograph refraction survey by North American Exploration Company (German company) in August 1926 for Magnolia‐Union Sulphur‐Harry Hanszen. 2. Torsion balance survey by Shell Oil Company in 1934. 3. Magnetometer survey by Atlantic Refining Company in 1936. 4. Torsion balance survey by Atlantic Refining Company in 1936. 5. Gravity meter survey by Magnolia Petroleum Company the latter part of 1942 and early part of 1943. 6. Three weeks’ seismic work by Petty Geophysical Engineering Company for Magnolia Petroleum Company in June 1943. 7. A few weeks’ work by General Geophysical Company for Cities Service Oil Company in June, 1943. 8. Detailed seismic survey by Independent Exploration Company for Magnolia Petroleum Company from November, 1943 to June, 1945. The discovery well, Magnolia’s No. 1 J. B. Morein, was completed December 28, 1945 through perforations from 11,520 feet to 11,530 feet, producing 208 barrels of 46.3 gravity oil and 770 MCF gas per day through 8/64 inch choke. There are three producing horizons in the upper part of the Wilcox group. The first, or Morein stringer, is approximately 5 feet thick and lies about 18 feet above the second, or Morein sand, which has 19 feet average production thickness. The third, or Deshotels sand, has an average productive thickness of 10 feet and is approximately 230 feet below the Morein sand. Twenty producers and five dry holes were drilled. The field has been unitized and is being water‐flooded. Total production of the field to January 1, 1954 was 2,498,373 barrels. December, 1953 production was 20,604 barrels.
ADVERSE EFFECTS ASSOCIATED WITH VARIABLY COMPOUNDED SEISMOGRAPH RECORDS
Authors: Mott‐Smith M.
Published: October 2002

Although the method of variably compounding seismic reflection records, in order to secure so‐called “Controlled Directional Sensitivity” has distinct advantages over the more generally used fixed compounding or so‐called “Multiple Recording” and other methods, a simple graphic analysis shows that this “variable compounding” also involves the introduction of adverse effects. Among these are a less directional sensitivity, the production of artificial “noise” which is added to that picked up from the ground, and the magnification of minor waves which the analyzer picks out at random. This graphic analysis shows that, if the two waves arrive simultaneously from different directions, they can be separated if they differ sufficiently in direction and not too much in amplitude. Exception is taken to the use of the term “diffraction” as applied to the wave scattered from the edge of a fault. The method is shown to be superior only in certain special cases, which are, perhaps, rather few.
SEISMIC WAVE TYPES IN A BOREHOLE
Authors: Riggs Emmet D.
Published: October 2002

Field measurements of near‐surface velocity, using a multiple seismometer array within the borehole, indicate the presence of a well developed secondary event. This type of wave has been generated under controlled conditions and from its characteristics identified as an interface type, generally known as a tube wave. The accuracy of formation velocity data need not be influenced by this event if appropriate measurement techniques are used.
A DEEP‐SEA SEISMIC REFLECTION PROFILE
Authors: Officer C. B.
Published: October 2002

This paper presents a detailed seismic reflection profile taken over the deep ocean. Clear sub‐bottom reflections and refractions are obtained which are interpretable to show the variation of velocity with depth. From the travel‐time difference between the bottom reflection and a prominent sub‐bottom reflection as a function of range and frequency and from the variation of the amplitudes of the bottom and sub‐bottom reflections with frequency and angle of incidence, the conclusion is reached that the sediment is dispersive, i.e, that the velocity of sound propagation through it is a function of frequency. Further it is concluded that at lower frequencies the velocity in the sediment near the bottom is less than that in the adjacent ocean. This rather unexpected geophysical phenomenon is explained theoretically in terms of propagation in a porous media. The low velocity sediment forms a wave guide between the higher velocity ocean above and the higher velocity sediment beneath. This resulant wave guide explains previously observed single‐frequency arrivals.
GEOPHYSICAL ACTIVITY IN 1954
Authors: Hammer Sigmund
Published: October 2002

Geophysical activity in explorations for petroleum on a global scale in 1954 was 6.3% lower than the record high of 1953. Notable increases in geophysical effort in Europe, the Middle East, and the Far East were not sufficient to overcome the very substantial decreases in the United States and Canada. The reduction occurred mainly in seismic operations, which decreased globally by 8.4%. Gravity activity was on the increase almost everywhere with the world‐wide rise of 7.1%. Magnetic and miscellaneous other geophysical methods also showed moderate increases in the neighborhood of one percent.
A LOW FREQUENCY ELECTRICAL EARTH MODEL
Authors: Pritchett William C.
Published: October 2002

A general earth model is described which simulates the earth when excited by currents either conductively coupled to the earth by electrodes or inductively coupled to the earth by loops. Consideration of model equations showed that a material with a resistivity of approximately [Formula: see text] ohm‐meters was desired for use in the model. Although suitable materials with this resistivity were not known, it was found that fine bronze wheel grindings held together by wax did have the required macroscopic resistivity. Using this model, surface measurements were made employing a modified Wenner spread “one mile” in length. Only minor anomalies resulted from a simulated salt dome “three‐quarters of a mile” in diameter and “one‐half mile” below the surface.
APPLICATION OF CONTINUOUS VELOCITY LOGS TO DETERMINATION OF FLUID SATURATION OF RESERVOIR ROCKS
Authors: Hicks Warren G. , Berry James E.
Published: October 2002

Recent studies of continuous acoustic velocity logs indicate that these logs may provide important assistance in differentiating gas, oil, and water saturations in reservoir rocks. In general, velocities are appreciably lower in sands carrying oil or gas than in water‐saturated sands of otherwise similar character. Specific examples from field logs illustrate this application. Laboratory measurements have been made of acoustic velocity of synthetic and natural rocks. Published studies, both empirical and theoretical, of other workers concerned with the transmission of sound in porous media have been considered. All of these at least qualitatively confirm the conclusions drawn from field data.
RESISTIVITY OF SANDSTONES AS RELATED TO THE GEOMETRY OF THEIR INTERSTITIAL WATER
Authors: Perkins F. M. , Osoba J. S. , Ribe K. H.
Published: October 2002

It is extremely desirable in the interpretation of resistivity measurements made on porous media containing saline water and hydrocarbons to have at hand a better knowledge of the geometry of the conducting salt water. One geometric characteristic is the tortuosity of the aqueous phase. A method was devised several years ago for the measurement of the tortuosity of completely brine‐saturated sands by the measurement of transit time of ions migrating through the aqueous phase under a potential gradient. This method has been improved and extended to the investigation of the tortuosity of sands containing both brine and oil. Results obtained to date on a group of sandstone samples containing water and oil indicate that there is a relation between the tortuosity of the aqueous phase, the brine content of the sand, the resistivity of the brine, and the resistivity of the gross sample. These results were used to relate the saturation exponent, n, which is customarily used in the interpretation of the electric log, to the tortuosity and apparent cross‐sectional area of the electrolyte through which electric current flows.
ATTENUATION OF SOUND IN ROCKS
Authors: Krishnamurthi M. , Balakrishna S.
Published: October 2002

An experimental method used for measurement of absorption of sound is described briefly in this paper and attenuation in the case of a few rocks has been determined at 3 frequencies in the range of 2 to 6 Mc/s. The results show that the absorption increases rapidly with increasing frequency in the case of most rocks investigated.
POLAR MOVEMENT AS INDICATED BY ROCK MAGNETISM
Authors: Howell Lynn G. , Martinez Joseph D.
Published: October 2002

Measurements of remanent magnetism have been carried out by geophysicists both in this country and in the British Isles in a broad sampling of Paleozoic sediments. The direction of magnetization of these rocks indicates that the positions of the earth’s magnetic poles were quite different in Paleozoic times from their positions today. Since it is felt that the magnetic poles are closely tied in with the spin axis of the earth, the locations of the magnetic poles, as averaged over space and time, should indicate the locations of the geographic poles. Determinations of magnetization of Mississippian concretions and other sediments of chemical origin in the Llano uplift area of Texas were made in our laboratory, and indicate pole positions in Carboniferous times consistent with observations made by Belshe in England and by Runcorn in Arizona. Cambrian pole locations, as found from samples in the same area, are included and compared with positions from other work. A few interesting data are shown from the Sawatch formation of Cambrian Age in Colorado.
RESPONSE OF DYKE TO OSCILLATING DIPOLE
Authors: Wesley James Paul
Published: October 2002

A dyke of sulfide ore may be geophysically prospected by observing its electromagnetic response to a slowly oscillating magnetic dipole source. An excellent first approximation of the fields generated is obtained by considering the idealized case of a dyke of infinite conductivity and vanishing thickness in a vacuum. Surprisingly, this idealized problem can be solved exactly in terms of a newly discovered Green’s function for Laplace’s equation (in three dimensions) which is simply expressed in closed form. The magnetic scalar potential and the magnetic field are given for final results.
TRANSIENT BEHAVIOR OF PATTERNS
Authors: Savit Carl H.
Published: October 2002

Seemingly contradictory conclusions on the transient behavior of patterns appear in two papers published in Geophysics, January, 1958 (White, J. E., “Transient Behavior of Patterns,” p. 26–43; and Savit, Carl H., Brustad, John T., and Sider, Joseph, “The Moveout Filter,” p. 1–25). Differences of computation method, produced by differences of emphasis, have resulted in different conclusions.
MAGNETIC ANALYSIS BY LOGARITHMIC CURVES
Authors: Hutchison Ralph D.
Published: October 2002

The standard expression for the anomaly of a magnetized dyke consists of two elementary functions which in practice are easily separable. Under certain conditions, these functions have a simple symmetry which makes them plottable as families of logarithmic master‐curves; and in each family there is a systematic change of shape corresponding to a depth/breadth parameter of the dyke. On this basis the problem of analysis can be made as simple and direct as the method commonly used for depth determinations by electrical resistivity. In addition to the dyke model, two other closely related classes are developed which thus provide master curves that can be used for a large variety of two‐dimensional anomalies.
AN EMPIRICAL VELOCITY DETERMINATION IN SOUTHERN OKLAHOMA
Authors: Oksa Donald R.
Published: October 2002

Lack of adequate velocity data can sometimes be overcome by the proper co‐ordination of seismic and geologic factors. The basic assumption that seismic and geologic data are directly correlatable must be utilized to its fullest extent. Upon this basis reliable basic seismic data of time and delta t values are computed with variations in the other parameters to make the computed seismic data closely match the known geologic conditions by one of several standard computing methods. The empirical fitting of the seismic data to match geologic conditions establishes the velocity gradient which can be then be extrapolated into immediately adjacent areas. An iso‐velocity section can also be prepared, if desired. Generally, it appears that iso‐velocity contours parallel formational strikes. The application of such empirically derived velocity data will result in seismic structural maps and cross‐sections which are compatible with actual geologic conditions. The value of the oftentimes neglected true dip section is shown and is actually an integral part of the analysis. The application of electronic computing techniques makes such determinations much more rapid and makes the method entirely feasible.
AMMONIUM NITRATE: ECONOMY BLASTING AGENT FOR OIL EXPLORATION
Authors: Martin Jack , Hall Thomas O.
Published: October 2002

Major savings for operators of seismic parties have been achieved by the use of prilled ammonium nitrate as a substitute for gelatin dynamite in areas where shot holes are dry. Pound for pound, the prills appear to have the same energy yield as 60 percent gelatin dynamite, and some improvement of records has been noted where prills are used. Safety problems are fewer with ammonium nitrate than with dynamite, and the development of efficient field handling techniques prevents the loss of production.
ON THE ELECTROMAGNETIC RESPONSE OF AN IMPERFECTLY CONDUCTING THIN DYKE
Authors: Wait James R.
Published: October 2002

The theoretical electromagnetic response from a thin dyke has been recently treated by Wesley (1958). In his first paper, the dyke was idealized by a perfectly conducting half‐plane, and the source was taken to be a magnetic dipole. The Green’s function he obtains is very simple and is in agreement with an earlier result (Bateman, 1932).
FIELD OF AN ALTERNATING MAGNETIC DIPOLE ON THE SURFACE OF A LAYERED EARTH
Authors: Slichter Louis B. , Knopoff Leon
Published: October 2002

The magnetic field near a vertical alternating magnetic dipole on the surface of a layered earth is computed for points on the surface. In the layer the dimensionless conductivity parameter is assumed to take the values 0, [Formula: see text], 1, and 4; in the homogeneous substratum, this parameter is assigned the values 0, [Formula: see text], 1, 4, and infinity. The induced field is computed at distances from the source [Formula: see text], 1, 2, 4, 8, and 16 times the layer thickness.
THE BLIND ZONE PROBLEM IN ENGINEERING GEOPHYSICS
Authors: Soske Joshua L.
Published: October 2002

General discussions of the so‐called “blind zone” in refraction seismograph studies have been regarded by most practical geophysicists as an academic treatment of a subject having little, if any, field application. The purpose of this paper is to illustrate that the consideration of the blind zone in specific cases definitely improves the correlations between the interpretations of refraction work and the engineering data obtained by core drilling. In this discussion the definition of the blind zone has been narrowed to refer only to that portion of the underground which lies between the surface layer and a high speed marker in a three‐layer problem and is not represented in the graph of the “first breaks.” This volume of material is not suggested by the first breaks because of the relative thicknesses of the layers and the effect of the extent to which the velocity of the third layer exceeds that of the second. This definition excludes any of those anomalous zones which may not be represented by the first breaks because of marked decreases of the seismic velocity. Portrayal of the blind zone on the graph of the first breaks cannot be obtained by merely rearranging recording distances from the shotpoint to the seismometers. The speed of the seismic wave in the blind zone is generally intermediate in value between that of the surface layer and the high speed marker zone. In ordinary practice it is often represented by the zone of the water table above a high speed bedrock surface.
WAVE PROPAGATION IN A LIQUID LAYER
Authors: Liu D. T.
Published: October 2002

In many areas offshore, the conventional seismic record has the appearance of a series of sine waves or simple odd harmonic combinations of sine waves, with a fundamental wave length four times the water depth. Burg, et al., in a ray theory treatment, ascribe this oscillatory phenomenon to guided energy traveling in the water layer. A solution of the pressure wave equation for a point source in the water layer has been obtained. It allows one to examine not only the frequency dependence with the depth, but also the transient amplitude response with depth and time. It is concluded that in most actual situations, the phenomenon cannot be wholly explained by the assumed mechanism, because the theory indicates too rapid a decay of the energy.
To: DISCUSSION OF “FREQUENCY ANALYSIS OF SEISMIC PULSES”
Authors: Sengbush R. L.
Published: October 2002

I want to call attention to errors in my comments on “Frequency Analysis of Seismic Pulses” that appeared in the February 1960 issue of Geophysics. Following Woodward in his book “Probability and Information Theory,” I used the notation “sinc” function. By definition, sinc χ=(sin πχ)/πχ. This function is intimately associated with sampling theory, although the notation is not widely used.
DUTIES OF A LOGGING CO‐ORDINATOR IN AN OPERATING COMPANY
Authors: Johnson Hamilton M.
Published: October 2002

A well logging co‐ordinator for an operating oil company is often considered to be only a “log analyst” but quantitative log analysis should constitute only a small part of his duties. Associated with the actual analysis are the compilation and preparation of auxiliary reservoir data, field research and evaluation of new tools and methods designed to solve problems of particular areas and conditions, the co‐ordination of logging programs with drilling programs and the development of interpretation techniques. For the company to achieve the most efficient use of its logging dollar, the co‐ordinator must maintain a constant check on log quality, conduct schools on formation evaluation for field personnel and serve as an advisor on unitization committees. It is helpful to him in realizing this program to have a logging research group within the overall research effort of the operating company to aid him in specific problems and to help him keep abreast of industry‐wide research.
GRAVITY OPERATIONS IN GUATEMALA
Authors: Nettleton L. L. , Elkins Paul
Published: October 2002

This paper describes the logistics and field methods used for a gravity survey over a large concession in the northwest corner of Guatemala. Almost the entire network of lines for gravity stations was cut through heavy jungle and heliports were cut at line intersections. Logistics of the operation were heavily dependent on aircraft, using helicopters for transportation from camps to heliports, amphibian aircraft from main base to field camps and chartered DC-3 aircraft from Guatemala City to main camp. Field conditions and operations are illustrated by photographs. Statistics of operation and station production are included but no gravity data are shown.
RECOMMENDED FORM FOR THE ACOUSTIC (CONTINUOUS‐VELOCITY OR SONIC) LOG
Authors: Widess M. B.
Published: October 2002

At the annual meeting of the Southern Seismic Well Shooting Association held in Shreveport on April 4, a motion was passed recommending to SEG that the Society take steps toward formulation of a recommended standard form for the acoustic (continuous‐velocity or sonic) log.
A CASE HISTORY OF THE BRONTE (ELLENBURGER) AND RAWLINGS FIELDS, COKE COUNTY, TEXAS
Authors: Phipps Rollin E.
Published: October 2002

The North Bronte Area interested Lion Oil Company on the basis of surface, isopachous and magnetic studies. A large block of acreage was acquired and explored by the seismograph. A well was drilled on the shooting and proved the shooting to be reliable. A velocity survey in this well, however, indicated that the map of the reflective event identified as Ellenburger was actually Caddo. Additional shooting was done before the Lion No. 1 Edwards, the discovery well of the Bronte (Ellenburger) Field, was drilled. The discovery well of the Rawlings Field was drilled by Humble on seismic information. There are eight producing zones in these fields. Shooting costs and permit fees have remained amazingly constant through the years.
THE DIRECTIVITY PROBLEM FOR A BURIED LINE SOURCE
Authors: Gilbert Freeman , Knopoff Leon
Published: October 2002

A method based on the first motion approximation is presented for determining the radiation pattern of a buried line source. If measurements at the surface are used to obtain the P and S components of the source, the multipolar distribution of the source may be determined. The multipolar distribution is not unique since several distributions can have the same radiation pattern. Some examples are presented for simple sources. The method is applicable to real sources or virtual sources such as centers of diffraction or scattering.
GEOPHYSICS, “GEOPHYSICS,” AND ENGINEERING
Authors: Drake C. L.
Published: October 2002

In an article in a recent issue of the Oil and Gas Journal (Gardner, 1961), entitled “Let’s make it the AA[Formula: see text]G Bulletin again,” the complaint was aired that the Bulletin is devoting less attention to oil finding and more to research and general geological problems. Contributions from “commercial” geologists have declined and university contributions have held steady while contributions from government survey people and researchers have increased markedly. The number of oil field studies printed has decreased from 32 in 1940–41 to 4 in 1960–61. The article suggests that the lack of papers from commercial geologists reflects a lack of interest in the profession, particularly by younger geologists, since the character of the editorial board has not changed.
PROPAGATION EFFECTS ON RADIAL RESPONSE IN INDUCTION LOGGING
Authors: Duesterhoeft W. C. , Smith H. W.
Published: October 2002

This paper considers the problem of the field of an alternating magnetic dipole on the axis of cylindrical boundaries separating isotropic conductive formations. The study accounts for attenuation, phase shift, and reflection in the conducting formations. Numerical results are presented for the voltage induced in a separated coaxial receiver coil. The results are applicable directly to induction logging theory.
SEISMIC WAVES COUPLED TO SONIC BOOMS
Authors: Oliver Jack , Isacks Bryan
Published: October 2002

Air‐coupled seismic waves of low frequencies were excited by aircraft‐generated sonic booms and detected by a hydrophone at moderate depth and a geophone on the sea floor. The experiments were conducted on the continental shelf off New Jersey.
THERMO‐TELLURIC CURRENTS GENERATED BY AN UNDERGROUND EXPLOSION AND OTHER GEOLOGICAL PHENOMENA
Authors: Tuman V. S.
Published: October 2002

If an atom bomb is detonated in an aquifer, superheated steam will be produced, giving rise to a pressure front in the capillaries. The high‐pressure vapor will force the neighboring fluid through capillary channels generating streaming electric potentials which we have called the thermotelluric potentials. In this note a preliminary study is made of the pressure front transient and a nonlinear differential equation is obtained. This equation can be solved, if necessary, numerically by difference methods utilizing a digital computer. However, instead some experiments were performed and the streaming potential was measured on a few very porous and permeable sandstones. The order of magnitude of the signal to be generated by such phenomenon is estimated using the experimental data, and some assumptions. It appears that in some cases the signal superimposed on the natural telluric field might be above the noise level. Thermo‐telluric potentials should also be present during an igneous intrusion and during the diffusion of hot water in geysers, etc. The possible use of the phenomenon of thermo‐telluric potentials in the study of underground geological activities is intriguing.
RECONNAISSANCE AEROMAGNETIC PROFILES, NORTHEAST TEXAS
Authors: Brod R. J. , Hammons R. H. , Hinrichs F. W.
Published: October 2002

The three aeromagnetic traverses of Figure 1, in East Texas, demonstrate the applicability of the conventional aeromagnetic method in this area. Flight line AA′ extends from the Sabine uplift across the East Texas Basin, Mexia‐Talco Fault zone, Balcones Fault zone, and Ouachita front to the Llano Uplift. Line BB′ extends from the Sabine Uplift through the northern portion of the East Texas Basin, across the Mexia‐Talco Fault zone to a point near the western boundary of Ellis County. Line CC′ extends in a northerly direction from the center of Montgomery County on the northern flank of the Gulf Coast Geosyncline through the East Texas Basin across the Mexia‐Talco Fault zone to the Red River.
REPLY BY D. RANKIN TO THE DISCUSSION BY J. T. WEAVER
Authors: Rankin D.
Published: October 2002

I am indebted to Weaver if he has indeed clarified certain points which I had previously considered to be obvious. Cagniard (1953) states explicitly the magnitude of the wavelengths in free space and it is further implicit in the work of Rankin (1962) that it is indeed this same electromagnetic field which is being considered. The plane wave aspect of the problem arises from the extent of and not the distance from the source so that truly it is the induction field and not the radiation field that is under discussion. I had believed, until this note by Weaver, that d’Erceville and Kunetz (1962) also considered a plane wave incident on the earth and in fact that I was merely following both Cagniard and d’Erceville and Kunetz in this matter. The consistency of the results would tend to confirm this belief.
On: “THE REFRACTION ARRIVAL IN WATER COVERED AREAS,” BY CHARLES B. OFFICER, JR. (GEOPHYSICS, OCT., 1953, pp. 805–819).
Authors: Meecham W. C.
Published: October 2002

This note is written concerning an error in the dependence of amplitude on range of refraction arrivals as proposed by C. B. Officer. He considered the problem of the propagation of a sound pulse in a liquid layer overlying a half‐space of liquid having a higher velocity. Officer is particularly interested in the refraction arrival, i.e. the pulse which travels most of the distance from source to receiver (in the lower medium) along the interface between the two media. He found an amplitude dependence on range like [Formula: see text]. It is the purpose of this communication to show that this dependence should be [Formula: see text] (which is in fact the usual dependence of such waves). The difficulty arises from the fact that the approximation used by Officer in (39) (equation numbers refer to Officer’s paper) is valid over an interval which decreases with range like [Formula: see text]. This extra factor is missing in the development.
REPLY BY AUTHOR TO DISCUSSION BY ARI BEN‐MENAHEM AND ARMANDO CISTERNAS
Authors: Negi J. G.
Published: October 2002

I sincerely thank Messrs Ben‐Menahem and Cisternas for their communications. In this detailed reply I would like to explain the following points more clearly: 1. I do agree with them about the incorrectness of equations (27) and (28) of Dyakonov. 2. At the same time I suspect incorrectness in the integral representation (1) of their last letter. In a following paragraph I am presenting the formula which is the appropriate one in my opinion. 3. Assuming the formula (1) of Ben‐Menahem and Cisternas to be correct, it will be seen that formula (35) in Dyakonov’s paper and formula (82) in my paper remain unaltered. Therefore, it can be concluded that the remark (c) in their last letter is completely unfounded. 4. In reply to their last point it may be mentioned that the prime purpose of my paper was to put down the formulae appropriate for studying the difficult problem of diffraction of electromagnetic waves by an inhomogeneous sphere when located in an infinite or semi‐infinite space. The particular treatment was chosen for its mathematical generality and the possible application in studying the effect of concentric and/or eccentric zoning over the inhomogeneous sphere.
SHEAR WAVES FROM EXPLOSIVE SOURCES
Authors: White J. E. , Sengbush R. L.
Published: October 2002

This experimental study of the generation of shear waves by explosive sources stemmed from Heelan’s theoretical result that pressure acting on the wall of a cylindrical hole in a solid should radiate shear waves quite as effectively as compressional waves. The measurements confirm this expectation, but good overall agreement was not achieved until expressions were derived which take into account radiation from strong water‐pulse waves in the shothole. Our results show that the ratio of shear‐to‐compressional amplitudes generated by an explosive source increases as the charge size decreases. At an angle of 45 degrees, the ratio is approximately unity for a charge consisting of 10 ft of Primacord. We found that the shot‐generated water pulse (tube wave) is a strong shear source, continuously generating shear energy in the formation as it travels in the borehole. This drastically affects the directivity of SV waves and in Pierre shale gives a pattern whose maximum is near‐vertical. This suggests the possibility of prospecting with shear waves, using a distributed charge detonated at shear velocity to generate substantial downward‐direction shear energy in the earth. However, the substantially larger attenuation of shear waves compared to compressional waves has discouraged us from pursuing this further.
THE VERTICAL GRAVITY GRADIENT IN BOREHOLE EXPLORATION
Authors: Thyssen‐Bornemisza Stephen
Published: October 2002

In past years vertical gravity‐gradient observations have been repeatedly suggested for the determination of in‐situ densities of rock formations penetrated by a borehole (Smith, 1950; Hammer, 1963). However, calculations made for a point mass to one side of a borehole show that the first vertical derivative of gravity, g, is influenced by this mass to a much greater degree than g itself, or the second vertical derivative. This should be borne in mind if attempts are made to measure vertical gravity gradients in a borehole.
THE UPWARD CONTINUATION OF AN AEROMAGNETIC ANOMALY IN WASHINGTON
Authors: Steenland Nelson C. , Gibbons W. D.
Published: October 2002

It is quite common to find large magnetic anomalies originating from igneous rocks, both extrusive and intrusive, especially when they occur at shallow depths. When such rocks crop out, it is straightforward to correlate a particular anomaly with the outcrop. Such is the case with a large observed anomaly in T 14–15N, R 5–6W, Pacific County, Washington, where a large observed anomaly on the USGS (1958) aeromagnetic map may have its source closely identified with an igneous outcrop designated as [Formula: see text], Eocene volcanics, on the geologic map of Washington.
A MOVING‐TIME‐WINDOW SIGNAL‐SPECTRA PROCESS
Authors: McGarr Arthur , Hofmann Renner B. , Hair George D.
Published: October 2002

Spectra of signals of short time duration may be obtained from either long or short samples. Long samples result in more accurate power‐density spectra, but most of the spectrum power will be contributed by noise. Spectra from short samples are significantly altered truncation effects. A process is described which makes use of the advantages of both methods. Truncation effects are reduced by “hanning” in the frequency domain. The average spectrum of noise immediately preceding the signal is subtracted from all spectra. A moving‐window process allows investigation of signal spectra as a function of time. Examples of the same earthquake signal recorded on several types of instruments illustrate the broad, total spectral content of P waves.
TECHNIQUES OF ON‐SITE INSPECTION
Authors: Westphal Warren H. , Rubin Sylvan
Published: October 2002

On‐site inspection of an unidentified seismic event comprises observations and measurements in a defined geographic area to distinguish between underground nuclear explosions and other sources of signals. If the event is determined to be a nuclear explosion, the detonation point must be located with sufficient precision to permit collection of radiochemical samples. This target will be a relatively small cavity or rubble zone buried at a depth at least ten times its diameter. A well‐executed test will be essentially devoid of surface evidences of emplacement activities and explosion. Suggested techniques of on‐site inspection include visual observations, aerial imaging, seismic‐noise monitoring, radiochemical and radioactivity exploration, electrical geophysics, and magnetic, geothermal, and gravity measurements. Some of these techniques are similar to those used by the exploration industry. Successful application to on‐site inspection problems requires intensive research and important modifications.
DETERMINATION OF BOUGUER DENSITY IN SHALLOW HOLES
Authors: Thyssen‐Bornemisza Stephen
Published: October 2002

Inherent uncertainties of conventionally determined Bouguer‐density values may seriously affect the more sophisticated interpretation of gravity field results, predominantly in areas of irregular surface lithology. To minimize the consequences of such “incorrect” density values geophysicists have introduced and suggested corrective procedures (Nettleton, 1939; Vajk, 1956; Grant and El Saharty, 1962; Thyssen‐Bornemisza and Stackler, 1962; Hammer, 1963).
A MILITARY ASPECT OF EXPLORATION GEOPHYSICS
Authors: Melton E. Roane
Published: October 2002

That branch of exploration geophysics using refraction and reflection methods of seismographing, employs equipment and methods similar to military sound ranging. Present methods and equipment used in geophysical seismographing show results from developments in the art of sound ranging during the last war. The accuracy obtained in sound ranging is considerably greater than that obtained in refraction shooting where the air wave is used to measure distance. Corrections are applied for direction and velocity of wind, and for temperature. Personnel in the sound ranging unit is organized similar to a geophysical field crew, having motor truck transportation, instrument operators, and record interpreters. However, the geophysical crew is more of a mobile outfit. In any future war, the geophysical personnel, particularly the exploration geophysicist, will be expected to place his specialized training at the disposal of the government.
Ground Water, C. F. Tolman, McGraw‐Hill, New York, 1937, 593 pp., 175 figs. $6.00.
Authors: Bader Glenn E.
Published: October 2002

Ground water is of general interest and of the utmost importance. Water wells have been used for several thousand years. The Bible tells of Abraham and Isaac digging successful water wells. However, there has been considerable mystery connected with ground‐water occurrence and movement. Even today the subject is connected with much popular superstition and misinformation. As an example, consider the forked water witch stick which is so commonly used to find hidden water streams.
Practical Seismology and Seismic Prospecting. L. D. Leet. D. Appleton‐Century Company, New York, 1938. x+430 pp. $6.00. (The Century Earth Science Series, Kirtley F. Mather, Editor.)
Authors: Slotnick M. M.
Published: October 2002

To most people interested in seismic prospecting, the title of the volume will perhaps be somewhat misleading. A large part of the book is devoted to earthquake lore in general; and those early chapters devoted to the geology of this subject, the reviewer found intensely interesting. On the other hand, the treatment on seismic prospecting, as the term is generally understood, is rather inadequate. One feels that the author might have done far more with the various theoretical considerations of instrumental technique, elastic theory, wave‐propagation and such. The treatment, mathematical and physical, cannot be considered convincing—in fact this writer feels that it is definitely superficial in most places.
EFFECT OF SEDIMENTARY THICKNESS ON SHORT‐PERIOD RAYLEIGH‐WAVE DISPERSION
Authors: McEvilly T. V. , Stauder William
Published: October 2002

Large differences in group velocities of short‐period Rayleigh waves from stripmine blasts for different propagation paths in the Ozark Uplift‐Illinois Basin area have been observed. Good well control in the area makes possible the construction of structural models of the sediments‐basement system for these paths. Theoretical group velocities computed for these models agree well with observations, thus explaining the large variations in velocities in terms of basement‐depth differences. This sensitivity of short‐period surface waves to sedimentary thickness suggests an inexpensive, single‐station technique of basin reconnaissance where commercial blasting is available.
DIRECT INTERPRETATION OF SELF‐POTENTIAL ANOMALIES CAUSED BY INCLINED SHEETS OF INFINITE HORIZONTAL EXTENSIONS
Authors: Paul M. K.
Published: October 2002

Self‐potential anomalies caused by inclined sheets of infinite horizontal extension may be interpreted in terms of two infinite line poles situated on the body at positions nearest and furthest from the free surface, respectively. The direct interpretation of such pairs of line poles in terms of their positions and strength is possible from the observed anomaly profile. The solution is unique in its own family, i.e., no pair of line poles other than that arrived at by the present method can give rise to the observed anomaly.
DETERMINATION OF THE VERTICAL DENSITY GRADIENT IN A BOREHOLE
Authors: Thyssen‐Bornemisza Stephen
Published: October 2002

In a recent paper (Thyssen‐Bornemisza, 1964) an equation was derived for borehole exploration stating equivalence of the third vertical derivative of the gravitational potential and the vertical density gradient. It is true that density information from underground gravity measurements can be obtained by the equations suggested in relevant publications (Goodell and Fay, 1964; Hammer, 1950; Smith, 1950; Thyssen‐Bornemisza, 1963) but the immediate translation from [Formula: see text] values observed in a borehole into density gradients may deserve special consideration. The close relation of the third vertical derivative to Poisson’s field equation may suggest a more generalised approach.
INTERNATIONAL GRAVITY BUREAU (I.G.B.)
Authors: Tardi P.
Published: October 2002

The usefulness of a world center for the collection and storage of gravity data is obvious to geophysicists and geodesists. The readers of our journal will be interested to read about the International Gravity Bureau (of the International Association of Geodesy) in Paris, whose mission is to assemble gravity data and integrate them into the world gravity net. In response to a request by Dr. L. L. Nettleton, Professor P. Tardi, Director of the Bureau, was kind enough to contribute a brief description of the Bureau and its activities for publication in Geophysics.
HORIZONTAL AND VERTICAL ARRAYS FOR TELESEISMIC SIGNAL ENHANCEMENT
Authors: Roden Robert B.
Published: October 2002

A model of teleseismic signal and surface‐mode noise is derived from wave‐propagation theory. Optimum Wiener multichannel frequency domain filters are designed to operate on the outputs of six seismometer arrays so as to pass signals and reject noise. The arrays studied include two 19‐element surface arrays, two 19‐element shallow‐buried arrays and two 6‐element vertical arrays where a 20‐db reduction in spatially uncorrelated noise is assumed to result from seismometer burial. It is found that there is very little difference among the outputs of the filter systems designed for the two surface arrays and the two vertical arrays. The performance of the systems designed for the shallow‐buried arrays found to be considerably better. For one particular array, the predicted signal‐to‐noise improvement resulting from the assumed effect of shallow burial varies from 5 to 15 db. The theoretical results are sensitive to the amount of uncorrelated noise assumed in the model. However, when the levels of incoherent noise are equal, it appears that a surface array will generally possess greater capability for rejection of coherent noise than will a vertical array with the same size and number of receivers. The performance of an array of either type appears to be quite insensitive to changes of geometry if the number of receivers and the maximum dimension are not changed very much. Although a vertical array will always be superior to a single deeply buried seismometer, the improvement in performance which may be obtained by increasing the number of receivers in a vertical array is much less than in the case of a surface array.
THE EFFECT OF A CONDUCTING OVERBURDEN ON ELECTROMAGNETIC PROSPECTING MEASUREMENTS
Authors: Lowrie W. , West G. F.
Published: October 2002

This paper reports an investigation by the scale‐model method of how the response of a horizontal‐loop electromagnetic system to a vertical, sheetlike conductor is modified by the presence of a conducting overburden. It was found that the overburden makes the vertical conductor seem more conductive and more deeply buried than it really is, and that the vertical conductor’s in‐phase anomaly may become reversed in sign.
INTERPRETATION OF THE MAGNETIC ANOMALIES OVER SOME PRECAMBRIAN DIKES
Authors: Strangway David W.
Published: October 2002

In this paper, some examples of the influence of the remanent magnetism of rocks on magnetic fields are presented. In the study, a series of dikes were investigated since, in this case, the geometry is simple and the fields can be calculated with some precision. A large number of samples were collected and the remanent magnetization and susceptibility measured. Using this information the expected curves for ground vertical component magnetic profiles and airborne magnetic profiles were computed. These were then compared with the actual observed profiles. A good correlation was found when both remanent and induced magnetization were considered. In determining the remanent magnetization intensity, samples that had unusually high Q values were rejected because these probably represented local effects due to lightning strikes. In addition, the mean value of the magnetization was determined by taking into account the scatter of directions of the measured NRM’s. The agreement between observed and computed data was good.
INSTRUMENT DETAILS AND APPLICATIONS OF A NEW AIRBORNE MAGNETOMETER
Authors: Jensen Homer
Published: October 2002

Since its invention and first use, the fluxgate magnetometer has had sensitivity, stability, speed of response, and other characteristics which were entirely suitable to the needs of both mineral and petroleum exploration, and which were compatible with the limitations and error functions of simple airborne surveying systems. The introduction of nuclear‐precession magnetometers employing the principle of quantum electronics has permitted and forced a revision of surveying systems and techniques to take advantage of the hundred‐fold increase in resolution they afforded. It appears that the new magnetometers have resolution capabilities beyond conventional survey needs, and measurement accuracy better than the accompanying survey positional accuracy.
A PHOTOELASTIC ANALYSIS OF STRESS WAVE PROPAGATION IN A LAYERED MODEL
Authors: Riley W. F. , Dally J. W.
Published: October 2002

Dynamic photoelasticity was used to study some fundamental aspects of wave propagation in layered media and to obtain information on the dynamic state of stress associated with the various waves generated by a point source explosion. Columbia Resin CR‐39 and aluminum were used to obtain a model with an acoustical impedance‐mismatch between layers of 6 to 1. A Cranz‐Schardin multiple spark camera, operating at approximately 200,000 frames per second, was used to record the dynamic isochromatic fringe patterns associated with the propagating stress waves. Small charges of lead azide were used to explosively load the models. Six different wave types were clearly identified. In the region near the explosive detonation, the predominant waves were the incident [Formula: see text] wave and the reflected [Formula: see text] waves from the interface and the free boundary. In regions away from the explosive detonation the headwaves ([Formula: see text], [Formula: see text], and [Formula: see text]) dominate since their rate of attenuation is much lower than the rate associated with the incident dilatational or the reflected shear waves. The data obtained in the form of isochromatic fringe patterns were converted to individual values of the principal stresses in several instances. The methods developed for this separation are applicable whenever the dilatational or distortional waves occur alone. The separation method requires no auxiliary data other than the isochromatic fringe orders and yields dynamic displacement data in addition to the individual values of the principal stresses.
LEAST‐SQUARES INVERSE FILTERING
Authors: Ford Wayne T. , Hearne James H.
Published: October 2002

Suppose we are given the autocorrelation function of a certain unknown sampled signal. Although a number of different signals might produce the given autocorrelation function, only one of these is minimum‐delay. Denoting this minimum‐delay unknown signal by the matrix K, the given autocorrelation may be written in the form K′K where K′ is the transpose of K. It is desired to determine approximately the inverse of this unknown signal K; that is, we wish to determine a vector X so that KX is as close to B′=(1, 0, 0, ⋯, 0) as possible in a least‐squares sense. If K were known, Rice shows that [Formula: see text] At first glance, the above formula appears useless as K′ is unknown. However, although K′ is indeed unknown, K′B has the form K′B=(c, 0, 0, ⋯, 0)′ where the scalar c simply plays the role of a scale factor. Thus, we determine X by simply selecting a convenient multiple of the first column of the inverse of the known matrix K′K. Although we do not present the details of the computer programming involved in the above calculation, we do present some simple examples to illustrate the process.
MAGNETOTELLURIC SOUNDINGS IN THE SOUTHWESTERN UNITED STATES
Authors: Plouff Donald
Published: October 2002

A total of 12 magnetotelluric soundings were made along a 460‐mile traverse line in the southwestern United States. Spectral analysis of digitized graphic records was used to determine apparent resistivities and phase differences for periods in the range 10–1000 sec. Interpretation of the plotted resistivities indicates that the geoelectric section to depths of the order of 300 km is divided into three principal layers. The layer nearest the surface has a resistivity of 200 ohm‐m or less. The next layer, which begins in Paleozoic carbonate rock or near the top of the Precambrian rocks, has a resistivity of 500 ohm‐m or more. Sample determinations indicate the resistivity of the lowest layer is in the range 5–100 ohm‐m and the depth to the top is in the range 20–150 km.