bluuebunny/crossref_metadata_2025 huggingface dataset:
How we diagnose and treat deep vein thrombosis
Authors: Hirsh Jack , Lee Agnes Y. Y.
Published: October 2002

Making a diagnosis of deep vein thrombosis (DVT) requires both clinical assessment and objective testing because the clinical features are nonspecific and investigations can be either falsely positive or negative. The initial step in the diagnostic process is to stratify patients into high-, intermediate-, or low-risk categories using a validated clinical model. When the clinical probability is intermediate or high and the venous ultrasound result is positive, acute symptomatic DVT is confirmed. Similarly, when the probability is low and the ultrasound result is normal, DVT is ruled out. A low clinical probability combined with a negative D-dimer result can also be used to rule out DVT, thereby obviating the need for ultrasonography. In contrast, when the clinical assessment is discordant with the results of objective testing, serial venous ultrasonography or venography is required to confirm or refute a diagnosis of DVT. Once a patient is diagnosed with an acute DVT, low-molecular-weight heparin (LMWH) is the agent of choice for initial therapy and oral anticoagulant therapy is the standard for long-term secondary prophylaxis. Therapy should continue for at least 3 months; the decision to continue treatment beyond 3 months is made by weighing the risks of recurrent thrombosis and anticoagulant-related bleeding, and is influenced by patient preference. Screening for associated thrombophilia is not indicated routinely, but should be performed in selected patients whose clinical features suggest an underlying hypercoagulable state. Several new anticoagulants with theoretical advantages over existing agents are undergoing evaluation in phase 3 studies in patients with venous thromboembolism.
Why the fair innings argument is not persuasive
Authors: Rivlin Michael M
Published: October 2002

The fair innings argument (FIA) is frequently put forward as a justification for denying elderly patients treatment when they are in competition with younger patients and resources are scarce. In this paper I will examine some arguments that are used to support the FIA. My conclusion will be that they do not stand up to scrutiny and therefore, the FIA should not be used to justify the denial of treatment to elderly patients, or to support rationing of health care by age.

There are six issues arising out of the FIA which are to be addressed. First, the implication that there is such a thing as a fair share of life. Second, whether it makes sense to talk of a fair share of resources in the context of health care and the FIA. Third, that 'fairness' is usually only mentioned with regard to the length of a person's life, and not to any other aspect of it. Fourth, if it is sensible to discuss the merits of the FIA without taking account of the 'all other things being equal' argument. Fifth, the difference between what is unfair and what is unfortunate. Finally, that it is tragic if a young person dies, but only unfortunate if an elderly person does.
ON SEISMIC COMPUTATIONS, WITH APPLICATIONS, II
Authors: Slotnick M. M.
Published: October 2002

This paper is a continuation of a previous one given, with a somewhat similar title, in which are discussed the travel‐times and other similar properties of the wave paths in a medium in which the seismic velocity is an integrable function of the depth. In this paper we consider similar properties of the waves from a point on the surface to a point in a “well” in such a medium.
TRUE GROUND MOTION FROM MECHANICAL SEISMOGRAPH RECORDS
Authors: Bryan A. B.
Published: October 2002

Records of several types of ground motion are obtained with two vertical mechanical seismographs of widely different characteristics, mounted on the same base and recorded on the same moving photographic paper. Companion records obtained are shown in one case to yield substantially the same calculated ground motion although the original records are very dissimilar.
SOME ASPECTS OF MULTIPLE RECORDING IN SEISMIC PROSPECTING
Authors: Klipsch Paul W.
Published: October 2002

Considerable attention has been given to the use of more than one geophone on each recording channel with the hope of increasing the signal‐to‐noise ratio, where “signal” is taken to mean “recorded reflection” and “noise” means any undesired recorded amplitude. The average expectancy of this gain is evaluated analytically, and the statistical distribution examined. Since at different instants this gain possesses different values dependent on a large number of causes, these causes are assumed to be random in nature; a justification of this and other assumptions is explained, and the distribution of gain in terms of frequency of occurrence is expressed in the form of a probability curve. From this analysis an answer can be inferred to the question, “if n is the number of geophones, what is the probability that a gain of [Formula: see text] will occur?”.
Prospeccao Geophysica em São Paulo. By Irnack Carvalho do Amaral and Henrique Capper Alves de Sousa. Bulletin 10 of the Department of Mineral Production, Republic of Brazil, Rio de Janeiro, 1936. (In Portuguese.)
Authors: Wilson John H.
Published: October 2002

Part I deals with the magnetic instruments, methods and anomalies found in the areas of São Pedro‐Xarqueada. Askania vertical and horizontal intensity magnetometers, and stationary instruments for photographic registration of diurnal and other changes, were used. Most of the anomalies were found to be related to diabase sills, lacoliths and dikes. Depth calculations by the methods of Tiberg, Haanel and Thalen did not correspond closely with depths found in wells, but were of the same order of magnitude. Depth to basement rocks could not be calculated from the magnetic results, and the authors suggest the use of seismic methods. Tables showing the magnetic properties of the rocks in the area are included.
REPEATED P-WAVES IN SEISMIC EXPLORATION OF WATER COVERED AREAS
Authors: Lay Roy L.
Published: October 2002

A secondary, and even a tertiary, P-wave has been observed under certain conditions in seismic exploration of water covered areas. It is shown that these events are caused by an oscillation at the shot point. The procedure for eliminating these disturbing phenomena is described.
GEOPHYSICAL OPERATIONS IN KUWAIT
Authors: Boots P. H. , McKee Alexander H.
Published: October 2002

This paper describes the general operations of the combined geophysical party, using gravity, magnetic and seismic methods, which made a survey of Kuwait in one working season. The organization of the party, the general conditions met, and the manner in which the operations were adapted to the country and its people are described. The geophysical results themselves are not included, but it may be remarked that the surveys described led to the discovery of one of the great oil fields of the world.
OPTICS OF RECORDING OSCILLOGRAPHS
Authors: Weinstein D. H.
Published: October 2002

This note reviews the results of A. C. Hardy and applies them to the design of lens and mirror systems of recording oscillographs, such as those used in seismic prospecting. Requirements are given for maximum intensity of illumination in the recording paper consistent with small moment of inertia of the moving mirror.
ON THE USE OF ELECTROMAGNETIC WAVES IN GEOPHYSICAL PROSPECTING
Authors: Horton C. W.
Published: October 2002

An approximate analysis of the behavior of electromagnetic waves in a conducting medium is given. The approximations consist of replacing pairs of electrodes by dipoles and of using only the first order images in the case of a layered earth. It is shown that under typical conditions one can measure the depth of an electrical interface 6,000 feet deep by means of electromagnetic waves. It is further shown that even a thin layer of salt water or oil bearing sand at a depth of 6,000 feet gives an effect that is easily measureable. The response of the earth to a d.c. step function is analysed for the case in which the displacement currents are negligible. This approximation is valid for all geological formations. The shape of a commutated direct current is shown as a function of the distance of travel.
GEOPHYSICAL HISTORY OF EAST LANCE CREEK AND LITTLE BUCK CREEK FIELDS, NIOBRARA COUNTY, WYOMING
Authors: Swan B. G.
Published: October 2002

A seismograph survey in 1936 by Continental Oil Company eastward from Lance Creek Field, along a projected surface extension of this fold, led to the discovery of East Lance Creek and Little Buck Creek fields. Maps are presented showing the results of this work and the structure as revealed by drilling wells and surface geology at early and later stages of development. Substantial agreement between the structures as mapped by subsurface and by seismograph is noted.
GEOPHYSICAL HISTORY OF THE EAST FIELD, JIM HOGG COUNTY, TEXAS
Authors: Hollingsworth W. E.
Published: October 2002

The geophysical work which led to the discovery of the East Field in Jim Hogg County, Texas was started in 1934, when a single line of torsion balance stations was run across the area. Core drilling followed in 1938 and 1939. Reflection seismograph work was done in 1942 and outlined the field. The discovery wells were drilled in 1942 and 1943.
GEOCHEMICAL HISTORY OF THE HARDY OIL FIELD, JONES COUNTY, TEXAS
Authors: Ransone W. R.
Published: October 2002

The exploration history of the Hardy oil field is unusual in that its discovery followed from drilling on a geochemical anomaly, in the immediate vicinity of which there was no evidence of closed structure either from a reflection seismograph survey which preceded, or from a core drill investigation which followed the geochemical survey. The geochemical survey, which covered a portion of Jones County, Texas, was initiated in August, 1942. The discovery well in the Hardy field was completed in November, 1943, and opened a new Canyon sand pay zone. Development of the field has shown that the sand pinches out across a nose, forming a typicalstratigraphic reservoir. Thus, as a result of that discovery and subsequent development, the predictions from all three exploration methods—geochemical, reflection seismograph, and core drill, have been confirmed.
THE USE OF GEOPHYSICS IN PROSPECTING FOR GOLD AND BASE METALS IN CANADA
Authors: Koulomzine T. , Brossard Leo
Published: October 2002

The Canadian Shield is an area of Pre‐Cambrian rocks some 2,000,000 square miles in extent, which produces a half‐billion dollars worth of minerals per year. The geophysical prospecting methods of most use here are magnetic and electrical. Geophysical methods, after recovering from an earlier period of disfavor, are now beginning to be properly appreciated by the local mining industry. Several examples of important recent geophysical discoveries are presented. Future expansion in this field appears inevitable.
MULTIPLE REFLECTIONS
Authors: Ellsworth T. P.
Published: October 2002

This is the lead paper of a symposium on the subject of multiple reflections. Possible types of multiple reflections are considered and compared with unusual reflections observed on records taken in the Northern Sacramento Valley of California. Geological and geophysical data are presented to demonstrate that a shallow basalt flow is producing identifiable multiple reflections. Consideration is given to the possible frequency of occurrence of multiple reflections in seismic surveys generally and limitations they may place upon seismic interpretations.
IS IT AN ANOMALY?
Authors: Tripp R. Maurice
Published: October 2002

A method is proposed and described whereby it is possible to examine statistically the data from a geophysical survey to determine the relative probability of its occurring as a result of pure chance. When the probability is less than 0.01, a technique is outlined for further “reducing” the data in an objective manner and testing anomalous areas for significance. The method is particularly applicable to highly variable data which result from random background fluctuations found in some of the modern prospecting techniques.
THE PRACTICAL VIEW IN GEOPHYSICAL EXPLORATION FOR METALLIC ORE BODIES
Authors: Armstrong L. C. , Davidson D. M.
Published: October 2002

This is a nontechnical paper dealing with the potentialities of geophysical methods in the search for metallic ore bodies which do not outcrop. It emphasizes what exploration engineers are entitled to expect as well as to demand from geophysical surveys. Harmful misconceptions and frustrations have arisen among mining men through lack of understanding of the possibilities of the various methods, and through confusion traceable to the loose claims and looser interpretation of results on the part of some geophysical surveyors. The miner should be made to understand that geophysical methods merely measure physical effects, either inherent, or induced, in various rock bodies, and that high geological competence is usually needed to judge whether anomalous measurements may be correlative with ore, likely ore‐bearing structures or with features totally unrelated to ore occurrences. Since they do not put any tags on ore bodies, as some have been led to believe, the capabilities and limitations of the methods need further clarification. The biggest hurdles to overcome before geophysics can reach a fuller measure of its true potentialities in ore finding are, first, the development of techniques for mitigating or eliminating the anomalous effects of overburden; second, development of methods for detection of disseminated metallic sulphide deposits; third, perfection of techniques of investigating the rocks surrounding bore holes for appreciable distances; fourth, the improvement of techniques for geophysical prospecting underground; fifth, independent consultation before a survey is started to weigh dispassionately the chances for success (geophysical surveys should be checked with much pains and precision by repeating traverses and readings); sixth, reduction in costs for all methods; and seventh, modification and improvement in efficiency of equipment with special attention to increasing depth range. Finally, there is a critical need for research, long‐range, indirect, fundamental research, as well as direct research on known ore deposits which have not been disturbed too much by development or mining. This latter will be most profitably carried out if undertaken by private mining companies on their own properties and with complete cooperation from their own geological staffs.
SEA‐BOTTOM SLOPE DETERMINATION FROM WATER SOUND ARRIVALS
Authors: Agocs W. B.
Published: October 2002

Previously it was shown how the time break could be determined on deep‐sea seismic records from the water sound arrivals. An extension of this problem has been made for the more general case of a sloping sea bottom. The depth of shot below the surface of the sea, shot‐detector distance and the direction and magnitude of the sea‐bottom slope may be determined by successive approximations. This is done, using the ratio of the difference in time of arrival of the direct water wave and the first reflection from the surface of the sea to the difference in time of the second and first reflection, and the ratio of the difference in time of arrival of the second and first reflections to the difference in time of arrival of the third and second reflections from the surface of the sea. The converse of the method could be used to determine sea‐bottom slopes in hydrographic surveys.
DERIVATION OF MAGNETIC AND GRAVITATIONAL QUANTITIES BY SURFACE INTEGRATION
Authors: Skeels D. C. , Watson R. J.
Published: October 2002

In an earlier paper by one of the authors, it was pointed out that if the vertical component of a gravitational or magnetic field is known over a horizontal plane surface of sufficient extent, all other components and derivatives of the field can theoretically be calculated by surface integration of the vertical component. In this paper, examples are given to show that within certain limits such calculations are not only theoretically possible but practically so. Examples are given of the calculations of curvatures from observed gradients and of horizontal magnetic intensity from observed vertical intensity, and the calculated values are compared with those obtained by observation. Examples are also given, based on artificial data, of the calculation of plumb‐line deflections from gravity and of the calculation of magnetic anomalies at a given elevation above the earth from data obtained at the surface. The purpose of these calculations is to demonstrate the nonindependence of the various derivatives of gravitational and magnetic potential.
GEOPHYSICAL EXPLORATION FOR LIMESTONE REEFS
Authors: Agnich F. J.
Published: October 2002

Various geophysical methods are discussed in relation to their possible value in locating limestone reefs, with special emphasis on the gravity meter and seismograph. The effects of possible velocity variations through reefs on reflections from below a reef body are examined. Relationships between the shallow and deep horizons indicate that time isopach maps of such seismic data extremely valuable. A suggested exploration procedure describes several detailing methods, and emphasizes the important role of the interpreter in solving the problems associated with exploration for limestone reefs.
ELEVATION SURVEYING BY PRECISION BAROMETRIC MEANS
Authors: Stripling A. A. , Broding R. A. , Wilhelm E. S.
Published: October 2002

A sensitive instrument for measuring changes in atmospheric pressure and adapted for use in elevation surveying is described. Differences in atmospheric pressure are measured by measuring the changes in volume of an isothermal gas chamber that are required to maintain the chamber at atmospheric pressure. The instrument is sensitive to a change in atmospheric pressure equivalent to an elevation differences of 0.1 foot. Some of the theoretical aspects relating barometric pressure to elevation are reviewed, and the practical limitations imposed by the erratic nature of the atmosphere are discussed. Two field techniques are described, and a typical survey around an eight mile loop of thirteen stations is presented in which the closure is 1.2 feet, and the average error is 0.8 foot.
NORMAL MODE PROPAGATION IN THREE LAYERED LIQUID HALF‐SPACE BY RAY THEORY
Authors: Officer Charles B.
Published: October 2002

The fundamental integral for normal mode propagation in a three liquid layered half‐space is derived by multiple reflections, and the physical significance of the characteristic equation is discussed.
GEOMAGNETIC SURVEY OF A PORTION OF SOUTHEASTERN NEW YORK STATE
Authors: Geyer Richard A.
Published: October 2002

A geomagnetic survey, using an Askania magnetometer, of portions of northern Westchester, Putnam and Dutchess counties in New York state totaling approximately one hundred and thirty square miles is described and more than five hundred observations of the vertical component of the earth’s magnetic field are analyzed. These data are plotted on a scale of 1:30,000 and the resulting isogam chart is used to correlate the observed major changes in the vertical component with variations in the geology of an area in which basement complex rocks outcrop. This survey demonstrates that a rather well defined relationship exists between changes in the vertical component values and the major gelogic characteristics, using an average (regional) station spacing of four stations per square mile. In addition, the probable presence, on the basis of the magnetic data, of additional unexposed amphibolite lenses and associated igneous intrusives is indicated in those areas of the Eastern Schist Zone where the glacial overburden and/or soil obscure the underlying formations. The use of statistical methods is demonstrated for evaluating magnetic data for various purposes including the determination of interformational boundaries and the correlation of pronounced changes in geologic and magnetic characteristics.
AN ELECTROMAGNETIC INTERPRETATION PROBLEM IN GEOPHYSICS
Authors: Slichter L. B.
Published: October 2002

An interpretation problem in electromagnetic prospecting is discussed. A flat earth in which the three electrical properties of material vary only with depth is subjected to an alternating inducing field produced by a dipole above the surface with axis perpendicular to the surface. Observations of the horizontal or of the vertical component of the magnetic intensity at the ground’s surface are supposed to be available at all distances. From these observations solutions for the three unknown functions are developed. When the magnetic permeability is variable, the solutions for the permeability and dielectric functions require observations at two different frequencies. The conductivity function may be found from observations at a single frequency. It is shown that the horizontal and vertical components of the magnetic field intensity are mutually dependent in the region above the ground’s surface; and formulae independent of the ground’s characteristics are deduced for expressing [Formula: see text] in terms of [Formula: see text], and vice‐versa. Here [Formula: see text] denotes a plane coincident with or above and parallel to, the earth’s surface.
SEISMIC EXPLORATION OF THE DENVER‐JULESBURG BASIN
Authors: Rummerfield B. F.
Published: October 2002

Recent developments in northeastern Colorado and southwestern Nebraska have resulted in a marked increase in seismic activity within the Denver‐Julesburg Basin. The low relief of many of the subsurface structures, coupled with the extraneous effects of weathered zone, elevation changes, surface deposits, and velocity variation taxes the resolving power of the seismic method and the interpretative ability of the geophysicist.
APPROXIMATION TO THE LATERAL VARIATION OF RESIDUAL GRAVITY DUE TO A FRUSTUM OF A VERTICAL CONE
Authors: Griffin W. Raymond
Published: October 2002

The equation for the subject title is presented in nondimensional form. The approximation consists of considering a frustum of a vertical cone in which the radii are small relative to the depth to its top. The dependent variable has been taken as being the ratio of the residual gravity (as defined in a previous publication by the author) to the maximum residual gravity. The independent variable was chosen as the ratio of the lateral distance (from the center line of the frustum to a given station) to the depth to the top of the frustum. The two parameters were chosen as being (a) The ratio of depth to the bottom of the frustum to that to its top, (b) The ratio of the bottom radius to that of the top radius. It is then shown that, for special values of the parameters, the equation gives the lateral variation of residual gravity due to cylinders, upright cones, and inverted cones as special cases. Tables of the principal functions, which occur in the equation, are given over practical ranges of values. Graphs of the equation are given. They cover the practical range for each of the variables and each of the parameters. Application of the equation is made to two Gulf Coast salt domes whose dimensions are rather well known from previous drilling. Graphs, showing the degree of correlation, are given. The conclusion is drawn that, despite the approximation involved in the derivation of the equation, and despite the departure of the ratio of the dimensions of the salt domes from that assumed, the correlation with the actual gravity values for two deep salt domes is remarkably close.
NOTE ON THE EFFECT OF RANDOM ERRORS IN GRAVITY SECOND DERIVATIVE VALUES
Authors: Ramaswamy G.
Published: October 2002

In an interesting paper “The Effect of Random Errors in Gravity Data on Second Derivative Values,” Thomas A. Elkins (1952) points out the need for eliminating the random component of gravity data before proceeding to interpret them with the aid of second derivative maps. There is a prima facie case for the elimination of random errors, if only to ensure reliability in results. The need, however, becomes more apparent if it is remembered: a. that the Second Derivative method of interpreting gravity (or magnetic) data is one of high resolving power, and b. that, therefore, errors creeping into those data may considerably vitiate the interpretation of those data.
AIRBORNE MAGNETOMETER PROFILE FROM PORTLAND, OREGON TO ALBUQUERQUE, NEW MEXICO
Authors: Agocs W. B. , Rollins J. C. , Bangs E.
Published: October 2002

An airborne magnetometer profile of the variations of the earth’s anomalous total magnetic field was obtained using a wing‐tip magnetometer installation in a flight from Portland, Oregon to Albuquerque, New Mexico. The magnetic data were obtained by flying at barometric altitudes ranging from 7,000 to 10,000 feet above mean sea level. The variations in the total magnetic field are tied to the known geology along the flight path, and the possible interpretations of the magnetic data are reviewed in light of the known general geology.
SUB‐SURFACE ELECTRICAL MEASUREMENTS ABOUT TWO PLANE INTERFACES
Authors: Buckner Guy O.
Published: October 2002

Many response curves have been calculated for multiple‐electrode logging devices passing through thin beds (Guyod, 1944, parts 5, 6, 7, 8, 9, 10, and 11). For conditions where one can assume equal resistivity material above and below the thin bed, all electrodes in a line normal to the interfaces, and bore hole effects negligible, a function [Formula: see text] is introduced to make possible rapid computations. Tables and examples are included.
PROPAGATION OF RADIO FREQUENCY ENERGY THROUGH THE EARTH
Authors: McGehee F. M.
Published: October 2002

Measurements have been made of some propagation characteristics in the earth of 1,614 and 1,700 kc radio frequency energy. The experiments were conducted at Carlsbad Caverns, New Mexico, and Mammoth Cave, Kentucky. Transmitters were set up on the surface 710 ft above an unwired tunnel in Carlsbad Caverns and the signal strength was measured at many points in the tunnels. A similar series of measurements was made in Mammoth Cave in a tunnel 270 ft below the surface. The data show that the attenuation constant is about 0.012 and 0.02 to 0.064 neper/meter at the two locations respectively. These values are in good agreement with theory.
THE METHOD OF CAGNIARD IN SEISMIC PULSE PROBLEMS
Authors: Dix C. Hewitt
Published: October 2002

The main procedures used by L. Cagniard to calculate seismic pulse motion have been carried through for the case of a point source in an infinite medium. This relatively simple case serves as a basis for a simplified exposition of Cagniard’s method. By using this case, we avoid cluttering the exposition with a large collection of algebraic details that tend to befog the main issues.
ATMOSPHERIC POTENTIAL GRADIENT MEASUREMENTS
Authors: Howell Lynn G.
Published: October 2002

Relative atmospheric potential gradient measurements were made in the neighborhood of a salt dome. Two sets of measurements were made simultaneously at two different points. Wulf‐type electrometers were used with thorium ionium nitrate collectors insulated with sulphur. A number of set‐ups were made and no significant variations in potential gradient were found.
SEISMIC RECORDER FOR MONITORING MAGNETIC TAPE
Authors: Loper George B.
Published: October 2002

A new recorder utilizing Polaroid “picture‐in‐a‐minute” film has been developed to monitor seismic data recorded on magnetic tape. Signals from 12 magnetic recording heads are applied through appropriate networks to conventional galvanometers in the monitor as the magnetic record is made. The optical system is arranged to make a miniature seismogram of conventional appearance on a standard 3×4 inch Polaroid print. The record is a satisfactory guide for the operator to evaluate the quality of the record on the magnetic tape without the need for playing it back.
REVIEW OF CURRENT DEVELOPMENTS IN EXPLORATION GEOPHYSICS
Authors: Dobrin Milton B. , Van Nostrand Robert G.
Published: October 2002

During the past year, exploration geophysics has made its greatest progress in the application to prospecting of instruments and techniques which were until recently only in the development stage. The most notable examples are magnetic recording and velocity logging, both of which are already being offered as commercial services. The use of magnetic recording permits greater flexibility in seismic interpretation; automatic time correction, facilitating compositing as well as preparation of record sections; and the ready storage of seismic data in a form suitable for any processing procedures that may be developed in the future. Interval velocity logs have given geophysicists a better understanding of the origin of reflections from a complexly layered section. This understanding should lead to a more realistic interpretation of reflection data, and may eventually make it possible to map stratigraphic as well as structural features. Other noteworthy developments in seismic prospecting during 1955 include new methods for generating seismic energy, novel approaches to the improvement of signal‐to‐noise ratio, and the application of high frequency techniques in oil exploration. Although current research in petroleum geophysics is concentrated more than ever on seismic techniques, there have been important developments in the application of other geophysical methods to petroleum prospecting, mining exploration, and engineering problems. The gamma‐gamma logger now gives density data which are sufficiently reliable for gravity interpretation; an induced polarization method has been successful in finding ground water; and airborne electromagnetic methods have been widely used in the search for base metals in Canada. A new type of airborne magnetometer based on nuclear magnetic resonance has gone into service in prospecting for iron ore in the western United States. This device is particularly adapted for use in light aircraft. The rapidity of current technological improvement in exploration geophysics is attributed to the acceleration of geophysical research activity in the oil industry after World War II, to productive fundamental research, and to a widespread attitude among geophysicists of dissatisfaction with existing techniques.
THE REFRACTION SEISMOGRAPH IN THE ALBERTA FOOTHILLS
Authors: Blundun G. J.
Published: October 2002

In the Alberta foothills the most valuable use of the refraction seismograph is for the definition of overthrust faulting in the Mississippian limestone which is overlain by a faulted, overthrust, and overturned Cretaceous section. Normally, two refracted arrivals are recorded with characteristic interval velocities of 14,000 ft/sec and 21,000 ft/sec, the former arising from an unknown Cretaceous marker, and the latter from the Mississippian. In contrast to a shot‐range of 65,000 ft required to record the refracted arrival from the Mississippian at a depth of 10,000 ft as the first event, a range of 20,000 ft permits recording it as the later event, with consequent improvement in the quality and reliability of the data, reduces the amount of surveying required together with smaller dynamite charges, and improves radio communication. A geophone spread of 6,300 ft with single geophones at 300 ft intervals recorded on 22 traces is recommended. Both in‐line and broadside refraction with the Mississippian arrival recorded as the later event have been used successfully with certain advantages to each method. The former permits continuous determination of the interval velocity of the refracted events as well as providing two‐way control; the latter is considerably faster, and often faulting may be observed directly on the seismograms without reduction of the data. Specimen seismograms are included to illustrate the two methods. Field operating conditions pertaining to survey tolerances, shot formation, size of dynamite charges, the weathering shot as a polarity check, filtering, geophone frequency, and costs are discussed.
GRAPHICAL SCALES FOR MAPPING POTENTIAL FUNCTIONS
Authors: Roman Irwin
Published: October 2002

Graphical scales can be prepared and used for rapid determinations of potential field values which depend only on the distances between two fixed points. The method can be applied to determine the potential at the surface of a homogeneous earth due to a current pole at its surface, and to the potential at the surface of the earth considered as an infinite insulator separated from the surface by a parallel plate of finite resistivity. Portions of two typical scales and two sets of equipotential curves drawn by use of the scales are shown.
THE EFFECT OF TOPOGRAPHY ON NEAR‐SURFACE VELOCITIES
Authors: Baillie W. , Rozsa T.
Published: October 2002

Fictitious seismic anomalies sometimes result from the use of inadequate techniques in making the surface corrections. The effect of topography on the velocities of the underlying layers, commonly referred to as load effect, is a factor which is generally neglected in routine seismic interpretation. The importance of analyzing the load factor is illustrated by an actual example in which a fairly attractive seismic anomaly is shown to be entirely due to velocity variations associated with surface topography. A method of correcting for load effect is discussed.
PHYSICS IN AMERICA AND THE AMERICAN INSTITUTE OF PHYSICS
Authors: Klopsteg Paul E.
Published: October 2002

The titles in your scientific program confirm the validity of the name of your society. You are physicists interested in the composition and content of the earth’s outer shell. Yours is one of the key professions on which the material welfare of the human race increasingly depends, and without which it could not long continue in its present state of well‐being. My own career, like that of most of you, derives from my interest in physics and its applications. With keen awareness of this community of interest, I am happy indeed, and honored as well, to speak to you about physics and the organization which has been serving it so effectively for more than a quarter century.
GRAVITY PROSPECTING FOR CHROMITE DEPOSITS IN CAMAGUEY PROVINCE, CUBA
Authors: Davis W. E. , Jackson W. H. , Richter D. H.
Published: October 2002

Detailed gravity surveys were made in Camaguey Province, Cuba, as part of a systematic exploration program conducted by the U. S. Geological Survey on behalf of the General Services Administration to locate deposits of refractory‐grade chromite. During the period August 4, 1954, to April 5, 1956, a total of 41,921 gravity stations were established in nine areas embracing about 11.8 square miles in the Camaguey chromite district. The results of the surveys were used in connection with information obtained in geologic investigations to guide exploratory drilling. Gravimeters with low scale constants were used in making measurements sufficiently accurate to delimit anomalies as small as 0.5 gravity unit. The measurements were made over 20×40 and 30×60 meter grids and at stations 20 and 30 meters apart, respectively, along intermediate traverses in anomalous areas. Gravity differences were determined by single observations at individual stations, observing base stations hourly, and re‐observing a few stations to check drift and accuracy of measurement. About 11 percent of the stations established had to be re‐run because of errors in closure, microseisms, and instrument trouble. A large number of anomalies were found and evaluated according to geology, areal extent, and gravity relief. Depths to disturbing hypothetical bodies were computed to guide drilling. Test drilling of 106 positive anomalies revealed that ten features overlie deposits of chromite and 89 occur over bodies of other dense materials. The other seven anomalies were not explained by materials found in drilling. Core drilling on five of the chromite deposits revealed about 236,000 tons of chromite. An additional estimated 12,000 tons are contained in three deposits which were not blocked out. No estimate was made of the tonnage in two small deposits.
GEOPHYSICAL CASE HISTORY OF THE ANDERSON RANCH FIELD, LEA COUNTY, NEW MEXICO
Authors: Swenumson Glen H.
Published: October 2002

The Northwest Shelf area of Southwest New Mexico has had an exceptionally rapid growth as an oil producing province. The Anderson Ranch field, discovered by the Continental Oil Company in 1953, is one of the typically prolific oil fields in this Northwest Shelf area. This field (Figure 1) is the most southwesterly of a series of Devonian oil fields in the Northwest Shelf area of New Mexico. It is located 22 miles west of Lovington, New Mexico in sections 2 and 11, T. 16 S.‐R. 32 E., Lea County, New Mexico. The Anderson Ranch area was first found to be anomalous by a shallow oil well drilled in 1927 which found the Rustler Anhydrite unusually high. Core drilling carried out in 1940 developed an Anhydrite nose over the area. A reflection seismograph survey was carried out in the period from 1950 to 1951 which succeeded in mapping a closed anticline in the face of many difficulties in obtaining usable seismograms. It is believed that the seismic map prepared for the deepest horizon was caused by multiple reflections. The anticline so revealed was drilled in a unitized drilling program and a well was completed in the Devonian for an initial potential of 1,968 barrels of oil per day. This was the discovery well.
DIRECTIVITY EFFECT OF ELONGATED CHARGES
Authors: Musgrave A. W. , Ehlert G. W. , Nash D. M.
Published: October 2002

After years of development it has been determined that the energy from the detonation of a low velocity explosive in an elongated column approaches a unidirectional pattern. This column is placed in the subweathering material extending [Formula: see text] to 2 wavelengths in lengths depending on the frequency of energy desired. A study of the theory of propagation showed that greater directivity can be obtained from the same length of charge by using a powder with a detonation rate less than the side wall velocity of the shot hole. As the detonation rate of the column is lowered relative to the side wall the directivity increases and the downward energy decreases. The optimum balance of these factors is a detonation rate about [Formula: see text] of the side wall velocity. Experiments on elongated charges indicate that a very important effect of directivity is the elimination of “ghosts” as well as the reduction of horizontal energy. Interpretation may be greatly facilitated by a reduction in unwanted energy. Character is no longer dependent upon hole depth. Records have a more uniform appearance. Elongated charges produce many of the same effects as shallow pattern holes, but under many circumstances they are easier or less expensive to use.
REFLECTIONS FROM MULTIPLE TRANSITION LAYERS PART II—EXPERIMENTAL INVESTIGATION
Authors: Berryman L. H. , Goupillaud P. L. , Waters K. H.
Published: October 2002

It has been shown that the velocity of longitudinal waves in a nylon rod is a linear function of the temperature for the range 20°C. to 100°C. Use is made of this property to study reflections from multiple transition layers.
SOME TECHNICAL ASPECTS OF REFLECTION SEISMIC PROSPECTING IN THE SAHARA
Authors: Pieuchot M. , Richard H.
Published: October 2002

The small signal‐to‐noise ratio encountered in the Sahara required the development of special techniques. The gentle dips and low frequencies permitted the use of a pattern of 100 shot holes recorded by an array of 100 or more geophones per trace with the linear dimensions of the arrays of the order of 100 m. The large structural dimensions allowed the compositing of as many as 5 records into a single trace. Seismic reflection exploration was made economically feasible by the use of pneumatic hammers for drilling and the less expensive nitrates for explosives. The experimental procedures leading to the selection of the techniques are described.
PARA‐ AND DIAMAGNETIC SUSCEPTIBILITIES IN NON‐FLUCTUATING WEAK FIELDS
Authors: Schriever William
Published: October 2002

A Coulomb torsion balance apparatus was developed with which absolute measurements of para‐ and diamagnetic susceptibilities could be made in non‐fluctuating field strengths of the order of 1 oersted. Solid specimens of the diamagnetic elements, bismuth, antimony, and cadmium, were measured in fields of 2.5, 5, and 10 oersteds, and the para‐magnetic powders, [Formula: see text], [Formula: see text], and [Formula: see text], in fields of 2, 3, and 5 oersteds. The susceptibilities decreased with increasing field strengths. A specimen of bismuth granules had lower susceptibilities than did the solid specimen made from the same supply of granules. A semi‐micro balance apparatus also was constructed for absolute measurements in fields ranging between 100 and 1,000 oersteds. The susceptibilities of the diamagnetic specimens and a water specimen were measured. The solid bismuth, antimony, and cadmium specimens and a water specimen exhibited constant susceptibilities. The susceptibility of the bismuth‐granule specimen increased regularly from −4.67 to [Formula: see text] C.G.S. when the field increased from 100 to 900 oersteds. The value found for water [Formula: see text] agreed well with the International Critical Tables value [Formula: see text].
THE USE OF CRACOVIAN COMPUTATION IN ESTIMATING THE REGIONAL GRAVITY
Authors: Fajklewicz Zbigniew
Published: October 2002

The author uses the method of least squares in cracovian form and second order polynomials for estimating the regional gravity field. Expressions yielding the regional field are obtained very rapidly by using the inverse cracovians of the coefficients as given in the present paper, and there is no need of electronic digital computers for the computation. The equivalent of the entire work done by a computer of this kind in constructing the formula of the regional field, when effected by this method, takes no more than 20 minutes. The method is exemplified by the treatment of two gravity anomalies from the territory of Poland. The author stresses the fact that electronic computers adapted to the use of cracovians and characterized by a very high versatility may be applied in the method.
AN IMAGE ANALYSIS OF MULTIPLE‐LAYER RESISTIVITY PROBLEMS
Authors: Roman Irwin
Published: October 2002

The Kelvin method of images is expressible by a transflection at a boundary. The original source is augmented by a supplement and a complement. The supplement contributes to the potential on the same side of the boundary as the source, but it lies at the optical image position of the source in the boundary. The complement lies at the position of the source but contributes to the potential on the opposite side of the boundary. For two or more boundaries, there are two exterior regions and one or more interior regions. For a source in the top layer, a primary sequence starts with a downward transflection and a secondary sequence with an upward transflection. To each primary sequence of transflections there corresponds a secondary sequence with an upward transflection at the upper boundary ahead of it. The exterior images are not transflected again. Successive transflections occur at adjacent boundaries, suggesting a link of two transflections. To a sequence of links, called a chain, there corresponds an associated sequence, obtained by dropping the last transflection. Exterior images follow from interior, associated from chain, and secondary from primary. Thus, only primary, interior, chain images need to be traced. Each potential is the sum of terms of the form m/r where m is the strength of a specific image, r is the distance of that image from the test point, and the sum includes all images contributing to that potential. The addition of each boundary introduces images and potentials that must be added to those existing prior to the introduction, but it does not otherwise alter them. For the three‐boundary problem, the separate image strengths are determined by simple multiplication after a kernel polynomial is calculated. The latter is a finite polynomial in the reflection‐factor at the middle boundary and can be tabulated. For the images of a specific potential and depth group, the strengths satisfy a recursion formula that serves as a check on direct evaluations.
A LOSS MECHANISM FOR THE PIERRE SHALE
Authors: Horton C. W.
Published: October 2002

A theoretical study is made of a fairly simple model of an elastic solid in which losses are attributed to both the shear modulus and the bulk modulus. Each of these elastic parameters is represented by a circuit containing two springs and one dashpot. This is a modification of the usual Kelvin solid that has finite stiffness at infinite frequency. The four relaxation times introduced in the model are determined to fit the experimental data presented by McDonal et al. (1958). It is shown that one can obtain a very good representation of their experimental data with the model described above. The wave equation for an elastic solid is given in a canonical form so that one can compare easily the behavior of different models of the elastic parameters.
ON THE ELECTROMAGNETIC RESPONSE OF A CONDUCTING SPHERE TO A DIPOLE FIELD
Authors: Wait James R.
Published: October 2002

The electromagnetic coupling between an electric and a magnetic dipole in the presence of a spherical ore body is discussed in the present paper. It is shown that both electric and magnetic modes must be considered even though all dimensions are small compared to the wave length. The results have application to a geophysical prospecting scheme where the exciting fields are set up by a straight insulating wire grounded at its end points and the secondary fields are detected by an ungrounded closed wire loop.
CORRECTION TO THE PAPER, “WATER REVERBERATIONS—THEIR NATURE AND ELIMINATION” BY M. M. BACKUS
Authors: Kalisvaart F. , Seriff A. J.
Published: October 2002

On page 240 of this very useful and stimulating paper, there appears to be an error in equation (14). The multiplier representing the number of different permutations of the ray‐path segments for a given j, k, n is given as (1) [Formula: see text], and this formula has apparently been used to compute the curves in Figures 7, 8, and 9. The number of permutations is actually larger and is given by the multiplier (2) [Formula: see text]. Since these multipliers are identical for k=0 and k=j−1, the examples in Figure 6 and the curves in Figures 7, 8, and 9 for j=0, 1, and 2 are correct. For j⩾3, sizable differences do occur; however, the qualitatively important features of the curves given do not change.
RADIOACTIVITY OF VOLCANIC SEDIMENTS IN BRAZOS COUNTY, TEXAS
Authors: Russell William L. , Steinhoff R. O.
Published: October 2002

The relation between the field unit of gamma radiation intensity, microroentgen per hour, and the laboratory units, expressed in concentration of radioactive elements, was determined by measuring the radiation intensity over a level rock surface and measuring the gamma radioactivity of the same rocks in the laboratory. The available data indicate that one percent potassium equivalent of gamma radioactivity is [Formula: see text] radium equivalents, [Formula: see text] potassium equivalents, [Formula: see text] thorium equivalents, and produces a gamma radiation intensity of 0.57 microroentgen per hour over a flat surface. Measurements of volcanic sediments of Upper Eocene and Miocene age in Brazos County, Texas, show gamma‐ray emissivities of 4.5 to 10.9 percent potassium equivalents of gamma‐ray emissivity. This is about the same as ordinary shales. The mixture of volcanic particles with clastic sediments in these samples suggests that the radioactivity of the original volcanic matter may possibly have been reduced by weathering.
THE SPECIFICATION AND TESTING OF A SEISMIC‐REFRACTION SYSTEM FOR CRUSTAL STUDIES
Authors: Warrick R. E. , Hoover D. B. , Jackson W. H. , Pakiser L. C. , Roller J. C.
Published: October 2002

A new seismic‐refraction system built for the U. S. Geological Survey for crustal studies has been tested in the laboratory and shown to meet strict performance specifications for broad frequency response, low noise, high gain, and high dynamic range. The inherent advantages of magnetic recording, with selective filtering on playback, were demonstrated in field tests by the recovery of weak events that otherwise would be obscured by high seismic noise.