ALBERT

Notes: We present a new method for the extraction and removal of the source wavelet from the reflection seismogram. In contrast to all other methods currently in use, this one does not demand that there be any mathematically convenient relationship between the phase spectrum of the source wavelet and the phase spectrum of the earth impulse response. Instead, it requires a fundamental change in the field technique such that two different seismograms are now generated from each source-receiver pair: the source and receiver locations stay the same, but the source used to generate one seismogram is a scaled version of the source used to generate the other. A scaling law provides the relationship between the two source signatures and permits the earth impulse response to be extracted from the seismograms without any of the usual assumptions about phase.We derive the scaling law for point sources in an homogeneous isotropic medium. Next, we describe a method for the solution of the set of three simultaneous equations and test it rigorously using a variety of synthetic data and two types of synthetic source waveform: damped sine waves and non-minimum-phase air gun waveforms. Finally we demonstrate that this method is stable in the presence of noise.

Notes: In this paper a theorem is demonstrated which allows—after the introduction of a suitable dipole kernel function or dipole resistivity transform function—to write the apparent resistivity function as an Hankel transformable integral expression.As a practical application of the theorem a procedure of quantitative interpretation of dipole soundings is suggested in which the dipole resistivity transform function obtained after inversion of the original dipole apparent resistivity data is used to control the goodness of the set of layering parameters which have been derived with our previous method of transformation of dipole sounding curves into equivalent Schlumberger diagrams.

Notes: The Hankel transform theorem can be applied to the inversion of gravity data for the buried sphere, the horizontal cylinder, and the vertical rod. This new approach leads to exact solutions of the transforms for the assumed bodies. A comparison with the classical procedure by Fourier transform reveals that for the sphere and the vertical rod, the Hankel transform is preferable.

Notes: Air guns have been used in various applications for a number of years. They were first used in coal-mining operations and were operated at up to 16000 psi charge pressures. Later, single air guns, operated at 2000 psi, found application as an oceanographic survey tool. Air gun arrays were first used in offshore seismic exploration in the mid-1960's. These early arrays were several hundred cubic inches in total volume and were operated at 2000 psi; they were either tuned arrays or several large guns of the same size with wave-shape kits. Today's arrays have total volumes greater than 5000 cu in. and are typically operated at 2000 psi. Recently, higher-pressure, lower-volume arrays operated at 4000–5000 psi have been introduced; guns used in these arrays are descendants of the coal-mining gun.On first thought one would equate increased gun pressure linearly with the amplitude of the initial pulse. This is approximately true for the signature radiated by a “free-bubble” (no confining vessel) and recorded broadband. The exact relation depends on the depth at which the gun is operated; from solution of the free-bubble oscillation equation, the relation is 〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR700:GPR_700_mu1"/〉 If Pc,1= 6014.7 psia, Pc,2= 2014.7 psia and PO, 1=PO, 2= 25.8 psia (corresponding to absolute pressure at 25 ft water depth), then 〈displayedItem type="mathematics" xml:id="mu2" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR700:GPR_700_mu2"/〉 Experiments were conducted offshore California in deep water to determine the performance of several models of air guns at pressures ranging from 2000 to 6000 psi and gun volumes ranging from 5 to 300 cu in. At a given gun pressure, the initial acoustic pulse Pa correlated with gun volume Vc according to the classical relation 〈displayedItem type="mathematics" xml:id="mu3" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR700:GPR_700_mu3"/〉 For 1 ms sampled data the ratio 〈displayedItem type="mathematics" xml:id="mu4" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR700:GPR_700_mu4"/〉 varied between 4.5 and 5.5 dB depending on gun model. Pulse width of the 2000 psi signatures indicated they are compatible with 2 ms sample-rate recording while pulse width of the 6000 psi signatures was greater, indicating they are less compatible with 2 ms sample-rate recording.Conclusions reached were that 2000 psi air guns are more efficient than higher pressure guns and are more compatible with 2 ms sample-rate requirements.

Notes: Numerous electrodes, already used in geophysics or just perfected by us, have been compared by measuring the three main characteristics which interest the user: noise spectrum, temperature coefficient and polarization with its stability versus time.Among the most used unpolarizable electrodes, silver-silver chloride (Ag-AgCl) are the best ones. But a systematic research of all different possible metal-salt couples, have led us to use lead-lead chloride (Pb-PbCl2) for the following reasons: noise as low as the one of Ag-AgCl at 1 Hz and even lower for the low frequencies (0.4 μV at 1 Hz and 1.2 μV at 0.01 Hz for peak to peak value and ΔF=F), temperature coefficient about ten times weaker (−40 μV/°C instead of −450 μV/°C) and also better long time stability of the polarization (1 mV/month instead of 2 at 10 mV/month).We have been using these electrodes since 1977 as “tube” electrodes which are very easy to use. They allow us to record correctly the fast variations thanks to their low noise, the very slow variations, their low temperature coefficient and their stability, and this with telluric lines only about 100 m long.

Notes: The compression of seismic signals which have propagated through a dispersive medium can be achieved by a frequency-domain transformation. This transformation is formally related to the dispersion characteristic of the medium and is independent of phase and group velocities. By defining a suitable cost-function to measure the degree of dispersion of a time- signal, an iterative technique can be employed to find that transformation which gives minimum dispersion.In this paper, we assume that the inverse of the dispersion characteristic can be adequately approximated by a finite polynomial in the region of maximum signal energy density. The coefficients of this polynomial are the parameters of dispersion of the medium. These parameters can be estimated both in the presence of noise and in the case of signals made up of multiple arrivals.The techniques developed in this paper are applied to seismic signals which have been recorded underground by a set of geophones designed to detect and map discontinuities in coal-seams. Results of dispersion estimation and signal compression are discussed for data collected in the Blackshale seam, Pye Hill Colliery, near Derby, in the United Kingdom.

Notes: Sign reversals have been observed with the one-loop version of the TEM method in an area near Cloncurry, Queensland. This is the only area in which such a response has been recorded in seven years of field surveys by the Australian Bureau of Mineral Resources.The geology of the area consists mainly of pyrrhotitic graphitic shale, which has resistivities as low as 0.1 Ωm and frequency effects up to 30%. The sign reversals could be due to magnetic phenomena, reflections from layers, or complex conductivity effects.

Notes: A crucial step in the use of synthetic seismograms is the estimation of the filtering needed to convert the synthetic reflection spike sequence into a clearly recognizable approximation of a given seismic trace. In the past the filtering has been effected by a single wavelet, usually found by trial and error, and evaluated by eye. Matching can be made more precise than this by using spectral estimation procedures to determine the contribution of primaries and other reflection components to the seismic trace. The wavelet or wavelets that give the least squares best fit to the trace can be found, the errors of fit estimated, and statistics developed for testing whether a valid match can be made.If the composition of the seismogram is assumed to be known (e.g. that it consists solely of primaries and internal multiples) the frequency response of the best fit wavelet is simply the ratio of the cross spectrum between the synthetic spike sequence and the seismic trace to the power spectrum of the synthetic spike sequence, and the statistics of the match are related to the ordinary coherence function. Usually the composition cannot be assumed to be known (e.g. multiples of unknown relative amplitude may be present), and the synthetic sequence has to be split into components that contribute in different ways to the seismic trace. The matching problem is then to determine what filters should be applied to these components, regarded as inputs to a multichannel filter, in order to best fit the seismic trace, regarded as a noisy output. Partial coherence analysis is intended for just this problem. It provides fundamental statistics for the match, and it cannot be properly applied without interpreting these statistics.A useful and concise statistic is the ratio of the power in the total filtered synthetic trace to the power in the errors of fit. This measures the overall goodness-of-fit of the least squares match. It corresponds to a coherent (signal) to incoherent (noise) power ratio. Two limits can be set on it: an upper one equal to the signal-to-noise ratio estimated from the seismic data themselves, and a lower one defined from the distribution of the goodness-of-fit ratios yielded by matching with random noise of the same bandwidth and duration as the seismic trace segment. A match can be considered completely successful if its goodness-of-fit reaches the upper limit; it is rejected if the goodness-of-fit falls below the lower one.

Notes: If the conductivity of any one of the layers of a horizontally stratified earth varies exponentially with depth with or without a discontinuity at the interface, the corresponding expressions for apparent resistivity for Wenner- and Schlumberger-sounding arrays can be formulated. The general case has been broadly divided into three categories for mathematical simplicity. All previous discussions of this problem can be regarded as particular cases of the present study.

Notes: The physical properties of the serpentinized pyroxenitic and saxonitic rocks from stratiform ultramafic complexes of Roro, Singhbhum distrct, India, are examined using principal factor (R-mode) analysis technique. The variations and inter-relations of these properties reflect the compound effects of two processes—(a) degree of serpentinization, and (b) mineralogical and other changes attendant to serpentinization. Factor analysis is thus shown to be an effective tool for petrophysical inferences.

Notes: The problem of numerical evaluation of apparent resistivity curves is treated by finite difference modeling. The models proposed are set up in cylindrical coordinates and yield the potential field due to a point source located in a radially symmetric environment. The Schlumberger configuration, widely used for surface measurements, is emphasized. However, the treatment is equally applicable to other similar situations such as the computation of synthetic electric logs when the resistivity of the borehole fluid is different from that of the surrounding uniform or stratified medium. Moreover, the individual layers may not necessarily be isotropic.The medium under investigation is discretized by using a very coarse system of horizontal and vertical grid lines whose distance from the source increases logarithmically; consequently, the physical dimensions of the medium can be made “infinite” without affecting the numerical size of the model. Finer features such as a thin but anomalously resistive or conductive bed which would ordinarily be missed in coarse discretization are accurately taken into account, since the calculations are done in terms of the Dar Zarrouk parameters derived from the exact resistivity distribution of the model. This enables one to compute the potential field by inverting a small sparse matrix. When the medium comprises only a few layers, the efficiency of the finite-difference model is comparable to that of the known analytical methods; for more complicated structures, however, the finite-difference model becomes more efficient. The accuracy of finite-difference results is demonstrated by comparing them with the corresponding analytically obtained data.

Notes: A new method of estimating seismic stacking velocity from reflection seismograms is based on Fibonacci search technique and provides the highest rate of reduction of the interval of uncertainty of the stacking velocity. A review of the Fibonacci search strategy is presented, the application of the method is illustrated with synthetic and field examples.

Notes: The paper relates primarily to the borehole and the side bed correction charts for Latero-logs 3 and 7. Versions of some of these charts published by different companies—or even by the same company in different years—exhibit significant variations. Usually, such publications do not contain adequate information on how the charts were constructed and do not explain why discrepancies occur.Because of these reasons, an attempt has been made in this paper to reconstruct the borehole correction chart for Laterolog 7 and the shoulder bed correction charts for Latero-logs 3 and 7. For the latter two, the results found differ substantially from those published earlier.The paper demonstrates how departure (response) curves and correction charts for the lateral and the Laterolog 7 sondes can be computed from those for the normal sonde. An apparent resistivity formula is suggested for Laterolog 7 in which all currents that exist in the ground at the time of measurement and that produce the signal are monitored and used. Response curves and correction charts for Laterolog 7, based on such a formula, are presented as illustrations.

Notes: The quality of results of migration before stack is sensitive to inaccuracies in the velocity field applied. This does not hold if only traces of similar sources-receiver distances (common offset traces) enter the migration process. In this case, velocity deviations generate minor shifts in travel times of migrated interfaces but no deterioration in quality. These time shifts are proportional to both the velocity error and the square of the source-receiver distance.The above observations suggest the following migration scheme: migrate separately the traces of the various common offset planes or groups of neighbouring common offset planes; for every common midpoint plane and as a function of travel-time perform a residual NMO search to find trajectories t) =t)o+px)2 of maximum coherency along which migrated events are aligned; correct for residual NMO and stack the migration results obtained in the various common offset planes to obtain the final migration result.This process not only takes care of inaccurate migration velocities but also corrects partly for effects of refraction.It is shown by means of an example that good migration results are generated even with a considerably deviating velocity field.

Notes: It is shown that the so-called Kirchhoff-summation operator is of a very wide-band nature and even contains an evanescent part. As a consequence, discretization may cause serious aliasing errors, particularly for small extrapolation steps. It is proposed to use in all practical cases band-limited versions of the summation operator, the spatial cut-off frequency being determined by the spatial Fourier spectrum of the coherent noise.

Notes: In the Andes mountains of North Chile seismic refraction measurements revealed the existence of a buried graben structure. The special geological environment permitted the deduction, by detailed analyses of diffraction patterns and delayed arrival times, of a low velocity layer underneath a high velocity ignimbritic sheet.The gravity method was chosen as an economic secondary aid to trace the course of the buried structure. This unusual combination of detailed gravity measurements following a general seismic survey was not only successful in detecting and tracing a buried structure, but also provided complementary data about the deeper subsurface conditions.

Notes: A Kunetz equation is often used as the starting point in the development of solutions for the inversion of one-dimensional, noise free, normal incident seismograms, for which |ro|= 1. In this paper we demonstrate a need for a Kunetz-type equation in which filtered signals can be used, so that noise effects can be reduced. We then show that an infinite number of Kunetz-type equations exist for the lossless wave equation in layered media. Finally, we show that it is indeed valid to formulate and solve the inverse problem using filtered signals.

Notes: A theory for the bipole-dipole method of resistivity sounding is developed. Bipole-dipole apparent resistivities are related to Schlumberger apparent resistivities at two spacings. The theory can also be used to compute exact dipole-dipole apparent resistivity curves providing an improvement over the existing techniques which involve far field approximations. A comparison of bipole-dipole and dipole-dipole systems reveals the similarity between the two. However, the resolution of the bipole-dipole system depends on the azimuth angle. The flexibility of the theoretical expressions lead to a generalized field scheme independent of the bipolar or dipolar nature of the current source.

Notes: The combined observation of first and later arrivals in shallow seismic refraction surveys, particularly on hard rock terrains, is discussed. Details of experimental weathered-zone investigations by the correlation refraction method in a granite terrain (i.e. field procedure, seismograms obtained, plotting of the data, and identification of the waves are presented). Complete travel time data and interpreted subsurface sections of a few test refraction surveys are included. In one instance the interpreted results of normal and converted refracted wave data have been tested by drilling at three points along a 220 m long profile.

Notes: A Bremmer Series decomposition of the solution y(t) to the lossless wave equation in layered media is 〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR71:GPR_71_mu1"/〉 where the yj(t) are physically meaningful constituents (i.e., y1(t) are primaries, y2(t) are secondaries, etc.). This paper reviews Mendel's state space models for generating the constituents; reviews Bremmer's integral equation models for generating the constituents; and demonstrates how Mendel's state space models can be obtained by a careful decomposition of Bremmer's integral equation models. It shows that Mendel's equations can be viewed as approximate numerical solutions of Bremmer's integral equations. In a lossless homogeneous medium, the approximations become exact.

Notes: The interpretation of vertical electrical sounding data can be facilitated by the application of the reciprocal geoelectric section. If an apparent resistivity field curve has a descending right end, the apparent resistivity curve of the reciprocal geoelectric section can be obtained by the application of linear filter theory; from this the total transverse resistance of the geoelectric section can be calculated without having to interpret the field curve. In addition, Orellana's auxiliary point method can now be extended to interpret three and four layer apparent resistivity curves of all types.This paper summarizes the properties of the resistivity transform curve, the apparent resistivity curve, and the apparent resistivity curve of the reciprocal geoelectric section, with several new applications.

Notes: Past design of marine source arrays has been based on one or more of the following principles:〈list xml:id="l1" style="custom"〉(i) simultaneous operation of multiple identical sources to increase radiated signal strength by simple addition;(ii) superposition of wavelets of different fundamental frequency to achieve a total pulse of desired, front-loaded form (e.g. mixed volume air-gun arrays);(iii) horizontal spacing of units or groups to achieve spatial filtering effects.The phenomenon of interaction between sources, affecting the loading experienced by each, has usually been ignored, or else avoided by wide spacing of units. However, interactions can significantly affect the efficiency and frequency response, in a way that can be favourable.Calculations are presented for sources emitting continuous or long duration signals, showing the energy efficiency as a function of frequency for arrays in a variety of configurations. Interaction effects are significant for inter-source spacings smaller than or comparable with the wavelength—not, as is often stated, up to a distance related to the radii of the sources. The results show that potential exists for tailoring the frequency response of a source system, according to the application, by simple spatial rearrangement of units.Similar effects occur with interacting impulsive sources, but it is shown that different criteria apply for the optimum arrangements of units.

Notes: This paper deals with the practical problem of processing magnetic data in the field, and it shows how the parameters describing a geological contact can be obtained quickly and conveniently on the basis of five measurements. The complete interpretation can be performed in the field using a programmable calculator. For a small ground-party the method greatly improves the quality of the field-work and the interpretation of the magnetic data. The method has been applied to the data from a magnetic survey over the Mooki Fault (Gunnedah-Manilla, N.S.W.), and the results are discussed as an illustration of the efficacity of the method as a field procedure.

Notes: The iterative estimation process of residual static corrections published earlier is further analyzed.The convergence and convergence rate of the iterative solution are analysed for components of different relative wave length with results of both theoretical and practical value.Relative wave length components practically determinable and indeterminable are defined.One model example is presented for illustrative purposes.

Notes: The observation of shear waves is finding more interest in seismic exploration, especially for the determination of additional lithologic parameters, e.g. Vp/Vs. We demonstrate the observation of converted waves in routine seismic work by means of horizontal geophones. Field technique and data processing permit acquisition and interpretation of converted waves in connection with routine seismic measurements. A special interpretation of the recorded converted waves results in the shear wave velocity and the Vp/Vs relation.

Notes: The transient response of a conductive shell-shell model in the one-loop version was obtained analytically. The results indicate that four zones, namely early, late early, intermediate, and late zone can be identified in the total transient characteristic of the model. In case the measurements are carried out in the late early zone, a conductive target appears as a resistive one. It is suggested that the optimum time of measurement should be so selected as to fall in the intermediate zone.

Notes: A careful examination of the seismic refraction technique details the general assumptions and processes on which it is based. It is apparent that the normal interpretive process of determining velocity by hand fitting time breaks, while necessary to identify the refractors, is subject to imprecision.We describe a digital technique that calculates velocity and its precision from the time break measurements. The technique also facilitates examining for the possibility of systematic errors. Having observed the kind of imprecision that was apparent with velocity we extended our study to layer thicknesses (and thus depth) and found that the imprecision was significantly magnified.The technique and our claims for it are supported by an example of its application to a refraction survey in the Sturt Block, Western Australia.

Notes: A stacked seismic section represents a wave-field recorded at regularly spaced points on the surface. The seismic migration process transforms this recorded data into a reflectivity display. In recent years, Jon F. Claerbout and his co-workers developed migration techniques based on the numerical approximation of the wave equation by finite difference methods. This paper describes an alternative method, termed ASD (for Accurate Space Derivative), and its application to the wave equation migration problem. In this approach to the numerical solution of partial differential equations, partial derivatives are computed by finite Fourier transform methods. This migration method can accommodate media with vertical as well as horizontal velocity variations.

Notes: On seismograms recorded at sea bubble pulse oscillations can present a serious problem to an interpreter. We propose a new approach, based on generalized linear inverse theory, to the solution of the debubbling problem. Under the usual assumption that a seismogram can be modelled as the convolution of the earth's impulse response and a source wavelet we show that estimation of either the wavelet or the impulse response can be formulated as a generalized linear inverse problem. This parametric approach involves solution of a system of equations by minimizing the error vector (ΔX = Xobs– Xcal) in a least squares sense. One of the most significant results is that the method enables us to control the accuracy of the solution so that it is consistent with the observational errors and/or known noise levels.The complete debubbling procedure can be described in four steps: (1) apply minimum entropy deconvolution to the observed data to obtain a deconvolved spike trace, a first approximation to the earth's response function; (2) use this trace and the observed data as input for the generalized linear inverse procedure to compute an estimated basic bubble pulse wavelet; (3) use the results of steps 1 and 2 to construct the compound source signature consisting of the primary pulse plus appropriate bubble oscillations; and (4) use the compound source signature and the observed data as input for the generalized linear inverse method to determine the estimated earth impulse response—a debubbled, deconvolved seismogram. We illustrate the applicability of the new approach with a set of synthetic seismic traces and with a set of field seismograms.A disadvantage of the procedure is that it is computationally expensive. Thus it may be more appropriate to apply the technique in cases where standard analysis techniques do not give acceptable results. In such cases the inherent advantages of the method may be exploited to provide better quality seismograms.

Notes: According to data presented by YU.A. Kosigin, 84% of all endogenous mineral deposits are in some direct or indirect relation with the fractures of the earth's crust. Therefore the discovery and the study of the spatial disposition of the fractures is the most important object for geophysicists. Abyssal fractures are of particular interest.By geophysical methods one can find the geometrical parameters of abyssal fractures such as their extent, the depth of formation, the breadth of the zones, and the amplitude of the relative displacement of separated blocks.The methods determining these parameters are widely known. A calculation of the difference in the levels of the erosion cuts of the blocks are of particular interest under shield conditions. A method to calculate this difference by gravity interpretation of “step” anomalies and by using the gradient model of the earth's crust is proposed.A comparision of the results of gravimetry and magnetometry with those of deep seismic soundings shows that the fractures of the first and the second order in the Ukrainian shield cut the earth's crust and part of the upper mantle so they can be qualified as abyssal fractures.In the Ukrainian shield the spatial regularities of the fractures determined by geophysical methods can be used for the prognosis of the ore deposits.

Notes: The interpretation of electrical sounding data for a subsurface with monotonic continuous variation of the resistivity with depth is becoming increasingly necessary. The contribution of this article is the derivation of the solution for the Wenner and the Schlumberger apparent resistivity functions for a resistivity varying as a real power of a linear positive function of the depth. The interpretation of sounding data in these cases can be used to estimate the variation of the porosity or the salt content of the pore water with depth.

Notes: During the past four or five years, Vertical Seismic Profiles have been run in a large number of wells and in a variety of geological provinces with the object of assisting the seismic data processor and improving the geological interpretation.The special properties of the Vertical Seismic Profile, which allows the separation of the upward and downward travelling components of the recorded waveform, provides a means of studying the acoustic response of the earth in detail. Deconvolution of the data in particular gives a clearer understanding of the mechanics of multiple reflections and the way in which they may obscure primary reflections in the vicinity of the well.The primary reflection response of the earth can be observed with greater resolution than conventional seismic data permits, making correlation with lithology more precise, and allowing a good estimate of the reflection coefficient series to be determined. Inversion of the seismic traces to produce an acoustic impedance log leads to better definition of the sedimentary sequence and is of particular interest in predicting lithologic variations ahead of the drilling bit.In addition, Vertical Seismic Profile data can be used to assess parameters in areas such as deconvolution and signal band width for the evaluation of conventional seismic data.

Notes: An analysis of the equivalence phenomenon, analogous to that encountered in resistivity sounding, has been made for electromagnetic (frequency) sounding with the following systems: horizontal coplanar coils, perpendicular coils, vertical coplanar coils, and vertical coaxial coils. Cases analyzed are three-layer H and K type resistivity distributions. The theoretical responses for the EM sounding systems have been computed by the digital linear filter method using short filters. An analysis has been made of the resolution by the four EM systems considered f the equivalence effect. It is concluded that from the equivalence point of view electromagnetic (frequency) sounding has relatively better resolution compared to resistivity sounding for the H type three-layer cases. For the K type three-layer cases electromagnetic (frequency) sounding provides a serious problem in resolution similar to that encountered in resistivity sounding. Empirical relationships have been established for the H and K type cases respectively in order to numerically quantify the equivalence involved in electromagnetic (frequency) sounding.

Notes: The normal moveout velocity of a reflecting bed is a function of the dips and curvatures of all overlying velocity interfaces. Now let the (N– 1)th velocity interface be a non- (or badly) reflecting bed, whereas the other interfaces, including the base of the Nth layer, reflect satisfactorily, and let the velocities UN– 1 and UN of the (N– 1)th and Nth layer, respectively, be known. Then the normal moveout velocity for the base of the Nth layer, if known in one direction at a certain part of the surface of the earth, provides a second order differential equation in the horizontal coordinates x and y for the depth ZN – 1(x, y) of the unknown interface.The mathematics becomes rather simple in the case of two-dimensional geological structures. For this case and N= 2 the differential equation mentioned can be solved by stepwise integration or by iteration. One of the many possible applications of the new concept is the determination of the structure of the base of an overthrusting sheet.

Notes: The asymptotic approximation of Pekeris is replaced by two new procedures referred to as the two-point method and the multilayer method, other steps in the direct interpretation remaining unmodified. The new methods are based on the assumption that there are at least one or two consecutive sample points of the kernel curve containing the information on a particular layer and containing no information on the deeper layers. In any step, the identified covering layers are accumulated and the interpretation progresses to the successive deeper layer.The multilayer method is oriented towards interpretation of data severly contaminated by noise. The elimination of noise with simultaneous averaging of layer parameters is performed in the domain of Dar Zarrouk parameters.

Notes: Multiple sea-floor reflections in deep water often are not effectively suppressed by either CDP stacking nor standard predictive deconvolution methods. These methods fail because the reflection coefficient varies markedly with angle of incidence and also because of the variation of arrival time with offset and because of dip. For a reasonablly flat sea-floor, multiples of various orders and the primary sea-floor reflection which have all been reflected at nearly the same angle lie along a straight line through the origin in time-offset space. This line is called the “radial direction.” The multiples which lie along this line show a systematic relationship because they all experience the same water-bottom reflection effect. In other words, multiples behave in a stationary manner along the radial directions on multi-trace seismic records. A technique of multi-channel predictive deconvolution, called “Radial Multiple Suppression,” utilizes this aspect to design Wiener operators for the prediciton and suppression of water bottom multiples.The effectiveness of the technique is demonstrated by the study of field records, autocorrelations, velocity analyses, and stacked sections before and after Radial Multiple Suppression processing.

Notes: A new technique is developed for generating a short seismic pulse from the bubble pulses which are radiated by an air-gun. The new technique, which is useful in well velocity surveys and vertical seismic profiling, can be implemented by firing a single air-gun several times at the same depth but with different chamber pressures.A record obtained by this procedure from a well-geophone clamped at a depth of 2450 m gave a maximum peak-to-peak amplitude within the first 100 ms of the effective seismic pulse at least ten times any later peak-to-peak amplitude.

Notes: A seismic source array is normally composed of elements spaced at distances less than a wavelength while the overall dimensions of the array are normally of the order of a wavelength. Consequently, unpredictable interaction effects occur between element and the shape of the far field wavelet, which is azimuth-dependent, can only be determined by measurements in the far field. Since such measurements are very often impossible to make, the shape of the wavelet—particularly its phase spectrum—is unknown.A theoretical design method for overcoming this problem is presented using two scaled arrays. The far field source wavelets from the source arrays have the same azimuth dependence at scaled frequencies, and the far field wavelets along any azimuth are related by a simple scaling law. Two independent seismograms are generated by the two scaled arrays for each pair of source-receiver locations, the source wavelets being related by the scaling law.The technique thus permits the far field waveform of an array to be determined in situations where it is impossible to measure it. Furthermore it permits the array design criteria to be changed: instead of sacrificing useful signal energy for the sake of the phase spectrum, the array may be designed to produce a wavelet with desired amplitude characteristics, without much regard for phase.

Notes: Man's engineering activities are concentrated on the uppermost part of the earth's crust which is called engineering-geologic zone. This zone is characterized by a significant spatialtemporal variation of the physical properties status of rocks, and saturating waters. This variation determines the specificity of geophysical and, particularly, geoelectrical investigations.Planning of geoelectric investigations in the engineering-geologic zone and their subsequent interpretation requires a priori) geologic-geophysical information on the main peculiarities of the engineering-geologic and hydrogeologic conditions in the region under investigation. This information serves as a basis for the creation of an initial geoelectric model of the section. Following field investigations the model is used in interpretation. Formalization of this a priori) model can be achieved by the solution of direct geoelectric problems. An additional geologic-geophysical information realized in the model of the medium allows to diminish the effect of the “principle of equivalence” by introducing flexible limitations in the section's parameters. Further geophysical observations as well as the correlations between geophysical and engineering-geologic parameters of the section permit the following step in the specification of the geolectric model and its approximation to the real medium. Next correction of this model is made upon accumulation of additional information. The solution of inverse problems with the utilization of computer programs permits specification of the model in the general iterational cycle of interpretation.

Notes: The computation of the electrical potential created by a source of direct current in a horizontally stratified earth is easy, and it is now a common practice to interpret, by manual or automatic procedures, the maps of apparent resistivity or of mise-à-la-masse surveys.The study of 3-D cases requires a computer cost too high for a general use, and the available techniques usually refer only to an anomalous body embedded in a stratified medium. In fact, it often happens that the surface of the ground cannot be regarded as a plane, an assumption which can cause large discrepancies between the observed and the calculated potentials. A first estimate of these discrepancies can be made by assuming that the earth's surface makes a dihedron and the underground consists either of one homogeneous medium or of several media whose plane interfaces pass through the edge of the ground surface dihedron. Although very schematic, this approximate model can provide a useful information on the effect of the relief.

Notes: Alfano L. 1980, Dipole-Dipole Deep Geodectric Soundings over Geological Structures, Geophysical Prospecting 28, 283–296.The dipole-dipole array is used for deep vertical geoelectric soundings for practical reasons. However, the data obtained are often too scattered and the quality is lower than that of a Schlumberger sounding. The mathematical transform from these fields data to the corresponding Schlumberger ones is needed. It is demonstrated that for more general underground structures different from plane parallel stratifications, only the continuous polar dipole-dipole array permits a general and reliable transform of this type. It follows that any other dipole-dipole array, (for instance the azimuthal, equatorial, parallel, perpendicular, etc.), are useless over complex structures, or in the presence of irregularities on the ground surface.

Notes: A new method of Vibroseis deconvolution has been recently proposed by the authors. This discussion describes the effects of noise on the application of this method. The initial deconvolution step involves estimating the spectrum of the Vibroseis wavelet by homomorphic filtering. It is shown that noise causes problems with phase estimation. Hence, the Vibroseis wavelet is assumed to be zero phase. Examples demonstrate that zero phase cepstral filtering is a robust wavelet estimation approach for noisy data. The second step of the deconvolution method forms an impulse response model by a spectral extension method. Although this step can improve the resolution of seismic arrivals, it must be applied with caution in view of the deleterious effects of noise.

Notes: Geophysical interpretation consists of the identification of geological parameters carried out in the state of uncertainty. From this follows that the identificative model must correspond to the degree of uncertainty. As uncertainty measure of the surveyed material the informative distance between different interpretive models is introduced. The influence of the measurement noise and the accuracy of measurement devices as well as the number of measurement sets worked out simultaneously for this survey is analyzed. Numerical examples indicate that the material considered to be not interpretable from the point of view of a certain accurate model may be interpreted by the use of a less accurate model.

Notes: Tracers are used widely to determine the direction and velocity of ground-water movement. Failures of tracer tests are most commonly a result of incorrect choice of tracers, insufficient concentrations of tracers, and a lack of an understanding of the hydrogeologic system being tested. Some of the most useful general tracers are bromide chloride, rhodamine WT, and various fluorocarbons. For certain purposes, dyed clubmoss and baker's yeast have proved valuable. Many radionuclides including 3H, 82Br, and 198Au are almost ideal for numerous purposes, but radiation hazards associated with their use together with local, State, and Federal regulations have discouraged widespread field applications in recent years within the United States.

Notes: The Tucson, Arizona, metropolitan area has 450,000 inhabitants and is expected to have nearly 800,000 inhabitants by the year 2000. Tucson is totally dependent on ground water drawn from two basin aquifer systems for its water supplies, as are agricultural, mineral and industrial operations in the area.Municipal, agricultural, mineral and industrial ground-water withdrawals in the two basins amount to some 376,000 acre-feet per year (AFY). Dependable ground-water supplies in the two basins amounts to about 80,000 AFY. Thus, the two aquifer systems are overdrafted by approximately 296,000 AFY, 80 percent of which is by irrigation agriculture.In Arizona, ground water belongs to the owner of the land overlying the aquifer. To ensure adequate ground-water supplies, the City of Tucson has been purchasing and retiring farmlands in one of the basins. However, litigation that reached the Arizona Supreme Court led the Court to rule that the City could pump only 2.4 AFY per acre of farmland retired. The City has retired about 12,000 acres in the basin and in 1978 withdrew some 20,000 AFY of ground water for municipal use.Retiring these farmlands to secure water rights impacts on area economy and creates weed problems for farmers who own land near the retired lands. The City of Tucson budgets about $50,000 annually for weed control.A possible alternative to retiring farmlands and to cultivating crops that require heavy irrigation is cultivating arid-adapted vegetation that has economic potential. Jojoba (Simmondsia chinensis) is a shrub native to the Sonoran Desert that appears to be an economically viable arid-land crop. It needs about 1.5 AFY per acre compared with traditional crops grown in the Southwest that have average needs of 4 AFY or more.The economic value of jojoba is based on the oil extracted from its seeds. It is a unique, unsaturated oil composed of nonglyceride esters consisting almost entirely of straight-chain acids and alcohols. Such oils are difficult to synthesize in commercial quantities, and the only known natural source is the sperm whale, an endangered species.If farmers in the basin cultivated jojoba, water use could be reduced by about 2.5 AFY per acre, from 4 AFY per acre for traditional crops to 1.5 AFY for jojoba. Even if the City of Tucson had to subsidize farmers at a rate of $40 per acre for the 10 years it takes jojoba to produce economically feasible yields, the City would save more than 50 percent of the cost to purchase and retire farmlands and still be able to draw water from the basin for municipal uses.This dual use of water in the basin would permit agriculture to continue its contribution to area economy while the City could continue meeting its water needs by piping water out of the basin into the metropolitan area. However, implementing this plan would require changing Arizona ground-water laws.

Notes: Median nitrogen concentrations of ground water and water from streams in Nassau County were statistically analyzed on an areal and temporal basis and by individual well to compare concentrations of nitrogen in ground water beneath sewered and unsewered areas. The comparison is discussed in terms of hydrogeologic conditions and major point and nonpoint sources of nitrogen.Although no significant differences in median nitrate concentrations during the 25-year period of record were observed between the sewered and unsewered areas, recent (1972–76) ammonium and nitrate data suggest a relative improvement in water quality in the sewered area. This finding is based on (1) significantly lower ammonium and nitrate concentrations in stream water of the sewered area during base flow, (2) significantly lower median ammonium concentrations in ground water in the sewered area, (3) significant decreasing long-term nitrate trends in water from 8 of 13 wells in the sewered area where records were sufficient for analysis, and (4) significantly lower median nitrate concentrations near the water table beneath the sewered area.The lack of significant difference between median nitrate concentrations in the sewered and unsewered areas may be in part due to sampling bias and to the considerable length of time necessary for ground water in the sewered area, which was contaminated by cesspool and septic-tank effluent before sewering, to reach a point of discharge in a stream or bay.In addition, ammonium leached from landfills and nitrate originating from nonpoint sources such as fertilizers and animal wastes, cannot be removed by sewers and may be obscuring water-quality improvements brought about by sewering.

Notes: Analyses of several hundred ground-water samples from over 100 wells, and water table elevations measured in about 60 wells were used to determine the sources, distribution and movement of organohalide contaminants within two unconsolidated aquifers in South Brunswick Township, New Jersey. 1,1,1-trichloroethane and other organic contaminants were found to have migrated more than 3,000 feet from one source to a public supply well. Lithologic logs from existing wells and monitor wells drilled for the investigation indicate that the Old Bridge aquifer, used for domestic supplies, is underlain by a clay aquitard (Woodbridge clay?) which in turn is underlain by the Farrington sand, a very productive and heavily pumped aquifer used for public supply. Well logs and water elevations were used to define the existence and location of a breach or window in the clay formation. This feature recharges the deeper aquifer and has allowed organic contaminants to reach the Farrington after contaminating wells screened in the upper unit. A large-capacity well has been contaminated as a result. Water table altitudes were used to show the possible existence of a second breach in the clay layer that may allow organics to reach a second public supply well screened in the lower aquifer within the next few years.

Notes: At a flyash landfill in southeastern Wisconsin, dry ash has been placed directly in contact with a shallow sand and gravel aquifer. Substantial modification of ground-water quality has occurred primarily by sulfates, calcium and magnesium. However, after eight years, the contamination has spread less than 200 meters from the site in a permeable aquifer. In addition, toxic metals contained in the ash have proven quite immobile in the ground water. Fortuitous location of the disposal site in alkaline sediment upflow from ground-water discharge in a marsh appears to have limited the extent of contamination.

Notes: The hydraulic properties (hydraulic conductivity, specific storage and porosity) of coal and the sediments that surround the coal must be known or estimated to properly evaluate the environmental impact of coal strip mining on ground-water flow systems. Published and unpublished data have been summarized from five study areas in North Dakota, three areas in Wyoming, two areas in Montana and two study sites in Alberta. Coal and sand beds form important aquifers in the region. Both materials have hydraulic conductivities of about 2 × 10−6 m.s−1 and specific storage values on the order of 5 × 10−6 m−1. Aquitards in the region consist of clayey silt to clay bedrock and pebble−loam (in parts of the region). The aquitards are fractured to varying degrees resulting in a wide range of measured hydraulic conductivity values. The aquitards are, in general, 100 to 1,000 times less permeable than the aquifers. Specific storage values of the aquitard material is on the order of 3 × 10−4 m−1. The hydraulic conductivity of strip mine spoils has a six order of magnitude range with a mean of 8 × 10−7 m.s−1. Variability is due to a number of factors including spatial variation of overburden lithology, method of spoil handling and contouring and time of year during which the spoil is handled. The hydraulic conductivity of the coal shows wide spatial variability within a given mine site. Variability of coal hydraulic conductivity between mines within North Dakota is less than within a given mine. Within the Northern Great Plains the permeability of coal may increase slightly from east to west.

Notes: It was proposed that the horizontal extent of the ground-water mound is limited for finite times of recharge from strip basins even in infinite aquifers. A method of identifying the extent of the ground-water mound using solutions of the equation of flow for finite aquifers was suggested. These solutions were obtained using two different procedures of linearization, those of Baumann and Hantush, and Laplace transforms. The resulting expressions were of a general nature and the equations of Hantush for infinite aquifers were shown to follow as a special case. The range of validity of the two procedures of linearization was tested using experimental results from sand tank models of finite aquifers, available in literature. The Baumann linearization was valid (correct to within ±5 percent of experimental values) up to a water table rise less than 0.4 times the initial height of the water table. The Hantush linearization was valid (correct to within ±2 percent of experimental values) for the entire range of water table rise studied, i.e. up to three times the initial height of the water table. The Hantush procedure was thus shown to have wider applicability. However, both procedures were found to yield results which have satisfactory agreement with experimental results over larger ranges than earlier reported for infinite aquifers.The effect of variation of the horizontal extent of the recharge mound on the water table profile was studied by treating the limit of the horizontal mound itself as a parameter. The water table rise was computed using the Hantush linearization procedure for different values of the ratio B/L (B/L = 15, 20, 25, 30, 35, 40 and ∞) where 2B is the horizontal extent of the mound and 2L the width of the recharge strip. The finite extent of the ground-water mound in an infinite aquifer was given by that value of B/L for which the predicted profile was identical to that produced when B/L =∞.

Notes: As the volume of hydrogeologic literature increases, researchers are finding it more difficult to identify and locate information. The National Water Well Association's Library/Information Center is a central source of ground-water information. In addition to collecting books, journals, and reports relevant to ground-water research, the Library/ Information Center conducts both manual and computer literature searches. A bibliographic data base of hydro-geologic references is in development.

Notes: The time-consuming curve construction and, in some cases, curve matching, and the gross approximations of aquifer geohydrologic properties, can be supplanted by a simple, speedy, accurate, and inexpensive analysis of pumping test data by a handheld programmable calculator.With such calculators—in actuality, minicomputers-pumping test data can be analyzed within seconds, while the test is ongoing, and pumping test time and expense can be reduced, while still securing representative values for transmissivity and storage coefficients.

Notes: Ground-water modeling is an area of current research. As such, new techniques and applications continually evolve. In addition to being influenced by the necessity to solve certain problems, recent developments in modeling are influenced by the state of model evolution and computer capabilities.

Notes: An evaluation of sources of nitrogen in an urban area indicates that it may be difficult to distinguish effects on the quality of underlying ground water. In Nassau County two principal sources of nitrogen are human waste water and fertilized turf. The effects of these sources, combined with other sources such as domestic animals and precipitation, are such that management of one source, i.e. the removal of waste water via sewers, may be less effective than expected.

Notes: A numerical model is presented that solves the partial differential equations describing the motion of salt water and fresh water separated by a sharp interface. The areal equations are based on the Dupuit approximation and are obtained from partial integration over the vertical dimension. Finite-difference techniques are applied and the utility of several solution schemes is tested. The most efficient and accurate solution scheme uses block line-successive over-relaxation. Examples are given to: (1) test the model, (2) evaluate the Dupuit approximation, and (3) demonstrate the application to a field situation. The results show that the model is in good agreement with an analytical solution, but under severe conditions the Dupuit approximation may be inappropriate. The model is applied to a field area near Kahului, Maui, Hawaii and results extend the analysis of the problem beyond previous efforts.

Notes: Ground-water discharge was found to be the primary cause of flood peaks generated at two small wetland controlled basins in eastern Massachusetts. Within the wetlands, ground water rose rapidly following precipitation and in near synchronization with stream levels indicating a close coupling between ground water and the stream. Stream hydrographs were separated into baseflow and surface runoff by a dynamic technique which matches the hydrograph of an index well with the stream hydrograph to determine the moment of maximum ground-water discharge. Hydrograph analysis showed that for both wetlands ground water was the major component of all flood peaks and accounted for approximately 93% of the total annual discharge.

Notes: Ground-water quality has been monitored at a fly ash disposal site. The monitoring technique consists of electrical resistivity soundings, and profiles in conjunction with analysis of water samples from 33 wells on the site. In addition laboratory measurements were made on samples from the well borings to determine the changes in resistivity of each lithology as a function of water saturation, and the temperature and conductivity of the pore fluid.For a line approximately perpendicular to the ground-water flow, we were able to detail the subsurface lithology using electrical sounding, and in conjunction with the laboratory studies, it was possible to determine the vertical and horizontal extent of the contamination for that cross section.Electrical profiles, which were taken on a monthly basis, were able to monitor the changing concentration of leachate after the profiles were corrected to a common ground-water temperature.

Notes: Step-testing of wells penetrating a jointed, fractured, sometimes cavernous limestone-dolomite artesian aquifer showed characteristic patterns of extreme variation in specific capacity at different discharge rates. The application of principles developed by Jacob for well-loss determinations, and subsequent modifications by others, did not yield meaningful results. It was found that a log-log relationship between discharge and drawdown, through a large number of steps, could be used to evaluate the degree of nonlinear head losses in and near the well bore and make possible the extrapolation of drawdowns at higher discharge rates. This technique also has been used to estimate transmissivity which, in at least one instance, was confirmed by the subsequent evaluation of observation-well data by both straight-line and type-curve methods. The easy use and rapid initial evaluation of test data afforded by this method gave rise to the name “Cheat Sheet.”

Notes: An investigation of waste-migration patterns from a septic system indicates that complex patterns result from minor variations in regolith adsorptive capacity and texture, local hydrology, and possibly soil microbiology. The existence of multichemical, bifurcating plumes suggest that monitor wells arranged up and downgradient and capable of multilevel sampling are essential to adequately delineate contaminant migration in ground water. The data also indicate that sampling for a single constituent could yield misleading information about the nature and distribution of other ground-water contaminants. The ability for chemical removal by the regolith is in direct response to minor variations in silt- and clay-sized particle content and corresponds to Langmuir adsorption isotherms. Silt- and clay-sized particles are dominantly organic in origin. Minor iron and aluminum hydroxyoxides and clays are present.Substrate samples, when collected at regular intervals and analyzed for adsorbed constituents and textural variability, provide an integrated picture of the distribution of waste chemicals through time. Such samples also provide insight into the mechanics of plume configuration and flow characteristics within the regolith. The study shows that regolith adsorption data are essential to the determination of life expectancy of the regolith as a contaminant treatment system.

Notes: The Orange County Water District in Southern California imports approximately 75 percent of its supply from aqueducts drawing waters from the Colorado River and Northern California. Twenty-five percent comes from natural flow in the Santa Ana River and local precipitation. Only about one-half of the aqueduct water is treated and distributed in pipelines. The other one-half is applied to infiltration basins and ponds for ground-water recharge. This allows communities within the District to draw ground water as their major supply, which is supplemented by aqueduct water purchased after treatment by the Metropolitan Water District of Southern California. The economic advantages of ground-water recharge, as opposed to direct use of surface supplies, include eliminating water treatment, minimizing the size of pipe networks to distribute potable supplies, and reducing the requirement for storage reservoirs. However, using the basin aquifers as a reservoir to balance cyclic supply and demand creates two possible problems: excessive pumping lowers the fresh-water table below sea level, and infiltration can result in a gradual increase in the level of dissolved salts in the ground water. Sea-water intrusion has been greatly reduced by injection wells that provide a hydraulic barrier between the salt water and fresh inland water. Salt accumulation in the basin is a more serious long-term problem since the salinity in the Colorado River water is increasing. Greater use of less salty Northern California water and reducing unwanted seepage of waste waters containing high dissolved solids are two of the remedial measures being implemented at present.

Notes: A serious type of clogging occurs in wells which abstract anaerobic water from the shallow aquifer in the river region in The Netherlands. These clogged wells can easily be regenerated by means of sodium hypochlorite (15%). The figure for the specific yield after regeneration approximates to the figure on commissioning.During the pumping to waste to clear the well after regeneration, the types of reaction products present in the spent chlorine solution were investigated. From this it can be deduced that the chlorine solution added was utilised mostly for the oxidation of iron sulphides. The remainder was used mainly for the oxidation of organic material. At the same time, calcium carbonate went into solution and iron carbonate was formed. During the regeneration of a number of wells, some silt was also removed.Although information can be obtained in this way about the composition of the materials removed, it is impossible to form any concept of the nature in which these substances are present around the clogged wells.

Notes: Four case histories illustrate the various roles that digital computer simulation models can play in ground-water exploration. The case histories describe their use in evaluating aquifer parameters and characteristics, in estimating ground-water recharge, in resolving data inconsistencies, and in determining the optimal allocation of exploration funds. The models are especially useful in identifying data deficiencies and inconsistencies.

Notes: A nitrogen powered, all-glass-Teflon, continuous delivery, noncontaminating pump system is described. Continuous flow rates up to 45 gal-hr-1 (2.84 1-sec-1) are obtainable. The system was developed and field tested to sample water wells with static heads greater than 32 ft (10 m) for measurements of trace level organics. The system is equally applicable to environments such as marine, lake, and other unconfined water or fluid systems. Also, the analysis can be extended to inorganic and microbial assays in that the sample obtained is unaltered with respect to chemical, physical, and biological properties.

Notes: .A test-injection well was drilled to a depth of 3,200 feet (976 m) to determine the feasibility of deep underground injection of 50 mgd (190,000 m 3/day) ADF of secondary treated waste water in south Dade County, Florida. Geological formation samples and water samples were collected and analyzed during the drilling of the well and geophysical logging was performed in the well at several stages. At this site, the Floridan aquifer extends from a depth of 920 feet (281 m) to 1,680 feet (512 m) and generally consists of limestone which is fossiliferous in part. Water from this aquifer is brackish, with chlorides ranging from 700 mg/l at the top to 15,000 mg/l at the bottom. The strata from 1,680 feet (512 m) to 2,790 feet (851 m) are essentially nonwater-producing and act as a confining bed between the Floridan aquifer and the Boulder Zone.The Boulder Zone begins at 2,790 feet (851 m) in depth and consists of a very hard, fractured, cavernous, dark dolomite. The water from this aquifer is very similar to sea water. The subsurface temperature gradient at this site is reversed from the normal gradient, cooling with depth at an average rate of approximately 0.4° F (0.22°C) per 100 feet (30 m). The injection zone extends from approximately 2,830 feet (863 m) to 2,920 feet (891 m) in depth. Results of pumping tests indicate that the Boulder Zone is very transmissive and has a good confining bed above it.

Notes: A major potential failure mode of thermoplastic well casing is collapse. The casing may be subjected to a collapsing pressure during grouting operations, backfilling, well development or simply from lateral soil pressure. Since the strength of thermoplastic materials significantly decreases at elevated temperatures, it is important to know how casing collapse resistance varies with temperature.A series of experiments have been performed to determine the collapse resistance of poly (vinyl chloride) (PVC) and acrilonitrile-butadiene-styrene (ABS) well casing over a wide range of temperature. Results indicate that collapse resistance is inversely proportional to a function of the outside diameter-to-wall thickness ratio as indicated in the ASTM F480 standard and that collapse resistance decreases by approximately ½ psi per degree Fahrenheit increase in temperature above room temperature.

Notes: Due to chemical reactions between steel casing and stored water in capped artesian wells, the pH, Eh, TDS, major and trace ion concentrations and saturation indices can be significantly, but relatedly altered from their aquifer values. To obtain true aquifer water samples, either all the stored water must be flushed from the well or a sampling tube must be used to ensure that the water is taken from within the aquifer. Flushing time can be calculated from well dimensions and best be monitored in the field by measuring temperature and electrical conductivity.This study has been made of confined wells in a fissured limestone, but the reactions which occur are likely to be common to aquifers of different hydrogeology.

Notes: Field investigations in Paradise Valley, Arizona, conducted during 1974 and 1977, delineated areas of ground water with up to 132 mg/1 nitrate. Two alternative interpretations are developed as to possible sources of the excess nitrate. The first is a conventional interpretation identifying the use of nitrogenous fertilizers as the primary source and disposal of treated waste-water effluent as a secondary source. An alternative interpretation identifies the source as a sand and gravel unit that is interpreted as a braided-stream deposit, located about 152 m (500 ft) below the land surface. The source of the nitrate may have been NH4Cl leached from tuffs in the adjacent Superstition Mountains, subsequently oxidized to nitrate and deposited in abandoned channels of the braided-stream complex. At present, it is not possible to make a definitive choice among the possible nitrate sources.

Notes: Monitoring the chemistry of ground water near in-situ uranium leach mines is complicated by chemical variations unrelated to the mining operation that result from (1) spatial differences in the aquifer environment, and hence, in the water chemistry, (2) inconsistent or inadequate sampling procedures, and (3) errors in chemical analyses. Differences in the chemistry of water from place to place in the aquifer should be identified in pre-mining baseline studies and must be taken into account during monitoring of the leaching operation, because natural waters of chemistry different from that established at a particular well during the baseline sampling period may be drawn into the monitoring well by pumping. The most important factor in developing proper sampling techniques is the configuration of the well and pumping equipment; if the pump intake is set near the point where water enters the well, and if the pumping rate is kept low to reduce turbulent mixing of waters in the well, it is not necessary to pump a full well-bore volume before collecting a sample. Errors in chemical data can be eliminated by proper storage and handling of the samples and by careful checking of the analyses for chemical balance and eliminating the analyses that do not balance properly. Interpretation of the chemical data should be made only after assuring that these monitoring problems have been taken into account.

Notes: Abstract. Microcomputers can be a major tool for the hydrologist. Small and portable, microcomputers can be useful for the acquisition and modeling of an aquifer while on site. This would result in very low cost for computer usage and fast processing time. Their low cost makes the availability almost universal. Tests were run on the TRS-80 system using the Prickett finite difference model and the Theis equation. The results indicate that with the exception of memory storage no problems should arise. With newer generations of microcomputers core memory storage will no longer be a problem.

Notes: Polynomial approximations have been developed for the infinite series embodied in the Theis equation. These have the following advantages when programmed for use on computers or hand calculators: (1) they are easy to program; (2) they are computationally efficient; and (3) they eliminate round-off errors.

Notes: The Fort Payne Formation of Early Mississippian (Osagean) age crops out over extensive areas of central Tennessee, south-central Kentucky, and northern Alabama. Specific formation lithologies are known to have been modified locally through weathering into an artesian aquifer along the Eastern Highland Rim of central Tennessee. The shallow aquifer can be divided into two parts; uppermost is a highly permeable chert gravel zone that is in hydraulic communication with a lower zone of interconnected solution cavities within bedrock. The gravel, at depths as great as 24.4 m (80 ft), fines upward into the clay-sized chert of the upper confining bed. The lower confining bed is the Chattanooga Shale of Late Devonian to Early Mississippian age.Field and petrographic studies of the Fort Payne Formation indicate that the aquifer has developed near the base of the unit. The chert gravel portion of the aquifer has developed from silicified dolowackestones of the Beaver Creek Limestone Member and from interbedded Fort Payne dolostones. The lower portion of the aquifer occurs within preferentially weathered, silicified and non-silicified dolosiltstone.

Notes: A survey of the requirements of State regulatory agencies responsible for monitoring ground-water quality at waste disposal sites was conducted in order to gain a concise profile of monitoring practices across the country, and also to provide the basis for a monitoring manual to serve as technical background and guidance for the citizens of Minnesota. The survey considered a variety of topics including the regulatory framework for requiring monitoring, chemical parameters analyzed, recommended methods of monitoring well construction and sample collection, laboratory quality control, data interpretation, and post-operational monitoring requirements.The survey showed that most State monitoring programs are in their infancy. Many States, however, are beginning to devote serious effort and manpower commitments to the development of monitoring programs, although there is considerable divergence of opinion regarding how these programs should be conducted. Federal legislation establishing minimum performance criteria instead of detailed operating requirements for waste disposal sites will increase the need for sound water monitoring programs at these sites in the future.

Notes: The ground-water system in many of the irrigated areas of the Colorado River Basin is derived almost entirely from deep percolation of irrigation water and seepage from irrigation conveyance and tail-water collection systems. Salt pickup rates from irrigated soils in the basin vary in the different areas. Among the high salt pickup areas is the Grand Valley in western Colorado, estimated at 8 tons/acre/year. Water entering the ground-water supply from irrigation practices in the valley amounts to about 145,000 acre-feet/year and contributes about 690,000 tons/year to the salt load of the Colorado River. Samples of base-flow water from the weathered Mancos Shale aquifer in the valley vary in salinity from about 1,500 to about 9,000 mg/l with a mean of 4,100 mg/l; while water samples from alluvial aquifers range from 305 to 124,000 mg/l with a mean of about 11,500 mg/l. Base-flow returning to the river in the drains and washes has concentrations that average about 4,200 mg/l.Water losses and quantities of irrigation return flows can be reduced by improving farm irrigation efficiencies and by partial or complete lining of canals, laterals, and ditches. Increasing on-farm irrigation efficiency through system improvements and irrigation scheduling is the most cost-effective measure. However, achievement of higher efficiencies will require changes in water laws to encourage conservation and revised water pricing policies that discourage waste.

Notes: .Calcium hydroxide ground-water seepage, highly mineralized, with a pH measured as high as 12.7 has been discovered in the Yarmouk Valley of Jordan. The origin of the seepage is rainfall recharge through over 100 meters of portlandite-rich rock. The portlandite [Ca(OH)2] was formed by thermal metamorphism of calcite due to (spontaneous) combustion of organic-rich marl and limestone. The pH is believed to be the highest ever reported for natural ground water.

Notes: Due to the growing demand for bottled mineral waters, a study was undertaken to determine the quality of fourteen different brands of still and sparkling bottled waters. Objective testing showed a wide variance in taste as waters have different tastes and individual preferences are the rule. By analytical means, the mineral content of most of the tested waters met U.S.E.P.A. standards; however, some samples had unacceptable levels of sulfate, hardness, and other constituents. Cost comparisons show a wide variation in price, with all the tested waters many times more than normally available tap waters.

Notes: Partial differential equations may be used to describe a large number of problems in ground-water hydrology. Without a solution, however, these equations are of little value. Only a simplified subset of the general equations can be solved by analytical means, and these often describe idealized situations that are limited in application. Numerical solution of these equations using high speed digital computers offers a logical alternative.

Notes: The low organic concentration and high specific surface area that characterize ground-water recharge environments allow biofilms to predominate microbial kinetics. Consideration of the kinetics of substrate utilization and growth of biofilms indicates that microbiological activity occurs very near the injection well. The aggregate substrate expressed, for example, as chemical oxygen demand, can be considered the primary substrate; the biofilm's growth is supported through the utilization of the aggregate primary substrate. Individual trace organic compounds, none of which could support biofilm growth alone, are utilized as secondary substrates. Although biodegradable, secondary substrates that have slow utilization kinetics will pass through the biologically active zone undegraded. Field data from the ground-water recharge project in Palo Alto, California, illustrate that naphthalene and heptaldehyde are biodegraded, while other compounds, such as chloroform and chlorobenzene, pass through the biologically active zone without biodegradation.

Notes: The expression 〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:0017467X:GWAT137:GWAT_137_mu1"/〉 is a handy tool for predicting aquifer parameters using all the drawdown and recovery data obtained during step-drawdown tests or periods of cyclic or intermittent pumping.For inefficient wells the expression 〈displayedItem type="mathematics" xml:id="mu2" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:0017467X:GWAT137:GWAT_137_mu2"/〉 fits pumping wells better. The data from conventional step-drawdown tests of pumping wells can be used to obtain T, C, and y. If the data fail to fit the ideal, they may be used to interpret local hydrologic conditions.

Notes: Grouting of water wells is commonly done to increase the well life and to protect the water supply. When Portland cement-based grouts cure, a by-product of the process is heat of hydration which causes increased temperatures in the vicinity of the well casing. Since thermoplastic casing materials lose significant strength at elevated temperatures, it is important to know what range of temperature increases might be associated with the grouting operation.A series of experiments has been performed to determine these temperature increases. Wells were simulated in the laboratory and temperatures monitored throughout the casing-grout-soil system. Results indicate that under certain circumstances the casing temperature could increase by as much as 180° F; however, for nominal 1 1/2-inch grout thicknesses, casing temperature increases between 17° F and 26° F were measured.

Notes: Through the years the Theis equation has played an important role in ground-water hydrology. Comparison of experimental pumping-test data with this theoretical curve by graphic means has been a standard method of determining aquifer transmissivity and storage. The purpose of this paper is to present a technique and an algorithm to automatically fit experimental pumping-test data to the Theis equation by obtaining the “best” transmissivity and storage in the least squares sense through the use of sensitivity analysis. The automated fit for pumping-test data developed in this work should be a useful tool for the ground-water hydrologist. Use of the technique is simple, quick, and inexpensive, and has the advantage of always being objective. As a measure of the error in fitting, the rms deviation in drawdown is calculated for the “best” transmissivity and storage.

Notes: The assumptions inherent in the theoretical analysis of constant drawdown overflow tests are difficult to achieve in practice. This paper shows that, even if there is a restriction in the flow which causes some delay in the achievement of the constant drawdown condition, the theoretical discharge curve is followed once the constant drawdown condition is reached. Recovery tests following overflow are also examined and it is shown that the discharge used in the calculation should be the discharge at the instant that the test is stopped. Further, it is demonstrated that if well and formation losses occur, the aquifer response is distinctly different from that of the theoretical analysis.A brief description is given of an alternative method of analysis using a numerical model. A preliminary study of a field test yields promising results.