ALBERT

Notes: Specific electrical resistivity of natural waters contains information on their genesis. The authors propose to conduct mass and regime observations of this parameter in river and stream beds.The electrical resistivities in streams flowing from under a glacier reveal details formed at the same time as the glacier. Observations in the beds of big rivers show a gradual increase in water salinity overlain by reductions by inflowing glacial waters.The diurnal and annual trend of changes in the electrical conductivity of water associated with the change in the balance of glacial and ground waters has been established near to glaciers.Resistivity observations help to locate discharge sites of sub-permafrost waters, for water.

Notes: The VLF response of laterally inhomogeneous and anisotropic models is calculated numerically using the finite element method.Some results are presented for a slab model in terms both of the polarization parameters, i.e., the tilt angle and ellipticity of the magnetic polarization ellipse, and the amplitude ratio |Hz/Hx|.On the basis of both the ellipticity and the tilt angle, it is possible to discriminate between a poor conductor and a good one. The direction of the dip can be determined from the anomaly profiles of all diagnostic parameters. The effect of the conductive overburden is most noticeable on the ellipticity profile: one observes attenuation for a poor conductor and “negative attenuation” for a good conductor. The anomaly profiles for anisotropic cases are consistent with the ones of the isotropic cases.

Notes: Master curves are presented for three-layer earth-sections, the electrical resistivity in the intermediate layer of which has a linear variation with depth. A new approach is proposed to interpret the sounding data with the help of RMS difference in apparent resistivity values.

Notes: Basic Laterolog devices employ a measure-current focusing technique to provide well logs of formation resistivity that feature sharp vertical definition combined with a depth of investigation much improved over those of normals of comparable spacings.To develop the concept of measure-current focusing, a disk-electrode arrangement analogous to a guard-ring capacitor is considered first, leading finally to consideration of a real sonde in a cylindrical borehole. In the latter, auxiliary currents are adjusted to maintain substantially at zero the vertical potential gradients above and below the central measure-current electrode; this has the effect of focusing the measure-current beam.However, prediction of sonde responses on the basis of current patterns can in some cases be misleading. Indeed, for a given Laterolog array, one may use a (reciprocalmode) current pattern radically different from the one defined by the basic (direct-mode) measure-current focusing scheme and still obtain the same resistivity measurement. This feature is illustrated for Laterolog 3 by use of transfer impedances, and demonstrated for certain more general cases using the reciprocity theorem.Comparisons of Laterolog responses across typical thin beds, both non-invaded and invaded, with those of normal devices of a comparable range of spacings illustrate the improved vertical resolution obtained with Laterolog devices. The examples also show the different magnitudes of the auxiliary currents (thenceforth designated “bucking”- or “focusing” currents) used in the direct and reciprocal modes and illustrate how these currents must continuously vary in order to maintain the focused condition as the sonde moves through the bed.Finally, briefly considering possible applications of Laterolog-type arrays in surface prospecting, it is shown that a one-dimensional array laid out on the surface does not provide the same degree of measure-current focusing as is obtained in a borehole. Some improvement is obtained with a combination of two crossed linear arrays. Much more is obtained using a circular array.

Notes: Inferior reflection quality in the Gulf of Suez at the target depth interval is attributable in part to surficial multiple reflections. An excellent example of the latter is observed on a typical seismic line in the northern portion of the Gulf. An increase in prominence of the multiple reflections appears associated with decreasing depth to a dipping highvelocity layer.Inversion of a second-order polynomial time-distance function, fitted to the observed refraction onset time-distance values, gives the velocity-depth function for sediments between the water bottom and a high-velocity layer. Velocities thus determined increase non-linearly with depth from a value near water velocity at the water bottom. Depths to the high-velocity layer are obtained from the associated head-wave linear time-distance function and by ray tracing in the overlying sediments.As the high-velocity layer approaches the water bottom from sub-water depths exceeding 0.6 km to a depth of 56 m, intensity of the multiple reflections increases to the extent of completely dominating individual records to a time of at least 3 s. The estimated plane-wave normal-incident reflection coefficient at the top of the high-velocity layer increases with decreasing depth to this layer, approaching 0.5 at the shallowest depth. This strong reflection coefficient further substantiates the existence of multiple reflections between the high-velocity layer and water layer. However, existence of water-layer multiples cannot be ruled out. The estimated water-bottom reflection coefficient is approximately 0.3, a substantial value. Multiple reflections of considerably less intensity are apparent where the high-velocity layer is deepest, and it is likely that such are waterlayer multiple reflections. Unfortunately, water-layer multiple reflections and multiple reflections between the water surface and high-velocity layer cannot be separated by their coincidence with time-distance (normal moveout) curves, the configuration of each visibly matching the curves equally well.

Notes: Seismic exploration techniques which have been developed for oil prospecting contribute a valuable means for surveying coal measures. Since the object is to detect minor faults within the first 1500 m, rather than structural features at great depth, the new technique requires much higher resolution in the early part of the traditional seismic cross-section.Higher resolution means broader bandwidth, which must be obtained by extending the high frequency end of the spectrum. This is achieved (a) by scaling down the explosive charge size and using single geophones instead of groups, and (b) by reducing the sampling interval in space and time. Noise which does not scale down includes static anomalies and ground-roll. The consideration of statics, ground-roll, and the high-cut filtering effect of the near surface layers forces the use of deep shot holes and, where possible, deep detectors. This approach is confirmed by experiments and has been implemented on a regular basis in production.It is demonstrated that the present technique will clearly resolve faults with a vertical throw of about 5 m at 800 m depth.

Notes: Correlations between longitudinal velocities and rock mechanic parameters such as fracture frequencies and “Rock Quality Designation” (RQD) values have been studied, based upon velocity data from various rock types and different geographical locations.The dispersion of values at different sites studied is on average ± 0.8 cracks per meter and for the RQD values ± 3.5%. Within sites the dispersion of individual values relative to the average for the site is ± 1.0 – 2.0 cracks per meter and ± 2 – 6% for the RQD values.The deviations are rather moderate, especially when considering the variation of rock type involved in the studies: amphibolite, granite, gneiss, meta-anorthosite, pegmatite, porphyry, quartzite, and mylonite. The studies thus confirmed earlier assumptions that there is a strong correlation between longitudinal velocity and fracturing and that the velocities can be used to give rather accurate predictions of the quality of rock masses for construction purposes. The accuracy of the predictions increases if the velocity level of the more competent rock is taken into account.The correlation between velocity and fracturing is related to jointed but unweathered igneous and metamorphic rock and cannot be applied without introducing serious errors to a site where the rocks present a higher degree of alteration and weathering.Comparisons between rock permeability and longitudinal velocity proved that a more reliable general correlation is not likely to be found.By comparing the elastic moduli Edyn, μ, and k with ø, Vp/V8, and k/μ, indications have been obtained where the optimum rock conditions for a certain site are to be encountered. This has been verified by a similar comparison where the elastic moduli have been replaced by fracturing values.The value of the longitudinal velocity as a means to evaluate rock quality increases if the position of the velocity in the range of the Poisson's ratio has been established.The average relationships between longitudinal velocities and the corresponding elastic moduli proved to be:The values from each site differ from the average values with about ± 2 GPa for Edyn and about ± 1 GPa for μ and k.It was confirmed that in igneous and metamorphic rocks longitudinal velocities ≤ 4000 m/s generally indicate rock masses where heavier tunnel support will be needed. This velocity limit corresponds to an average fracture frequency of about 10 cracks per meter and a RQD value of about 65 %. The prediction of the tunnel reinforcements needed at a particular site will, however, be improved if the general velocity level of the more competent rock is considered.

Notes: The Minimum Entropy Deconvolution (MED) technique of Wiggins (1977) represents a breakthrough in deconvolution and will undoubtedly find wide application in many fields. MED does not require any phase assumptions about the disturbing function and seeks a deconvolved output which consists of the smallest number of large spikes consistent with the input data.The efficiency of MED is much improved when an exponential transformation is incorporated into the algorithm. This is particularly true when the input traces contain additive noise. In this case the noise suppression characteristics of MED are considerably enhanced by the transformation and the identification of smaller spikes is improved. This paper also presents a kurtosis criterion of simplicity rather than the varimax norm introduced by Wiggins. It appears that for a multiple trace input the kurtosis measure leads to improved results.

Notes: Long leg multiples can be suppressed by a method which provides an alternative to weighted common-depth-point stacking and multichannel stacking filtering. The suppression is achieved by coherency weighting whereby the time-dependent weighting factor decreases as the semblance of the multiple reflections increases.The algorithm of the method is described. Its efficiency is discussed in relation to the input data and results of its application to marine seismic data are presented.For practical application, the stacking velocity of the multiples has to be known. As the process is based on stacking velocities, different types of multiples can be handled, for instance water-bottom multiples or internal multiples. The parameter analysis shows that the degree of multiple suppression can easily be controlled by adapting the parameters of the procedure to the field conditions.During the suppression of multiples, the primaries are saved according to the moveout differences between the two. The non-linear behaviour of the process causes signal suppression and distortion effects, which have to be corrected by AGC normalization and low-pass filtering.Among the various applications available, only the suppression of long leg water-bottom multiples is treated here. The results show that their suppression on the basis of moveout differences is efficient even when standard length streamers are used in regions with water depth of up to 1500 m and more, if the stacking velocity of the primaries is about 10 to 20% higher than that of the multiples. Even if those parts of the primaries which are masked by the multiples are suppressed in the individual common-depth-point gathers by the procedure, the remaining primaries in the AGV stacked section are largely uncovered by the multiple suppression.

Notes: Investigation of fluctuating earth-currents has led to a simple method of eliminating the noise superimposed on the signal in geoelectrical resistivity surveys. The similarity of the potential fluctuations, simultaneously measured at different locations, is used to calculate the direction and magnitude of the potential gradient. Contour maps of equipotential lines were made, both from disjointed gradient measurements using a numerical approximation method and from a network of measured potential differences. These contour maps were compared with potential fields calculated for simple homogeneous models. A good fit was obtained with the field of a conducting plate. When this is subtracted from the measured field, the result is a map that shows anomalies that can be correlated with geological structures.

Notes: The calculation of potential field anomalies on different levels below the measuring level permits to localize the singular points related to the sources of anomalies.It is possible to achieve considerable improvement of the resolution of this method〈list xml:id="l1" style="custom"〉1) filtering of analytical downward continuation,2) the use of the magnitude of the gravitational vector,3) calculation of physe changes.The numerical examples confirm these assumptions.

Notes: For constrained inversion of potential field data within the framework of generalized inversion an analysis of data error variances leads to confidence limits for the model parameters. For that purpose Pseudo-hyper-ellipsoids can be used to describe the nonlinear behaviour of the given inverse problem, and upper and lower bounds can be added to those parameters of which some independent knowledge is available. A gravity example is treated to show the application of the method.

Notes: Existing techniques of deconvolution of gravity anomalies are principally based on upward and downward continuation of measured fields. It can be shown that a unique set of linear filters, depending only on geometrical parameters, relates density distribution at a given depth to gravity measured on the surface. A method to compute the filter coefficients is developed. Very accurate reconstitution of theoretical models of intricate shape, prove the validity of the linear relationship. One of these sets of linear filters is applied to a field case of underground quarries.

Notes: Model tank inline resistivity profiles with Wenner and two-electrode systems obtained over two vertical, parallel, infinitely conducting dykes submerged in water show that the two-electrode resistivity anomalies resolve better than the four-electrodes Wenner. anomalies. In contrast, the broadside resistivity anomalies obtained with a Wenner configuration resolve much better than those obtained with two-electrode configuration over an identical ground structure.

Notes: Inspired by the linear filter method introduced by D. P. Ghosh in 1970 we have developed a general theory for numerical evaluation of integrals of the Hankel type:〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR876:GPR_876_mu1"/〉Replacing the usual sine interpolating function by sinsh (x) =a· sin (ρx)/sinh (aρx), where the smoothness parameter a is chosen to be “small”, we obtain explicit series expansions for the sinsh-response or filter function H*.If the input function f(λ exp (iω)) is known to be analytic in the region o 〈 λ 〈 ∞, |ω|≤ω0 of the complex plane, we can show that the absolute error on the output function is less than (K(ω0)/r) · exp (−ρω0/Δ), Δ being the logarthmic sampling distance.Due to the explicit expansions of H* the tails of the infinite summation 〈displayedItem type="mathematics" xml:id="mu2" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR876:GPR_876_mu2"/〉 ((m−n)Δ) can be handled analytically.Since the only restriction on the order is ν 〉 − 1, the Fourier transform is a special case of the theory, ν=± 1/2 giving the sine- and cosine transform, respectively. In theoretical model calculations the present method is considerably more efficient than the Fast Fourier Transform (FFT).

Notes: For detailed determination of refractor velocities of in-line reversed profiles, two principally different systems have been employed, the ABC method and Hales's method. The two systems differ in the travel-path arrangements used. The more conventional approach to the problem, the ABC method, makes use of critically refracted rays converging on a common surface position, while Hales's method deals with the common position on the refractor surface from which critically refracted rays diverge towards the ground surface.Because of the travel-path system used, Hales's method has proved to be particularly applicable to high-relief structures and to cases where the refractor lies at considerable depth. Some of the ambiguities in more commonly used interpretation techniques can be solved by Hales's method.Some attention has also been paid to errors caused by non-critical refractions and to the diffraction problem.

Notes: In contrast to the conventional deconvolution technique (Wiener-Levinson), the spike-, predictive-, and gap-deconvolution is realized with the help of an adaptive updating technique of the prediction operator. As the prediction operator will be updated from sample to sample, this procedure can be used for time variant deconvolution. Updating formulae discussed are the adaptive updating formula and the sequential algorithm for the sequential estimation technique. This updating technique is illustrated using both synthetic and real seismic data.

Notes: A numerical technique is developed to solve the three-dimensional potential distribution about a point source of current located in or on the surface of a half-space containing arbitrary two-dimensional conductivity distribution. Finite difference equations are obtained for Poisson's equations by using point- as well as area-discretization of the subsurface. Potential distributions at all points in the set defining the half-space are simultaneously obtained for multiple point sources of current injection. The solution is obtained with direct explicit matrix inversion techniques. An empirical mixed boundary condition is used at the “infinitely distant” edges of the lower half-space. Accurate solutions using area-discretization method are obtained with significantly less attendant computational costs than with the relaxation, finite-element, or network solution techniques for models of comparable dimensions.

Notes: The Wiener filtering scheme is obtained for a multichannel complex system utilizing the “block-Toeplitz” property of autocorrelation matrix. A numerical example is given to elucidate the application of the filter design. The study also outlines Burg's maximum entropy method to include the multi-channel complex realm.

Notes: An algorithm for separation of signals according to their coherency is proposed. The algorithm, called Superstack, is used on common depth point data after normal moveout corrections have been applied. The algorithm can be regarded as an iterative stacking procedure. After each stack, input values are changed depending on the consistency of the output of the previous stack.The Superstack algorithm is able to provide better separation of signals showing a different degree of horizontal consistency (coherency) than the normal horizontal stack.All noise signals in a CDP-gather may be assumed to show less horizontal consistency than the primary reflections. On this basis the algorithm will give an improved primary/multiple and an improved primary/noise ratio.The Superstack is very general, should not be especially expensive in terms of computer time, and can easily be implemented in routine processing.

Notes: Computations of the time-domain electromagnetic response of a multi-layered earth have been carried out for different source-receiver coil systems. The primary excitation is a train of half-sinusoidal waveforms of alternating polarity. The conversion into the time-domain involves Fourier series summation of the matched complex mutual coupling ratios of the layered earth models computed by a digital linear filter method. As an example, the response of a perpendicular coil system on the ground surface for two source-receiver separations has been presented for a five-layer earth model. This has been compared with the responses of homogeneous, two-layer, three-layer, and four-layer models.Next, the investigations have been extended to study the problems of equivalence of three-layer models, the intermediate layer of which is either conductive or resistive. For an intermediate conductive layer (H-type), the studies show that in the early portion of the signal the interpretation of a true three-layer earth is possible to some extent, whereas the ambiguity due to equivalence persists in the late samples. On the other hand, for an intermediate resistive layer (K-type), the three-layer earth and its equivalent model cannot be distinguished from each other over the entire sampling period.On the basis of a computational approach, equivalence has been empirically established as √h/ρ=constant for H-type earth-sections, and as h2ρ=constant for K-type earth sections, where h and ρ are respectively the thickness and resistivity of the intermediate layer.

Notes: It has been found that the Wiener-Hopf least-squares method is a very successful tool for the determination of resistivity sounding filters. The values of the individual filter coefficients differ quite appreciably from those obtained by the Ghosh procedure. These differences in the filter coefficients, however, have only a negligible effect on the output of the filter. It seems that these differences in the coefficients correspond to a filter function of a rather narrow frequency band around the Nyquist frequency, which is only very weakly present in the input and output functions.

Notes: A method is presented to derive approximate versions of the wave equation which allow finite-difference migration for very steep dips (〉 50°). It is shown that for conventional finite-difference schemes, in addition to the dip limitation, the maximum acceptable frequency should be specified. A finite-difference migration technique is proposed in the frequency domain. It is derived that finite-difference wave field extrapolation in the frequency domain consists of a space-variant convolution procedure for each frequency component, the space-variance being defined by the lateral variation in the velocity.Finally it is shown that with finite-difference migration, particle velocity data can be easily obtained from pressure data.

Notes: The relationship between two finite-difference schemes (15° and 40°) and the Kirchhoff summation approach is discussed by using closed form solutions of Claerbout's approximate versions of the wave equation. Forward extrapolation is presented as a spatial convolution procedure for each frequency component. It is shown that downward extrapolation can be considered as a wavelet deconvolution procedure, the spatial wavelet being given by the wave theory. Using this concept, a three-dimensional model for seismic data is proposed.The advantages of downward extrapolation in the space-frequency domain are discussed.Finally, it is derived that spatial sampling imposes an upper limit on the aperture and a lower limit on the extrapolation step.

Notes: A least squares estimation procedure is used to estimate the pulse-shape, amplitude function, and arrival time of multiple reflected signals. The estimates of the multiple reflections are subtracted from the data which are subsequently processed by standard methods. The estimation algorithm is applied continuously along the seismic line for each shot point or common datum point. In some cases it is advantageous to apply a pulse-shaping filter prior to using the estimation algorithm.The effectiveness of the technique is demonstrated by studying common shot point gathers, velocity analyses, and stacked sections derived from field data.

Notes: From gravity it is well known how to determine the excess mass and the horizontal center of mass of the disturbing body. We show that a magnetic body—under rather weak assumptions—possesses excess magnetization and centers of magnetization (both horizontal and vertical), which can be uniquely determined from measurements. It also follows that the vertical center of mass can be uniquely determined from the vertical derivative of the gravity field.

Notes: Work carried out in several volcanic areas in Armenia has led to a combination of geophysical methods for hydrogeological problems. Prospecting of interlava and sublava water flows is done by electrical profiling and vertical electrical sounding. When mapping the relief of sublava water-resisting rocks, the electrical sounding (ES) method is widely used. This is based on the evaluation of lava resistivity. The method discussed allows to determine the most probable value of this parameter, by using statistical methods.

Notes: Mallick and Roy solved the problem of determining the apparent resistivity function for a three-layer stratification in which the central layer is a transition layer with linear change of the conductivity with depth. In the present paper the problem is solved for a transition layer with linear change of the resistivity with depth, a type of change that seems to be more common in nature than the type considered by Mallick and Roy. The solution is extended to layer stratifications involving an arbitrary number of transition layers and of homogeneous layers. The solution is given in the form of a modification of the recurrence relation that was derived by Pekeris for homogeneous layers.

Notes: A numerical method is proposed for solving the problem of steady current flow. The electrodynamic model is replaced by the equivalent stationary charge distribution obtained by Poisson's analysis, in which the surface integral equation for field intensity is reduced to a set of simultaneous linear algebraic equations by means of the method of sub-areas. The solution of the set allows the calculation of an approximation for the charge density distribution on the discontinuity surfaces of conductivity.The method is valid for complex conductivities, whereby the apparent phase shift of IP can be calculated from the complex potential or field intensity. The phase shift anomaly calculated as an application is very similar to the corresponding frequency effect anomaly.The method allows the calculation of the mise-à-la-masse effect as a solution to a potential problem, in which the primary current electrode is located within the body to be surveyed.

Notes: A new approach is presented for the suppression of multiples reflected at the surface of a horizontally layered fluid or elastic medium, recorded at non-zero offsets from the source. The scheme used is to extract the effect of the free surface in the frequency-wavenumber domain and then to replace this surface by a non-reflecting boundary. The multiple suppression operator requires a detailed knowledge of the source time function and the elastic properties of the medium between the source and the surface.For a stratified fluid or a liquid layer overlying a stratified elastic medium, complete multiple suppression can be achieved with noise free data. If only the vertical component is available for an elastic medium an approximate approach may be used which removes most of the multiple energy. Good results may be achieved with this multiple suppression scheme in the presence of noise. The method is designed to be used before records are stacked in a CDP gather.

Notes: This paper deals with a new method of quantitative interpretation of induced polarization soundings in the frequency-domain. From the general expression of the apparent frequency-effect for soundings carried out on a multi-layered earth the application of Hankel's inversion theorem allows to introduce a new function, called here the “frequency-effect transform”. The new interpretation method consists of two steps: 1) the inversion of field data to obtain the frequency-effect transform graph and 2) the analysis of this graph to derive the layering parameters. The first step is performed by means of a slightly revised version of a simple numerical procedure, previously suggested by the author for the inversion of d.c. resistivity sounding data. The second step is carried out by a complete curve-matching procedure, applied directly on the transform graph. This implies suitable master curves, whose preparation doesn't meet all the mathematical difficulties which are present when preparing master curves of the apparent frequency-effect function.

Notes: Theoretical seismograms for an explosive source in a multilayered elastic medium are constructed by Fourier synthesis and plane wave superposition. The calculation scheme which builds up a reflection matrix layer by layer in the frequency and wave number domain allows the inclusion of attenuation and a choice of the level of internal multiples in each layer.Comparative calculations of theoretical seismograms for an elastic model and in the acoustic approximation, neglecting shear, show that the main differences arise at large offsets. The inclusion of shear waves leads to lower reflected P wave amplitudes at the end of the spread but only small amounts of converted phases.

Notes: The exact localization of subterranean cavities and the determination of their dimensions is very important for the planning of geotechnical and mining activities. It is a complicated geophysical task often at the limit of detection. Nevertheless geophysical investigation is the only alternative to a dense and expensive grid of boreholes. This report tests the usefulness of geoelectrical resistivity methods for cavity detection under some new aspects. The basis for evaluation was a theoretical analysis of different conventional and focussing measuring arrays and of special arrays for a geoelectrical research between two boreholes.The limit of detectability of a cylindrical cavity of defined cross-section and depth was calculated for the different measuring arrays on the basis of computation of the apparent resistivity ρa. Furthermore, the influence of possible errors (current supply of the electrodes and the distance between the electrodes) is discussed for focussed systems.The second part of the article is directed at the behaviour of the apparent resistivity ρa, the disturbing potential δVd caused by the cavity and the normal potential δV0 of the measuring array all in relation to a homogeneous earth. Some new results are presented.In the last part of the article theoretical results are compared with some field measurements.

Notes: Two different methods for the construction of an approximation to bicubic splines for interpolating irregularly spaced two-dimensional data are described. These are referred to as the least squares line (LSL) and linear segment (LINSEG) construction procedures.A quantitative test is devised for investigating the absolute accuracy and efficiency of the two spline interpolation procedures. The test involves (i) laying of artificial flight lines on the analytically known field of a model, (ii) interpolation of field values along the flight lines and their subtraction from the original field values to compute the residuals. This test is applied on fields due to four models (three prism models and one dyke model) placed at different depths below the flight lines, and for each case the error estimates (the mean error, the maximum error and the standard deviation) are tabulated.An analysis of the error estimates shows in all cases the LSL interpolation to be more accurate than the LINSEG, although the latter is about 50% faster in computer time. The relative accuracy and efficiency of the LSL interpolation is also tested against a recent method based on harmonization procedure, which shows the latter to be more precise, though much slower in speed.

Notes: The blind zone problem is examined with a view to provide a simple means of solving the problem in the general case of arbitrary number of refraction layers constituting the overburden to the masked layers. Considering the first arrival refraction interval corresponding to the masked layer which reduces to zero under blind zone conditions, a method to solve the problem is presented. Derivation of the critical distance expression is also included and convenient solutions to compute the thicknesses of the blind zone and its immediate overlayer are worked out. Based on test calculations on some known instances, the efficacy of the method is illustrated. A Fortran program for use when large numbers of refraction layers are involved under the overburden or when more than one masked layer is encountered is available from the authors.

Notes: In the mathematical theory of seismic signal detection and parameter estimation given, the seismic measurements are assumed to consist of a sum of signals corrupted by additive Gaussian white noise uncorrelated to the signals. Each signal is assumed to consist of a signal pulse multiplied by a space-dependent amplitude function and with a space-dependent arrival time. The signal pulse, amplitude, and arrival time are estimated by the method of maximum likelihood.For this signal-and-noise model, the maximum likelihood method is equivalent to the method of least squares which will be shown to correspond to using the signal energy as coherency measure. The semblance coefficient is equal to the signal energy divided by the measurement energy. For this signal model we get a more general form of the semblance coefficient which reduces to the usual expression in the case of a constant signal amplitude function.The signal pulse, amplitude, and arrival time can be estimated by a simple iterative algorithm. The effectiveness of the algorithm on seismic field data is demonstrated.

Notes: A general treatment of end corrections in gravity and magnetic modeling is presented. The well-known 2-D formulae of Talwani and Talwani and Heirtzler become slightly changed to represent a 2 1/2–D body, i.e. a body of polygonal cross section with the tails In the strike direction cut off.

Notes: Geophysical methods can be applied to investigate the harmful effect of man's activities on the environment: the study of specific electrical resistivities and natural electric fields of filtrational origin makes it possible to control the penetration of exogenic pollutants into soil as well as desalinization and secondary salinization of soils; electrometric and seismometric methods allow to observe the groundwater level near water reservoirs thus evaluating the harmful effect of backing up natural groundwater flow; contrasting properties of bedrocks and rocks in a landslide body permit application of seismic and electrical prospecting methods. Observation of the changes in specific electrical resistivities with time on the slopes of quarries is an effective method of assessing slope stability and predicting landslide hazard.Mining activities, groundwater pumping, and oil extraction are the main causes of endogenic pollution of geological medium; surface and borehole geophysical methods make it possible to assess vertical and horizontal displacements of the interfaces between salty and fresh subterranean waters resulting from an extensive exploitation of water supply sources; activation of geodynamic processes associated with mining activities is determined from the data of ‘regime’ electrometric, seismometric, gravimetric, and inclinometric observations. Geophysical methods are applied widely for studying the intensification of physico-geological processes under the impact of man. A specific object of electrometric investigations is degradation of permafrost and intensification of karst processes in soluble rocks.The principal advantage of geophysical investigations lies in the possibility of creating high spatial and temporal density of observations permitting an extensive employment of statistical methods in the assessment of the impact of man on the geological medium.

Notes: An economic and precise processing system for microgravity surveys is presented. Three computer processing modes covering areal ground and underground measurements, measurements in vertical shafts, and measurements of vertical gravity gradients with a 3 m high tower are dealt with.Diagrams for manual calculation of gravity effects of prismatic walls, vertical shafts, and horizontal galleries, as well as programs for calculation of accurate terrain corrections and corrections for gravity effects of bodies with complicated ground-plan are proposed.The method of processing microgravity data is two to three times quicker than any traditional way, with maximum accuracy preserved in resulting gravity micro-anomalies. Applications from the field of mining geophysics and archaeology are included.

Notes: Few studies have been performed on the occurrence of enterovirus contamination of ground water. In this study, 99 ground-water samples were examined for the presence of enteroviruses, total bacteria, fecal coliforms, and fecal streptococci by standard methods. Enteroviruses were isolated from 20% of the samples. Viruses were isolated from 12 samples which contained no detectable fecal organisms per 100 ml. No statistical correlation between presence of virus and bacteriological indicators could be determined. The widespread failure of current bacteriological standards to indicate the presence of potentially pathogenic enteroviruses in ground water is an area of concern that requires more study.

Notes: Flow to wells in leaky artesian aquifers is intimately related to changes in aquitard storage, well storage capacity, and degree of well penetration. The manner and extent to which these and other factors affect water levels may be evaluated with aquifer test data. Families of type curves describe time-drawdown in the aquifer and aquitard under complex aquifer and well penetration conditions. Analysis of leaky artesian aquifer test data is possible with the array of equations derived largely in the 1950's through 1970's. Erroneous data analysis will result unless complicating factors are fully recognized and taken into account. A review of leaky artesian aquifer test evaluation methods is presented in this paper together with the field application of selected methods to foster greater use of current theories.

Notes: Illinois aquifers furnish approximately 233 mgd (10.2 m3/s) of water to 677 public-water supplies outside the six-county area of northeastern Illinois. Ground water is usually obtained from sand-and-gravel deposits in the glacial drift or from limestone or sandstone formations in the underlying bedrock. The most favorable ground-water conditions are found in the northern third and the southern tip of the State, while, elsewhere, major aquifers are sand-and-gravel deposits of the Mississippi, Illinois, buried Mahomet, Wabash, Ohio, Kaskaskia, and Embarrass valleys.A brief review was made of data and information in the State Water Survey files for each public ground-water supply, and an assessment was given as adequate, marginal, or deficient, in terms of present demands. Twenty-four supplies were studied in greater detail, including calculations of aquifer sustained yields. The study indicated that 39 supplies were marginal and four were judged deficient in meeting current demands. The majority of the marginal and deficient supplies are located in the central third of the State; but so are most of the supplies (outside of north-eastern Illinois).The study represents the first of a three-part plan to: (1) define problem areas and determine priorities for studies in greater detail, (2) conduct regional studies, including test drilling, in problem areas to determine how great the water resource is, and (3) determine the water resource alternatives available to public ground-water supplies that are found to be inadequate.

Notes: An industrial waste liquid containing organonitrile compounds and nitrate ion has been injected into the lower limestone of the Floridan aquifer near Pensacola, Florida since June 1975. Chemical analyses of water from monitor wells and backflow from the injection well indicate that organic carbon compounds are converted to CO2 and nitrate is converted to N2. These transformations are caused by bacteria immediately after injection, and are virtually completed within 100 m of the injection well. The zone near the injection well behaves like an anaerobic filter with nitrate respiring bacteria dominating the microbial flora in this zone.Sodium thiocyanate contained in the waste is unaltered during passage through the injection zone and is used to detect the degree of mixing of injected waste liquid with native water at a monitor well 312 m (712 ft) from the injection well. The dispersivity of the injection zone was calculated to be 10 m (33 ft). Analyses of samples from the monitor well indicate 80 percent reduction in chemical oxygen demand and virtually complete loss of organonitriles and nitrate from the waste liquid during passage from the injection well to the monitor well. Bacterial densities were much lower at the monitor well than in backflow from the injection well.

Notes: Abstract. This investigation was to determine whether data on irrigation-well registration forms as reported by well drillers can be used in hydrologic studies. Transmissivity maps were prepared for Hamilton County, Nebraska using only specific capacity values computed from yield and drawdown data, as reported on irrigation well-registration forms. On one map each control point was the mean of the transmissivity values calculated for all wells in a section. On a second map each control point was the mean of the means for four contiguous sections sharing a common corner. The second map was similar to that of a previously prepared map based on control point values computed from specific capacities of selected wells, test hole logs, and geologic interpretations. These results suggest that reported registration data for a given area have a normal population distribution. In situations where individual data are unverified the data base can be treated as samples of a population where the mean of the means of several samples for adjacent areas is representative of actual field conditions.

Notes: A new method of testing anisotropic, inhomogeneous multiple aquifer systems developed by the author makes use of small diameter bore construction techniques and enables simultaneous testing of superposed aquifers and aquitards (aquicludes).Because of the low cost of the method the hydraulic properties of the multiple aquifer system can be determined at many sites distributed throughout the area of interest, enabling simulation of the local and regional ground-water flow conditions and other hydrological characteristics of the system.Since its development in 1964 the technique improved and was employed in ground-water investigations. Data and results from the inhomogeneous, anisotropic multiple aquifer system west of Melbourne are given.

Notes: Chemical and isotopic analyses were made of water from wells in and downgradient from a landfill to determine chemical and isotopic effects of generation and migration of leachate on ground water. The distribution and wide concentration range of oxygen and methane permit the delineation of an anaerobic zone, a regional oxygenated zone and an intermediate zone. The ratio of reduced nitrogen to nitrate indicates location of reducing fronts as the leachate migrates. The pH of the native ground water is low (≥5.0) primarily because of the low pH of rainfall and the lack of calcareous or other soluble minerals in the aquifer material. The pH is higher (∼6.6) in the leachate because of generation of carbon dioxide, ammonia, and methane. The native ground water has a low TDS (80 mg/l) while the leachate has an average TDS of 2800 mg/l and is primarily a NaHCO3 type water. Sulfate concentrations are extremely low and H2S was not detected.We suggest that a major source of cations may be their exchange from the clays by the ammonium generated in the leachate. High concentrations of Fe and Mn are attributed to a source in the refuse but more important to reduction of oxide cements and coatings resulting from degradation of organic matter. The main source of bicarbonate is from organic degradation with minimal CO2 from the soil zone. At one landfill site 52% of the total alkalinity is attributed to organic compounds, mainly organic acid anions. The δ13C of bicarbonate in the leachate is exceedingly heavy (+18.400/00) which results from fractionation during the formation of methane. The 10 per mil deuterium enrichment of water may be due to decomposition of deuterium-enriched compounds and bacterial processes that preferentially consume the lighter hydrogen isotope.

Notes: Rapid fissure flow has been recognised as an important factor in understanding the hydraulic behaviour of the Lincolnshire Limestone aquifer of eastern England. A study of the hydrogeology of a Lincolnshire Limestone spring-fed catchment enables three zones of discharge to be defined, based on their relative elevation along the valley floor. Comparison of the discharge characteristics of each zone reveals the existence of rapid ground-water flow associated with a discrete fissure system. Comparison of spring discharges and ground-water storage during a period of “high,”“low” and “typical” recharge enables a conceptual flow model of the aquifer to be constructed. A two-layered model is proposed, in which the secondary zone (upper unit) is characterised by higher transmissivity and lower storativity than the primary zone (lower unit). In addition, there is evidence of a rapid increase in transmissivity with water-table elevation in the secondary zone. The areal distribution of the secondary zone is associated with a net work dry valleys. The spatial distribution of the two zones is explained by geological structure, lithological variations and the post-glacial history of the area. A two-layered model is developed with these concepts in mind in order to simulate the spring discharges. Once proven, the model can be integreated with the regional hydrogeology and incorporated into existing digital models of the aquifer.

Notes: Abstract. An evaluation was made of the usefulness of the gamma-ray logger in delineating glacial-drift and bedrock stratigraphy in southwestern Ohio. The logger was useful in delineating gross stratigraphic units in a glacial outwash aquifer. The gamma log also provided a clearer indication of the clay content of sand and gravel units than did the driller's log.On the uplands, away from the valleys filled with glacial outwash, the logger could not be used to locate the thin, poorly-sorted, interstadial sand and gravel deposits between thicker till sheets. It could, however, be used to distinguish formational contacts in the upper Cincinnatian Series.

Notes: Injection of waste liquids into Florida's subsurface is physically feasible in many places but should be accompanied by monitoring of the waste-receiving aquifer system in addition to the injection facility. Monitoring of the interaction of factors including hydrogeologic conditions, well construction, waste volumes and characteristics, and potable-water sources is desirable to assure that fresh-water resources are not being adversely affected. An effective aquifer-system monitoring program includes on-site wells located close to an injection well and open to the next-higher permeable stratum, satellite wells located hundreds to several thousands of feet from an injection well and open to the receiving aquifer, and regional wells located miles from individual injection wells and open to the receiving aquifer. An extensive aquifer-system monitoring program associated with two waste-injection facilities near Pensacola, Florida, has provided data which have aided hydrologists to understand the aquifer system's response to the injection and, accordingly, to evaluate the potential for affecting the area's fresh-water resources.

Notes: Overexploitation of ground water in Krishni-Hindon interstream region (Lat. 29°05′N-29°29′N and Long. 77°19′E-77°32′E) in Uttar Pradesh, India, prompted us to carry out aquifer modeling studies. The area lies in Gangetic alluvial plain. The interconnections in the phreatic aquifer and the lower semiconfined aquifer led to the assumption of a single-story aquifer for which an R-C analog model was constructed.The input-output quantities in the model have been simulated using current/voltage generators and current sinks which are appropriately programmed in time-domain with the help of wave-form synthesizers for a realistic representation of the field system.The model study shows that the aquifer can sustain the present output rate of 200 mcm/year without much damage to the ground-water regime. In another scheme, an annual increase of 5% in exploitation rate, shows deleterious effects on the aquifer. Decreased rainfall/ droughts would worsen the situation.The influence of hydraulic connectivity between the aquifer and the Krishni-Hindon river system is quite significant. If the present exploitation rate were to continue for 20 years, the annual inflow to the aquifer from rivers is estimated to increase by about 36.0 mem.More hydrogeological data is required for further validation and refinement of the model.

Notes: Generally, the 208 planning approach is deficient in a number of ways. Its origin lies in Public Law 92-500, which focuses on protection of surface water and special uses of water for fish, wildlife, and recreation. Little ground water is used for these purposes. Nonpoint sources have not been defined in terms that have hydrogeologic significance. Local and State regulatory agencies have often been unsuccessful in controlling ground-water pollution, yet the 208 approach tends to disregard the reasons for this situation. The reasons for ground-water pollution in an area must be understood before meaningful control measures can be enacted. These include both technical and institutional problems.Planners are placed in the forefront of many 208 programs at the local level and often their backgrounds are inadequate in ground water. There is a great lack of ground-water professionals in regulatory agencies involved, particularly in the Southwest. This deficiency is paramount at high levels and in many regional offices of EPA. There are no provisions in the approach to insure that qualified ground-water geologists or hydrologists will be involved. Academic training in ground water is presently oriented toward ground-water development and not pollution. Lastly, public participation is greatly limited by the general lack of knowledge regarding ground water and its pollution.Successful 208 programs in terms of ground water have been enacted when ground-water professionals have had major roles. Changes are necessary in the academic training of ground-water geologists and hydrologists. The public must be educated concerning the long-term consequences of ground-water pollution. Lastly, ground-water professionals must assume the leadership in ground-water protection.

Notes: It is herein submitted that the nearly universal phrase “shall not cause pollution of the ground waters and surface waters” written into the State regulations for waste disposal operations not only refutes a sound technical alternative, but is impractical, uneconomical and often unworkable.It is a fact that all ground waters are not created equal, as governed by certain irrefutable physical laws including the water budget equation and Darcy's Law which states that the quantity of ground water available is subject to wide variation from location to location. While an aquifer is a relative term, major, minor and nonaquifers can be identified within a given geographic area with respect to cost-effective ground-water resource development. Likewise, the natural quality of ground water is also a significant variable with certain parameters often exceeding drinking-water standards. The land application of wastes overlying the ground waters of an area should, therefore, also be subject to a certain degree of flexibility for prudent management of both the waste operation and the ground-water resources.Numerous investigations and empirical data can be cited to substantiate the fact that many wastes and their associated leachates can be safely assimilated into the environment with reliance on attenuation and controlled degradation of ground water by utilization of a mixing zone or zone of renovation with a specified distance from a disposal operation. As increased emphasis is placed on the land disposal/management of wastes/residuals and as the cost of these operations continue to mount, it is strongly recommended that controlled ground-water degradation be utilized in those areas where a “true” ground-water resource does not exist. Protection of such a “true” ground-water resource is obviously necessary as our demands for a potable water supply also continue to grow.

Notes: Ground-water computer models are, certainly, toys which provide intellectual stimulation. They can be useful tools for advancement of the ground-water profession, but I believe that they have been blown out of proportion and that this might cause irreparable damage to our profession.It is important to see where computer models fit into the ground-water problem-solving process. I believe that ground-water computer programs are simply a complicated “turn the crank” tool for making projections. They're one type of tool out of several which requires aquifer and confining bed characteristics to facilitate making projections. A second approach for making projections involves the direct extrapolation or manipulation of data which does not require transmissivity, storage coefficient, leakance, and other interpreted characteristics. Further, I believe that the collection and evaluation of data are of greater importance than the projection methods and/or tools in arriving at answers.Advantages of ground-water computer models include: speedy analyses once a program is working, ability to handle many parameters, and utilization of a large data base. The disadvantages include: use of computer models as end goals, tendency for misapplications, time-consuming setup, a waste of time and money in some cases, and diversion of human talent from useful ground-water work.

Notes: While it is true that waterborne diseases are still with us, and probably always will be, we cannot classify them as a current threat in the sense that they were 100 years ago. The discovery that chlorine would disinfect water supplies removed these diseases from a “current threat” category to the “historical lesson” category. We are not faced with unknowns which we are unable to attack. We have only to look at what others have done to protect themselves and follow the same or improved practices.If the record of waterborne outbreaks in public water supplies in this country from the end of World War II up to the present is examined, it will be found that all are caused by breakdowns in disinfection procedures or carelessness. The record is replete with statements such as “improper disinfection after repair,”“breakdown or lack of disinfecting equipment,”“back siphonage,” and other similar statements all pointing to failure to follow practices which the history of water treatment has shown to be necessary for protection against waterborne disease. Carelessness allows recurrence of disease outbreaks. If the lessons of history were followed, the conquest of waterborne disease transmission by public water systems could be complete.

Notes: The increasing use of ground water and its true role as a source of water supplies in the United States have sometimes been interpreted incorrectly. The total use of ground water has indeed increased tremendously during the last 20 years (by almost 80%), but so has the total use of water (over 70%). And ground water is still far from being a primary source of water supplies. In 1975, only 20% of the total amount of water withdrawn in the United States for various uses came from ground-water sources.Statistical analysis of ground-water data for the period 1950-1975 has shown that the ground-water usage is changing only very slowly. Relation of ground-water use to total water use expressed in percent was used as an indicator of changes of ground-water use patterns. This percentage has not changed significantly, and it has fluctuated around 19%. In 1975, only 6 States used more ground water than surface water for their water supplies, and in 23 States ground-water use was less than 10% of total use. Even more unfavorable is the magnitude of change in ratio of ground-water use relative to total water use. From 1955 to 1975 only 13 States show an increase in the ratio. In 28 States the ratio has decreased, and in 7 it has remained the same.

Notes: An objective view of the need for ground-water quality standards requires that an individual recognize the value that ground water contributes to the water supply needs of our nation. A vast number of people living in rural areas and a large number of communities are dependent upon ground water as their sole source of water for domestic, industrial, commercial, and agricultural needs.This large use and dependency upon ground water dictates that these resources are valuable and must be protected for both present day and future uses. There are many examples where present methods of disposal of wastes generated in America have not been satisfactory from an environmental standpoint, with an exception of projects where disposal sites have been properly designed, operated, and managed for protection of the ground water.One possible solution for ground-water protection is the establishment of ground-water quality standards. The purpose of such standards is to protect the public health and welfare and maintain the quality of ground waters in all usable aquifers for individual, public, industrial, and agricultural water supplies. A legal basis must exist and the prescribed steps must be followed as dictated by the rule making process. The primary aim of such standards is to prevent the degradation of ground waters such as they will not become a public health hazard or harm the users of the ground water.The backbone of such a standard rests on the completion of a hydrogeological study which is necessary to determine background water quality information, set up the monitoring program and outline sampling to determine when water quality changes are taking place and what is a significant change.

Notes: Half the population depends on ground water for domestic uses. Use is increasing 25 percent per decade. Ground water is generally used with little or no treatment.Some persons would transfer the discharge of our waste products from contaminated surface streams to the land and thus relatively clean ground waters.No standards exist that protect ground-water quality. Research necessary to give assurance that natural interaction of waste water and soils will remove, to acceptable levels, potentially harmful contaminants, organic and inorganic, that permeate today's waste streams and today's health concerns, has not been done.Success reports on land treatment of waste water have a not evaluated deterioration of ground water from organic contamination. Most waste waters contain synthetic organics in varying concentrations. EPA recommends their reduction in drinking water to the lowest possible level.Most instances of ground-water contamination have been discovered after drinking water is contaminated. Unless the public is willing to treat ground water as it does water from surface streams, greater control of land disposal practices must be exercised. Current practice does not indicate the necessary controls are contemplated or recognized. It follows that the widespread use of the land treatment alternative is, in reality, an accident waiting to happen.

Notes: The Nation's ground-water resources constitute a vast and often unprotected resource. The Environmental Protection Agency is about to launch a number of programs designed to protect what is, in many cases, a virtually non-renewable resource. Separate regulatory activities mandated under the Safe Drinking Water Act, the Resource Conservation and Recovery Act and the Clean Water Act must be carefully coordinated if they are to be effective.The current implementation efforts within the agency are being framed in view of our major principles which will be the focus of public comment in the months ahead. These principles are:First, the administration of the related programs will be a cooperative effort involving Federal, State and local governments, all of which must participate in formulating the program if it is to be effective.Second, the focus of the programs will be on the prevention of contamination rather than on its treatment at the point of withdrawal.Third, the applicable standards will be based primarily on technology rather than ambient ground-water quality considerations since the effects of discharges upon ambient quality are complex, difficult to predict, and of long duration.Fourth, there is a need to balance environmental protection, energy development and continued economic prosperity objectives so that the resulting programs fully protect public health while being realistically implementable.All of us—government, industry and citizens, through acts of commission or omission—have contributed to the potential problem. We must work together if we are to get on with the important task of protecting the quality of the Nation's ground-water resources.

Notes: Instrumental neutron activation analytical data, for eighteen trace elements (Ba, Co, Cr, Cs, Hf, Rb), Sb, Sc, Ta, Th, La, Ce, Nd, Sm, Eu, Tb, Yb, Lu), Hd2O and Fe203 in eleven French geoche-mical reference samples are presented and discussed briefly.

Notes: Les roahes carbonatées et siliaatées appar-tiement à un domaine de compositions dans lequel la mesure d'un fond libre d'interférence ou d'une rate diffusée du tube peut permettre à la fois de aorriger les effets de pures absorptions et d'étalonner les fonds sous les raies analytiques. Cette propriété est illustrée sur I'exemple du dosage de 6 éléments en traces dans 30 standards géoahimiques.La méthode proposée permet d'obtenir dans un domaine de concentration de 1 à 2000 ppm des ré-sultats dont la qualité est à rapprocher de la trés grarde rapidité de rmise en oeuvre.

Notes: 37 geochemical reference samples, issued mostly by the U.S. Geological Survey and the “Centre de Recherches Pétrographiques et Géochi-miques”, have been analysed for more than twenty trace elements using instrumental neutron activation technique. The results are compared with published data; in most oases, the agreement is good.

Notes: Trace element data compiled on, geoshemical reference samples present invariably skewed distributions. It is proposed to treat such data as lognormally distributed and to compute geometric means (Xgm) as probable values. As examples, the Xgm values derived for some trace elements in some rock reference samples are compared with the “recommended” values and with the “gamma” values of Christie.

Notes: Total carbon and sulfur were determined on a variety of geochemical reference samples such as rocks, sediments, minerals and ores by a method of infrared absorption following combustion in a high-frequency induction furnace. The sample was burned with an accelerator of iron powder and tungsten chips, and the carbon and sulfur dioxide in the evolved gases have been determined directly by a simultaneous infrared analyzer. The agreement between present results and other data is generally good.

Notes: Small programmable calculators have recently become available that will allow many routine pumping or injection well calculations to be made rapidly, accurately and inexpensively. Programs and example calculations are given for the exponential integral and multiple well-multiple rate pumping or injection well equations using water well and oilfield units. The programs are for the TI 59 card programmable calculator.

Notes: Because of the relatively low stiffness properties of thermoplastic materials, casings made from these materials may be more susceptible to collapse. For many applications, when a surrounding material tends to support the casing, the casing resistance to collapse should be significantly increased. The Morley equations of equilibrium for two radial collapse pressure loading conditions were modified to include the support of the surrounding medium and were solved using the Galerkin method. Parametric studies were conducted for typical water well casings and restraint values. Simple collapse prediction formulas are proposed for predicting collapse for the two loading conditions considered. Collapse pressures predicted by the proposed formulas for uniform collapse pressure are approximately 25% lower than those values predicted by the current ASTM formula. Collapse pressures for linearly varying pressure were found to be 12% higher than the corresponding values for uniform pressure. When the radial stiffness of the surrounding medium is included in the analysis, the collapse pressure resistance of the casing was found to be significantly increased over the collapse resistance of an unsupported casing.

Notes: Precise geophysical surveys across ground failure zones related to ground-water withdrawal at nine sites in Picacho basin in south-central Arizona indicate that earth fissures in alluvium near exposed bedrock are spatially associated with local gravity and magnetic anomalies ranging from local highs to convex-upward changes in slope. We interpret the gravity anomalies, which range from 0.1 to 1 mGal with half-widths of 50 to 300 m (160 to 980 ft), to be caused by convex-upward irregularities in the bedrock surface underlying the alluvial aquifer. Most irregularities are inferred to be at depths less than 250 m (820 ft). Bedrock irregularities were not detected beneath failures that are more than 2 km (1.2 mi) from bedrock outcrop. The association of earth fissures with zones of variable aquifer thickness suggests that differential compaction is occurring near these fissures. Theoretical estimates, based on the finite element method, of horizontal strains generated by localized differential compaction suggest that this mechanism is the dominant source of horizontal tension causing earth fissures in Picacho basin. Our analysis indicates that tensile strains at fissures at the times of their formation ranged from 0.1 to 0.4 percent.Prediction of the location of earth fissures near exposed bedrock in Picacho basin and in adjacent basins with similar geologic settings appears feasible by delineation of convex-upward bedrock irregularities. Failures far from exposed bedrock, however, may not be as readily predicted on this basis. If the rheological properties and thicknesses of subsurface materials are known, prediction of the magnitude of water-level decline required to induce sufficient differential compaction to cause failure at potential earth fissures appears feasible.

Notes: On September 30, 1977, a large industrial plant in Fernandina Beach, Florida, shut down six artesian wells that had been pumping continuously for several weeks from the Floridan aquifer. Two wells continued pumping until November 20, 1977, at which time the shutdown wells were restarted. A water-level recorder on an observation well recorded the changing water level following shutdown and startup. Pumping rates of the wells ranged from 400,000 to 590,000 cubic feet per day (11,000 to 16,000 cubic meters per day). Distances from the pumped wells to the observation well range from 660 to 7,920 feet (200-2,420 meters). Analysis of the water-level data was further complicated because the wells were neither turned off nor restarted simultaneously; during recovery one well was restarted and pumped for several hours; and at the beginning of startup, a well that had been pumping continuously during the shutdown was turned off. The Cooper-Jacob graphical method, based on the principle of superposition and using values of specific drawdown or specific recovery (s/Q) and weighted logarithmic mean of the distance squared divided by time 〈inlineGraphic alt="inline image" href="urn:x-wiley:0017467X:GWAT525:GWAT_525_mu1" location="equation/GWAT_525_mu1.gif"/〉, was applied to determine the aquifer coefficients for the upper water-bearing zone of the aquifer. A transmissivity of 30,000 feet squared per day (2,800 meters squared per day) and a storage coefficient of between 2.5 × 10-4 and 4.0 × 10-4 were computed.

Notes: A sequence of simple statistical tests was used to interpret the data from a routine water sampling project for a stream that was contaminated with effluent from a sewage treatment plant. The contamination of this stream was apparent from the murky condition of the water and its pungent odor. The outlet of the sewage treatment plant enters the stream at its origin.The chemical variables analysed were Ca, Mg, Na, K, Cl, nitrates, TDS, and hardness. Background data from other streams in this drainage basin and data from the stream under investigation were subjected to cluster analysis in order to classify the sampled area into geochemical provinces. The contaminated stream under investigation comprised one province and the background streams constituted another province. A linear regression performed on the data showed a statistically significant decrease of several variables with increasing distance from the outlet of the sewage treatment plant. An abrupt decrease in concentration of iron some 450 m below the plant outlet implied the presence of two populations with different means, which was statistically verified with a trimmed t-test.Use of these simple tests greatly facilitated interpretation of the data.

Notes: Geochemical factors controlling water chemistry in an influent stream and adjacent flood-plain sediments were determined during a four-year study. The stream has a drainage basin that is similar to many streams draining carbonate terranes in the eastern United States. It receives sewage effluent, farm and urban runoff and supplies recharge to an aquifer under extensive development.Water beneath the flood plain, springs, and channel were calcium bicarbonate as expected; however, the prevalent chemical character of soil water beneath the channel was sodium bicarbonate. HCO3 within soil water beneath the stream is three times (1,500 mg/l) that beneath the flood plain, Na+ is two orders of magnitude greater (400 mg/l), K+ reaches 10 mg/l which is twice as great while CA2+ and Mg2+ may be one-fifth as high as concentrations beneath the flood plain with ranges from 15 to 20 mg/l and 5 to 10 mg/l respectively. Waters 3 to 7 feet (0.9 to 2.1 m) below the flood plain contain intermediate Na+ values from 25 to 75 mg/l.Ion exchange appears to be the mechanism accounting for the sodium bicarbonate water observed under the channel. The same relationship should occur in other areas with available carbonate rock, base exchange minerals, and an organic source.

Notes: From the 195O's to the early 1970's expansion of sanitary sewerage in southwest Nassau County contributed to progressive declines in ground-water levels. Since the early 197O's, however, 10 years after the area was fully sewered, water levels have not declined significantly, which suggests that the water table may have reached a new equilibrium position. Double-mass-curve analyses show that during 1953-76 the average weighted ground-water levels in a 32-square-mile (83-square-kilometer) part of the sewered area declined 12.2 feet (3.73 meters) more than those in the unsewered area to the east. However, by 1973 this decline was 13.5 feet (4.1 meters). Finite-difference digital-model results indicate that 3.6 feet (1.1 meters) of the relative 1953-76 decline was due to pumping in adjacent Queens County and that most of the remaining decline was a result of sewerage. Streamflow within the sewered area decreased in response to the lowered ground-water levels, and ground-water levels in the adjacent unsewered area were also lowered because of the sewerage.

Notes: One of the most valuable and practical tools the ground-water manager can use is the computer model, be it wellfield, conjunctive, solute transport, or statistical. Although these models vary in complexity, the end product is purely a function of the user's ability to select the appropriate level of modeling for a particular project. Any professional working in the field of hydrogeology should adapt to and use ground-water models to be truly efficient.

Notes: Land application of treated waste water can provide unique opportunities, not only for a final high level of waste-water treatment but for reuse of nutrients as well. Recent laws passed by Congress have made it necessary to consider land treatment when planning and designing new waste-water treatment facilities. The three types of land treatment commonly used are (1) irrigation, (2) overland flow, and (3) rapid infiltration. Selection of the most appropriate type of land treatment for a specific site is based on several considerations, including soil conditions, geology, topography, proximity to surface and subsurface water, and climate.Ensuring the protection of ground water is essential when siting or designing a land treatment system. Ground water is an important natural resource, having considerable impact on human life and well-being as well as high economic value. Safeguarding this important resource from contamination includes careful site selection, appropriate pretreatment of waste water prior to its application, and a program of regularly scheduled monitoring to ensure that the waste water is being properly renovated for safe release to the environment.Utilization of municipal sludge on land for agricultural production is encouraged by federal law, as is land treatment of waste water. Sludge contains concentrated wastes, and there are practical limitations on the levels of heavy metals, salts, and toxic substances in sludges applied to agricultural lands. Sludge is generally stabilized before being applied, to destroy pathogens, and reduce weight, volume and odor.Several case studies of successful land treatment systems presently in operation are presented to demonstrate the viability of the land treatment concept.

Notes: Control of epidemic waterborne disease of an infectious nature has been made practical through modern drinking-water treatment practices. Certainty of such control depends upon treatment plant reliability. The possibility of the transmission of newly recognized infectious diseases by the water route must be considered. The presence of trace amounts of chemicals in drinking water that are potential agents of chronic disease, particularly cancer, poses many questions concerning the safety of our water supplies.

Notes: Few would argue that ground-water pollution is a problem and that serious ground-water pollution problems do exist. As serious as some isolated ground-water pollution problems are, regionally and nationally, it is only a limited problem. An industrial landfill may result in a leachate plume contaminating ground water over an area of up to several square miles downgradient from the disposal site. Municipal landfills or chemical/petroleum spills can result in polluted ground water over areas measured in square miles. Surrounding these areas of ground-water pollution, however, are tens and hundreds of square miles of area where the ground water moving through the aquifers maintains its natural good quality. The ratio of good quality to contaminated water is such that ground-water pollution can really only be considered as a limited problem.The problem will most likely remain limited as existing and future regulations continue to restrict the poor disposal practices that have been responsible for much of the past and existing pollution problems. Technology has advanced to the point that with proper management and sound governmental regulations, control, isolation and cleanup of contamination sources and areas of polluted ground water can be so effective that migration of the pollution front can be stopped and actually reversed with time.The same technology that provided us with the new chemicals and the wastes that show up in water analyses, has also provided us with the means of detecting many more contaminants at much lower levels of concentration in a water sample than was possible 50, 25 or even 10 years ago. One must thus ask, has ground-water pollution really become a national crisis, or do we just know more about an old problem made apparently more complicated by our own technological advances?

Notes: Proposals to establish national ground-water quality standards appear to be premature, and redundant because of the geohydrologic and geochemical factors governing the occurrence and development of ground water. Although it can be reasoned that there is no “good time” to establish additional governmental standards (and the resultant additional governmental regulations), it can also be strongly argued that now is a “bad time” to consider establishment of the proposed standards.First, a present mood of the general public is away from more governmental involvement in the business and private sectors, and a rebellion against the increasing cost of government. Second, the applicability and workability of present Federal (and some State) laws that could be used to adequately protect ground-water quality, have yet to be implemented or otherwise sufficiently tested.The full force and effect of the Water Pollution Control Act (PL 92-500 with amendments) has yet to be implemented, and Congress is still considering its “oversights” in their drafting of same.The Safe Drinking Water Act (PL 93-523), particularly those sections designed or usable to protect ground-water quality, have yet to be tested by the EPA. Like PL 92-500, the deadline for implementation of parts of PL 93-523 has long since passed.And the far-reaching effects on ground-water quality protection that three other federal laws-the Resource Conservation Recovery Act (PL 94-580); the Toxic Substances Control Act (PL 94-469); and Surface Mining Control and Reclamation Act (PL 95-87)—are totally unknown, since the procedures for full implementation of these acts have yet to be developed.Therefore, it appears that establishing a new ground-water quality control act prior to testing existing law and thereby learning from their flaws or shortcomings, could result in unnecessary proliferation of law without its reasonable testing.This appears to be good time to interrupt the geometric progression that tends to spawn additional laws when laws are developed ahead of their established need.Equitable and workable ground-water quality protection could be fostered through the enactment of the long overdue requirements for the integration of surface-and ground-water development and management structures. This integration would decrease inefficiency of use of these water resources—which are actually inseparable in identity to their users, the American taxpayers.

Notes: Recent research has expanded our understanding of the suitability of waste disposal in various hydrogeologic settings. Although more research is needed, our knowledge can provide a basis for preparing guidelines for action that will protect ground water from waste disposal practices. It is impossible, however, to prevent accidental spills, unlawful dumping, and ground-water contamination or pollution resulting from some old, unregulated waste disposal practices. Therefore, more than 170 case histories of subsurface contamination or pollution were studied to evaluate the effectiveness of remedial action in different geologic environments. The case studies indicate that the severity and extent of ground-water contamination is determined by (1) the hydrogeologic setting, (2) the nature of the contaminant, and (3) the effectiveness of regulatory action.Industrial wastes are the most common sources of ground-water contamination. The most serious incidents are those that pollute or threaten water supplies and those that cause a fire or explosion. Once ground water is contaminated, remedial action is time consuming and expensive. Each incident must be handled as a separate problem. Although prompt action is essential to limit contamination and minimize remedial action, no strategies have been established for rapid response to contamination or pollution problems.Ground-water contamination will continue, but its impact can be reduced. The role of hydrogeologists in regulatory agencies should be strengthened to provide proper evaluation of potential sources of contamination and to aid in remedial action when ground water is contaminated. Cooperative efforts to develop strategies will ensure proper handling of future emergencies.

Notes: The opportunity to begin formulating a national ground-water quality protection program is at hand. In building the new program we should use the host of lessons learned in the experience of related environmental programs. This is necessary so that the new program will be realistic at the outset and congruent with the integrated planning and management of the ground- and surface-water resources of the nation.The keystone of program development, implementation, and evaluation is and will continue to be water quality standards. To the extent that the goal “Safe Drinking Water for Americans” has already been established, the point-of-use regulations (IPDW Regs and the RPDW Regs), should serve as water quality objectives thus facilitating ground-water program formulation and evaluation. The major regulatory thrust of the program, the water quality standards, must be technology-based site selection, construction and operational standards, with only limited monitoring in a conventional water supply and water pollution control context.