ALBERT

Notizen: This paper compares the growth accounting approaches to aggregate productivity measurement and analysis of three major researchers: E. F. Denison, D. W. Jorgenson, and J. W. Kendrick. The investigetors are compared in terms of their treatment of a number of crucial elements, including measurement of output and of capital and labor inputs (including composition or quality changes), total factor productivity growth, economies of scale, and intensity of demand (for output). Judged by the standard of the neoclassical economic theory of production-the only generally accepted basis for input aggregation-Denison departs significantly from the production theory framework in his measurement of output and capital input, Kendrick to some degree in his measure of capital input, and Jorgenson not at all. The effects of these departures are illustrated with reference to the recent productivity slowdown. The probable near-term future utility of growth accounting methods for productivity analysis is assessed, and some related econometric modeling issues are noted.

Notizen: This article reviews the problems involved in updating the results of international comparisons, in terms of an analytic framework focusing upon the sources of differences between various forms of extrapolation and direct comparisons. The factors identified as important are conservation of prices of the base period and weight inconsistency. The reliability of updating is undoubtedly affected by the length of the period over which the data are extrapolated. A program of regular benchmark comparisons at approximately five-year intervals with updating for the intervening years is attractive, since it permits checking by forward and backward interpolation. Where there are large deviations, however, averaging is not an acceptable solution.

Notizen: Index number accuracy is affected by formula specification and sampling error. The authors argue that an index formula should be “ideal” and “exact” (with reference to the range of economically plausible aggregator functions) to be economically justified. These indices are invariant in the homothetic case, as well as in certain non-homothetic scenarios. Empirically, based on foreign trade data for Egypt from 1885-1961, the set of economically justified indices are virtually identical, supporting the theoretical argument that “instrumental error” or “formula variance” should be a negligible factor contributing to index number error. In a discussion of sampling error, on the other hand, the authors criticize earlier work and propose an upper and lower bound. Using the same data, these limits imply that sampling error may be a serious problem for many indices.

Notizen: The United Nations (SNA) and the Canadian (CSNA) Systems of National Accounts treat interest as a factor return to capital. The difficulties arising from the use of this concept cast doubt upon the basic premise. For example if the usual method of measuring value added by the summation of primary inputs is applied to industries mainly engaged in the lending of money, the results show negative production. This has led to the necessity of imputing bank interest in order to avoid negative income originating in the banking industry. Arguments are being put forward to extend this practice to certain other financial non-bank areas as well to offset the negative product emerging with increasing frequency as a result of higher levels of interest transactions.The proposed alternative is based on the contention that interest paid and received for the borrowing and lending of money should be treated in the same manner as the purchase and sale of other services. For the production accounts, for example, this would mean that interest paid by business would be treated as an intermediate expense of the paying industry and as revenue of the receiving industry. The adoption of this approach would therefore eliminate the need for the imputation of banking services and clear up the ambiguities encountered in treating interest on the public and consumer debt, issues which are also not unrelated to the present treatment of interest.

Notizen: The present investigation is the first attempt to calculate gross capital stocks for 19 industries which together cover the whole Austrian economy. A production-oriented concept of capital formed the basis of the investigation; the estimation procedure follows that of C. Almon et al. In contrast to the traditional perpetual-inventory methods, Almon's modified estimation technique combines the advantages of differentiated cumulation containing a logistical retention function with relatively moderate requirements with respect to investment data. A thorough description of this estimation technique is given in the third section of the paper, combined with a number of comparative model calculations. These demonstrate very clearly that capital stock figures calculated according to the Almon method rarely deviate from those found with the help of the traditional inventory method, which requires considerably more information and uses more complicated calculation procedures. Finally, the sectorally disaggregated capital stock estimates calculated according to the Almon method are presented with some interpretative remarks.

Notizen: This paper reports upon the first official application of the estate multiplier method of estimating the wealth distribution to French data. It is based upon a sample of estate duty returns filed during the period September-December 1977. The sampling rate was 5 percent for estates under one million francs, and 100 percent for estates over this level, giving a total of 5031 records. The data available did not permit a breakdown by type of asset. It did, however, permit classification of estates by age, sex, and occupation of decedent. Experiments were conducted using five different sets of mortality multipliers. The set of mortality multipliers judged most appropriate leads to an estimate of aggregate net wealth that is 77 percent of that given in the national balance sheet of the national accounts. Comparison of the distributions of wealth derived in these estimates suggest that the figures are consistent with those found in other countries.

Notizen: This paper describes the construction of a disaggregated system of 262 national accounts for the U.K. economy in 1975. The objective is to remove the discrepancies between income, expenditure, production and financial estimates which occur in practice. This is done with the aid of a generalized least squares algorithm for adjusting national accounts with subjective estimates of reliability of the various account items. The balanced system of accounts provides the cross-section data base needed for the estimation of a consistent multisectoral dynamic model of the U.K. economy and yields the classification converters and input-output tables necessary for such a model.

Notizen: On the basis of rough estimates from the expenditure as well as from the income side, it is suggested that the national product per head of the Roman Empire at the death of Augustus (AD 14) was somewhat below 400 sesterces (31 g gold) yielding an aggregate national product of fully HS 20 billion for a population of 55 million and that these figures were approximately valid from the late first century BC to the mid-second century AD. The share of government expenditures in national product was very low, probably not above five percent, and that of gross capital expenditures even lower, probably not in excess of two percent. An attempt is also made to appraise the concentration of personal income and it is estimated that the 600 senatorial families, representing approximately the top 0.04 per m of the population, received about 0.6 percent of total personal income while the share of the top three percent of income recipients was in the order of 20–25 percent of total personal incomes. The second part of the article compares these estimates as well as a few indicators of the standard of living and of welfare in the early Roman Empire with the corresponding figures for a few countries before the industrial revolution and for mid-20th century less developed countries.

Notizen: Expanded measures of government product normally include imputations for the services of government capital. This article discusses several approaches to measuring the value of the services of government capital and focuses on the conceptual and empirical difficultes associated with making such imputations. In addition, four sets of alternative estimates for 1948–79 are presented.

Notizen: The estimation procedure for purchasing power parities is generally divided into two parts, one for calculating transitive PPP's within basic headings and a second beyond this most detailed level up to gross domestic product. This paper only concerns the first step. It provides a description of the work carried out by the European Communities in 1980 within the United Nations International Comparison Project (ICP) framework. The estimated PPI's for basic headings are put forward together with the procedures for product selection and specification, the classification used for these purposes and the impact on the estimation of transitive PPP's. Instead of the country-product dummy (CPD) method used in the ICP, a revised Elteto-Köves-Szulc (EKS) procedure is proposed in which the estimation method and product selection constitute one integrated procedure.

Notizen: A set of international comparisons is developed for 124 countries over the three post World War II decades, 1950-80. A Data Table is presented which gives, for most countries and most years, real product estimates for three different national income concepts and for the major subaggregates consumption, investment, and government. Detailed comparative price level estimates are provided as well.

Notizen: The trend in the concentration of U.S. wealth from 1958 through 1976 is examined in some detail and summary data are used to extend the period over which the trend is observed back to 1922. The data suggests a long-run secular decline in the concentration of U.S. wealth with a rather sharp decline in 1976, the last year for which measurements were made. Although the secular decline in wealth concentration is supported by numerous observations across 50 years, the precipitous decline measured between 1972 and 1976 should be interpreted with caution because it undoubtedly reflects the substantial downward revaluation which occurred in the stock market from 1972 (most recent previous observation) to 1976. This is not to argue that wealth holders at the top of the distribution were not made significantly less affluent by the revaluation, but that the 1976 observation includes a large cyclical component. Future observations which include the subsequent upward revaluation in the stock market are expected to show levels of concentration comparable to or only slightly below those for 1958 through 1972.

Notizen: The paper begins by stating various aspects of the national economic accountant's “company-establishment problem.” Six possible approaches to the problem are briefly outlined. The paper concentrates on one approach based on new developments in business accounting theory and practice, namely divisional-reporting procedures. The division represents the smallest operating entity capable of reporting both a complete set of production (income) statistics and a set of related financial (balance-sheet) statistics. When companies are owned and controlled by the same interests, namely the enterprise, each division reports on an enterprise-wide basis. In this important case, the traditional company-establishment problem has an enterprise-division-establishment resolution.There is considerable emphasis on clarifying the issues needed for systematic development of divisional-reporting to meet the requirements of a national statistical agency. Key aspects are the provision of appropriate conceptual distinctions relating to statistical structure of corporate organizations and patterns of intercorporate ownership consolidation. Practical experience gained by the U.S. Federal Trade Commission's line of business reporting program is also highlighted. Two tables show details with respect to a proposed divisional income statement and balance-sheet statement that a systematically developed division-reporting unit can provide. The tables are related to existing statistics yielded by traditional company- and establishment-reporting units. In effect the paper is part of a movement giving national economic accounting more microdata dimensions. Future research must integrate the proposed new statistical reporting unit within systems of national accounts presently constructed on the basis of a dual sectoring classification.

Notizen: This paper brings together discussions of Geary–Khamis indexes now available only in scattered sources, and considers their application to a range of uses. The first section traces the development of the method from its initial proposal by Geary in 1953, with the aid of a numerical example illustrating differences among various formulations. The second section considers the least squares properties of Geary-Khamis indexes and some related variants. The final section considers adjustments to the method required for regionalization and spatio-temporal bilateral and multilateral comparisons, as well as to take account of the nature of available data.

Notizen: This is the first of a series of papers giving the solution of the inverse problem in seismic exploration. The acoustic approximation is used together with the assumption that the velocity field has the form 〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR998:GPR_998_mu1"/〉 . The forward problem is then linearized (thus neglecting multiple reflected waves) and the inverse problem of estimating δ is set up. Its rigorous solution can be obtained using an iterative algorithm, each step consisting of a classical Kirchhoff migration (hyperbola summation) plus a classical forward modeling step (circle summation).

Notizen: The response of a seismic model to excitation by a source can be represented in terms of the action of reflection and transmission operators for portions of the structure. This approach provides a flexible framework for both modeling and processing problems.The operator development provides a physical description of the wave propagation process and, via the expansion of reverberation operators, gives a mechanism for assessing the accuracy of approximate developments. The representation suggests new ways of developing modeling algorithms by balancing the computational effort expended on minor and major features of the model.For processing problems, the operator representation shows the relation of processing stages to the seismic wave field and thereby indicates effective sequences of operations. For migration it is possible to specify an ideal pre-stack migration procedure in terms of the inverse of the propagation operators and to examine the problems which need to be overcome by practical algorithms.

Notizen: A numerical method is presented for direct interpretation of resistivity sounding measurements. The early part of the resistivity transform curve derived from field observations by standard methods is approximated by a two-layer curve. The resistivity of the first layer is determined from the arithmetic mean of the successive computations which are carried on each of three successive discrete values of the resistivity transform curve. Using this mean value of the resistivity, the thickness of the first layer is computed from the sample values in pairs of the resistivity transform curve. After these determinations, the top layer is removed by Pekeris's reduction equation. The parameters of the second layer are obtained from the discrete values of the reduced transform curve (which corresponds to the second part of the resistivity transform curve) by the same procedure as described for the first layer.The same computational scheme is repeated until the parameters of all intermediate layers are obtained. The resistivity of the substratum is determined from the reduction equation.

Notizen: In odd-depth structure the two-way traveltime to each boundary is constrained to be an odd integer. The odd-depth property of a model is exposed to possible refutation under a seismogram test. Test function is a simple transformation of a synthetic seismogram. For an odd-depth model the test function has identically the value 1.The testability of a synthetic seismogram over an odd-depth structure provides a method of deterministic deconvolution. There is no need of specialized assumptions, like the minimum-phase property, about the source wavelet. The deconvolution may be performed in the absence of the early segment of a seismogram.

Notizen: Zero-offset-source VSP surveys provide information about the subsurface only within the Fresnel zone centered at the well. Offsetting the source location moves the reflection zones away from the well thus providing lateral cover.Conventional processing of this type of data gives rise to a distorted image of the subsurface. Using a simple ray-tracing scheme, this image may be reconstructed into the more familiar coordinate system of the surface seismic section. This simple data-independent mapping is based on the assumption of horizontal layering and requires a vertical velocity profile.The technique of placing the source away from the borehole was first applied to the single-offset-source VSP survey. However, data from any survey geometry (such as deviated well with rig source, walkaway VSP, etc.) can be mapped to the coordinate system defined by the appropriate seismic section.To obtain the best results from this type of survey the target area must be defined and simple modeling techniques used to optimize the source location(s). These pre-survey modeling methods may also be used to anticipate—and hence avoid a number of problem areas which experience has highlighted.The data from any VSP survey is the result of a realizable experiment and as such obeys the wave equation. This implies that the wave equation may be used to migrate the data to its true subsurface location. Theoretically, such a process is more secure than ray-tracing techniques, although its practice presents many difficulties.

Notizen: A mathematical expression for potential of a direct current point source in an inhomoge-neous anisotropic earth is derived. The coefficient of anisotropy is given by f= (σr/σz), where σr and σz are the conductivities parallel and perpendicular to the bedding plane. It is assumed that σz varies with depth, whereas σr varies transversely. This potential may be useful in interpretation of geoelectrical data in specified geological situations. Master curves for Wenner and Schlumberger configurations are presented

Notizen: Total magnetic intensity contour maps for the study region (between 2°E to 10°E and 56°N to 60°N) were digitized and converted to a regular grid of 285 × 285 points. The study area measures approximately 444 km × 444 km and the grid spacing is thus 1. 56 km. The International Geomagnetic Reference Field for 1975 was gridded for the above-used net, and from the two data sets a further grid of the ▵T field was generated. A large number of profiles were constructed which were suitable for depth determinations. The regular grid ▵T data is also convenient for the computation of the second vertical derivative. Using the method of vertical prisms of Vacquier et al. (1963), a large suite of curvature-depth indices was measured to complement the depths obtained from the intensity slopes and from boreholes which reach the crystalline basement. The depth to the magnetic basement has been contoured, and the resulting map is shown to be in good agreement with what is known about the deeper geology of the study area.The work reported here is part of a research project supported by Amoco Norway, BP Petroleum Development Ltd, Elf Aquitaine, Esso Exploration and Production, Norwegian Gulf, Norsk Hydro, Mobil Exploration Norway, Norwegian Petroleum Directorate, Royal Norwegian Council for Scientific and Industrial Research (NTNF), Norske Shell, and Statoil.

Notizen: Geophysical inversion involves the estimation of the parameters of a postulated earth model from a set of observations. Since the associated model responses can be nonlinear functions of the model parameters, nonlinear least-squares techniques prove to be useful for performing the inversion. A common type of inversion applies iterative damped linear least squares through use of the Marquardt-Levenberg method. Traditionally, this method has been implemented by solving the associated normal equations in conventional ways. However, Singular Value Decomposition (SVD) produces significant improvements in computational precision when applied to the same system of normal equations. Iterative least-squares modeling finds application in a wide variety of geophysical problems. Two examples illustrate the approach: (1) seismic wavelet deconvolution, and (2) the location of a buried wedge from surface gravity data. More generally, nonlinear least-squares inversion can be used to estimate earth models for any set of geophysical observations for which an appropriate mathematical description is available.

Notizen: In this study we derive expressions for particle displacement or particle velocity anywhere inside a stratified earth and at its surface due to horizontal torque source located in the top layer. Equivalently, invoking Green's function reciprocity theorem, the solution applies also to the case of a surface or subsurface source when the resulting displacement or velocity is measured within the top layer.In order to evaluate the closed-form analytical solution economically and accurately it is advisable to introduce inelastic attenuation. Causal inelastic attenuation also lends the necessary realism to the computed seismic trace. To provide proof that the analytical solution is indeed correct and applicable to the multilayer case, a thick uniform overburden was assumed to consist of many thin layers. The correctness of the computed particle velocity response can be very simply verified by inspection. The computed response can also serve as a check on other less accurate methods of producing synthetic seismograms, such as the techniques of finite differences, finite elements, and various sophisticated ray-tracing techniques.It is not difficult to construct horizontal surface torque source. It appears that such source is well suited for seismic exploration in areas with a high-velocity surface layer. A realistic source function is analyzed in detail and normalized displacement response evaluated at different incidence angles in the near and the far fields.In an effort to distinguish the features of an SH torque seismogram from a pressure seismogram two models with identical layerings and layer parameters have been set up. As expected the torque seismogram is very different from the compressional seismogram. One desirable feature of a torque seismogram is the fast decay of multiples.Exact synthetic seismograms have many uses; some of them, such as the study of complex interference phenomena, phase change at wide angle reflection, channeling effects, dispersion (geometrical and material), absolute gain, and inelastic attenuation, can be carried out accurately and effortlessly. They can also be used to improve basic processing techniques such as deconvolution and velocity analysis.The numerical evaluation of the analytical solution of the wave equation as described in this paper has a long history. Most of the work leading to this paper was carried out by one of us (M. J. K.) in the years 1957 to 1968 at the Geophysical Research Corporation. However, the full testing of the various computer codes was carried out only very recently at the Phillips Petroleum Company.

Notizen: In South and Central Goa iron ore occurs in two parallel belts with the general NW-SE Dharawar trend. The ore occurrence, however, is not continuous. There are barren zones as well as zones of very high concentration in some of which there are mining activities.Landsat MSS data have been interpreted over a zone covering both mineral belts in order to delineate the ore occurrences. As a guide line a known ore-bearing area has been considered along with the unknown zones.On the basis of two-dimensional plotting of gray level values it has been found that the MSS bands 4 and 7 are most suitable for the studies over iron-rich areas in Goa. Two techniques are described here for the processing of the MSS data; the separation of residual from the regional and MSS band-ratioing. It is observed that (i) the gray level residual maps of MSS bands 4 and 7 are of use in demarcating the iron-ore-bearing zones, and (ii) an existing mine, an abandoned mine, and a proved iron ore zone could be delineated by MSS band-ratioing. On the basis of the latter technique, a few areas with ore occurrence potential have been indicated.

Notizen: The most common source of seismic energy is an explosion at some depth in a borehole. The radiated waves are reflected not only at the subsurface layers but also at the free surface. The earth's surface acts as a generator of both P- and S-waves.If the source depth is much less than the dominant wavelength the reflected waves resemble closely the waves generated by a single force. Theoretical seismograms were computed with different methods to look for the relevance of the surface-reflected waves. The numerical experiments show reflected shear waves even for small shotpoint—receiver distances. Due to their polarization these waves can be detected most easily on in-line horizontal geophones. The existence of these waves was examined during a conventional survey in Northern Germany. Conventional data analysis shows a large variability in the νp/νs ratio. The method used here produced a shear-wave section with a rather good signal-to-noise ratio down to 4 s S-wave reflection time.

Notizen: We describe the concept of physico-geological models (PGMs) in geophysical exploration. They represent a “general model”, a spatial combination of a set of particular models (disturbing bodies). The modeling is called complete, incomplete or approximate, depending on the degree of characterization of the PGM by parameters such as dimension, shape and petrophysical property. Each of the three modeling types can be realized as a conceptual, and analytical, or a material PGM. Both deterministic and stochastic PGMs exist; deterministic models are mainly used to investigate the possibilities of a geophysical method, while stochastic models serve to substantiate complex geophysical interpretations.Depending on the geological problem, PGMs are subdivided into multi-alternative models (geological mapping, prediction, general prospecting) and double alternative models (specialized prospecting).An exploration-oriented classification of the PGMs of mineral deposits is discussed. According to this classification the variety of known genetic deposit types is reduced to a limited number of generalized PGM types. The development of typical PGMs is illustrated with examples of magnetitic deposits of Siberia.

Notizen: A new mode of operation for the Turam electromagnetic exploration system is proposed in which the transmitter loop is placed across the expected trend of a conductor and the receiver is operated along lines parallel to one side of the transmitter. The concept appears to offer several benefits which include greatly extended traverse length, the use of large coil spacing, rejection of the effects of conductive environments, and consistency in the indication of target dip.

Notizen: Experiments were carried out on seven sites in Fermanagh to investigate the yield loss caused by leatherjackets in grassland. Populations on the sites ranged from 65,000 to 865,000 ha−1 and significant damage was recorded from all sites except the least populated. Greater yield increases were obtained by controlling leatherjackets in September when compared with control in March. Regression models were fitted and it was found that 125,000 leatherjackets ha−1 in March caused a yield loss of 50 kg herbage dry matter (DM) ha−1 by mid-May. Based on these figures the average yield loss to leatherjackets in Northern Ireland, from 1965 to 1982, was 208 kg DM ha−1. Controlling leatherjackets in September, rather than March, increased the potential avoidable yield loss by a factor of 2.72. The average yield loss at first silage cut is therefore 566 kg DM ha−1. On average, 100,000 ha grassland in Northern Ireland may be suffering an annual loss of 1t herbage DM ha−1.

Notizen: The utilization of sown and indigenous plant species was studied in three experiments in which plots were stocked with similar live weights of sheep and goats. In the first experiment the animals grazed plots containing 0–5 ha of rush (Juncus effusus)- infested reseeded pasture and 0–5 ha of unimproved blanket bog. The second and third experiments took place on old rush-infested improved pasture; in one experiment two levels of herbage mass of grass were provided while in the other the rushes were cut in spring or remained uncut.The goats grazed the rushes readily in all three experiments. Reduction in herbage mass of grass increased utilization of rushes by goats although these animals still grazed rushes when grass supply was plentiful. Sheep scarcely grazed J. effusus even when hard-pressed by shortage of grass. Both sheep and goats grazed J. acutiflorus.In Experiment I sheep utilized reseeded pasture more heavily than did goats. Sheep grazed similar proportions of the leaves of grass and clover while goats grazed a lower proportion of clover leaves as compared with grass. Among the grasses sheep discriminated in favour of Lolium perenne whereas goats did not. On the blanket bog vegetation, Eriophorum vaginatum and Calluna vulgaris were grazed both earlier in the season and more heavily by goats than by sheep.The relationships between sward structure and grazing height in accounting for differences in species selection by sheep and goats are briefly discussed. The possibility of using goals to control coarse weeds in hill pasture and for strategic grazing to manipulate floristic composition is outlined.

Notizen: The performances of a rising-plate meter and a single-probe electronic capacitance meter were compared for estimating the herbage mass of irrigated pastures both before and after grazing by dairy cows. Mean CV for the rising plate meter and the single-probe meter were 12.7% and 13.3% respectively when herbage mass was measured before grazing, and 21.8% and 15.4% respectively immediately after grazing. These coefficients of variation indicate that while the performance of the two meters was similar when herbage mass was measured before grazing, the single-probe meter was a more precise instrument for estimating herbage mass after grazing.Trampling of herbage prior to measurement had a major effect on the regressions of both meters; the regression intercept was increased by 2800 kg dry matter (DM) ha−1 for the rising-plate meter and by 2580 kg DM ha−1 for the single-probe meter. The slopes of the graphs, however, remained unchanged.It was concluded that while the single-probe meter performed better than the rising-plate meter for estimating the mass of post-grazing herbage when trampling was negligible, the large effect that trampling had on the post-grazing calibration regressions precluded both instruments from general use in dairy cattle research. This indicates that another technique is required in circumstances in which pastures are heavily trampled.

Notizen: Only a very limited number of species, including red fescue (Festuca rubra), perennial ryegrass (Lolium perenne), timothy (Phleum protense) and white clover (Trifolium repens) are considered as suitable for wet hill land. Detailed comparison of red fescue, perennial ryegrass and timothy on contrasting acid brown earth and stagnogley soils from 1966 to 1969 at Pant-y-dŵr Hill Centre (305 m OD) highlighted the advantages of red fescue in annual DM production and its more even distribution over a longer growing season but also indicated drawbacks of slow initial establishment and lower feed quality. In vitro DOMD of red fescue averaged 645 g kg−1 over the year compared with 690 g kg−1 for perennial ryegrass and timothy. Assessment of a narrow range of species under surface seeding conditions on a stagnogley soil from 1971 to 1975 confirmed the value of red fescue in DM production and persistence. The results are discussed in relation to the characteristics required in herbage species for hill land improvement.

Notizen: High-yielding grass-legume mixtures play an important role in forage-animal systems but finding compatible and adapted species can sometimes be difficult. The objective of this study was to examine productivity of perennial ryegrass and orchardgrass in pure stands with N and in mixtures with legumes.Broadcast sowings were made on conventionally prepared seedbeds in August 1979 and May 1980 on a Hagerstown silt loam soil (fine, mixed mesic Typic Hapludalf). When sown alone orchardgrass cv. Pennlate and perennial ryegrass cv. Reveille received rates of N ranging from 0 to 448 kg ha−1 a−1. The grasses were also grown in mixtures with alfalfa cv. Arc, red clover cv. Arlington, or birds foot trefoil cv. Viking. The same legumes were sown alone. Four legume seed rates were used in both the pure legume and mixed stands.Orchardgrass-N swards were more productive than ryegrass-N swards over 3 years. More dry matter (DM) was harvested from pure stands of

Notizen: Fungicide applied to plots of perennial ryegrass cv. S24 in the autumn of 1981 significantly increased tiller number and total dry matter accumulation in February and March of 1982. However, fungicide application in the autumn of 1982 failed to increase tiller number or dry matter accumulation in the spring of 1983. It is suggested that fungicide application in autumn 1981 prevented the death of tillers caused by fungal attack after snow covered the plots in December 1981.

Notizen: A mathematical model of grass production and utilization on a dairy farm is described. Using the model an assessment has been made of the extent to which financial uncertainty arising from year-to-year variability in grass yields, coupled with a preference among farmers for minimizing risks, may explain the relatively low stocking rates and observed nitrogen usages on many dairy farms in England and Wales. The degree of risk has been equated with the probability of profits in a particular year being less than those required to cover the consumption needs and short-term borrowing requirements of the farmer. The results of the analysis indicate that a strategy of minimizing risks may lead to a significantly lower stocking rate than one of maximizing profits. Thus, considerations of risk may lead to stocking rates which are suboptimal from the viewpoint of economic and biological efficiency. However, there is no evidence to suggest that the comparatively low average usage of nitrogen on dairy farms in the UK is determined by risk considerations. On the contrary, increasing nitrogen usage lowers the apparent financial risk at a given stocking rate.

Notizen: The herbage dry matter (DM) harvested, N response and herbage quality of monocultures and mixtures of Holcus lanatus (local ecotype) and Lolium perenne (cv. S24) were compared in a field experiment. The species were seeded in the proportions 100:0, 75:25, 50:50, 25:75 and 0: 100; three rates of N were applied (150, 300 and 450 kg ha−1) and five or six cuts were taken in each of four harvest years. H. lanatus established poorly in the seeding year and in the first full harvest year L. perenne contributed 1, 54, 76, 89 and 99% of the total herbage DM harvested from the five sward types (mean of N treatments). Only a small decline in the L. perenne content of the swards occurred during the experiment.Total amounts of herbage harvested were significantly lower for H. lanatus monoculture than for the other sward types in three of the four harvest years However, L perenne monoculture yielded significantly more total DM than mixtures with H lanatus in only one of the four harvest years. The five sward types did not differ overall in response to N fertilization. Nitrogen, phosphate and potassium content of the herbage was greatest for H. lanatus monoculture and decreased with increasing proportions ofL perenne present in the mixtures.Thus the presence of a high proportion of H. lanatus in mixture with L. perenne cv. S24 had

Notizen: Two experimental populations of Italian ryegrass selected for high and low magnesium content were established as swards, harvested fresh daily and offered to sheep. Chemical analysis of the crops showed a 44% higher Mg and a 22% higher Ca concentration in the high-Mg selection but no significant differences between the selections for the other minerals.Blood and rumen contents were sampled throughout the feeding period and voluntary intake, digestibility and mineral balances for Na, K, Mg, Ca and P were determined. Magnesium intake, apparent availability and retention were significantly greater with the high-Mg selection. There were no significant differences in the plasma-mineral concentrations and all were within the normal range. Rumen fluid from animals fed the high-Mg selection had a higher proportion of soluble Mg and a higher Na:K ratio in the supernatant liquor.

Notizen: A perennial ryegrass sward was managed by continuous stocking with sheep (April–September) for 4 successive years after sowing. The sward was grazed to maintain a leaf (lamina) area index (LAI) close to 1.0. Areas of the sward were released from grazing on three occasions: once during summer in the third year after sowing, and twice during spring and summer in the fourth year after sowing. There were marked changes in the structure and physiology of the continuously stocked sward following release from grazing. After several successive years of continuous stocking, the sward comprised a large population of small tillers and the small LAI resulted in consistently low rates of photosynthesis. Following release from grazing, photosynthesis increased markedly as the LAI increased but this change was associated with the loss of a large proportion of the population of tillers. There were seasonal differences in the pattern of changes in photosynthesis and tiller numbers following release from grazing which were not apparent under continuous stocking. The changes in the structure and physiology of the sward following release from grazing suggest that the net accumulation of herbage in areas of sward from which the animals are excluded, for instance using cages, may be an unreliable estimate of production under continuous stocking.

Notizen: A randomized block experiment was conducted to compare unwilted and wilted grass silages and the effects of the feed additive monensin sodium on the silage intake and performance of finishing beef cattle. Two regrowths from a predominantly perennial ryegrass (cv. S24) sward were ensiled either without wilting or after field wilting for 3 d (dry matter (DM) concentrations 161 and 266 g kg−1 respectively). Both silages were treated with formic acid (2·6 and 30 litre t−1 respectively) and were well preserved. The silages were offered ad libitum to forty-eight Charolais-cross cattle (thirty-two steers and sixteen heifers, mean initial live weight 351 kg) for 145 d. All animals received 2·2 kg concentrates per head daily and half of those on each silage treatment received in addition 200 mg monensin sodium per head daily. Silage DM intake was 5.04, 504. 5·48, 5·63 ± 0.134 kg d−l; fasted liveweight gain was 0·69, 0·77. 0·64 and 0·73 ± 0.033 kg d−l and carcass gain was 0·47, 0·50, 0·40 and 0·45 ± 0·020 kg d−1 for the unwilted silage without and with monensin and the wilted silage without and with monensin respectively. It is concluded that wilting grass of low DM concentration for 3 d prior to ensiling reduced the performance of finishing beef cattle below that obtained from well-preserved unwilted silage in spite of a higher DM intake being achieved with the wilted silage. The inclusion of monensin sodium in a silage-based diet increased performance without significantly affecting feed intake.

Notizen: Formic acid, sodium diacetate, propionic acid and two of its ammonium salts, ammonium isobutyrate and tributyl phosphate, were examined for their antimicrobial effects with cultures of micro-organisms typical of the microflora of moist hay. The assays, which were conducted at pH 5, 6, 7 and 8, revealed that all potential preservatives discriminated against actinomycetes in particular and were least effective against fungi. In addition, it was apparent that antimicrobial properties were enhanced under slightly acid conditions and for this reason the use of mixtures of organic acids and salts in commercial hay preservatives is justified. Tributyl phosphate not only had the strongest antimicrobial properties of the compounds tested but was also the least affected by pH.

Notizen: Yields of grass were measured on three dairy farms in 1981. Farm 1, on free-draining loamy soil over chalk, produced 10.3 t DM ha−1 using 336 kg N ha−1. Farm 2, on poorly-drained loam over Oxford clay, produced 12.8 t DM ha−1 using 354 kg N ha−1. Farm 3, on loam over clay with some free-draining sandy loam, produced 9.5 t DM ha−1 with 169 kg N ha−1. Allowing for differences in soil nitrogen and summer rainfall these yields were quite close to expectations from experimental results, despite considerable poaching damage to some swards.Animal production records were kept and all livestock were weighed every 6 months, so as to calculate the utilized metabolizable energy (UME) output from grassland on each farm. These were 73, 62 and 59 GJ ha−1 on farms 1, 2 and 3 respectively.The UME output, expressed as a proportion of the yield of grass (converted to ME), was taken as the ‘efficiency of utilization’ of grass. This was 70% on farm 1,44% on farm 2 and 58% on farm 3. Results are presented separately for the summer and winter 6 months. Utilization by grazing appeared to be markedly reduced under very wet soil conditions. Major losses occurred in the conservation of grass.The results begin to establish a valuable base of data from commercial farms.

Notizen: The establishment and growth of white clover (cv. Grasslands Huia) was investigated in two experiments with seeds sown in slots cut in old permanent pasture in early May 1982. In the first experiment, fully protected from pests and diseases, either 50 (low), 100 (medium) or 200 (high) seeds were sown evenly per metre length of slot; 100 seeds were also sown in a clumped pattern unevenly. In the second experiment, the effects of various combinations of molluscicide, insecticide and fungicide were investigated.Nine weeks after sowing there were 27, 37, 34 and 62 seedlings m−1 on the low, medium even, medium uneven and high seed-rate treatments, representing percentage establishments of 54, 37, 34 and 31 respectively. By September, however, there were no significant differences between the dry weights m−l of any of the treatments. In the second experiment, damage by slugs occurred early in treatments without molluscicide and caused a mean reduction of 70% in seedling establishment. As a result significantly smaller dry weights m−1 of clover were recorded in September in these than in other treatments. Failure to protect against insects resulted in smaller seedlings.The results indicated that variations in seed rate within the range investigated were not critical but that failure to protect against pests decreased percentage establishment and subsequent growth.

Notizen: Masham ewes were stocked at 12(L), 16(M) or 20 (H) ewes ha−1, with 1·8 lambs per ewe on average, on two blocks (A and B) in both 1976 and 1977. Silage was offered at pasture to the ewes in early lactation and as stocking rate increased from 12 to 16 and then 20 ewes ha−1, 47, 73 and 100 kg DM per ewe was consumed respectively. Silage was cut mainly in the autumn and 179, 100 and 9 kg per ewe was made for L, M and H respectively. More variation between treatments was measured in net herbage accumulation in summer than spring and 11·4, 10·0 and 9·7t DM ha −1 was grown over the whole season for L, M and H respectively as a mean of both years.High intakes of herbage OM were measured with values up to 40 g per kg live weight for BL lambs in 1976. Rapid lamb growth was achieved. There were effects of stocking rate on lamb performance and for L, M and H the respective growth rates to 4 weeks were 266, 248 and 247 g d−1; growth rates to sale were 274, 263 and 252 g d−1; days to sale were 124, 126 and 129; mean carcass weights were 17·7, 17·1 and 16·7 kg. Most ewes lost weight in early lactation, especially AH and BH in 1976, but there were no stocking rate effects on ewe weight change in 1977.

Notizen: Classical methods of interpretation of reflection seismic data are such that interpretation and processing usually occur in the “collected” frame of reference. However, in recent times other data planes have gained increasing acceptance in seismology as a viable alternative. Through linear transformations applied to a record section, both the t—p- and p—x-planes can be produced. The r—p-domain may be obtained from the t—x-plane by a transformation known as slant stacking. Normal practice has been to do most of the data processing in the t—x-plane and then transforming to the r—p-plane. However, many of the procedures used in the t—x-domain can be modified for use in the t—p-plane to increase the coherence.Velocity inversion may be carried out either in the r—p-domain or further transformed to the p—x-plane where the modified Herglotz-Wiechert inversion may be applied. To perform the inversion, the t—p-wavefield is converted to a p—x-representation by the use of a new linear transformation technique, the cross-stack. By a simple sampling process along a particular p—x-trajectory, the Herglotz-Wiechert method can be used to reconstruct an acceptable velocity model of the subsurface. A comparison of derived velocity structures is made between that produced by the Herglotz-Wiechert technique and that of the Dix method.

Notizen: The computation of static corrections requires information about subsurface velocities. This information can be obtained by different methods: surface wave analysis, short refraction lines, downhole times, uphole times and first arrivals from seismograms.For pure shear waves generated by SH sources the analysis of first arrivals from seismograms combined, if necessary, with short refraction lines has proved to be most accurate and economic.A comparison of first-arrival plots from P- and S-wave surveys of the same line measured in areas of unconsolidated sediments in northern Germany illustrates the characteristic differences between the two velocity models. P-waves show a marked velocity increase at the water table from about 600 to 1800 m/s. S-wave velocities of the same strata increase gradually from about 100 to 400 m/s. As a consequence, S-wave models are vertically and laterally more complex and, in general, show no significant velocity increase at a defined boundary as P-wave models do. Therefore, other suitable correction levels with specific velocities must be chosen.A comparison of “tgd-corrections” (correction time between geophone position and datum level) for P- and S-waves in areas of unconsolidated sediments shows that their ratio is different from the P-/S-velocity ratio for the respective correction level because of the greater depth of the S-wave refractor. Therefore, P- and S-waves are influenced by different near-surface anomalies, and time corrections calculated for both wave types are largely independent.

Notizen: Forward filters to transform the apparent resistivity function over a layered half-space into the resistivity transform have been derived for a number of sample intervals. The filters have no apparent Gibbs' oscillations and hence require no phase shift. In addition, the end points of the filter were modified to compensate for truncation. The filters were tested on simulated ascending and descending two-layer cases. As expected, “dense” filters with sample spacing of In (10)/6 or smaller performed very well. However, even “sparse” filters with spacing of In (10)/2 and a total of nine coefficients have peak errors of less than 5% for p1:p2 ratios of 10–6 to 106. If a peak error of 5.5% is acceptable, then an even sparser filter with only seven coefficients at a spacing of 3 In (10)/5 may be used.

Notizen: The concept of minimum phase is clarified for geophysicists by collecting in one place the properties of minimum phase functions. The “earliest energy arrival” property in the time domain, the “minimum phase-slope property” in the frequency domain, and of the role of causal all-pass filters are demonstrated. The emphasis is placed on keeping the mathematics within the realm familiar to geophysicists and on making clear the somewhat imperfect match between physical continuous time functions and their associated discrete time representations.

Notizen: Volcanic maar structures sometimes contain important groundwater reserves. The volcanic formations of the Beaunit maar have a much higher magnetization than their granite substrata. The structure of the maar and its volcanoclastic infill can therefore be defined by magnetic surveying and resistivity soundings. Resistivities of the geological formations present in the Beaunit maar are comparable to those recorded in other volcanic systems. The geophysical data, confirmed by drilling tests, contain useful information on the hydrogeological regime of the volcanic system under investigation.

Notizen: In migration procedures, the velocity profile of the subsurface is the most important input information. Since, in general, this information is only approximately known, errors in the migration output due to errors in the velocity input occur in all practical applications. In migration, velocity errors and depth errors can be interchanged. This interchange property is perfect in the paraxial approximation. From this result it follows that migration with incorrect velocities may still yield correctly migrated data if the imaging principle is modified. This attractive property can be used in the stripping version of migration (recursive migration).

Notizen: The presence of the water layer in marine seismic prospecting provides an effective waveguide for acoustic energy trapped between the sea-bed and the sea-surface. This energy persists to large ranges and can be the dominant early feature on far-offset traces. On airgun records, there is commonly a lower frequency set of arrivals following the water-trapped waves. These arrivals are not as obvious with higher frequency watergun sources. By using a combination of intercept-time/slowness (τ—p) mapping on observational data and theoretical modelling, we are able to identify the origin of the events. If a very rapid increase in a seismic wavespeed occurs beneath the sea-bed sediments, a new waveguide is formed bounded by the sea surface and this transition zone. The low frequency waves are principally guided within this thicker waveguide. Numerical filtering in the τ—p domain followed by trace reconstruction is very effective in removing the low frequency noise.

Notizen: The efficacy of the magnetotelluric and audiomagnetotelluric (MT/AMT) methods for detailing the structure of a hypothetical geological section is investigated by using the singular value decomposition (SVD) technique. The section is representative of southeastern Turkey, which is mostly covered by basalt and is a prime area for oil exploration. One of the geological units, the Germav shale at a depth of 600 m, is a problem layer for electromagnetic surveys because of its very low resistivity (on average 3 Ωm) and highly variable thickness across the area (200–900 m). In the MT frequency range (0.0004–40 Hz) its total conductance—or, since its resistivity is known from resistivity log information, its thickness—is the best resolved model parameter. The total depth to the Germav shale and the resistivity of the Cambrian/Precambrian basement are the marginally resolved parameters. In the AMT frequency range (4–10000 Hz) the resistivity of the surface basalt layer strongly affects the resolution of the other, less important, model parameters which are the total depth to the Germav shale and the total conductance of the Germav shale. The errors in the measurements determine the number of model parameters resolvable, and are also important for interpretation of the geological model parameters to within a desired accuracy.It is shown that statistical evaluation of the MT and/or AMT interpretations by using an SVD factorization of the sensitivity matrix can be helpful to define the importance of some particular stage of the interpretation, and also provides a priori knowledge to plan a proposed survey. Arrangements of MT and AMT observations, together with some Schlumberger resistivity soundings, on a large grid will certainly provide three-dimensional detailed information of the deep geoelectric structure of the area.

Notizen: A method for interval velocity analysis is formulated on the basis of wavefield extrapolation, i.e., on the basis of wave-equation migration. When this scheme is applied to multioffset seismic sections or to an ensemble of CMP gathers, it allows for the proper treatment of dipping events. The underlying assumptions are that local velocities should be derived from data associated with events within the interval under consideration. To minimize the effect of the region above the layer of interest, the data are first extrapolated to the top of the analysis interval. Subsequent analysis of these data then pertains to the events within this interval. Velocity estimation consists of repeated wavefield extrapolations through the analysis interval using a set of trial velocities. The optimal velocity is chosen on the basis of coherency measures designed to express the collective phase agreement among a set of offset Fourier modes. The reliability of this approach to interval velocity estimation is demonstrated on synthetic multi-offset data.

Notizen: A statistical treatment of MT data from the Pannonian Basin, Hungary, based on the distortion theory of the S-effect suggests that the local increase in crustal conductivity is connected with deep fractures.Field model measurements have recently been carried out in a shallow, quasi two-dimensional basin of well known tectonics using MT station distances of 1–3 km. The results of the investigation and numerical modelling of near surface distortions, support the idea that deep fractures (faults) contain the conducting formations. According to 2-D model computations, several conducting dykes at considerable depths can cause anomalies which are indiscernible from an anomaly due to a conducting layer. The significance of these results is discussed from the point of view of geothermal energy exploitation.

Notizen: A principal use of the vertical seismic profile (VSP) is to determine the variation of seismic velocity with depth. Presented here is a discussion of the errors involved with the time picks of a VSP survey and several methods currently used to calculate a velocity section from these time picks. Another technique is proposed, based on the least-squares inversion of the traveltimes, to arrive at a better estimate and statistical description of the velocity section. This technique uses the Levenberg-Marquardt damped least-squares formulation and ray tracing through a horizontally-layered medium to iteratively refine the velocity section. The accuracy and robustness of the procedure are investigated by inverting noisy traveltime curves and comparing these results to the original model velocity section. Agreement is found to be good. One interesting feature of the inverse procedure is that, for certain geometries, it can resolve a few velocity layers, even though there are no measurements made inside those layers. Three actual VSP surveys are analyzed and compared to their corresponding sonic logs. In two of the surveys, it appears that there is some velocity dispersion. Velocity changes associated with gas saturation are evident on one of the surveys.

Notizen: It is well recognized that in order to realize the full potential of the Vibroseis technique, one needs to ensure accurate phase locking and a meaningful cross-correlation. To achieve these two important objectives we require an accurate estimate of the compressional stress wave radiated by the vibrator into the ground.In this paper a simple method (subject of a patent application) is developed for predicting the compressional stress waves radiated by a vertical vibrator. The main feature of the proposed method is that it involves the field measurement of the acceleration of the reaction mass and the baseplate, respectively.The method is illustrated by computing the compressional stress waves generated by a typical vertical vibrator radiating into ice, chalk, sand, and mud. It is shown that for a seismic vibrator radiating into hard ground the pressure of the downgoing P-wave is 180° out of phase with the baseplate velocity. It is also shown that when the driving force of the seismic vibrator has a flat amplitude spectrum, the amplitude spectrum of the downgoing P-wave falls off by 6 dB/octave towards low frequencies.

Notizen: Bedding on a scale small in comparison to the wavelength results in transverse isotropy. On the other hand, anisotropy has been observed in the field, particularly with horizontally polarized shear waves. In this article velocity data from 23 wells are used to estimate the resulting transverse isotropy and to compare these data with anisotropy observations reported in the literature. Since the well data were compressional velocity (or rather transit time) only, the corresponding shear velocity data were estimated on the basis of a reasonable—though arbitrary—assumption of Poisson's ratio. Actual densities were used wherever they were available; for the remainder of the data, density was assumed to be constant throughout the averaging interval.The anisotropy data estimated on this basis were generally considerably smaller than the observational data that have been reported in the literature. Although both the above assumptions—functional dependence of Poisson's ratio on transit time and constant density—tend to underestimate anisotropy, and although 23 wells is but a small subset of all available data, it appears unlikely that bedding alone could cause anisotropy of the magnitude reported.

Notizen: In land seismic surveys spectrum equalization can increase the quality of seismic data in a selected frequency band. The power of lower frequencies in the spectrum of input traces is generally greater than that of higher frequencies, particularly in land seismic surveys because of ground roll. In order to improve the quality of seismic data it is necessary to raise the energy of higher frequencies to the same level as that of lower frequencies, without alteration of the phases.The first step of the method is to compute the amplitude spectrum of each input trace to determine a weighting function which is then applied to the amplitude spectrum in order to balance it. The function is the inverse of the short wavelength variation of the amplitude spectrum. The short wavelength variation can be obtained by interpolation between average values of the modulus of the amplitude spectrum computed in narrow bands within a selected band of frequencies. Another way of obtaining the short wavelength variation is to apply a low-pass filter to the amplitude spectrum. The calculations are readily performed in the frequency domain by the Fourier transform.Spectrum equalization is automatically adjusted to each trace and does not modify the average amplitude in the time domain. However, as the frequency band and energy of the ground roll both vary according to the distance from the shot, spectrum equalization tends to make the spectrum of output traces independent of the offset distance.The use of spectrum equalization before any two-dimensional filtering improves ground roll elimination. Continuity and resolution of horizons are also increased by spectrum equalization before CDP stack.Several examples of applications of spectrum equalization to seismic land and marine surveys are shown.

Notizen: A thin superparamagnetic layer on the earth's surface greatly affects the transient electromagnetic response of a conducting ground. The effect of the layer is most evident for singleloop transient electromagnetic data where transient voltages decay as 1/t. Even when a separate transmitter and receiver are used, the effect of the superparamagnetic layer is still pronounced. In this case the effect of the 1/t term in the equation is much less. More dominant now is a 1/t2 term. The effect of the superparamagnetism can readily be seen in the analytical expressions for the apparent resistivities. If the presence of the superparamagnetic layer is not recognized, then the apparent resistivities decrease with time rather than approach the true value of the host rock.

Notizen: The use of very long streamers in marine seismic surveys makes the response offset dependent. Line equalization networks are used to balance this effect.In this paper the response of the transformerless streamer system driving a charge amplifier is analyzed. Examples are given for a seismic cable 2500 m long, showing that the delay and the reduction in amplitude of the streamer impulse response in the absence of leakage are of the order of 1 ms and 0.6 dB, respectively. This means that the line equalization network currently used with the transformerless streamer system is not needed. We have also demonstrated that the presence of leakage resistance across the hydrophone group render the sensitivity of the transformerless streamer system offset dependent.

Notizen: Different sets of filter coefficients for the linear filter technique for the computations of resistivity and EM sounding curves are evaluated for several electrode and coil configurations. Instead of this procedure, the two-electrode filter can be used for computations of Wenner, Schlumberger, and dipole—dipole apparent resistivity model curves by defining convolutional expressions which contain the new input functions in terms of the resistivity transform function. Similarly, the Schlumberger filter performs the computations of dipole—dipole apparent resistivity model curves. The Wenner, Schlumberger, and dipole—dipole filter functions are defined in terms of the two-electrode filter using the new convolutional expressions. A relationship between the Schlumberger and dipole—dipole filter functions is given.The above arguments are adopted for the computations of EM sounding curves. It is shown that the EM filter for the horizontal coplanar loop system (which is identical to the two-electrode filter) performs the computations of the mutual coupling ratios for perpendicular, vertical coplanar, and vertical coaxial loop systems. In the same way, the Schlumberger filter can be used to compute vertical coaxial sounding curves. The corresponding input functions are defined in terms of the EM kernel for all convolutional expressions presented.After these considerations, integral expressions of the mutual coupling ratios involving zero-order Bessel function are derived. The mutual coupling ratio for the vertical coaxial loop system is given in the same form as the mutual coupling ratio for the vertical coplanar loop system.

Notizen: Field results of shallow seismic reflections obtained with a propane-oxygen detonator (POD) are presented. The survey site was in a tin-mining area of the Kinta Valley in Malaysia. The shallow and irregular limestone bedrock is overlain by alluvial “tailing” and virgin sediments. Sizes of such mining areas can range from about 320 ± 320 m2 to 900 ± 900 m2. The survey was intended to delineate the topography of the bedrock, which is of vital importance in tin ore exploration and exploitation. The equipment included single- and 12-channel signal enhancement seismographs, the POD, a hammer and thumper. The inexpensive and portable POD generates directional waves of reproducible form, variable energy of high frequency, and only a few surface waves at short offsets. Reflections at around 200 Hz were obtained from the shallow bedrock at about 25 m as well as from very shallow lithological interfaces. The interpretation of seismograms is supported by drill-hole lithological sections and synthetic seismograms. The data illustrate the successful use of shallow reflections for mapping irregular bedrock. Reflection seismics can provide better horizontal and vertical details than the refraction method. Further improvements based on the data-processing flexibility of new signal enhancement seismographs and synthetic seismograms are suggested.

Notizen: Dynamic elastic moduli like E, μ, K and μ of the foundation rock of a dam have been determined by finding Vp- and Vs-velocities by seismic refraction with a hammer as source. Some parameters such as “fracture frequency” and “rock quality designation” (RQD) of the foundation rock have been derived using “average regression curves” and Vp-velocities. By comparing K/μ with Vp/Vs, a few locations showing weathered conditions have been demarcated. This compares well with RQD values of those locations.

Notizen: Using homogeneous full-space and half-space models, we show that induced-polarization properties of the medium influence the inductive coupling between two circuits. It is suggested that existing methods to interpret electromagnetic sounding data should be viewed with caution if the electro-chemical dispersion is not taken into account.

Notizen: A synthetic seismogram that closely resembles a seismic trace recorded at a well may not be at all reliable for, say, stratigraphic interpretation around the well. The most accurate synthetic seismogram is, in general, not the one that displays the smallest errors of fit to the trace but the one that best estimates the noise on the trace. If the match is confined to a short interval of interest or if the seismic reflection wavelet is allowed to be unduly long, there is considerable danger of forcing a spurious fit that treats the noise on the trace as part of the seismic reflection signal instead of making a genuine match with the signal itself. This paper outlines tests that allow an objective and quantitative evaluation of the accuracy of any match and illustrates their application with practical examples.The accuracy of estimation is summarized by the normalized mean square error (NMSE) in the estimated reflection signal, which is shown to be(/n)(PN/PS)where PS/PN is the signal-to-noise power ratio and n is the spectral smoothing factor. That is, the accuracy varies directly with the ratio of the power in the signal (taken to be the synthetic) to that in the noise on the seismic trace, and the smoothing acts to improve the accuracy of the predicted signal. The construction of confidence intervals for the NMSE is discussed. Guidelines for the choice of the spectral smoothing factor n are given.The variation of wavelet shape due to different realizations of the noise component is illustrated, and the use of confidence intervals on wavelet phase is recommended.Tests are described for examining the normality and stationarity of the errors of fit and their independence of the estimated reflection signal.

Notizen: There are numerous modeling techniques commonly employed for the computer simulation of seismic wave propagation. The capabilities of these techniques vary according to the theoretical foundations and subsequent approximations upon which the algorithms are based. This paper constitutes a comparative review of seven modeling methods: geometric ray theory, asymptotic ray theory, generalized ray theory, Kirchhoff wave theory, Fourier synthesis, finite differences, and finite elements.These methods can be categorized as ray or wave, acoustic or elastic, and can be contrasted according to their relative abilities to simulate such behavior as wave interference effects, diffractions, and mode conversions. As is implied by their names, geometric ray theory and asymptotic ray theory are both ray methods. The other five methods provide wave theory simulations. Geometric ray theory and Kirchhoff wave theory are normally implemented in acoustic form, while the other methods are readily adapted for computing elastic theory solutions. Generalized ray theory and Fourier synthesis are more limited in the complexity of geological model they can accommodate than are the other techniques. The methods which typically demand the greatest computer resources are the finite-difference and the finite-element techniques. All methods can incorporate at least some multiple events. Diffractions, however, are only inherent in the solutions computed by Kirchhoff wave theory, finite differences and finite elements. Attenuation is readily incorporated in both the Fourier synthesis and the finite-element methods.As an example of the application of seismic modeling, a geological model representative of a typical petroleum exploration target is used to compare vertical seismic profiles calculated by different modeling methods.

Notizen: The cross-hole variant of the magnetometric resistivity (MMR) method requires two bore holes in the vicinity of a conductive target. In the first, two fixed current electrodes are located, one above the other. They are linked to a low frequency current source by cables, the whole system forming a vertical current bipole. In the second, a sensitive coil measures the axial magnetic field as a function of depth. For a uniform earth, if both holes are vertical, the measured component vanishes by symmetry. However, the presence of a local conductor channels the current and causes an anomalous magnetic component which is interpreted to indicate the position, shape and relative conductance of the target.Mineral deposits are often lamellar in form. The conductive disc is the simplest bounded lamella for which MMR responses may be computed. It is excited by a single current source on its axis. The second source and the surface of the earth are assumed to be far away, a valid assumption for down-hole measurements.The numerical method introduces a new integral equation describing the interaction of current dipoles located in the plane of the disc. The equation is solved analytically for a disc of infinite radius, a layer, and the result is compared with a corresponding known boundary value solution.The computed radial current in the disc and the magnetic field generated by it are described in terms of a current channelling number. The magnitude of the computed field is of the order of one nanoTesla for a typical mining problem.

Notizen: Time horizons can be depth-migrated when interval velocities are known; on the other hand, the velocity distribution can be found when traveltimes and NMO velocities at zero offset are known (wavefront curvatures; Shah 1973).Using these concepts, exact recursive inversion formulae for the calculation of interval velocities are given. The assumption of rectilinear raypath propagation within each layer is made; interval velocities and curvatures of the interfaces between layers can be found if traveltimes together with their gradients and curvatures and very precise VNMO velocities at zero offset are known.However, the available stacking velocity is a numerical quantity which has no direct physical significance; its deviation from zero offset NMO velocity is examined in terms of horizon curvatures, cable length and lateral velocity inhomogeneities.A method has been derived to estimate the geological depth model by searching, iteratively, for the best solution that minimizes the difference between stacking velocities from the real data and from the structural model.Results show the limits and capabilities of the approach; perhaps, owing to the low resolution of conventional velocity analyses, a simplified version of the given formulae would be more robust.

Notizen: From a great variety of in situ shear wave experiments, i.e., reflection, refraction and borehole surveys in the shallow sediments of the north German plains, several specific properties have been derived. Shear waves (S) differ from compressional waves (P) in that:〈list xml:id="l1" style="custom"〉1they are not affected by the degree of water saturation. Thus, they provide a better correlation between the velocity Vs and (solid) lithology;2they generally have lower frequencies, but shorter wavelength and, hence, a better resolution of thin layers;3they have lower absorption Qs−1 and hence a better penetration in partially saturated and gas-containing sediments than P-waves.Correlations have been established between Vs and the confining pressure and between reduced Vs values and several lithological parameters like the grain size of sandy material. More lithological and hydrological information is obtained by using S- and P-wave surveys along the same profile. The best information on a sedimentological structure is obtained by the simultaneous observation of Vs, Vp, Qs and Qp.

Notizen: In the design of linear airgun arrays the interaction between the airguns is usually neglected. We review the different formulae which have been proposed for the minimum separation between airguns at which the interaction is negligible. These formulae can all be approximated by a linear function of a single variable.We have analyzed a large number of measurements in order to establish the amount of interaction between two airguns of various volumes at different pressures and depths. The resulting far-field signature has been measured and compared with the sum of the signatures from the two airguns measured in the same experimental situation. The changes in primary pulse amplitude, bubble period and primary/bubble peak-to-peak amplitude ratio were computed from the measurement data as a function of airgun separation, chamber volume, chamber pressure and airgun depth. The influence of a waveshape kit was investigated, and the effects of interaction and the effects of using a waveshape kit were compared.

Notizen: Almost all ray-tracing methods ignore the analysis of the amplitudes of seismic arrivals and therefore utilize only half of the available information. We propose a method which is a combination of ray-tracing imaging and transformation of the amplitudes of wide-aperture data.Seismic data in the conventional X-T domain are first transformed to the domain of intercept time τ and ray parameter p to recover the plane wave response. The next step is the derivation of a series of plane wave reflection coefficients, which are mapped as a function of τ and p. The reflection coefficients R(τ, p) for two arbitrarily chosen traces can then be used in our inversion method to derive a slowness-depth and a density-depth profile. It is shown that the inclusion of amplitudes of seismic arrivals (in this method, we consider the acoustic case) makes the inverse method highly stable and accurate. In a horizontally stratified medium one can recover separate profiles of velocity and density. Since this method utilizes large-offset data, it can be used for separate recovery of velocity and density to a greater depth.