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- Volume 35, Issue 4, 1987
Geophysical Prospecting - Volume 35, Issue 4, 1987
Volume 35, Issue 4, 1987
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TRACE INTERPOLATION IN SEISMIC DATA PROCESSING *
By V. BARDANAbstractTrace interpolation of spatially aliased seismic data is used to improve the quality of multi‐trace processing, especially that of migration. We consider non‐rectangular sampling lattices. After stating the real sampling requirements for (two‐dimensional or 3‐D) digitized signals, the paper explains geometrically the effect of migration and of the 2‐D dip filtering upon the aliased events, as well as our ability to interpolate traces from undersampled seismic data.
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A METHOD FOR DETECTION OF DIFFRACTED WAVES ON COMMON‐OFFSET SECTIONS*
Authors E. LANDA, V. SHTIVELMAN and B. GELCHINSKYABSTRACTA method of detection of diffracted waves on common‐offset sections is proposed. The method utilizes the main kinematic and dynamic properties of the diffracted waves. The detection algorithm is defined by an automatic procedure including phase correlation of the diffracted waves and the application of certain statistical criteria. This procedure enables us to make decisions with regard to the presence of the diffracted waves and also to estimate parameters of the scattering objects. The method is applied to synthetic and field data and, even for a relatively low signal‐to‐noise ratio, it gives reliable results.
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JOINT INTERPRETATION OF GRAVITY AND MAGNETIC DATA OVER AXIAL SYMMETRIC BODIES WITH APPLICATION TO THE DARNLEY BAY ANOMALY, NWT CANADA*
Authors R.E. CHAVEZ, R.C. BAILEY and G.D. GARLANDABSTRACTA method is presented for determining bounds of the properties of axial symmetric bodies from a finite number of gravity and magnetic observations based on Parker's theory of ideal bodies. Bounds on the density contrast and the intensity of magnetization are calculated as a function of depth to the top of the anomalous source, restricting the range of smallest possible solutions to fit the data.
The model studied is approximated by an array of vertical annuli cylinders, each of uniform density and magnetization. Linear programming algorithms based on the ideal body theory were used to calculate the distribution of these parameters within the body.
Simultaneous inversion of gravity and magnetic data is performed assuming a constant ratio between the density contrast and the intensity of magnetization and that a common body is responsible for both observed fields. The parameter k(|J|/δp) provides information about the rock type of the structure.
Interpretation of gravity and aeromagnetic data from Darnley Bay, NWT, Canada, indicated the presence of a shallow ultrabasic intrusion.
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TEMPERATURE ANOMALIES OVER UNDERGROUND CAVITIES*
More LessABSTRACTTheoretical and practical aspects of a new method for underground cavity localization are presented. The method is based on shallow temperature measurements. It is shown that such measurements can complement the geophysical methods most commonly used for cavity location.
The results from finite‐difference numerical calculations indicate possible origins of temperature anomalies–the existence of which is confirmed experimentally, primarily by field measurements. Temperature anomalies up to 1°C have been recorded over underground cavities. A satisfactory agreement between measurements and theory is found.
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GEOPHYSICAL MAPPING BY STATIONARY ELECTRIC AND MAGNETIC FIELD COMPONENTS: A COMBINATION OF POTENTIAL GRADIENT MAPPING AND MAGNETOMETRIC RESISTIVITY (MMR) METHODS*
By L. SZARKAABSTRACTA combined application of two independent direct current geoelectric methods, potential gradient mapping (PM) and magnetometric resistivity (MMR), is proposed for the investigation of high‐resistivity basement structures.
From a one‐dimensional relation between horizontal electric and magnetic fields (due to currents originating from point electrodes placed on the surface of a two‐layered half‐space having a high‐resistivity basement) several advantages of the combined PM‐MMR method are shown for two‐dimensional and three‐dimensional basement structures. Three‐dimensional models have been studied by analogue modeling experiments.
This new mapping method embraces two parameters: the horizontal electric conductance map, derived from the ratio of the related electric and magnetic components, and the gradient map of their product. A close relation between structural forms and anomaly maps is obtained by using two orthogonal source‐electrode layouts.
Based on model results a two‐channel measuring instrument was developed. The method and the instrument were tested near Sopron where a gradual deepening of, and faults in, the Paleozoic basement were found.
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TRANSFORMATION OF DIPOLAR, WENNER AND TWO‐ELECTRODE CURVES TO SCHLUMBERGER APPARENT RESISTIVITY SOUNDING CURVES*
Authors BUDDHADEB BANERJEE and B. J. SENGUPTAABSTRACTA simple mathematical technique based on regressional analysis allows the transformation of dipolar, Wenner and two‐electrode apparent resistivity sounding curves to Schlumberger ones. The algorithm is suitable for a programmable pocket calculator and the accuracy is very high. This has been demonstrated by comparing Schlumberger master curves with transformations of master curves for the other configurations for the same model.
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INTERPRETATION OF TRANSIENT EM COMMON‐LOOP ANOMALIES BY RESPONSE CHARACTERISTICS*
By R.D. OGILVYABSTRACTTheoretically exact type curves for a semi‐infinite thin conductor are presented for various dip, angles, depth of burial and conductance. The study shows that the common‐loop response shape is sensitive to small changes in conductor dip, but is affected more subtly by comparable strike variations. For large sheet conductors a decrease in the strike angle results in a broadening but unlike that for a finite plate there is no reduction in peak amplitude. For dipping conductors, response asymmetry and the direction and magnitude of peak amplitude displacement can be used to assess the disposition and quality of the conductor. A generalized interpretation scheme is proposed, based on dimensionless response characteristics and normalized decay curves, to facilitate the rapid in‐field determination of conductor dip, conductance and depth of burial, for any time regime.
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Volumes & issues
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Volume 72 (2023 - 2024)
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Volume 71 (2022 - 2023)
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Volume 70 (2021 - 2022)
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Volume 69 (2021)
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Volume 68 (2020)
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Volume 67 (2019)
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Volume 66 (2018)
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Volume 65 (2017)
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Volume 64 (2015 - 2016)
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Volume 63 (2015)
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Volume 62 (2014)
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Volume 61 (2013)
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Volume 60 (2012)
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Volume 59 (2011)
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Volume 58 (2010)
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Volume 57 (2009)
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Volume 56 (2008)
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Volume 55 (2007)
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Volume 54 (2006)
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Volume 53 (2005)
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Volume 52 (2004)
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Volume 51 (2003)
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Volume 50 (2002)
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Volume 49 (2001)
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Volume 48 (2000)
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Volume 47 (1999)
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Volume 46 (1998)
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Volume 45 (1997)
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Volume 44 (1996)
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Volume 43 (1995)
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Volume 42 (1994)
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Volume 41 (1993)
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Volume 40 (1992)
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Volume 39 (1991)
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Volume 38 (1990)
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Volume 37 (1989)
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Volume 36 (1988)
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Volume 35 (1987)
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Volume 34 (1986)
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Volume 33 (1985)
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Volume 32 (1984)
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Volume 31 (1983)
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Volume 30 (1982)
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Volume 29 (1981)
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Volume 28 (1980)
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Volume 27 (1979)
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Volume 26 (1978)
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Volume 25 (1977)
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Volume 24 (1976)
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Volume 23 (1975)
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Volume 22 (1974)
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Volume 21 (1973)
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Volume 20 (1972)
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Volume 19 (1971)
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Volume 18 (1970)
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Volume 17 (1969)
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Volume 16 (1968)
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Volume 15 (1967)
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Volume 14 (1966)
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Volume 13 (1965)
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Volume 12 (1964)
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Volume 11 (1963)
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Volume 10 (1962)
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Volume 9 (1961)
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Volume 8 (1960)
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Volume 7 (1959)
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Volume 6 (1958)
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Volume 5 (1957)
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Volume 4 (1956)
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Volume 3 (1955)
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Volume 2 (1954)
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Volume 1 (1953)