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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Inorganic chemistry 27 (1988), S. 871-873 
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 77 (1955), S. 5482-5488 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 79 (1957), S. 5608-5611 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 78 (1956), S. 4896-4900 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 129 (1989), S. 295-307 
    ISSN: 1420-9136
    Keywords: Large mine tremors ; source parameters ; ground motion parameters ; Klerksdorp mining district ; Carletonville mining district
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An investigation of ground motion, recorded using broad-band, wide dynamic-range digital seismographs, of large mine tremors from two South African mining districts with different geologic settings, reveals some essential differences in both seismic source and ground motion parameters. In the Klerksdorp district where the strata are offset by major throughgoing normal faults, the largest tremors, with magnitudes ranging as high as 5.2, tend to be associated with slip on these pre-existing faults. Moreover, the seismic source and ground motion parameters are quite similar to those of natural crustal earthquakes. In the Carletonville district, by contrast, where substantial faults do not exist, the large-magnitude tremors appear to result from the failure of relatively intact rock and cause seismic stress drops and ground motion parameters higher than normally observed for natural shocks. Additionally, there appears to be an upper magnitude limit of about 4 in the Carletonville district. Detailed analyses of an exceptionally large event recorded locally from each of these districts serve to highlight these contrasts.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 129 (1989), S. 497-511 
    ISSN: 1420-9136
    Keywords: Seismic coda ; quality factorQ ; localized scatterers ; fractured rock ; stope environment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A single scattering model was used to analyse the temporary changes in the mean density of scattered waves in a discrete random medium. The model of the mean energy density, originally proposed bySato (1977) for spherical radiation and isotropic scattering, has been modified and applied to a medium in which the scatterers are confined to a specified volume. The time variation of the early part of the mean energy density function for the different source durations was investigated. The dominant effect on the theoretical mean energy density is caused by the specified volume containing scatterers. The duration of the source pulse influences the early part of the coda fort/t 0〈1.2, wheret is the lapse time measured from the source origin time, andt 0is arrival time of the body wave. The analysis of the coda signal of micro-events occurring immediately in front of the face enables us to estimate the size of the fracture zone induced by the stope. The model of the mean energy density of coda for a medium containing scatterers close to the seismic source was used to analyse a large number of events recorded close to an advancing mine face in a deep level gold mine in South Africa. The coda decay rate has two trends: the first, with a steep decay of coda, is produced by a larger deviation of rock parameters and/or larger size of the scatterers; the second trend, which decays more slowly, has the corresponding mean-free path ranging from 20 m to 200 m. The analysis indicates that the rock mass about 15–20 m from the stope contains a large proportion of fractured and blocked rock, which is the source of scattering. The scattering of theS-wave was much stronger and more stable, with the mean-free path varying from 11 m to 45 m. This is due to the shorter wavelength of theS wave in comparison with theP wave. The quality factor for theP coda wave varies from 30 to 100 in the fracture zone of stope and outside this zone it has a value of 300. The quality factor of theS wave varies from 20 to 78 in the equivalent volume. For rock surrounding the stope the ratioQ sp −1 /Q ss −1 varied from 0.31 to 0.69. This suggests that the radii of scatterers are smaller than 3.5 m.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 75 (1953), S. 2733-2736 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 75 (1953), S. 2729-2732 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 108 (1992), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The structure of the central Kaapvaal Craton of southern Africa has been investigated by deep seismic sounding, using mine tremors as energy sources. Seismometers were deployed at approximately 10km intervals on two profiles stretching between major mine tremor source regions. Mine tremors are rich in shear energy enabling joint interpretation of P- and S-waves and produce substantial energy at frequencies as low as 1 Hz. Record sections are presented for both P- and S-waves, and the traveltimes and amplitudes interpreted using 2-D ray-tracing techniques. Synthetic seismograms computed for a 1-D velocity model by the reflectivity method compare well with the observed data. A generalized seismic model of the Kaapvaal Craton has the following features: supracrustal strata 0–10 km thick; upper crystalline basement with P-wave velocities of 6.0–6.2 km s−1; the boundary between upper and lower crust at a depth of 14–18 km; a lower crust with a relatively uniform seismic velocity in the range 6.4–6.7 km s−1; and the crust/mantle transition over 1–3 km with the Moho at a depth of about 35 km. The lower crust is found to be seismically attenuating and has a Poisson's ratio of about 0.28. It is also known to be electrically conductive. These observations are in accord with the presence of hydrated mantle rock at the base of the crust.The velocity–depth model of the Kaapvaal Craton is similar to models derived for other Archaean cratons. The Proterozoic provinces adjacent to the Kaapvaal craton are significantly thicker, and have an intermediate- to high-velocity layer developed at the base of the crust. This is interpreted to indicate a change in the process of crustal growth, with basaltic underplating becoming more important since the Archaean. This change is attributed to a change in the composition of the upper mantle. The higher temperatures in the Archaean mantle led to the eruption of komatiitic lavas, resulting in an ultradepleted mantle unable to produce significant volumes of basaltic melt. Proterozoic crust developed above fertile mantle, and subsequent partial melting resulted in basaltic underplating and crustal inflation.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 65 (1961), S. 2211-2213 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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