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  • 1
    Electronic Resource
    Electronic Resource
    TERRESTRIAL HEAT FLOW IN THE SWISS ALPS (1956)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 7 (1956), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: iTerrestrial heat flow has been measured in three Alpine railroad tunnels. The geothermal gradients were calculated from temperatures measured during the construction of the tunnels, and corrections for topographic irregularities were made. The thermal conductivity of 113 rock specimens from the vicinity of the tunnels was measured. The heat flow in the Gotthard tunnel was found to be 1.6 10-6 cal/cm2 sec, in the Simplon 2.2 10-6 cal/cm2 sec, and in the Loetschberg 1.9 10-6 cal/cm2 sec. Most of the flux at the surface can be attributed to radioactive decay in a thickened crust, but a non-uniform distribution of radioactive elements may be required to explain the relatively high heat flow in the Simplon and Loetschberg tunnels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1956.tb05563.x
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  • 2
    Electronic Resource
    Electronic Resource
    The conductivity of the crust and mantle beneath the Kapuskasing Uplift: electrical anisotropy in the upper mantle (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 113 (1993), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The Kapuskasing Uplift has been interpreted as an oblique cross-section of up to 25 km of crust and thus provides the opportunity to examine the properties of exposed mid- to lower-crustal material. A magnetotelluric (MT) survey mapped a remarkably uniform upper crust and provided no evidence for upper crustal conductive zones that could be related to the often observed increase in mid and lower crustal conductivity. The only shallow conductive anomaly is related to the Ivanhoe Lake Cataclastic Zone but its electrical signature does not appear to extend more than one kilometer in depth.A regional apparent resistivity curve was determined from MT data and confirmed by subsequent controlled source electromagnetic surveys. Regional curves are essential for proper structural interpretation but are often difficult to determine because of electric field distortions. The data show a decrease in resistivity at depths below 15 km which is typical of continental crust in many areas of the world.There is a clear difference in orthogonal apparent resistivity and phase curves at periods greater than 10 s which is most pronounced in a N65d̀E and N25d̀W coordinate frame. Two different models are proposed to explain the data. The first consists of a conducting 2-D slab of approximately 50 km width in the lower crust and striking N65d̀E. The strike direction is consistent with a number of regional structural trends but there is no other direct supporting evidence for it. The second model invokes either micro or macro electrical anisotropy in the upper mantle. There is considerable evidence for seismic anisotropy in the region. The electrical anisotropy could be the result of preferential conduction along the c-axis of olivine crystals, hydrogen dissolved in the olivine lattice with preferential conduction along the a-axis, or possible alignment of dykes, joints and faults in the upper mantle. If the anisotropy is related to strain induced orientations of crystals or fabric, it will provide evidence for the motions of the mantle associated with plate tectonics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1993.tb00901.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Derivation ofK-indices using magnetograms constructed from digital data (1984)
    Springer
    Surveys in geophysics 6 (1984), S. 431-437 
    Details
    ISSN: 1573-0956
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The purpose of this study is to investigate the feasibility of deriving the traditionalK index from magnetograms plotted from recorded digital data. Digital magnetic data from Ottawa Observatory are available for theX, Y, andZ components in the form of 1 min averaged values and spot values at selected sampling intervals of 1 sec or greater. It is found that the lowerK values tend to be biased downward by one level when a digitizing interval greater than 30 sec is used for construction of the artificial magnetograms. However, for digitizing intervals of 30 sec or less the reconstructed analogue plots are just as reliable as standard-run Ruska magnetograms for the derivation ofK.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01465558
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  • 4
    Electronic Resource
    Electronic Resource
    Time-dependence of electromagnetic transfer functions and their association with tectonic activity (1980)
    Springer
    Surveys in geophysics 4 (1980), S. 97-114 
    Details
    ISSN: 1573-0956
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Laboratory experiments and theoretical considerations have suggested that anomalous dilatant regions can develop in the earth's crust during the period of strain accumulation prior to an earthquake. For moderate and major earthquakes such anomalous regions could be tens or even hundreds of kilometers in extent and should be detectable at the surface with appropriate survey or sounding techniques. Since electrical resistivity is one of the rock properties likely to be strongly modified in a dilatant zone, magnetotelluric impedance and geomagnetic transfer functions might be expected to show time-dependent precursory effects if monitored over a period of time above the focal region of an impending earthquake. Such experiments have been conducted in Japan and in other parts of the world and several examples of resitivity changes in the crust prior to earthquake occurrence have been reported. These results and their association with local seismicity are reviewed in this paper. The available evidence indicates that transfer functions and impedance can display significant time-dependent response to changing crustal conditions in some regions. However, the correspondence between these effects and earthquake occurrence is usually not very clear.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01452961
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    Paper (German National Licenses)
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