Abstract
A review of in situ stress measurements at eight regional localities in Africa south of the 15°S parallel shows that average directions of the horizontal principal stresses are N—S and E—W. These directions agree with principal stress orientations deduced from earthquake fault plane solutions. However, the maximum and minimum principal horizontal stresses are not consistently oriented parallel to either the N—S or E—W direction; they may vary within an individual region because of local geological structures and from region to region. At the sites within the Witwatersrand sediments (all at depths greater than 500 m) the maximum stress tends to lie NW—SE but at three of the four sites outside the Witwatersrand sediments (all at depths less than 500 m) this stress is oriented approximately N—S.
The data reported here are compared with horizontal stresses predicted for Southern Africa by Solomon, Sleep and Richardson (1975) from various plate tectonic driving force models. The agreement between orientations is fair for all sites but only the deép sites in the Witwatersrand sediments have comparable stress magnitudes.
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Gay, N.C. (1977). Principal Horizontal Stresses in Southern Africa. In: Wyss, M. (eds) Stress in the Earth. Contributions to Current Research in Geophysics (CCRG). Birkhäuser, Basel. https://doi.org/10.1007/978-3-0348-5745-1_1
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DOI: https://doi.org/10.1007/978-3-0348-5745-1_1
Publisher Name: Birkhäuser, Basel
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