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Moment tensors of ten witwatersrand mine tremors

Pure and Applied Geophysics PAGEOPH

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DOI: 10.1007/BF00879963

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Abstract

Ground motions, recorded both underground and on the surface in two of the South African Gold mining districts, were inverted to determine complete moment tensors for 10 mining-induced tremors in the magnitude range 1.9 to 3.3. The resulting moment tensors fall into two separate categories. Seven of the events involve substantial coseismic volumetric reduction-??V together with normal faulting entailing shear deformation ??AD, where the summation is over fault planes of area A and average slip D. For these events the ratio-??V/??AD ranges from 0.58 to 0.92, with an average value of 0.71. For the remaining three events ??V is not significantly different from zero; these events are largely double-couple sources involving normal faulting. Surprisingly, the two types of source mechanism appear to be very distinct in that there is not a continuous distribution of the source mix from ??V=0 to-??V?????AD. Presumably, the coseismic closure indicates substantial interaction between a mine stope and adjacent shear failure in the surrounding rock, under the influence of an ambient stress for which the maximum principal stress is oriented vertically. ?? 1992 Birkha??user Verlag.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Moment tensors of ten witwatersrand mine tremors
Series title:
Pure and Applied Geophysics PAGEOPH
DOI:
10.1007/BF00879963
Volume
139
Issue:
3-4
Year Published:
1992
Language:
English
Publisher location:
Birkha??user-Verlag
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
781
Last page:
800
Number of Pages:
20