ISSN:
1420-9136
Keywords:
Induced seismicity
;
earthquake source mechanism
;
implosive moment tensor component
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
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-ΔV together with normal faulting entailing shear deformation ΣAD, where the summation is over fault planes of areaA and average slipD. For these events the ratio-ΔV/ΣAD ranges from 0.58 to 0.92, with an average value of 0.71. For the remaining three events ΔV 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 ΔV=0 to-ΔV≈ΣAD. 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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00879963
