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.
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References
Aki, K., andRichards, P.,Quantitative Seismology: Theory and Methods (Freeman Cooper, San Francisco, Calif. 1989).
Borcherdt, R. D., Fletcher, J. B., Jensen, E. G., Maxwell, G. L., Van Schaack, J. R., Warrick, R. E., Cranswick, E., Johnston, M. J. S., andMcClearn, R. (1985),A General Earthquake-observation System (GEOS) Bull. Seismol. Soc. Am.75, 1783–1825.
Cook, N. G. W.,The seismic location of rockbursts.InProc. Fifth Rock Mechanics Symposium, (Pergamon, New York 1963), pp. 493–516.
Feignier, B., andYoung, R. P. (1992),Moment Tensor Inversion of Induced Microseismic Events: Evidence of Nonshear Failures in the −4<M<−2 Moment Magnitude Range, Geophys. Res. Lett.19, 1053–1056.
Gane, P. G., Seligman, P., andStephen, J. H. (1952),Focal Depths of Witwatersrand Tremors, Bull. Seismol. Soc. Am.42 239–250.
Gay, N. C. (1975),In situ Stress Measurements in Southern Africa, Tectonophysics29, 447–459.
Gay, N. C., andWainwright, E. H. eds. InProc. Ist Int. Conf. on Rockbursts and Seismicity in Mines (SAIMM, Johannesburg 1984) 363 pp.
Gay, N. C., Spencer, D., Van Wyk, J. J., andVan Der Heever, P. K. (1984),The control of geological and mining parameters in seismicity in the Klerksdorp mining district. InProc. Ist Int. Conf. on Rockbursts and Seismicity in Mines (SAIMM, Johannesburg 1984), pp. 107–120.
Geller, R. J. (1976),Body Force Equivalents for Stress Drop Seismic Sources, Bull. Seismol. Soc. Am.66, 1801–1804.
Gibowicz, S. J.,The mechanism of seismic events induced by mining. InProc. 2nd Int. Conf. on Rockbursts and Seismicity in Mines (Balkema., Rotterdam 1990) pp. 3–27.
Hanks, T. C., andKanamori, H. (1979),A Moment Magnitude Scale, J. Geophys. Res.84, 2348–2350.
Johnson, L. R. (1974),Green's Function for Lamb's Problem, Geophys. J.37, 99–131.
Jost, M. L., andHerrmann, R. B. (1989),A Student's Guide to and Review of Moment Tensors Seismol. Res. Letters60, 37–57.
Joughin, N. C. (1966),The Measurement and Analysis of Earth Motion Resulting from Underground Rock Failure, Ph. D. Thesis Univ. of the Witwatersrand, Johannesburg, South Africa, 153 pp.
Knopoff, L., andRandall, M. J. (1970),The Compensated linear-vector Dipole: A Possible Mechanism for Deep Earthquakes, J. Geophys. Res.75, 4957–4963.
McGarr, A. (1976),Seismic Moments and Volume Changes, J. Geophys. Res.81, 1487–1494.
McGarr, A. (1991),Observations Constraining Near-source Ground Motion Estimated from Locally Recorded Seismograms, J. Geophys. Res.96, 16,495–16,508.
McGarr, A. (1992),An Implosive Component in the Seismic Moment Tensor of a Mining-induced Tremor, Geophys. Res. Lett.19, 1579–1582.
McGarr, A., andBicknell, J. (1990),Synthetic seismogram analysis of locally recorded mine termors InProc. ISRM-SPE Int. Symp. Rock at Great Depth 3, 1407–1413.
McGarr, A., Spottiswoode, S. M., andGay, N. C. (1975),Relationship of Mine Tremors to Induced Stresses and to Rock Properties in the Focal Region, Bull. Seismol. Soc. Am.65, 981–994.
McGarr, A., Bicknell, J., Sembera, E., andGreen, R. W. E. (1989),Analysis of Exceptionally, Large Tremors in Two Gold Mining Districts of South Africa, Pure and Appl. Geophys.129, 295–307.
Potgieter, G. J., andRoering, C. (1984),The influence of geology on the mechanisms of mining-associated seismicity in the Klerksdorp gold field InRockbursts and Seismicity in Mines (eds. Gay, N. C., and Wainwright, E. C.) (SAIMM Symposium Series No. 6), (Johannesburg 1984) pp. 45–50.
Rudajev, V., andSileny, J. (1985),Seismic Events with Nonshear Components: II Rockbursts with Implosive Source Component, Pure and Appl. Geophys.123, 17–25.
Sileny, J. (1989),The Mechanism of Small Mining Tremors from Amplitude Inversion, Pure and Appl. Geophys.129, 309–324.
Spottiswoode, S. M. (1980),Source Mechanism Studies on Witwatersrand Seismic Events, Ph. D. Thesis Univ. of Witwatersrand, Johannesburg, South Africa, 109 pp.
Stickney, M. C., andSprenke, K. F.,Seismic Events with Implosional Focal Mechanisms in the Coeur d'Alene Mining District, Northern Idaho, J. Geophys. Res. in press.
Stump, B. W., andJohnson, L. R. (1977),The Determination of Source Properties by the Linear Inversion of Seismograms, Bull. Seismol. Soc. Am.67, 1489–1502.
Teisseyre, R. (1980),Some Remarks on the Source Mechanism of Rockbursts in Mines and on the Possible Source Extension, Acta Montana55, 7–14.
Van der Heever, P. (1982),The Influence of Geological Structure on Seismicity and Rockbursts in the Klerksdorp Goldfield, M.S. Thesis, Rand Afrikans University, 160 pp.
Van der Heever, P. (1984),Some technical and research aspects of the Klerksdorp seismic network, InRockbursts and Seismicity in Mines (eds. Gay, N. C., and Wainwright, E. H.) (SAIMM Symposium Series No. 6) (Johannesburg, South Africa) pp. 349–350.
Wong, I., andMcGarr, A.,Implosional failure in mining-induced seismicity: A critical review. InRockbursts and Seismicity in Mines (ed. Fairhurst C.) (Balkema, Rotterdam 1990) pp. 45–51.
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McGarr, A. Moment tensors of ten witwatersrand mine tremors. PAGEOPH 139, 781–800 (1992). https://doi.org/10.1007/BF00879963
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DOI: https://doi.org/10.1007/BF00879963