Linzer, LM, Hildyard, M W, Spottiswoode, S M & Wesseloo, J 2019, 'Do stopes contribute to the seismic source?', in W Joughin (ed.), Proceedings of the Ninth International Conference on Deep and High Stress Mining
, The Southern African Institute of Mining and Metallurgy, Johannesburg, pp. 427-444, https://doi.org/10.36487/ACG_rep/1952_32_Linzer
Parameters such as source location, seismic moment, energy, source size and stress drop are routinely calculated from mining-induced seismic data. Seismic moment tensors are inverted less routinely because their calculation is more complex and their accuracy depends on the network geometry, amongst a number of other factors. The models utilised in the source parameter calculations, the most well-known of which is the Brune model, were developed for the global seismicity problem and assume a solid, homogeneous earth model. However, the tabular ore bodies in South African gold and platinum mines are mined extensively and the excavations (stopes) can extend for many kilometres. The seismic source mechanisms on deep-level gold mines are generally compatible with shear failure, see Hoffmann et al (2013), whereas the source mechanisms of events at intermediate-level bord and pillar mines in the platinum district are more compatible with pillar failure and accompanying stope closure, see Spottiswoode et al (2006) and Malovichko et al (2012).
This paper investigates the influence of the stope on seismic inversions for the scalar moment, corner frequency/source radius, stress drop through numerical modelling using WAVE3D. The main objective is to determine whether the source parameters calculated from the recorded waveforms are due to a combination of the stope and pillar sources, rather than being related only to the shear source in the pillar. The modelled source is shear failure in a pillar where the fault daylights into the stope. The results show that the stope appears to have an appreciable effect on the seismic inversions. The seismic moment and source radius of the shear source in the pillar are larger for the model with a stope compared to the model with no stope. The stress drop for the case with a stope is less than the applied stress drop, which could be an effect of the apparently larger source. This work provides a possible explanation of the second corner frequency often observed in the spectra of seismograms recorded in South Africa platinum mines. This has implications for the accurate determination of source parameters and the assessment of the intensity of shaking in stopes.
Brune, J.N. (1970). Tectonic stress and the spectra of seismic shear waves from earthquakes, Journal of Geophysical Research, vol. 75, pp. 4997 – 5009. (Correction, Journal Geophysical Research, 1971, vol. 76, pp. 5002).
Churcher, J. M. (1990). The effect of propagation path on the measurement of seismic parameters, 2nd International Symposium on Rockbursts and Seismicity in Mines, Minneapolis, Minnesota, Fairhurst, Charles (ed), A. A. Balkema, Rotterdam, Netherlands, pp. 205 – 209.
Cichowicz, A. (2001). The meaningful use of peak particle velocity at excavation surface for the optimisation of the rockburst support criteria for tunnels and stopes. Final report GAP709b, Safety in Mines Research Advisory Committee, Johannesburg, 33 pp.
Cundall, P.A. (1992). Theoretical basis of the program WAVE. Unpublished internal report, COMRO (now CSIR Natural Resources and the Environment), South Africa, pp. 1 – 12.
Daehnke, A. (1997). Stress wave and fracture propagation in rock, PhD Thesis, Institute of Mechanics of the Vienna University of Technology, 409 pp.
Daehnke, A. and Hildyard, M.W. (1997). Dynamic fracture propagation due to stress waves interacting with stopes. Proceedings of 1st Southern African Rock Engineering Symposium (SARES), Johannesburg, South Africa, pp. 97 – 108.
Daehnke, A., Rossmanith, H.P. and Knasmillner, R.E. (1996). Using dynamic photoelasticity to evaluate the influence of parting planes on stress waves interacting with stopes. International Journal for Numerical and Analytical Methods in Geomechanics, vol. 20 (2), pp. 101 – 117.
Donovan, S.J., Hildyard, M.W., Linzer, L.M., Roberts, D. and Vogt, D. (2006). Collaborative modelling and analysis technology: Modelling and analysis activities for the geoscience applications, CSIR internal report, pp. 1 – 122.
Durrheim, R.J. (2012). Functional specifications for in-stope support based on seismic and rockburst observations in South African mines. Proceedings of the Sixth International Seminar on Deep and High Stress Mining. Potvin, Y. (ed). Australian Centre for Geomechanics, Perth, pp. 41 – 55.
Gibowicz, S.J. (1990). Seismicity induced by mining. Advances in Geophysics, vol. 32, 1–74 pp.
Gibowicz, S.J. and Kijko, A. (1994). An Introduction to Mining Seismology, Academic Press, San Diego, California.
Hanks, T.C. and Kanamori, H. (1979). A moment magnitude scale. Journal of Geophysical Research, vol. 84, pp. 2348 – 2350.
Hildyard, M.W. (2001). Wave interaction with underground openings in fractured rock, PhD Thesis, University of Liverpool, 283 pp.
Hildyard, M.W. (2007). Rocha Manuel Rocha Medal Recipient: Wave interaction with underground openings in fractured rock. Rock Mechanics and Rock Engineering, vol. 40, pp. 531–561.
Hildyard, M.W., Daehnke, A., and Cundall, P.A. (1995). WAVE: A computer program for investigating elastodynamic issues in mining. Proceedings of 35th U.S. Symposium on Rock Mechanics, Balkema, pp. 519-524.
HILDYARD, M.W., NAPIER, J.A.L. and YOUNG, R.P. (2001). The influence of an excavation on ground motion, Proceedings of the 5th Symposium on Rockbursts and Seismicity in Mines (RaSiM 5), Johannesburg, September 2001, South African Institute of Mining and Metallurgy, pp. 443-452.
HILDYARD, M.W. and YOUNG, R.P. (2002). Modelling wave propagation around underground openings in fractured rock. Special issue on induced seismicity, Pure and Applied Geophysics, Trifu, C. (ed). 159, pp. 247-276.
HOFFMANN, G., MURPHY, S., SCHEEPERS, L. and VAN ASWEGEN, G. (2013). Surface stress modelling of some shear slip seismic events that occurred in Anglogold Ashanti’s tabular mines. 8th International Symposium on Rockbursts and Seismicity in Mines, St Petersburg and Moscow, 1–7 September 2013. Geophysical Survey of Russian Academy of Sciences, pp. 219–231.
IDE, S. and Beroza, G.C. (2001). Does apparent stress vary with earthquake size? Geophysical Research Letters, vol. 28 (17), pp. 3349-3352.
Linkov, A.M. and Durrheim, R.J. (1998). Velocity amplification considered as a phenomenon of elastic energy release due to softening. Proceedings of the 3rd international conference on mechanics of jointed and faulted rock, Rossmanith H.P. (ed). Vienna, Austria, 6–9 April, Balkema, Rotterdam, pp. 243–248.
Linzer, L.M. and Hildyard, M.W. (2005). New criteria for rockmass stability and control using integration of seismicity and numerical modelling In: Hildyard, M.W., Napier, J.A.L., Spottiswoode, S.M., Sellers, E., Linzer, L.M. and Kataka, M.O. SIMRAC Final Project Report: SIM 02 03 01, 185 pp.
MALOVICHKO, D., VAN ASWEGEN, G. and CLARK, R. (2012). Mechanisms of large seismic events in platinum mines of the Bushveld Complex (South Africa). Journal of the Southern African Institute of Mining and Metallurgy, vol. 112, no. 6, pp. 419 – 429.
McKenzie, C. (2017). PPV to PPV: towards estimating the site effect due to surface waves generated along surface excavations. MSc Dissertation, University of Leeds, pp. 118.
Milev, A.M., Spottiswoode, S.M., Noble, B.R., Linzer, L.M., van Zyl, M., Daehnke, A. and Acheampong, E. (2002). GAP709: The meaningful use of peak particle velocities at excavation surfaces for the optimisation of the rockburst criteria for tunnels and stopes. SIMRAC Final Project Report. Report no: 2002 – 0305 (a).
Raffaldi, M., Johnson, J.C. and Chambers, D. (2017). Numerical study of the relationship between seismic wave parameters and remotely triggered rockburst damage in hard rock tunnels. Deep Mining 2017: Eighth International Conference on Deep and High Stress Mining, Wesseloo, J. (ed.) 373-386 pp.
Ryder, J.A. (1988). Excess shear stress in the assessment of geologically hazardous situations. Journal of the Southern African Institute of Mining and Metallurgy, 88(1), pp. 27-3.
Spottiswoode, S.M. (1993). Seismic attenuation in deep-level mines, 3rd International Symposium on Rockbursts and Seismicity in mines, Balkema, pp. 409 – 414.
SPOTTISWOODE, S.M. and MCGARR, A. (1975). Source parameters of tremors in a deep level gold mine. Bulletin of the Seismological Society of America, vol. 65, pp. 93–1.
Spottiswoode. S.M., Scheepers, J.B. and Ledwaba, L. (2006). Pillar seismicity in the Bushveld Complex. SANIRE 2006 - FACING THE CHALLENGES, South African National Institute of Rock Engineering.
Uenishi, K. (1997). Rayleigh pulse dynamic triggering of interface slip. PhD Thesis, Vienna University of Technology, pp. 1 – 178.
Van Aswegen, G and Butler, A.G. (1993). Application of quantitative seismology in South African gold mines. 3rd International Symposium on Rockbursts and Seismicity in mines, Balkema, pp. 261 – 266.
Wang, X. and Cai, M. (2015). Influence of wavelength-to-excavation span ratio on ground motion around deep underground excavations, June 2015, Tunnelling and Underground Space Technology.
Zhang, P., Swan, G. and Nordlund, E. (2015). 1-D numerical simulation of velocity amplification of P-waves travelling through fractured rock near a free surface. Journal of the Southern African Institute of Mining and Metallurgy, vol. 115(11), pp. 1121 – 1126.