Abolfazlzadeh, Y & McKinnon, SD 2017, 'Stress field characterisation in Nickel Rim South Mine using seismic stress inversion', in J Wesseloo (ed.), Deep Mining 2017: Proceedings of the Eighth International Conference on Deep and High Stress Mining
, Australian Centre for Geomechanics, Perth, pp. 247-256, https://doi.org/10.36487/ACG_rep/1704_16_Abolfazlzadeh
Knowledge of stresses is important for many aspects of mine design, but conventional methods of measuring stresses produce estimates at only a limited number of points in space and time. Furthermore, stresses are known to be affected by geological structures, particularly faults, but mapping of how the stress field is affected by such structures is not currently possible. Therefore, there is a compelling reason to consider the use of techniques that can map such local stress field variations. The method of seismic stress inversion is utilised to address this limitation and its application is illustrated using seismic data collected from Nickel Rim South Mine (NRS) located in Sudbury, Ontario, Canada. NRS is a modern mine using blasthole open stoping with backfill as a means of bulk mining. The ellipsoidally shaped orebody is located between 1,160 and 1,710 m below ground surface, strikes east–west and is steeply dipping. Although the NRS host rock and orebody are relatively massive with high strength, the mine is structurally complicated. Many faults appear to influence the stress field, in addition to being the sources of seismic events. The seismic monitoring array in NRS has good coverage over the active volume of the mine and consists of uniaxial and triaxial geophones and accelerometers. This combination of sensors results in a large catalogue of events with good focal sphere coverage that permits source mechanism analyses to be performed. Extensive filtering has been applied to the seismic data to improve the quality, and for the stress inversion process the first motion stress inversion (MOTSI) software is used. MOTSI only uses the first motion polarities and estimates the stress tensor components with more complete uncertainties compared to other nonlinear methods. To facilitate development and refinement of the seismic stress inversion process, numerous clusters of seismic events over a period of seven months during the early stages of mining were initially analysed so as to minimise perturbations caused by the interaction between mining and geological structures. More than 500 manually processed events throughout the mine are utilised for the stress inversions. Results show that the clusters in the earlier stages of mining and further away from excavation boundaries demonstrate reasonable agreement with pre-mining stress estimates based on overcoring and breakouts.
Keywords: microseismic monitoring, seismicity, stress mapping, seismic stress inversion
Abers, GA & Gephart, JW 2001, ‘Direct inversion of earthquake first motions for both the stress tensor and focal mechanisms and application to southern California’, Journal of Geophysical Research, vol. 106, no. 26, pp. 523–526.
Angelier, J 1990, ‘Inversion of field data in fault tectonics to obtain the regional stress-III. A new rapid direction inversion method by analytical means’, Geophysical Journal, vol. 103, pp. 363–376.
Angelier, J 1994, ‘Fault slip analysis and palaeostress reconstruction’, in PL Hancock (ed.), Continental Deformation, Pergamon Press, Oxford, pp. 53–100.
Baird, A, McKinnon, SD & Godin, L 2009, ‘Stress channelling and partitioning of seismicity in the Charlevoix seismic zone’, Geophysical Journal International, vol. 179, pp. 559–568.
Baird, A, McKinnon, SD & Godin, L 2010, ‘Relationship between structures, stress and seismicity in the Charlevoix seismic zone revealed by 3-D geomechanical models: Implications for the seismotectonics of continental interiors’, Journal of Geophysical Research, vol. 115.
Bott, MHP 1959, ‘The mechanics of oblique slip faulting’, Geological Magazine, vol. 96, pp. 109–117.
Delvaux, D & Sperner, B 2003, ‘Stress tensor inversion from fault kinematic indicators and focal mechanism data: the TENSOR program’, in D Nieuwland (ed.), New Insights into Structural Interpretation and Modelling, Geological Society, London, pp. 75100.
Etchecopar, A, Vasseur, G & Daignieres, M 1981, ‘An inverse problem in microtectonics for the determination of stress tensors from fault striation analysis’, Journal of Structural Geology, vol. 3, pp. 51–65.
Gephart, JW 1990a, ‘FMSI: a FORTRAN program for inverting fault/slickenslide and earthquake focal mechanism data to obtain the regional stress tensor, Comp’, Computer and Geosciences, vol. 16, pp. 953–989.
Gephart, JW 1990b, ‘Stress and the direction of slip on fault planes’, Tectonics, vol. 9, no. 4, pp. 845–858.
Gudmundsson, A & Homberg, C 1999, ‘Evolution of stress fields and faulting in seismic zones’, Pure and Applied Geophysics, vol. 154, pp. 257–280.
Ljunggren, C, Chang, Yanting, Janson, T & Christiansson, R 2003, ‘An overview of rock stress measurement methods’, International Journal of Rock Mechanics & Mining Sciences, vol. 40, pp. 975–989.
McKinnon, SD & Garrido, I 1998, ‘Fracture initiation, growth, and effect on stress field: a numerical investigation’, Journal of Structural Geology, vol. 20, no. 12, pp. 1673–1689.
McKinnon, SD 2006, ‘Triggering of seismicity remote from mining excavations’, Rock Mechanics and Rock Engineering, vol. 39, no. 3, pp. 255–279.
McKinnon, SD & Labrie, D 2006, ‘Interpretation of stresses adjacent to the Cadillac Fault assuming marginal large-scale rock mass stability’, in M Lu, CC Li, H Kjorholt & H Dahle (eds), Proceedings of the International Symposium on In-situ Rock Stresses, Taylor & Francis, Balkema, pp. 409–417.
Michael, AJ 1984, ‘Determination of stress from slip data: Faults and folds’, Journal of Geophysical Research, vol. 89, pp. 11517–11526.
Michael, AJ 1987, ‘Stress rotation during the Coalinga aftershock sequence’, Journal of Geophysical Research, vol. 92, no. B8, pp. 7963–7979.
Snelling, PE, Godin, L & McKinnon, SD 2013, ‘The role of geological structure and stress in triggering remote seismicity in Creighton Mine, Sudbury, Canada’, International Journal of Rock Mechanics and Mining Sciences, vol. 58, pp. 166–179.
Turichshev, A & Brummer, Rk 2008, In-Situ Rock Stress Measurements at the 1480 Level of the Nickel Rim South Project, Itasca Consulting Canada Inc., Xstrata Nickel, Nickel Rim South Project.
Urbancic, TI, Trifu, C-I & Young, RP 1993, ‘Microseismicity derived fault-planes and their relationship to focal mechanism, stress inversion, and geologic data’, Geophysical Research Letters, vol. 20, no. 22, pp. 2475–2478.
Urbancic, TI, Trifu, C-I, Sampson-Forsyth, A & Bawden, WF 1994, ‘Potential for using focal mechanism and stress inversion studies to characterize active faulting in mines’, Proceedings of the Fourth South American Congress on Rock Mechanics, Santiago, May 1994.
Wallace, RE 1951, ‘Geometry of shearing stress and relation to faulting’, The Journal of Geology, vol. 59, pp. 118–130.
Worotnicki & Walton RJ 1976, ‘Triaxial “hollow inclusion” gauges for the determination of rock stress in situ’, Proceedings of the Symposium on Investigation of Stress in Rock: Advances in Stress Measurement, International Society for Rock Mechanics, Lisboa, pp. 1–8, supplement.