This paper is hosted with the kind permission of the Universidad de Chile, Eighth International Conference & Exhibition on Mass Mining, 2020.
Nizkous, I, Smith-Boughner, L, Shumila, V, de Beer, W & Angus, D 2020, 'Multi-attribute microseismic analysis to evaluate the evolution of in situ stress: imaging the complex relationship between stress and structure', in R Castro, F Báez & K Suzuki (eds), MassMin 2020: Proceedings of the Eighth International Conference & Exhibition on Mass Mining
, University of Chile, Santiago, pp. 1268-1276, https://doi.org/10.36487/ACG_repo/2063_94
Safe operations in the mining environment require mitigation of geomechanical risks through monitoring of production induced micro earthquakes. In this study we assess dynamic stress changes in an underground block caving mine in a tectonically active area during peak production activity and a following short period of relative inactivity. We analyse the collective behaviour of microseismic events (Dynamic Parameters Analysis or DPA) together with passive seismic tomography and stress inversion to get an integrated
picture of the complex stress evolution processes occurring within the mine. These approaches provide complementary information for interpretation of the complex spatial and temporal stress evolution. DPA shows a cyclical process of loading and stress relaxation in the abutments of the cave during the period of study. Seismic tomography recovers compressional velocity variations correlating with the stress field behaviour observed in DPA. A region of high velocity within the rock mass is observed to undergo a
loading process with local stress increase, while a region of low velocity rock mass undergoes stress relaxation with high intensity plastic deformation. Seismic moment tensor mechanisms show uniformity in the south abutment of the cave with predominantly tensile crack closure mechanism, which coincides with the region of low velocity. The high velocity region exhibits some tensile fracture opening with consistent tensile fracture closure failure type along the abutments of the cave. The principal stress
directions vary around the mine abutment and display an additional level of complexity related to vertical distribution of the events. The maximum principal stress σ1 in the south abutment of the cave appears to be consistently vertical.
Baig, AM, Bosman, K & Urbancic, TI 2017, ‘Temporal changes in stress state imaged through seismic tomography’, in J Wesseloo (ed.), Proceedings of the Eighth International Conference on Deep and High Stress Mining, Australian Centre for Geomechanics, Perth, vol. 1, pp. 269–273.
Ben-Zion, Y 2008, ‘Collective behaviour of earthquakes and faults: Continuum‐discrete transitions, progressive evolutionary changes, and different dynamic regimes’, Reviews of Geophysics, vol. 46, no. 4, RG4006,
Crowley, JW, Baig, A & Urbancic, T 2015, ‘4D tomography and deformation from microseismic data’, Proceedings of the 85th Annual Meeting of the Society of Exploration Geophysics, Society of Exploration Geophysicists, Tulsa.
de Beer, W, Smith-Boughner, L, Viegas, G, Bosman, K & Angus, D 2018, ‘Towards physics-based hazard assessment tools for developing blanket re-entry rules’, in Y Potvin & J Jakubec (eds), Proceedings of the Fourth International Symposium on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 545-552.
Gephart, JW & Forsyth, DW 1984, ‘An improved method for determining the regional stress tensor using earthquake focal mechanism data: application to the San Fernando earthquake sequence’, Journal of Geophysical Research, vol. 89, no. B11, pp. 9305–9320.
Hudson, JA, Pearce, RG & Rogers, RM 1989, ‘Source type plot for inversion of the moment tensor’, Journal of Geophysical Research: Solid Earth, vol. 94, no. B1, pp. 765–774.
Kostrov, BV & Das, S 1988 ‘Principles of Earthquake Source Mechanics’, Cambridge University Press, Cambridge.
Ma, X, Westman, EC, Fahrman, BP & Thibodeau, D 2016, ‘Imaging of temporal stress redistribution due to triggered seismicity at a deep nickel mine’, Geomechanics for Energy and the Environment, vol. 5, pp. 55–64.
Mercier, J-P, de Beer, W, Mercier, J-P & Morris, S 2015, ‘Evolution of a block cave from time-lapse passive source body-wave travel time tomography’, Geophysics, vol. 80, no. 2, pp. WA85–WA97,
Michael, AJ 1984, ‘Determination of stress from slip data: faults and folds: Journal of Geophysical Research, vol. 89, no. B13, pp. 11517–11526.
Price, D, Angus, DA, Garcia, A. & Fisher, QJ 2017, ‘Probabilistic analysis and comparison of stress-dependent rock physics models’, Geophysical Journal International, vol. 210, no. 1, pp. 196-209.
Smith-Boughner, L, Urbancic, T & Baig, A 2017, ‘Resolving sill pillar stress behaviour associated with blasts and rockbursts’, in J Wesseloo (ed.), Proceedings of the Eighth International Conference on Deep and High Stress Mining, Australian Centre for Geomechanics, Perth, pp. 257–267.
Urbancic, T, Smith-Boughner, L, Crowley, JW, Viegas, G, Baig, A & von Lunen, E 2015, ‘Characterizing the dynamic growth of a fracture network’, Proceedings of the Unconventional Resources Technology Conference, Society of Petroleum Engineers, Richardson,
Vavryčuk, V 2014, ‘Iterative joint inversion for stress and fault orientations from focal mechanisms’, Geophysical Journal International, vol. 199, pp. 69-77.
Veigas, G, Bosman, K, Angus, D, de Beer, W, & Urbancic, T 2018, ‘Mapping cave front growth utilising the collective behaviour of seismicity and velocity fields’, in Y Potvin & J Jakubec (eds), Proceedings of the Fourth International Symposium on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 577-588.
Verdon, JP, Angus, DA, Kendall, J-M & Hall, SA 2008 The effect of microstructure and nonlinear stress on anisotropic seismic velocities, Geophysics, vol. 73, no. 4, pp. D41- D51.
Westman, E, Luxbacher, K & Schafrik, S 2012, ‘Passive seismic tomography for three-dimensional time-lapse imaging of mining-induced rock mass changes’, The Leading Edge, vol. 31, pp. 338–345.
Young, R, & Maxwell, S 1992, ‘Seismic characterization of a highly stressed rock mass using tomographic imaging and induced seismicity’, Journal of Geophysical Research, vol. 97, pp. 12361–12373.