ORIGINAL PAPER Characterization of Aseismic Fault-Slip in a Deep Hard Rock Mine Through Numerical Modelling: Case Study Atsushi Sainoki 1 • Hani S. Mitri 2 • Damodara Chinnasane 3 Received: 11 November 2016 / Accepted: 20 June 2017 Ó Springer-Verlag GmbH Austria 2017 Abstract Seismic moment is a predominantly utilized parameter for assessing fault-slip potential when the numerical modelling of fault-slip is carried out. However, relying on seismic moment as an indicator for fault-slip might lead to incorrect conclusions, as fault-slip can be inherently seismic or aseismic. The present study examines the behaviour of a fault in Copper Cliff Mine, Canada, with a 3D numerical model encompassing major geological structures in the area of interest. Three types of numerical analyses are conducted, namely elastic and elasto-plastic analyses in static conditions and elasto-plastic analysis in dynamic conditions. The static analyses show that the fault most likely had undergone shear failure at the pre-mining stage. It is then demonstrated that mining activities induce further shear movements along the fault plane as well as within the fault material, as the fault is composed of thick, severely fractured materials. Notwithstanding the results, no large seismic events with M w [ 0.1 were recorded within the fault from microseismic-monitoring systems between 2006 and 2014, implying that the shear move- ments are aseismic and static. Furthermore, microseismic database analysis using 350,000 events that took place between 2004 and 2014 indicates that the fault is not seismically active. It is found from the dynamic analysis that the maximum slip rate during fault-slip is not more than 0.3 m/s, even when the fault-slip is simulated with an instantaneous stress drop. This result substantiates the assumption that the fault is not seismically active and shear movements are dominantly aseismic. It is therefore sug- gested that other factors such as stress re-distribution induced by the aseismic slip be considered in order to assess damage that could be caused by the fault move- ments. The present study sheds light on the importance of distinguishing aseismic from seismic fault-slip for opti- mizing support systems in underground mines. Keywords Aseismic fault-slip  Fault-slip potential  Dynamic analysis, underground mine  Numerical analysis 1 Introduction The shear slip behaviour of faults in response to stress re- distribution due to mining activities can be classified as either seismic, i.e. exhibiting high slip rate, or aseismic. The former is generally described as mining-induced fault- slip resulting in instantaneous shear movement of a pre- existing fault or sudden shear rupture through intact rock that is induced by stress re-distribution due to mining activities. The latter is characterized by quasi-static shear movement along the fault with a low slip rate that does not generate intense seismic waves. As mining-induced fault- slip generally leads to seismic events with large magnitude and could inflict devastating damage to underground openings (Ortlepp and Stacey 1994; Blake and Hedley 2003; Ortlepp 2000; Hedley 1992; Lizurek et al. 2015; Alber and Fritschen 2011), the proper evaluation of risk associated with mining-induced fault-slip is crucial not only for the safety of mine workers, but also for steady production. Mining-induced fault-slip has also been an important topic in the field of geophysics as investigations & Atsushi Sainoki atsushi_sainoki@kumamoto-u.ac.jp 1 International Research Organization for Advanced Science and Technology, Kumamoto University, Kumamoto, Japan 2 Department of Mining and Materials Engineering, McGill University, Montreal, Canada 3 Vale Canada Ltd, Vale Ontario Operation, Sudbury, Canada 123 Rock Mech Rock Eng DOI 10.1007/s00603-017-1268-1