The management of seismic risks in metalliferous mines operating in developed mining countries such as Australia, Canada, Chile and Sweden has been very successful during the last decade. The occurrence and magnitude of large seismic events in deep mines has continued to increase with mining reaching deeper horizons, yet, injuries and fatalities due to rockbursts remain very rare in these countries. Although there are many common practices used to manage seismic risks in mines, there is no recognised process to do so. In 2017, Newcrest Mining Ltd, in collaboration with the Australian Centre for Geomechanics (ACG), undertook a benchmarking campaign to document the different seismic risk management practices currently implemented in mines which are considered leaders in this area. Data was gathered from 16 mines operating in five countries, experiencing different degrees of seismicity. Analysis of the data from the benchmarking study led to a better understanding of seismic risk management practices applied in the industry. One of the important outcomes of this project was the development of a flowchart describing in detail a generic seismic risk management process. The process is broken into four different layers of activities: data collection, seismic response to mining, control measures, and seismic risk assessment. Within each layer of activity, there are a number of components, and within each component, there are a number of practices, which have been benchmarked and are discussed in this paper. In addition to providing a road map for managing seismicity in underground metalliferous mines, this work enables users to assess their own practices against standard and advanced practices in the management of seismic risks. A full description of the seismic risk management process is available to the mining industry at https:

The hazard posed from large seismic events is often high enough to warrant the exclusion or evacuation of personnel from underground workings. A period of exclusion is often determined following blasts or large events due to the increased risk. The period of exclusion until re-entry occurs is a decision for site geotechnical engineers and mine management that must balance the potential risk to personnel with lost production time and associated costs. There is currently no widely accepted method for determining re-entry times and mine sites typically develop their own rules for exclusions after blasts and large events. A systematic and evidence based approach to the development of re-entry protocols could potentially reduce the risk to personnel from an early re-entry or reduce the lost production from an unnecessary exclusion. Four methods of re-entry assessment have been considered in this paper. The seismic responses at three mines have been modelled and used to optimise each assessment method and gauge the relative success through back-analysis. These same techniques are available for other mines to review their own data and potentially improve their current re-entry protocols. The results of this research indicate that a real-time re-entry assessment method can offer improved outcomes compared to blanket re-entry rules by reducing the average exclusion time while still capturing the same number of large events. The incorporation of event size in the assessment can result in better results than the event count. Vallejos and McKinnon (2009) developed a probabilistic framework for re-entry assessment but this method was found to be less efficient than the blanket rule in the majority of cases in this study. The method would also result in more administration and uncertainty for mine planning and scheduling. Several potential improvements to the analysis techniques, and avenues for further research, have been discussed.

Many underground mines experience seismic events associated with rock mass failure which can be of sufficient magnitude to pose a significant hazard to operations. Probabilistic seismic hazard assessments are typically performed assuming a Gutenberg-Richter distribution for the frequency-magnitude relation for which the parameters are obtained from a best fit to the data. This distribution assumes self-similar data above the magnitude of completeness but this is not always valid. The breakdown in self-similarity can occur when there are multiple superimposed seismic sources, or when there are artificial noise sources such as orepasses and underground crushers. This paper introduces an alternative parametric technique to decompose a bimodal frequency-magnitude relation into two sub-distributions. The composite distribution method assumes that two separate distributions are underlying the observed frequency-magnitude behaviour. This assumption was tested with respect to a single Gutenberg-Richter model to describe frequency-magnitude behaviour. The hypercube optimisation algorithm was used to solve the parameters of the two superimposed distributions while minimising the residual sum of squares for the fit compared to the observed data. The mXrap software was used to implement the method at multiple underground mines for specific volumes and for grid-based analysis. The results show that locally, the seismic hazard can be severely underestimated if a single Gutenberg-Richter model is assumed but this can be improved with the composite distribution method.

Exposure to seismic hazard in mines is controlled through various evacuation, exclusion and re-entry procedures. The aim of exposure management procedures is to tactically reduce the safety risk by removing personnel from work areas during periods of elevated seismic hazard. Given that risk assessment is based on exposure, the design of exposure management procedures must also be risk-based. In practice, the decision to re-enter a workplace after an exclusion is generally only made based on an assessment of the seismic hazard, often using previously defined levels of tolerable seismic activity rates. The definition of tolerable seismic hazard, in the context of re-entry, is seldom quantitatively assessed based on risk. In order to move towards a comprehensive seismic risk management strategy, design methodologies must be able to quantify the impact of different exclusion and re-entry practices on risk. The appropriate re-entry practice can then be selected given the defined risk-based design acceptance criteria. There is still a long way to go before the risk-based design framework for exposure management procedures is complete. This paper reviews the current state of design of exposure management controls in the context of risk and discusses several important areas for further research.