Seismic risk assessment
The yellow area in the flowchart represents the risk assessment in the following figure that forms an integral part of mine management and the management of occupational health and safety. The management of seismic risk is performed within a broader risk management framework.
Figure: Flowchart of the seismic risk management process emphasising the data collection activities
Some level of risk assessment appears to be common practice on mines and is generally prescribed by national or state legislative bodies. The level of risk assessment varies from informal to formal and qualitative to quantitative.
Engineers typically perform experience-based, subjective evaluation of the consequences and probabilities associated with seismic hazards and evaluate its acceptance within the corporate risk matrix. Formal risk assessment techniques include the use of fault event trees with subjectively assigned component likelihoods. In our opinion, informal risk assessment should be limited to tactical decisions of limited consequence events and should not form the basis for strategic decisions.
Different levels of improvement are possible on the informal subjective risk assessment discussed in the previous paragraph.
The individual formal subjective risk assessment
The geotechnical engineer performs a risk assessment employing formal risk assessment techniques like fault event trees and assigns subjective probabilities to the components of such trees. This risk assessment is documented in a memorandum and the subjective probabilities listed. The documentation enables auditing and expert evaluation of the risk assessments. After the initial development of the fault event trees for a specific scenario, this process is not onerous.
Formal subjective risk assessment employing expert opinion
The employment of expert opinion to derive subjective probabilities in a formal risk assessment is well documented in geotechnical engineering context, for example, Vick (2002); and Baecher and Christian (2003). A panel of experts are selected and a facilitator manages the risk assessment according to well established processes. The risk assessment process is documented.
Quantitative risk assessment
Probabilistic calculations are performed to evaluate the probabilities required in the formal risk assessment employing fault and event trees. The calculation process and the risk assessment process is documented.