Seismic Hazard
Managing seismicity in mining is an important part of ensuring the continuous safety of underground crews and long-term mine sustainability. Most seismically active mines make use of a Seismic Risk Management Plan (SRMP) to ensure the necessary controls are in place.
Having detailed knowledge and an understanding of the seismic hazard is a vital element of the SRMP. This knowledge allows engineers and management to:
Communicate seismic hazard successfully to their employees
Helps to determine the excavation vulnerability to seismic events
Allows for strategic long-term planning to manage the risk better at depth
Makes it possible to evaluate the effectiveness of seismic control measures
Helps to identify sources of seismicity for better future design
Is used to calibrate and refine numerical models for improved forward design
The effective management of seismic risk is heavily reliant on the accurate description of seismic hazard. It allows mine management to focus on control measures and strategies that have a real impact on seismicity.
Describing the seismic hazard is generally a process of statistics. Any seismic hazard analysis technique aims to describe a seismically significant parameter (e.g. magnitude, PPV) in terms of the probability to exceed a certain value at a certain point in space, within a certain time period. Numerous statistical methods are employed in the mining and insurance industries and are easily accessed through a quick online search.
Below are some choice examples of seismic hazard plots from mXrap (a geotechnical software platform).
The evolution of the seismic hazard over time.
The current yearly probability of having an event of magnitude 1.5 or greater within 50m from an excavation.
The seismic hazard plotted as risk classes (more hazardous areas are indicated with the warmer colours).
Although the accessibility of seismic analysis techniques has greatly improved over the last decade and is widely used, there are still some severe shortcomings in how it is applied to systems aimed to mitigate seismic risk.
The main areas which are still not being effectively managed are:
Understanding sources of seismicity: Although the accurate description of seismic hazard is vital, it is just as important to understand why some areas of a mine have larger seismic hazards than other areas. These hot spots are indicative of sources of seismicity, and by understanding these sources, their future occurrence could be eliminated or strategically managed more effectively.
Communicating seismic hazard: There are many stakeholders who are impacted by seismicity, and therefore effective and routine meeting presentations, posters and reports (which are read) must be carried out. Seismic awareness creates trust and ensures this hazard is considered with the required level of attention by all parties.
Back analysis of the effect of control measures on seismic risk: Although many mines have seismic hazard reporting systems in place, it is uncommon for mines to document how the seismic hazard changes with control measure change. Such a system will ensure the implementation and upkeep of only effective control measures.
It can be challenging to fully understand seismicity and effectively interpret seismic hazard trends.
If you need assistance in getting the most out of your seismic hazard analyses, or just want to hear more on this subject, feel free to contact us for a meeting or phone conversation.