the gold mining areas
21 August 2006
A magnitude 5,3 seismic event occurred on 9 March 2005 at DRDGoldâs North
West Operations in the Klerksdorp District. The event and its aftershocks shook
the nearby town of Stilfontein causing serious damage to several buildings and
minor injuries to 58 people. At the mine, two mineworkers lost their lives and
3 200 mineworkers were evacuated under difficult circumstances.
The Chief Inspector of Mines appointed a team of experts led by Dr Ray
Durrheim of the Council for Scientific and Industrial Research (CSIR), to
investigate the risks to miners, mines and the public posed by large seismic
events in the gold mining districts. The team included seismologists, mining
and rock engineers, a hydrologist and a seismic public safety specialist from
California.
It was found that the seismic event that occurred on 9 March 2005 could be
ascribed to past mining. The chance that the event and its aftershocks were
solely due to natural forces is considered extremely small.
Seismic events will continue to occur as long as mining continues and for
some time after mining activities cease as events are likely to be triggered
when worked-out mines flood. It is unlikely that the magnitudes of the events
and intensity of the shaking will be significantly greater than the levels that
have been experienced so far. Nevertheless, it is recommended that seismic
monitoring networks be improved and that monitoring continues after mines
close. The seismic hazard should be taken into account when the future use of
mining land is being considered or any new buildings are designed.
Some buildings are considered to be vulnerable to damage and even collapse
during large seismic events, posing safety and financial risks. It is
recommended that a systematic survey be conducted to identify buildings that
require remedial measures.
Appropriate training should be provided to members of the emergency services
and safety drills should be practised regularly at public buildings such as
schools and hospitals so that panic is avoided should a seismic event occur.
(Many injuries are caused by falling masonry and shattered glass. People should
shelter under a table or in a doorway for the duration of the event rather than
attempt to flee). Municipal officials are aware of the risks posed by
seismicity and are incorporating these risks in their disaster management
plans.
Issued by: Department of Minerals and Energy
21 August 2006
