Gauteng warned of more quakes

Johannesburg – Residents of the Witwatersrand may in future experience more and bigger earthquakes due to water rising underground in mined-out basins.

It is unclear what will happen in reality, but the possibility exists that earthquakes will occur more regularly in Johannesburg and that some of them could register up to 5 on the Richter scale, said Olaf Goldbach, a geophysicist at the CSIR.

He was speaking at the CSIR’s bi-annual summit about the relevance of science and the application of research.

Far-reaching consequences

Goldbach said it was crucial that research is carried out soon about the link between the rising water levels and the increase in seismic activity, as it has far-reaching consequences for people and infrastructure such as buildings and roads.

“This again will have financial implications for insurers when buildings suddenly collapse.”

He referred to the earthquake last Thursday evening, which shook parts of the Witwatersrand, saying he believed it was linked to the rising water levels.

The earthquake registered 2.8 on the Richer scale and caused roof tiles to fall off.

“I sat in my home in Weltevreden Park and watched TV just after 21:00 on Thursday when the ground started shaking. I really think we will be experiencing more of this in future,” said Goldbach.

He only found out the next day that the earthquake’s epicentre was 11km southwest of the University of the Witwatersrand (Wits).

Acidic mine water

Goldbach said mine-related earthquakes are common in South Africa and yet residents don’t know what to expect.

He believes that earthquakes which register 5.3 on the Richter scale, like the one in Welkom in 2005 in which two people died and many houses suffered structural damage, could be waiting for the Witwatersrand.

Earthquakes also occurred in the vicinity of the Katze Dam shortly after the dam wall was completed and while it was being filled with water.

Goldbach said government had to urgently look into seismic activity, along with the devastating effects that acidic mine water is having on the environment.

The latest research pointed to mine water at some places being between 400m and 500m from the surface and rising by up to almost 1m per day.

Goldbach said it will cost an estimated R1bn to erect permanent infrastructure for the pumping out of water, while the pumping will cost R8m per month. “Who is going to pay it? Probably the taxpayer because the mine bosses are long gone.”

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