According to the Council for Geoscience (CGS), an offshore earthquake occurred just after midnight 60km off the Cape Town coastline. Picture: Henk Kruger/ANA/African News Agency
According to the Council for Geoscience (CGS), an offshore earthquake occurred just after midnight 60km off the Cape Town coastline. Picture: Henk Kruger/ANA/African News Agency

Cape Town tremor: A tremor is just the Earth ‘relieving stress’

By Marvin Charles Time of article published Nov 18, 2020

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Cape Town - Many Cape Town residents were stressed after third tremor in as many months struck in the early hours of Tuesday, but according to a professor at Stellenbosch University, the tremors are just a stress reliever for the Earth.

According to the Council for Geoscience (CGS), an offshore earthquake occurred just after midnight 60km off the Cape Town coastline. The earthquake registered 3.4 on the Richter scale.

In a statement, the CGS said: “Many reports have been received from residents of Cape Town who have reportedly experienced the tremor. It is not uncommon for tremors to occur in the ocean. There has been no tsunami warning issued and it is on that basis that we would like to assure the public that there is no cause for panic.”

Professor Alex Kisters, head of department at Stellenbosch University Earth Science, says there is nothing to worry about.

“Seismicity (tremors) are just part of the planet. The tectonic plates are rigid and move against each other. This movement causes the build-up of stresses and the episodic release of these stresses causes tremors.

“In other words, any tremor is a kind of stress release. It would be a much larger concern if nothing happened for a long time – then the stress build-up would be so large that in fact earthquakes (higher magnitude tremors) might happen. In other words, tremors are a ‘healthy’ process of relieving stress from the Earth’s crust, preventing larger stress releases and serious damage.”

In September, a 6.2-magnitude earthquake off the country’s south-east coastline sent shock waves to residents. At the same time a 2.6-magnitude quake (tremor) was felt 9km north of Cape Town.

Eskom spokesperson Sikonathi Mantshantsha said Koeberg Power Station was designed to withstand a magnitude 7 earthquake.

“The seismic event was felt in many parts of Cape Town, as well as on the Koeberg Nuclear Power Station site in Melkbosstrand.

“The power plant continued to operate as normal, with only a minor spike in vibrations on the turbine-driven feedwater pumps on both units. The station’s earthquake instrumentation system alarms were not activated as the impact did not exceed the plant threshold, confirming the tremor was well below the power plant’s design limits,” he said.

But according to the Southern African Faith Communities’ Environment Institute and the Koeberg Alert Alliance (KAA), the increase in seismic activity on the Milnerton fault line should be a major cause for alarm around the risks to the Koeberg Nuclear Power Plant,

KAA’s Peter Becker said: “Last month we raised our concerns when the first two earthquakes were brushed off by Eskom. Now there’s a third and more intense earthquake, South Africans need to be aware of the risks associated with an ageing nuclear plant.”

Cape Argus

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