Quake of shaky things to come
June was the warning. Yesterday was the big one. And there could be more on the way.
Geoscientist Chris Hartnady believes the June quake, which measured 4.9 on the Richter Scale, could easily have been a "foreshock" to yesterday's 5.5-magnitude earthquake that was felt as far away as 500km from its epicentre, near Orkney in North West.
Hartnady said the two quakes had raised real fears of an increase in the frequency of these tremors.
"The question now is how bad it is going to get and how often will they strike?
"[Yesterday's quake] occurred in a mining belt known for its high frequency of earthquakes. The worry now is by how much these will increase and the devastation that will come with them."
One person died as a result of the quake, which injured at least 21 people, trapped thousands of miners underground and damaged hundreds of homes.
In Khuma, a township near Orkney, residents were last night being moved because their homes were deemed unsafe.
Rutta Molojwa was not in her house when the front wall cracked. She was called home by neighbours and told not to go inside her house.
At 6pm, emergency service personnel from Tlokwe, near Potchefstroom, arrived to move affected families to a safe place for the night.
Annah Melato fought back tears as she described how her daugher, Yvonne Melato, had grabbed her four-month-old baby and run outside when the shaking started.
In Klerksdorp, Thembile Nyobonda, a resident of Jouberton, said there was no electricity in the township.
"The tremor lasted longer than usual and was much stronger," he said.
According to a staff member at an AngloGold hospital, electricity cuts were experienced throughout the mine.
Patients at a clinic in Kanana location were seen jumping out of windows during the tremor.
In Pretoria, the 27-storey Treasury building, Home Affairs's 19-storey head office and the offices of the public protector were evacuated by panic-stricken staff.
Home Affairs employee Matome Ramashala said: "I feared a stampede and had to shout for people to stop running. It was insane."
Jacques Engelbrecht, who works at the Treasury building, said many of his colleagues based on the top floors were so traumatised that they had refused to go back into the building.
"One told me she was thrown off her chair. She looked really spooked," he said.
Across the country disaster management services, including search and rescue teams, were put on high alert.
ER24 spokesman Luyanda Majija said they had gone to the scene in Orkney where a man was killed when a wall collapsed on him.
Residents around Johannesburg and Durban also reported experiencing the tremor.
It was felt as far afield as Botswana, Mozambique and Swaziland, and resulted in AngloGold Ashanti stopping its operations as it raced to bring thousands of miners stuck underground to the surface.
Hartnady said the strength the earthquake was graded at was expected to rise as more data became available.
"Earthquakes are caused by a slip on a fault line and the release of stored elastic energy. With a magnitude-5 earthquake like this, you would have a fault slip of possibly 10cm, which is substantial, especially when you look at the length of the fault line, which is nearly 5km long. It is definitely a substantial slip."
The question was whether mining had triggered the earthquake, he said.
"This part of Africa is in the vicinity of the African Rift system, which is being pulled apart by a few millimetres annually.
"With the natural stresses that build up and the crust in a critical state of stress, with a slip this big we have to look at mining activities as being a possible trigger."
The website earthquaketrack. com has recorded 20 earthquakes in the country in the past four years, six in North West.
The weakest measured 3.9 on the Richter scale.
"The effects of such an earthquake could be catstrophic, especially on mines," Hartnady said.
"In 2005 a mine in Stilfontein was devastated by an earthquake."
Ahmed Bham, an urban search-and-rescue structural specialist in Orkney, said damage had been minor but widespread.
"It came out of nowhere. No warning, just wham.
"The effects and fear were huge, with most damage occurring to mining houses.''
Professor Andrzej Kijko of the University of Pretoria's natural hazard centre said 95% of South Africa's earthquakes were caused by mining, especially around the areas of Klerksdorp, Welkom and Carletonville.
"Mining in South Africa is leading to enormous stress factors being created. If there is a natural fault weakness 6km underground the stresses caused by mining can easily activate it [the fault].
"In South Africa one can easily expect earthquakes of such magnitude to occur every five to seven years," he said.
Ian Saunders, project leader for earthquake analysis in the Council for Geoscience's department of Seismology, said the "million-dollar question" was whether the quake was mining-related or "natural".
He confirmed a team would be dispatched to the affected areas to conduct tests and analysis.
AngloGold Ashanti spokesman Stewart Bailey said the injured who were working at the Great Noligwa and Moab Khotsong mines were treated by emergency medical staff. The two most seriously injured sustained a severe gash to an arm and a broken leg.
Bailey said 3300 miners were underground when the quake struck, but by early evening all miners had been brought up from the shafts.
'The earth was twerking'
Thabiso TeeJay Thejane: "The Earth was twerking, don't stress."
Johannes Stajoster Mahasha, from Vaal University of Technology: "We saw the lecturer running from class leaving the students without saying a word 2 them."
Sello Morudu, from Botswana: "All the windows of my house are broken because of it."
Siviwe Gabela: "I screamed and left customer on the phone. I think am gonna get fired!"
@Qwabekazi: "The tremor wasn't felt in some towns - that how bad service delivery is."
@Mzoeloe: "Hospital food is so bad, the earth shook to try stop me from lifting a spoon of jelly and custard into my mouth."
@shugarplumfaire: "Scary being on ninth floor Charlotte Maxeke Hospital giving talk to oncology patients, floor shaking."
@Introspective: "I'm laughing at my mom... she ran outside... was ready to drive out of town."
@NA1CK3R: "I would like to apologise for the tremor... I mistakenly dropped my Nokia 3310!"