Quake strikes mine region
Many trapped underground as buildings shake in vast area centred on Orkney
JUNE’s earthquake was the warning. Yesterday was the big one. And there could be more on the way. Geoscientist Dr Chris Hartnady believes the June quake, measuring 4.9 on the Richter scale, could easily have been a “foreshock” to yesterday’s 5.5-magnitude quake that was felt from its epicentre near Orkney in North West and in areas 500km away.
Hartnady said this had raised real fears of an increase in the frequency of quakes. “The question now is how bad is it going to get and how often will they strike. It 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 comes with them.”
Yesterday’s quake left one person dead, at least 21 injured, thousands of miners stuck underground and hundreds of homes damaged. The two most seriously injured sustained a severe gash to an arm and a broken leg.
In Khuma township, near Orkney, residents were being moved last night as their houses were deemed unsafe.
Rutta Molojwa was not at home when her front wall cracked. She was called by neighbours to return and told not to go inside.
At 6pm, Tlokwe emergency services, based near Potchefstroom, arrived to move affected families to a safe place for the night.
Annah Melato fought back tears as she described how her daughter, Yvonne Melato, grabbed her fourmonth-old baby and ran outside when the ground started shaking.
“They say it is not safe to go in the house. They said it is too risky to sleep inside,” she said.
Thembile Nyobonda, a resident of Jouberton, Klerksdorp, said there was no electricity in the township.
A staff member at Anglo Goldmine hospital said electricity cuts were experienced throughout the mine. She said medical staff had been on standby following the tremor to attend to workers injured underground.
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 public protector’s offices 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 in the Treasury building, said many of his colleagues based on the top floors were so traumatised that they refused to go back into the building. “One told me she was thrown off her chair. She looked really spooked.”
Across the country disaster management services, including medical search and rescue teams, were put on high alert.
ER24 spokeswoman Luyanda Majija said the service had attended a scene 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.
Meanwhile, Hartnady said the strength of the earthquake 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 now was whether mining triggered the earthquake.
“This part of Africa is in the vicinity of the African Rift system which is being pulled apart by a few millimetres a year,” he said.
“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 epicentre of yesterday’s earthquake, 6km outside Orkney, is just kilometres away from where another quake, measuring 4.9 on the Richter scale, struck in June.
The website www.earthquaketrack.com has recorded 20 earthquakes in the country over the past four years, six occurring in the North West. The weakest measured 3.9 on the Richter scale.