UPDATE: Cause of the earthquake difficult to determine

UPDATE: 5 August, 4.30pm:

According to the Council for Geoscience’s manager of the seismology unit, Michelle Grobbelaar, it was difficult to determine the cause of the earthquake because the epicentre was in a mining area.

She explained that an earthquake was the sudden release of stress over a fault line causing a tremor.

However, she said a build-up of stresses under the earth’s surface could have multiple sources.

“We cannot prove either way whether it was a natural event or caused by mining activities, because we don’t know enough about the seismic history of the area before mining began.”

Meanwhile according to reports, AngloGold Ashanti said 17 employees at Great Noligwa and Moab Khotsong mines sustained minor injuries after the earthquake.

ER24 emergency services tweeted that no further injuries had been reported, and officials at the mines confirmed miners were now on the surface and no serious injuries had been reported.

“Received confirmation that no miners are trapped in #Orkney. Emergency services standing down. #earthquake #quakesa” they tweeted.

However, more tremors and aftershocks were expected.

“We are monitoring the situation in real time and have noticed further activity following the earthquake, and this is expected to continue for days or even months,” Grobbelaar said.

According to Grobbelaar, as a general rule of thumb another tremor of similar magnitude could be expected in the same region, but it could not be predicted when this would occur.

The earthquake was felt in many parts of the country, including most parts of Joburg which is 177km away from the epicentre in the North West; and as far away as Durban and Botswana.

UPDATE: 5 August, 2.30pm:

The Council for Geoscience has confirmed that the recent tremor was a 5.5 magnitude as measured on its local magnitude scale, and that the epicentre was located south of Orkney in the North West.

According to Joburg Emergency Services spokesperson Robert Malaudzi thus far no injuries or structural collapse had been reported in Joburg as a result of the tremor.

However, he said teams were monitoring the situation in order to respond to any potential incidents

Meanwhile, tweets by ER24 emergency services revealed the extent of damage caused in Orkney and neighbouring areas.

In a series of tweets, ER24 said mining operations had been stopped in some areas and ER24 officials have been placed on standby to assist with miners possibly trapped in Orkney.

“@ER24EMS @LocumGuy we have received reports that miners affected on one of the mines in #Orkney are safe and been brought to the surface,” it tweeted.

In earlier tweets, ER24 said that emergency services from Potchefstroom were now assisting at several mines but added that no alerts for evacuations had been issued.

ER24 tweeted that reports were received that houses had collapsed in Orkney, adding that the number of casualties was unknown but confirmed one fatality in Orkney after a wall collapsed on a man.

Remember last year’s tremor? Read about it here:

Expert – Tremor, not earthquake in Jozi

UPDATE: 5 August, 1.30pm:

According to the Council for Geoscience the tremor that was felt at about 12:20pm was widespread.

According to the manager of the seismology unit Michelle Grobbelaar, the tremor was felt in the council’s building based in Pretoria.

Information was limited as analysts were in the process of downloading and analysing the data, she said.

She said the magnitude of the tremor had yet to be determined but described it as “quite a big event”.

According to Grobbelaar, preliminary findings indicated that the epicentre was in the Klerksdorp region, however, this was still to be confirmed.

According to US Geological Survey’s website it was a 5.3 magnitude tremor and the epicentre was 6km east of Orkney.

However, confirmation of this information was still being sought from the Council for Geoscience.

5 August, 12pm:

A tremor shook the ground below the feet of Joburg residents at lunch time on Tuesday afternoon.

The tremors were felt in numerous areas across Johannesburg including: Parkhurst, Craighall, Rosebank, the CBD, Bryanston, Douglasdale, Lonehill, Kempton Park, Noordwyk, Halfway House, Springs, Fourways, Northcliff, Benoni, Roodepoort and Hartebeespoort.

Douglasdale resident Jof McLean said that his dog reacted10 seconds before they felt the tremor. “I was painting the stairs and the dog was lying in the sun upstairs. She shot down the stairs so quickly – running with her tail between her legs. She felt it before us.”

People all over the Northern Suburbs found the incident very scary. One Dainfern resident tried to evacuate his daughter and domestic worker from their house.

Arthur Muganwa said the lights flickered in his building in the CBD just before it happened. “I’m on the 20th floor and the building felt like it was swaying.”

In Randburg, Colleen Whitfield, said that she had to run around her house to stop things from falling off the shelves.

Most people felt the shake for at least 30 seconds, though some report it was up to a minute long.

Did you feel the tremor? Tell us what area you were in and your experience.