Johannesburg - Certain areas of Johannesburg felt the earth shake on Saturday.
News24's Naledi Shange said she felt the ground shake in Pimville, Soweto.
"I initially thought it was blasting somewhere around here. The ground shook for a few seconds," she said.
Funiwe Daweti also from Pimville said: "I heard a sound but I was indoors so I thought it was thunder."
Michelle Grobbelaar, unit manager at the seismology unit at the Council for Geoscience said the automatic system registered an event at 08:30 with a magnitude of about 2.5.
"[This] is quite small for people to feel but it could be that it is shallow and so I would not expect it to have been felt very widely," she said.
"This is still preliminary of course and our analysts would still need to confirm."
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People on Twitter said they felt the tremor in Newlands, Dobsonville and other areas of Soweto.
Eyewitness News tweeted that it had been inundated with calls from residents describing shaky grounds and trembling windows.
#EarthShake It is not clear what caused the shake which was felt in areas including Melville, Kagiso and parts of Soweto. EC— EWN Reporter (@ewnreporter) April 25, 2015