The U.S. Geological Survey said the earthquake's epicenter was four miles east of Orkney and 124 miles southwest of Pretoria at a depth of 6.2 miles.
The earthquake struck near the gold-mining town of Orkney at 12:22 p.m. local time.
Miners were evacuated from shafts around Orkney but at least nine miners had become trapped in 11 shafts.
The one reported death occurred when a wall collapsed.
Tuesday's quake was felt in neighboring Botswana and Mozambique.