The earthquake happened at 2:38 a.m. on Sunday and was centered just 6 kilometers south of Alberton, or roughly 16 kilometers southeast of central Johannesburg, according to seismologists.

The U.S. Geological Survey (USGS) said the earthquake had a magnitude of 5.0, while South Africa’s Council for Geoscience put it at 4.7. The quake struck about 10 kilometers below the surface, which is very shallow.

People said the shaking was strong enough to wake them up and some homes suffered relatively minor damage, but there were no immediate reports of injuries. “The whole house shook for about 40 seconds,” one resident in Alberton said.