Minor tremor in Johannesburg south overnight

A tremor was experienced in most parts of Johannesburg south on Tuesday night, including Roodepoort, Soweto and surrounding areas.

The city’s emergency services department confirmed the tremor, saying no injuries or damage was reported.

Gauteng Weather said on X a preliminary finding showed the tremor was a 2.4 magnitude, with its epicentre at Doornkop.

The Council of Geoscience on June 29, a tremor with a magnitude of 2.3 was recorded and one with a 2.5 magnitude on July 1 in Johannesburg south; a 2.8ML tremor was measured on June 20 2023 on the West Rand and surrounding areas around Roodepoort; and on June 11 2023, a 5 magnitude quake on the East Rand in Boksburg and surrounding areas. 

Regarding the June and July tremors, the council said its preliminary seismic findings indicated the probable epicentral area (Mooifontein tailings dams located southwest of the Johannesburg CBD) could lie between a network of fault or fracture structures that are intersecting each other, and over time the structures could fail due to the weight exerted by of the tailing dams’ stockpile of waste material.

“This is evident from the fault plane solutions of the main events and aftershocks, which show a strike-slip normal fault focal mechanism and stresses oriented approximately northeast-southwest.”

Another hypothesis, however, suggests past precipitation could form a water table within the tailing’s stockpile, the council said.

“Water infiltration through conduits could easily cause differential movements within the stockpile, leading to stress redistribution in underground fault/fracture structures and triggering of seismic events.”

TimesLIVE