Quake possibly linked to mining - professor

Pretoria - The 5.5 magnitude earthquake that struck the North West earlier this month could possibly be linked to mining in the area, a University of Pretoria academic said on Monday.

"What might happen, after enough mining, we are creating stresses, more and more stresses, and they are propagating deeper and deeper," the university's Natural Hazard Centre director Professor Andrezj Kijko said.

"We are adding stresses to already existing stresses, tectonic components... and then we are triggering [an] earthquake.

"We are talking about accelerating earthquakes, just by mining," Kijko said.

In 1992, based on work and research done previously, it was stated that earthquakes would occur in the Klerksdorp region in the North West around every 10 years, not exceeding a magnitude of 5.6.

Kiljko, speaking at the Council of Scientific and Industrial Research (CSIR) in Pretoria, said while it was possible to predict how often earthquakes took place, predicting the where, when, and size was not possible.

Professor Ray Durrheim, the Wits/CSIR South African Research Chair in Exploration, Earthquake, and Mining Seismology, said it was not simple to deduce whether an earthquake was directly caused by mining or not.

"It's on a continuum, from where it's purely induced by mining activities to where you are triggering a natural earthquake," he said.

"There is no doubt, if you look at our mining areas, the number of magnitude-three events you see in a place like Carletonville is 1 000 times higher than you get in an equivalent area on the San Andreas fault [in California]."

Durrheim, Kijko and several others published a report in 2006 titled "The risks to miners, mines, and the public posed by large seismic events in the gold mining districts of South Africa".

This followed the 5.3 magnitude earthquake that struck the Klerksdorp area on 9 March 2005.

A 31-year-old man was killed in a mining village near Orkney on 5 August this year when the 5.5 magnitude earthquake struck the region.

At least 34 miners were injured by the earthquake, and more than 600 houses damaged.