New research shows the size of man-made earthquakes is linked to how deep industry wastewater is injected into the ground.
South Africa has been considering shale gas development in the Karoo region. The gas, will be expensive to explore and extract, will be used as part of the country's energy mix.
Shale gas holds considerable advantages. But there are still a number of uncertainties around whether South Africa is ready for such a bold step.
Fracking fluids in Marcellus shale have contaminated groundwater but new study finds that the source is likely from surface spills, not leaks from underground wells.