‘No need for alarm bells’ over UCT Karoo earthquake swarm study, say industry experts

 Industry stakeholders this week reacted cautiously to news of an ‘earthquake swarm’ in the Leeu Gamka area of the Karoo in the Western Cape—66 earthquakes since 2007.

Details of the seismic activity, in an area previously thought to be stable, emerged from research by the University of Cape Town (UCT), recently published by Department of Geological Sciences researchers in the scientific journal Seismological Research Letters. The findings point to a “hidden fault beneath the Karoo Basin that appears to be critically stressed and capable of generating earthquakes,” UCT said in a press release issued earlier this month. “Their findings suggest that the geological conditions associated with induced seismicity in other shale gas regions worldwide may also exist beneath parts of the Karoo.”

Responding to Cape Chamber queries about the new findings, industry stakeholders cautioned against ‘alarmist’ conclusions stemming from the study. Seismic activity has been monitored for years, and the impact of shale gas exploration remains central to potential development.

“I am concerned that selected findings of an excellent PhD thesis by Benjamin Whitehead, entitled ‘Seismic Anomalies in Stable Continents: Exploring Earthquake Clusters and Hidden Faults in Southern Africa’, are being amplified and sensationalised in a way that is likely to cause alarm,” said one source with knowledge of the study. “I fear that this may undermine extensive efforts to assess the hazards and mitigate risks of any shale gas exploration and development.”

Multiple baseline surveys have been commissioned by the Petroleum Agency of South Africa to add to the Department of Environmental Affairs' (DEA) Strategic Environmental Assessment from 2016, the source says.

Another well-placed source said the study area near Leeu Gamka lay “outside the historical area of interest” for companies interested in fracking, with the area west of Beaufort West being the key potential fracking zone. The source adds that any fracking impact on seismic activity remains entirely hypothetical.

A former energy sector executive noted that the word ‘earthquake’ is often used emotively and is not synonymous with all seismic activity: “An earthquake is something felt by humans on the surface and would typically need to be at least 3 on the Richter scale. The micro-seismic events recorded for hydraulic stimulation in deep shales are tiny by comparison, and there are probably at least 10,000 such events occurring every day around the world quite naturally,” he says.

Whitehead clarifies that the earthquakes observed in the Karoo were natural and not caused by hydraulic fracturing. However, he points to international studies which show that wastewater injection and shale gas operations can reactivate pre-existing faults under certain conditions.

In his view, the latest findings should inform future planning rather than halt development.

“Our study provides the kind of geological evidence needed to make informed decisions about future exploration. Better seismic monitoring before development begins can be used to characterise baseline seismic activity and can help identify areas where additional precautions may be necessary,” he added.