Behind Botswana’s earthquake

SHARE   |   Monday, 10 April 2017   |   By Staff Writer
Behind Botswana’s earthquake

The mystery surrounding recent unexpected earthquake that ran across a large part of Southern Africa and had its epicenter in the Central Kalahari Game Reserve (CKGR) is beginning to unfold and while the Botswana Geoscience Institute in Lobatse claim it was caused by nothing other than natural causes, reports have surfaced alleging that fracking activities in the reserve are to blame. In his article published in The Daily Maverick this week, Jeffery Barbee points out that although there's not enough information to ascertain that indeed the earthquake was caused by fracking activities in the CKGR, one thing that is certain is that to produce gas from coal seams you need to pump out a lot of water that they sit in to let the gas “desorb”. This produced water is usually pumped back into the ground, somewhere nearby and very deep down which has been shown to change the basal pressure underground. And, he writes, the potential consequences of that? Earthquakes! According to Barbee, companies had been hydraulic fracturing, or fracking, in protected areas like the Central Kalahari Game Reserve for years, exploring for good gas returns from Botswana’s coal layers. The article pointed out a company that has ongoing gas project in the lower south-eastern corner inside and outside the Central Kalahari Game Reserve (CKGR) where they are apparently operating their ongoing gas project. The US Government Survey, which maps exact earthquake locations worldwide with precision according to the Daily maverick has in turn pointed out the tremor which shook much of the sub region this week is underneath the gas well drill sites where a local company has been operating for at least the last five years.

Despite these damning reports, Botswana Geoscience Institute maintains that the earthquake was due to natural causes. Mojaboswa Koketso, Botswana Geoscience Institute Deputy Director who is also a Geophysicist by profession, said as it is they were not aware of any fracking activities in the CKGR or any location near Moiyabana where the earth quake epicentre is located. “We attribute the earthquake to natural causes and we are yet to investigate these natural causes to ascertain if indeed they make sense,” said Koketso. Although he agreed that fracking is one of the manmade causes of earthquakes the world over, Koketso said fracking is the least of their worries looking at the location of the epicentre. However, he pointed out that fracking emits microscopic tremors which can only be detected and measured by a station closer to the activity. According to Koketso, Botswana Geoscience Institute currently does not have a seismic station except for one owned by Americans in Magothwane near Otse. Seismic readings and earthquake measurements are currently read and triangulated from other stations in the region. “The recent earthquake was detected by a station in South Africa,” he said. He also said although the Magothwane seismic station detected  the tremor, that is as far as it can do, hence they had to rely on their South African counterparts to measure its depth and locate its epicentre. He conceded that Moiyabana area does not constitute earthquake prone areas in Botswana currently pointing out that the Okavango region which forms part of an extension of the Eastern African Valley is one such hot spot. As it is Koketso said, they are still to measure the aftermath of the recent earthquake.

Fracking and Earthquakes
According to the American Geosciences Institute, to produce natural gas from shale formations, it is necessary to increase the interconnectedness of the pore space (permeability) of the shale so that the gas can flow through the rock mass and be extracted through production wells. This is usually done by hydraulic fracturing ("Fracking"). Fracking causes extremely small earthquakes, but they are almost always too small to be a safety concern. In addition to natural gas, fracking fluids and salt water trapped in the same formation as the gas are returned to the surface. These wastewaters are frequently disposed of by injection into deep wells. The injection of wastewater and salt water into the subsurface can cause earthquakes that are large enough to be felt and may cause damage." The last similar earthquake took place in the area that would later become Botswana in 1952.