Can the Ethiopian Dam trigger earthquakes in Africa?

Natural disasters such as earthquakes are frequently labeled as "acts of God," but some studies have quietly questioned if humans may have played a role.

The relationship between human activity and earthquakes is causing growing concern. The construction of major dams is one of the most significant human activities that can cause earthquakes.   Dams are designed to hold back large amounts of water, which can put pressure on the earth's crust. When the weight of the water is too much for the land to bear, the ground can shift and cause an earthquake.

A prime example of this occurred in China in 2008, when the researchers have gone public with evidence that stresses from water piled behind the new Zipingpu Dam may have triggered the failure of the nearby fault, a failure that went on to rupture almost 300 kilometers of fault and kill some 80,000 people. In 1967, impoundment behind the Koyna Dam in India triggered the largest known reservoir-triggered quake, a magnitude-6.3 temblor that killed 200 people. (Kerr and Stone, 2009).   Can these scenarios occur in Africa?

The Grand Ethiopian Renaissance Dam (GERD) on the Blue Nile, which is located in Ethiopia about 15 kilometres upstream (east) of the Sudanese border and is expected to be completed within the next several years, has been a source of contention from its commencement in 2011. Concerns have been raised in recent years regarding the GERD's potential to create earthquakes in the African region. The Nile River basin, where the GERD is located, is in an active seismic zone.

The weight of the water in the reservoir can cause the underlying rock to shift, potentially leading to an increase in seismic activity. This effect is known as reservoir-induced seismicity (RIS) or induced earthquakes, which can be triggered by the stress changes in the crust due to the water load on the surface and subsurface of the earth. In most cases (RIS) follows the impoundment, large lake-level changes, or filling at a later time above the highest water level achieved until then. Calculations of studies suggest that longer periods water level changes are more likely to cause deeper earthquakes. (Talwani, 1997). 

Studies have attributed increased seismic activity in the region by the GERD due to 74 billion cubic meters of water that can be held up in the dam reservoir (Yihdego, et all. 2017), which exerts pressure on the underlying geological structure. Results have revealed recently that the GERD impoundment will cause significant subsurficial stresses, and could possibly trigger seismicity in the region by examining Coulomb stress and hydrologic load centroid movements for several GERD impoundment and operational scenarios (Madson, and Sheng, 2021). However, it is not certain that the GERD's hydrological load changes will actually trigger local seismicity (Madson, and Sheng, 2021) the potential consequences of earthquakes caused by the GERD include damage to infrastructure, loss of life, and disruption to agriculture and irrigation.   

References

• Kerr, R. A., & Stone, R. (2009). A human trigger for the great quake of Sichuan? Science, 323(5912), 322-322.‏https://www.science.org/doi/10.1126/science.323.5912.322 
• Madson, A., & Sheng, Y. (2021). Coulomb stress analysis for several filling and operational scenarios at the Grand Ethiopian Renaissance Dam impoundment. Environmental Earth Sciences, 80, 1-17.‏
• Talwani, P. (1997). On the nature of reservoir-induced seismicity. Pure and applied Geophysics, 150, 473-492.‏
• Yihdego, Y., Khalil, A., & Salem, H. S. (2017). Nile River’s basin dispute: perspectives of the Grand Ethiopian Renaissance Dam (GERD). Glob. J. Hum. Soc. Sci, 17(4), p.9.