A series of earthquakes has rattled the Kariba area this week, leaving residents concerned despite assurances from authorities that there’s no immediate danger to the dam’s structural integrity. The Zambezi River Authority (ZRA), responsible for managing the Kariba Dam, has attributed the seismic activity to reservoir-induced seismic events, a phenomenon linked to water level fluctuations in the massive reservoir.
The most recent tremor, recorded on 23 December, registered a magnitude of 4.9 on the Richter scale. Its epicentre was located approximately 19 kilometres southeast of Kariba Dam, directly behind Antelope Island within the Kariba reservoir. This follows six other earthquake incidents reported since 1 December 2024, with magnitudes ranging from 4.1 to 4.7. The epicentres of these earlier earthquakes were situated between 19km and 40km southeast of Kariba town, either within the Kariba reservoir or the Charara Safari Area. A further earthquake of magnitude 4.3 on 11 December was recorded approximately 106km away from Kariba Dam in the Hurungwe District.
Despite the heightened seismic activity, ZRA chief executive Munyaradzi Munodawafa has moved to reassure the public. “The earthquakes that have been experienced in Kariba, Siavonga and surrounding areas since the construction of Kariba Dam are relatively small and have not generated large ground accelerations or vibrations as to cause concern regarding the safety of the dam wall,” he stated.
Following the tremors, ZRA conducted thorough inspections of the dam and analysed data from its monitoring instruments. “The inspections and analysis of data from the various monitoring instruments after the earthquakes… did not reveal any unusual observations and the dam continued to exhibit normal behaviour that is consistent with prevailing loading conditions,” the ZRA reported in a recent update.
The ZRA’s statement confirms that tremors of this nature are not uncommon in the Kariba region. Experts describe these as load-induced tremors, or more specifically, reservoir-induced tremors in the case of Kariba Dam. They are a natural consequence of the earth’s crust responding to the immense weight of water held within the reservoir.
The Kariba Dam, a joint venture between the governments of Zambia and Zimbabwe, is a vital piece of infrastructure providing hydroelectric power, water storage, and flood control for the region. Its construction, completed in 1963, marked a significant engineering achievement. Since the dam’s reservoir began filling, over 1000 tremors of magnitude 4.0 or greater have been recorded. This phenomenon is not unique to Kariba; similar seismic events have been observed at other large dams and reservoirs worldwide.
While the recent earthquakes have understandably caused concern among residents, the ZRA emphasises that most tremors in the Kariba area are barely perceptible. These reservoir-induced seismic events pose minimal risk to buildings or human life. The ZRA prefers the terms “tremors” or “seismic events” over the potentially alarmist term “earthquake”.
As a precautionary measure, the ZRA has urged the public to report any unusual observations or concerns to the relevant authorities. The ongoing monitoring of the dam and the surrounding area will continue to provide valuable data for assessing the long-term impact of reservoir-induced seismicity on the Kariba Dam and its environs.
