Why do so few serious earthquakes occur in South Africa?

South Africa is renowned for its beauty, rich cultural heritage, and unique biodiversity. However, one aspect of the country that is not often mentioned is its relative geological tranquillity. Unlike Some areas of the world which are prone to severe seismic events, South Africa enjoys a level of seismic stability that is quite astonishing. This lack of serious earthquakes can be attributed to several geological factors that set the country apart. To understand why it experiences such minimal seismic activity, we need to look at its geological characteristics and the science of tectonic activity.

Kaapvaal Craton: this extremely ancient and stable section of the Earth’s crust dates back over 2.5 billion years. It forms a large part of the country’s bedrock and has mostly remained unchanged over geologic timescales, which significantly reduces the likelihood of seismic events.

Distance from Tectonic Plate Boundaries: South Africa is geologically stable as it is located near the centre of the very large African tectonic plate, which is considered one of the most stable plates in the world.  Stresses are transmitted from plate margins into the interior which means that South Africa is far removed from the active areas where most seismic activity occurs.  The absence of interactions such as subduction, collision, and transformation in this plate’s area contributes to its tectonic stability

Absence of Subduction Zones: subduction zones, where one tectonic plate is forced beneath another, are major sources of significant earthquakes. The absence of these zones near South Africa further minimises earthquake risks.

Intraplate Seismic Activity: while seismic activity does occur within a tectonic plate, known as intraplate earthquakes, these events in South Africa are typically of lower magnitude and less frequent compared to countries found near plate boundaries.  However, incipient (young) rifts developing to the north across Botswana and Zambia and to the east off the coast of KZN add horizontal stresses to the interior’s crust. These cause local slippages and it is probable the seismic activity in the Jagersfontein area and in Namaqualand could be related to these stresses.

Mining Activity: South Africa experiences some seismic events related to deep-level gold mining mining activities (the average depth being 2 km but can be 4 km in some area); however, these human-induced earthquakes are generally less severe (and less frequent) than those caused by natural processes.  Nevertheless, the most pronounced seismic activity in South Africa remains human induced.

In conclusion, the primary reason for the relatively low occurrence of serious earthquakes in South Africa is its geological stability. The country’s location away from tectonic plate boundaries, the presence of the stable Kaapvaal Craton, its ancient rigid crust, the absence of nearby subduction zones, and the predominance of lower magnitude intraplate earthquakes all contribute to the reduced seismic risk. While human-induced seismic activity related to mining does occur, it typically results in less severe earthquakes compared to those caused by natural tectonic processes. Overall, South Africa’s position on one of the most stable tectonic plates in the world plays a crucial role in its low earthquake hazard.