A 5.7 magnitude earthquake was recorded in the southern coast of Africa, causing concern among residents online. However, according to Dr. Diego Quiros, a lecturer in Geophysics at the University of Cape Town, the public has little to worry about in terms of tectonic activity. The earthquake was confirmed by several geological agencies, including the United States Geological Survey (USGS), Helmholtz Society of Geosciences (GFZ/GEOFON), and European-Mediterranean Seismological Centre (EMSC).
The earthquake occurred approximately 500km from Marion Island, part of the Prince Edward Islands, which belongs to South Africa. However, it is also correct to say that the event was located between 1675 and 1690km from Gqeberha and 1930 and 1955km from Cape Town, depending on which agency's location is used. Dr. Quiros explained that the event's location, depth, origin time, and magnitude will have uncertainty, but the solutions from the three agencies lie within 30km of each other.
According to Dr. Quiros, a 5.7 magnitude earthquake would be considered moderate in terms of magnitude alone. However, given its remote location at a known tectonic plate boundary, its impact on the South African mainland is very minimal. Even for people present at Marion Island, which is 500km from the event, the impact should be small, and some might have felt the event.
The earthquake occurred in the plate boundary named the Southwest Indian Ridge, where tectonic plates move apart in some sections and slide horizontally past each other in other sections. Since 1970, roughly 50 events have been recorded along the boundary, but none have had a significant impact on South Africa. Dr. Quiros added that the boundary is unlikely to generate an event that would worry South Africans.
Dr. Quiros also addressed concerns about a potential tsunami, stating that for a tsunami to occur, a large portion of the ocean floor needs to move up or down. Given the location of this event on a tectonic plate boundary of the mid-ocean ridge type, it is not very likely that a tsunami would be generated. Most of the motion at this type of plate boundary is accommodated by plates sliding horizontally past each other, not up or down motion.
The USGS did not assign a tsunami flag to this event, which further reduces the likelihood of a tsunami. The factors that control tsunami generation include the magnitude of the event, the type of faulting, and the depth. In this case, the magnitude of 5.7 is relatively low, and the type of faulting is not likely to generate a tsunami.
In conclusion, while the 5.7 magnitude earthquake was significant, its remote location and the type of tectonic plate boundary where it occurred make it unlikely to have a significant impact on South Africa. Residents can rest assured that the risk of a tsunami or significant damage from the earthquake is minimal.
Key points
- The earthquake occurred at a known tectonic plate boundary, the Southwest Indian Ridge, where 50 events have been recorded since 1970, but none have had a significant impact on South Africa.
- The remote location of the earthquake and its relatively low magnitude of 5.7 make it unlikely to have a significant impact on the South African mainland.
- The type of faulting and the depth of the earthquake also reduce the likelihood of a tsunami being generated.
